Von Economo neurons (VENs), also called spindle neurons, are a specific class of mammaliancorticalneurons characterized by a large spindle-shaped soma (or body) gradually tapering into a single apicalaxon (the ramification that transmits signals) in one direction, with only a single dendrite (the ramification that receives signals) facing opposite. Other cortical neurons tend to have many dendrites, and the bipolar-shaped morphology of von Economo neurons is unique here.
Von Economo neurons were discovered and first described in 1929 by Austrian psychiatrist and neurologist Constantin von Economo (1876–1931).
Function
Von Economo neurons are relatively large cells that may allow rapid communication across the relatively large brains of great apes, elephants, and cetaceans.
Although rare in comparison to other neurons, von Economo neurons are
abundant, and comparatively large, in humans; they are however three
times as abundant in cetaceans.
Evolutionary significance
The discovery of von Economo neurons in diverse whale species
has led to the suggestion that they are "a possible obligatory neuronal
adaptation in very large brains, permitting fast information processing
and transfer along highly specific projections and that evolved in
relation to emerging social behaviors." The apparent presence of these specialized neurons only in highly intelligent mammals may be an example of convergent evolution.
Their restriction among the primates to great apes leads to the
hypothesis that they developed no earlier than 15–20 million years ago,
prior to the divergence of orangutans from the African great apes.
Recently, primitive forms of von Economo neurons have also been
discovered in macaque monkey brains and raccoons.
Allman and his colleagues have delved beyond the level of brain
infrastructure to investigate how von Economo neurons function at the
superstructural level, focusing on their role as «air traffic
controllers for emotions ... at the heart of the human social emotion
circuitry, including a moral sense. Allman's team proposes that von Economo neurons help channel neural
signals from deep within the cortex to relatively distant parts of the
brain. Specifically, Allman's team found signals from the ACC are received in Brodmann's area 10, in the frontal polar cortex, where regulation of cognitive dissonance
(disambiguation between alternatives) is thought to occur. According to
Allman, this neural relay appears to convey motivation to act, and
concerns the recognition of error. Self-control – and avoidance of
error – is thus facilitated by the executive gatekeeping function of the
ACC, as it regulates the interference patterns of neural signals
between these two brain regions.
In humans, intense emotion activates the anterior cingulate cortex, as it relays neural signals transmitted from the amygdala (a primary processing center for emotions) to the frontal cortex, perhaps by functioning as a sort of lens to focus the complex texture of neural signal interference patterns.
The ACC is also active during demanding tasks requiring judgement and
discrimination and when errors are detected by an individual. During
difficult tasks, or when experiencing intense love, anger, or lust,
activation of the ACC increases. In brain imaging studies, the ACC has
specifically been found to be active when mothers hear infants cry,
underscoring its role in affording a heightened degree of social
sensitivity.
The ACC is a relatively ancient cortical region and is involved with many autonomic
functions, including motor and digestive functions, while also playing a
role in the regulation of blood pressure and heart rate. Significant olfactory and gustatory
capabilities of the ACC and fronto-insular cortex appear to have been
usurped, during recent evolution, to serve enhanced roles related to
higher cognition – ranging from planning and self-awareness to
role-playing and deception. The diminished olfactory function of humans,
compared to other primates, may be related to the fact that von Economo
neurons located at crucial neural network hubs have only two dendrites
rather than many, resulting in reduced neurological integration.
In the fronto-insular cortex
At a Society for Neuroscience
meeting in 2003, Allman reported on von Economo neurons his team found
in another brain region, the fronto-insular cortex, a region which
appears to have undergone significant evolutionary adaptations in
mankind – perhaps as recently as 100,000 years ago.
This fronto-insular cortex is closely connected to the insula,
a region that is roughly the size of a thumb in each hemisphere of the
human brain. The insula and fronto-insular cortex are part of the insular cortex, wherein the elaborate circuitry associated with spatial awareness are found, and where self-awareness
and the complexities of emotion are thought to be generated and
experienced. Moreover, this region of the right hemisphere is crucial to
navigation and perception of three-dimensional rotations.
Concentrations
Anterior cingulate cortex
The
largest number of ACC von Economo neurons are found in humans, fewer in
the gracile great apes, and fewest in the robust great apes. In both
humans and bonobos they are often found in clusters of 3 to 6 neurons.
They are found in humans, bonobos, chimpanzees, gorillas, orangutans, some cetaceans, and elephants.
While total quantities of ACC von Economo neurons were not reported by
Allman in his seminal research report (as they were in a later report
describing their presence in the frontoinsular cortex, below), his
team's initial analysis of the ACC layer V in hominids revealed an
average of ~9 von Economo neurons per section for orangutans (rare, 0.6% of section cells), ~22 for gorillas (frequent, 2.3%), ~37 for chimpanzees (abundant, 3.8%), ~68 for bonobos (abundant/clusters, 4.8%), ~89 for humans (abundant/clusters, 5.6%).
Fronto-insular cortex
All of the primates examined had more von Economo neurons in the
fronto-insula of the right hemisphere than in the left. In contrast to
the higher number of von Economo neurons found in the ACC of the gracile
bonobos and chimpanzees, the number of fronto-insular von Economo neurons was far higher in the cortex of robust gorillas (no data for orangutans was given). An adult human
had 82,855 such cells, a gorilla had 16,710, a bonobo had 2,159, and a
chimpanzee had a mere 1,808 – despite the fact that chimpanzees and
bonobos are great apes most closely related to humans.
Dorsolateral prefrontal cortex
Von Economo neurons have been located in the Dorsolateral prefrontal cortex of humans and elephants. In humans they have been observed in higher concentration in Brodmann area 9 (BA9) – mostly isolated or in clusters of 2, while in Brodmann area 24 (BA24) they have been found mostly in clusters of 2–4.
Clinical significance
Abnormal
von Economo neuron development may be linked to several psychotic
disorders, typically those characterized by distortions of reality,
disturbances of thought, disturbances of language, and withdrawal from
social contact. Altered von Economo neuron states have been implicated in both schizophrenia and autism, but research into these correlations remains at a very early stage. Frontotemporal dementia involves loss of mostly von Economo neurons.
An initial study suggested that Alzheimer's disease specifically
targeted von Economo neurons; this study was performed with end-stage
Alzheimer brains in which cell destruction was widespread, but later it
was found that Alzheimer's disease doesn't affect the von Economo
neurons.
Tool use by animals is a phenomenon in which an animal uses any kind of tool in order to achieve a goal such as acquiring food and water, grooming, defense, communication, recreation or construction. Originally thought to be a skill possessed only by humans,
some tool use requires a sophisticated level of cognition. There is
considerable discussion about the definition of what constitutes a tool
and therefore which behaviours can be considered true examples of tool
use. A wide range of animals, including mammals, birds, fish,
cephalopods, and insects, are considered to use tools.
Primates are well known for using tools for hunting or gathering food and water, cover for rain, and self-defence. Chimpanzees have been the object of study, most famously by Jane Goodall,
since these animals are more-often kept in captivity than other
primates and are closely related to humans. Tool-use in other primates
are lesser-known as many of them are mainly observed in the wild. Many
famous researchers, such as Charles Darwin in his book The Descent of Man, mentioned tool-use in monkeys (such as baboons).
Both wild and captive elephants are known to create tools using their
trunk and feet, mainly for swatting flies, scratching, plugging
waterholes that they have dug (to close them up again so the water
doesn't evaporate) and reaching food that is out of reach. A group of
dolphins in Shark Bay use sponges to protect their beak while foraging. Sea otters will dislodge food from rocks (such as abalone) and break open shellfish. Carnivores (of the order Carnivora) can use tools to trap prey or break open the shells of prey, as well as for scratching.
Corvids (crows, ravens and rooks) are well known for their large brains (among birds) and tool use. New Caledonian crows
are among the only animals that create their own tools. They mainly
manufacture probes out of twigs and wood (and sometimes metal wire) to
catch or impale larvae. Tool use in some birds may be best exemplified in nest intricacy. Tailorbirds manufacture 'pouches' to make their nests in. Some birds, such as weaver birds build complex nests. Woodpecker finches
insert twigs into trees in order to catch or impale larvae. Parrots may
use tools to wedge nuts so that they can crack it open without
launching it away. Some birds take advantage of human activity, such as carrion crows in Japan which drop nuts in front of cars to crack them open.
Several species of fish use tools to crack open shellfish,
extract food that is out of reach, cleaning an area (for nesting), and
hunting. Octopuses gather coconut shells and create a shelter. They may also construct a fence using rocks.
Definitions and terminology
The
key to identifying tool use is defining what constitutes a tool.
Researchers of animal behavior have arrived at different formulations.
In 1981, Beck published a widely used definition of tool use. This has been modified to:
The external employment of an
unattached or manipulable attached environmental object to alter more
efficiently the form, position, or condition of another object, another
organism, or the user itself, when the user holds and directly
manipulates the tool during or prior to use and is responsible for the
proper and effective orientation of the tool.
Other, briefer definitions have been proposed:
An object carried or maintained for future use.
— Finn, Tregenza, and Norman, 2009.
The use of physical objects other
than the animal's own body or appendages as a means to extend the
physical influence realized by the animal.
— Jones and Kamil, 1973
An object that has been modified
to fit a purpose ... [or] An inanimate object that one uses or modifies
in some way to cause a change in the environment, thereby facilitating
one's achievement of a target goal.
— Hauser, 2000
Others, for example Lawick-Goodall, distinguish between "tool use" and "object use".
Different terms have been given to the tool according to whether
the tool is altered by the animal. If the "tool" is not held or
manipulated by the animal in any way, such as an immobile anvil, objects in a bowerbird's bower, or a bird using bread as bait to catch fish, it is sometimes referred to as a "proto-tool". Several studies in primates and birds
have found that tool use is correlated with an enlargement of the brain
as a whole or of particular regions. For example, true tool-using birds
have relatively larger brains than proto-tool users.
When an animal uses a tool that acts on another tool, this has been termed use of a "meta-tool". For example, New Caledonian crows
will spontaneously use a short tool to obtain an otherwise inaccessible
longer tool that then allows them to extract food from a hole. Similarly, bearded capuchin
monkeys will use smaller stones to loosen bigger quartz pebbles
embedded in conglomerate rock, which they subsequently use as tools.
Rarely, animals may use one tool followed by another, for example, bearded capuchins use stones and sticks, or two stones. This is called "associative", "secondary" or "sequential" tool use.
Some animals use other individuals in a way which could be
interpreted as tool use, for example, ants crossing water over a bridge
of other ants, or weaver ants using conspecifics to glue leaves together. These have been termed "social tools".
Borderline examples
Play
Play
has been defined as "activity having no immediate benefits and
structurally including repetitive or exaggerated actions that may be out
of sequence or disordered". When play is discussed in relation to manipulating objects, it is often used in association with the word "tool".
Some birds, notably crows, parrots and birds of prey, "play" with
objects, many of them playing in flight with such items as stones,
sticks and leaves, by letting them go and catching them again before
they reach the ground. A few species repeatedly drop stones, apparently
for the enjoyment of the sound effects. Many other species of animals, both avian and non-avian, play with objects in a similar manner.
Fixed "devices"
The impaling of prey on thorns by many of the shrikes (Laniidae) is well known.
Several other birds may use spines or forked sticks to anchor a carcass
while they flay it with the bill. It has been concluded that "This is
an example of a fixed device which serves as an extension of the body,
in this case, talons" and is thus a true form of tool use. On the other
hand, the use of fixed skewers may not be true tool-use because the
thorn (or whatever) is not manipulated by the bird. Leopards perform a similar behaviour by dragging carcasses up trees and caching them in the forks of branches.
Use of bait
Several species of bird, including herons such as the striated heron (Butorides striatus), will place bread in water to attract fish. Whether this is tool use is disputed because the bread is not manipulated or held by the bird.
Captive orcas have been observed baiting and catching a bird with a regurgitated fish, as well as showing similar behaviour in the wild.
Learning and cognition
Tool use by animals may indicate different levels of learning and cognition. For some animals, tool use is largely instinctive and inflexible. For example, the woodpecker finch of the Galápagos Islands use twigs or spines as an essential and regular part of its foraging
behaviour, but these behaviours are often quite inflexible and are not
applied effectively in different situations. Other tool use, e.g. chimpanzees using twigs to "fish" for termites, may be developed by watching others use tools
and may even be a true example of animal teaching. Tools may even be
used in solving puzzles in which the animal appears to experience a "Eureka moment".
In mammals
Primates
A Western lowland gorilla, G. g. gorilla, using a stick possibly to gauge the depth of water
Tool use has been reported many times in both wild and captive primates, particularly the great apes.
The use of tools by primates is varied and includes hunting (mammals,
invertebrates, fish), collecting honey, processing food (nuts, fruits,
vegetables and seeds), collecting water, weapons and shelter.
Tool manufacture is much rarer than simple tool use and probably
represents higher cognitive functioning. Soon after her initial
discovery of tool use, Goodall observed other chimpanzees picking up
leafy twigs, stripping off the leaves and using the stems to fish for
insects. This change of a leafy twig into a tool was a major discovery.
Prior to this, scientists thought that only humans manufactured and used
tools, and that this ability was what separated humans from other
animals. In 1990, it was claimed the only primate to manufacture tools in the wild was the chimpanzee. However, since then, several primates have been reported as tool makers in the wild.
Both bonobos and chimpanzees have been observed making "sponges"
out of leaves and moss that suck up water and using these for grooming.
Sumatran orangutans will take a live branch, remove twigs and leaves and
sometimes the bark, before fraying or flattening the tip for use on
ants or bees. In the wild, mandrills have been observed to clean their ears with modified tools. Scientists filmed a large male mandrill at Chester Zoo
(UK) stripping down a twig, apparently to make it narrower, and then
using the modified stick to scrape dirt from underneath his toenails. Captive gorillas have made a variety of tools.
Chimpanzees and bonobos
Chimpanzees (Pan troglodytes)
are sophisticated tool users with behaviors including cracking nuts
with stone tools and fishing for ants or termites with sticks. These
chimpanzees not only use these sticks to fish out their meal, but they
in fact build their own 'tool kits' to do so, as observed in the
Republic of Congo. They first use a smaller stick to break open the
termite or ant mound, then use a large stick to make holes in the prey's
colony, and then insert a 'fishing probe' into the hole and pull out
all the termites or ants that have gathered on the stick. There are more limited reports of the closely related bonobo (Pan paniscus)
using tools in the wild; it has been claimed they rarely use tools in
the wild although they use tools as readily as chimpanzees when in
captivity, It has been reported that females of both chimpanzees and bonobos use tools more avidly than males.
Wild chimpanzees predominantly use tools in the context of food
acquisition, while wild bonobos appear to use tools mainly for personal
care (cleaning, protection from rain) and social purposes. Wild bonobos
have been observed using leaves as cover for rain, or the use of
branches in social displays.
Hunting
Research
in 2007 showed that common chimpanzees sharpen sticks to use as weapons
when hunting mammals. This is considered the first evidence of
systematic use of weapons in a species other than humans. Researchers
documented 22 occasions when wild chimpanzees on a savanna in Senegal fashioned sticks into "spears" to hunt lesser bushbabies (Galago senegalensis).
In each case, a chimpanzee modified a branch by breaking off one or two
ends and, frequently using its teeth, sharpened the stick. The tools,
on average, were about 60 cm (24 in) long and 1.1 cm (0.4 in) in
circumference. The chimpanzee then jabbed the spear into hollows in tree
trunks where bushbabies sleep.
There was a single case in which a chimpanzee successfully extracted a
bushbaby with the tool. It has been suggested that the word "spear" is
an overstatement that makes the chimpanzees seem too much like early
humans, and that the term "bludgeon" is more accurate, since the point
of the tool may not be particularly sharp.
This behaviour was seen more frequently in females, particularly
adolescent females, and young chimps in general, than in adult males.
Chimpanzees often eat the marrow of long bones of colobus monkeys with the help of small sticks, after opening the ends of the bones with their teeth.
A juvenile female was observed to eat small parts of the brain of an
intact skull that she could not break open by inserting a small stick
through the foramen magnum.
On another occasion, an adult female used three sticks to clean the
orbits of a colobus monkey skull after she had just eaten the eyes.
In Gombe National Park in 1960, Jane Goodall observed a chimpanzee, David Greybeard, poking pieces of grass into a termite
mound and then raising the grass to his mouth. After he left, Goodall
approached the mound and repeated the behaviour because she was unsure
what David was doing. She found that the termites bit onto the grass
with their jaws. David had been using the grass as a tool to "fish" or
"dip" for termites.
Soon after this initial discovery of tool use, Goodall observed David
and other chimpanzees picking up leafy twigs, stripping off the leaves,
and using the stems to fish for insects. This modification of a leafy
twig into a tool was a major discovery: previously, scientists thought
that only humans made and used tools, and that this was what separated
humans from other animals.
Other studies of the Gombe chimps show that young females and
males learn to fish for termites differently. Female chimps learn to
fish for termites earlier and better than the young males.
Females also spend more time fishing while at the mounds with their
mothers—males spend more time playing. When they are adults, females
need more termite protein because with young to care for, they cannot hunt the way males can.
Populations differ in the prevalence of tool use for fishing for invertebrates. Chimpanzees in the Tai National Park only sometimes use tools, whereas Gombe chimpanzees rely almost exclusively on tools for their intake of driver ants.
This may be due to difference in the rewards gained by tool use: Gombe
chimpanzees collect 760 ants/min compared to 180 ants/min for the Tai
chimpanzees.
Some chimpanzees use tools to hunt large bees (Xylocopa
sp.) which make nests in dead branches on the ground or in trees. To
get to the grubs and the honey, the chimpanzee first tests for the
presence of adults by probing the nest entrance with a stick. If
present, adult bees block the entrance with their abdomens, ready to
sting. The chimpanzee then disables them with the stick to make them
fall out and eats them rapidly. Afterwards, the chimpanzee opens the
branch with its teeth to obtain the grubs and the honey.
Chimpanzees have even been observed using two tools: a stick to
dig into an ant nest and a "brush" made from grass stems with their
teeth to collect the ants.
Collecting honey
Honey
of four bee species is eaten by chimpanzees. Groups of chimpanzees fish
with sticks for the honey after having tried to remove what they can
with their hands. They usually extract with their hands honeycombs from
undisturbed hives of honey bees and run away from the bees to quietly
eat their catch. In contrast, hives that have already been disturbed,
either through the falling of the tree or because of the intervention of
other predators, are cleaned of the remaining honey with fishing tools.
Tai chimpanzees crack open nuts with rocks, but there is no record of Gombe chimpanzees using rocks in this way. After opening nuts by pounding with a hammer, parts of the kernels
may be too difficult to reach with the teeth or fingernails, and some
individuals use sticks to remove these remains, instead of pounding the
nut further with the hammer as other individuals do: a relatively rare combination of using two different tools. Hammers for opening nuts may be either wood or stone.
Chimpanzees in the Nimba Mountains of Guinea, Africa, use both stone and wooden cleavers, as well as stone anvils, to chop up and reduce Treculia fruits into smaller bite-sized portions. These fruits, which can be the size of a volleyball
and weigh up to 8.5 kg, are hard and fibrous. But, despite lacking a
hard outer shell, they are too large for a chimpanzee to get its jaws
around and bite into. Instead, the chimpanzees use a range of tools to
chop them into smaller pieces. This is the first account of chimpanzees
using a pounding tool technology to break down large food items into
bite-sized chunks rather than just extracting it from other unobtainable
sources such as baobab
nuts. It is also the first time wild chimpanzees have been found to use
two distinct types of percussive technology, i.e. movable cleavers
against a non-movable anvil, to achieve the same goal. Neighbouring
chimpanzees in the nearby region of Seringbara do not process their food in this way, indicating how tool use among apes is culturally learnt.
Collecting water
When
chimpanzees cannot reach water that has formed in hollows high up
inside trees, they have been observed taking a handful of leaves,
chewing them, and dipping this "sponge" into the pool to suck out the
water.
Both bonobos and chimpanzees have also been observed making "sponges"
out of leaves and moss that suck up water and are used as grooming
tools.
Orangutans
Orangutans (genus Pongo) were first observed using tools in the wild in 1994 in the northwest corner of Sumatra. As with the chimpanzees,
orangutans use tools made from branches and leaves to scratch, scrape,
wipe, sponge, swat, fan, hook, probe, scoop, pry, chisel, hammer, cover,
cushion and amplify. They will break off a tree branch that is about
30 cm long, snap off the twigs, fray one end and then use the stick to
dig in tree holes for termites.
Sumatran orangutans use a variety of tools—up to 54 types for
extracting insects or honey, and as many as 20 types for opening or
preparing fruits such as the hard to access Neesia Malayana. They also use an 'autoerotic tool'—a stick which they use to stimulate the genitals and masturbate (both male and female).
In parts of Borneo, orangutans use handfuls of leaves as napkins to
wipe their chins while orangutans in parts of Sumatra use leaves as
gloves, helping them handle spiny fruits and branches, or as seat
cushions in spiny trees.
There have been reports that individuals in both captivity and in the
wild use tools held between the lips or teeth, rather than in the hands. In captivity, orangutans have been taught to chip stone handaxes.
Orangutans living in Borneo
scavenge fish that wash up along the shore and scoop catfish out of
small ponds for fresh meals. Over two years, anthropologist Anne Russon
saw several animals on these forested islands learn on their own to jab
at catfish with sticks, so that the panicked prey would flop out of
ponds and into the orangutan's waiting hands. Although orangutans usually fished alone, Russon observed pairs of apes catching catfish on a few occasions.
On the island of Kaja in Borneo, a male orangutan was observed using a
pole apparently trying to spear or bludgeon fish. This individual had
seen humans fishing with spears. Although not successful, he was later
able to improvise by using the pole to catch fish already trapped in the
locals' fishing lines.
Sumatran orangutans use sticks to acquire seeds from a particular fruit. When the fruit of the Neesia
tree ripens, its hard, ridged husk softens until it falls open. Inside
are seeds that are highly desirable to the orangutans, but they are
surrounded by fibreglass-like hairs that are painful if eaten. A Neesia-eating
orangutan will select a 12 cm stick, strip off the bark, and then
carefully collect the hairs with it. Once the fruit is safe, the ape
will eat the seeds using the stick or its fingers. Sumatran orangutans will use a stick to poke a bees' nest wall, move it around and catch the honey.
Orangutans have been observed using sticks to apparently measure
the depth of water. It has been reported that orangutans use tools for a
wide range of purposes including using leaves as protective gloves or
napkins, using leafy branches to swat insects or gather water, and
building sun or rain covers above the nests used for resting. It has been reported that a Sumatran orangutan used a large leaf as an umbrella in a tropical rainstorm.
Orangutans produce an alarm call known as a "kiss squeak" when
they encounter a predator like a snake or a human. Sometimes, orangutans
will strip leaves from a branch and hold them in front of their mouth
when making the sound. It has been found this lowers the maximum
frequency of the sound i.e. makes it deeper, and in addition, smaller
orangutans are more likely to use the leaves. It has been suggested they
use the leaves to make themselves sound bigger than they really are,
the first documented case of an animal using a tool to manipulate sound.
Gorillas
A gorilla pushing a stick into the ground and using it as a stabilizing stick while dredging aquatic herbs
There are few reports of gorillas using tools in the wild. Western lowland gorillas (Gorilla gorilla gorilla)
have been observed using sticks to apparently measure the depth of
water and as "walking sticks" to support their posture when crossing
deeper water.
An adult female used a detached trunk from a small shrub as a
stabilizer during food gathering, and another used a log as a bridge.
One possible explanation for the absence of observed tool use in wild
gorillas is that they are less dependent on foraging techniques that
require the use of tools, since they exploit food resources differently
from chimpanzees. Whereas chimpanzees and orangutans
feeding involves tools such as hammers to crack open nuts and sticks to
fish for termites, gorillas access these foods by breaking nuts with
their teeth and smashing termite mounds with their hands.
Captive western lowland gorillas have been observed to threaten
each other with sticks and larger pieces of wood, while others use
sticks for hygienic purposes. Some females have attempted to use logs as
ladders.
In another group of captive gorillas, several individuals were observed
throwing sticks and branches into a tree, apparently to knock down
leaves and seeds.
Gorillas at Prague zoo have used tools in several ways, including using
wood wool as "slippers" when walking on the snow or to cross a wet
section of the floor.
Monkeys
Tool use has been observed in capuchin monkeys
both in captivity and in their natural environments. In a captive
environment, capuchins readily insert a stick into a tube containing
viscous food that clings to the stick, which they then extract and lick. Capuchins also use a stick to push food from the center of a tube retrieving the food when it reaches the far end, and as a rake to sweep objects or food toward themselves. The black-striped capuchin (Sapajus libidinosus)
was the first non-ape primate for which tool use was documented in the
wild; individuals were observed cracking nuts by placing them on a stone
anvil and hitting them with another large stone (hammer). Similar hammer-and-anvil use has been observed in other wild capuchins including robust capuchin monkeys (genus Sapajus) It may take a capuchin up to 8 years to master this skill. The monkeys often transport hard fruits, stones, nuts and even oysters to an anvil for this purpose. Capuchins also use stones as digging tools for probing the substrate and sometimes for excavating tubers. Wild black-striped capuchin use sticks to flush prey from inside rock crevices. Robust capuchins are also known at times to rub defensive secretions from arthropods over their bodies before eating them; such secretions are believed to act as natural insecticides.
Brehm states, on the authority of
the well-known traveller Schimper, that in Abyssinia when the baboons
belonging to one species (C. gelada) descend in troops from the mountains to plunder the fields, they sometimes encounter troops of another species (C. hamadryas), and then a fight ensues. The Geladas roll down great stones, which the Hamadryas try to avoid...
Darwin continued:
Brehm, when accompanying the Duke
of Coburg-Gotha, aided in an attack with fire-arms on a troop of baboons
in the pass of Mensa in Abyssinia. The baboons in return rolled so many
stones down the mountain, some as large as a man's head, that the
attackers had to beat a hasty retreat; and the pass was actually for a
time closed against the caravan.
These rather anecdotal reports of stone throwing by baboons have been corroborated by more recent research on chacma baboon (Papio ursinus)
troops living on the desert floor of the Kuiseb Canyon in South West
Africa.
Stoning by these baboons is done from the rocky walls of the canyon
where they sleep and retreat when they are threatened. Stones are lifted
with one hand and dropped over the side. The stones tumble down the
side of the cliff or fall directly to the canyon floor. The researchers
recorded 23 such incidents involving the voluntary release of 124
stones.
A subadult male from a captive group of Guinea baboons (Papio papio)
learned, by trial-and-error, to use a tool to rake in food. He then
used the tool 104 times over 26 days, thereby providing the group with
most of its food.
In April 2018, after four captive baboons managed to escape from their enclosure at Texas Biomedical Research Institute,
a 55-gallon barrel left on its side in the pen as an enrichment device
was found to have been stood erect next to the perimeter wall, enabling
its use as a jumping platform to escape.
In the wild, mandrills have been observed to clean their ears with modified tools. Scientists filmed a large male mandrill at Chester Zoo
stripping down a twig, apparently to make it narrower, and then using
the modified stick to scrape dirt from underneath its toenails.
In Thailand and Myanmar, crab-eating macaques
use stone tools to open nuts, oysters and other bivalves, and various
types of sea snails (nerites, muricids, trochids, etc.) along the
Andaman sea coast and offshore islands.
A troop of wild macaques which regularly interact with humans have
learnt to remove hairs from the human's heads, and use the hair to floss
their teeth.
Elephants
Elephants show an ability to manufacture and use tools with their trunk and feet. Both wild and captive Asian elephants (Elephas maximus) use branches to swat flies or scratch themselves.
Eight of 13 captive Asian elephants, maintained under a naturalistic
environment, modified branches and switched with the altered branch,
indicating this species is capable of the more rare behaviour of tool
manufacture. There were different styles of modification of the
branches, the most common of which was holding the main stem with the
front foot and pulling off a side branch or distal
end with the trunk. Elephants have been observed digging holes to drink
water, then ripping bark from a tree, chewing it into the shape of a
ball thereby manufacturing a "plug" to fill in the hole, and covering it
with sand to avoid evaporation. They would later go back to the spot to drink.
Asian elephants may use tools in insightful problem solving. A
captive male was observed moving a box to a position where it could be
stood upon to reach food that had been deliberately hung out of reach.
Elephants have also been known to drop large rocks onto an electric fence to either ruin the fence or cut off the electricity.
Researchers
pushed a pole with a conical sponge attached along the substrate to
simulate sponging behavior by dolphins. They videotaped this experiment
to learn what prey was available on the seafloor and why a sponge would
be beneficial to foraging rather than echolocation.
A community of Indo-Pacific bottlenose dolphins (Tursiops sp.) in Shark Bay, Western Australia, made up of approximately 41-54 animals, are known to use conical sponges (Echinodictyum mesenterinum) as tools while foraging. This behavior, termed "sponging", occurs when a dolphin breaks off a sponge and wears it over its rostrum while foraging on the seafloor. Sponging behavior typically begins in the second year of life. During sponging, dolphins mainly target fish that lack swim bladders and burrow in the substrate.
Therefore, the sponge may be used to protect their rostrums as they
forage in a niche where echolocation and vision are less effective
hunting techniques. Dolphins tend to carry the same sponge for multiple surfacings but sometimes change sponges. Spongers typically are more solitary, take deeper dives, and spend more time foraging than non-spongers. Despite these costs, spongers have similar calving success to non-spongers.
There is evidence that both ecological and cultural factors
predict which dolphins use sponges as tools. Sponging occurs more
frequently in areas with higher distribution of sponges, which tends to
occur in deeper water channels. Sponging is heavily sex-biased to females. Genetic analyses suggest that all spongers are descendants of a single matriline, suggesting cultural transmission of the use of sponges as tools. Sponging may be socially learned from mother to offspring. Social grouping behavior suggests homophily (the tendency to associate with similar others) among dolphins that share socially learned skills such as sponge tool use. Sponging has only been observed in Shark Bay.
Indo-Pacific bottlenose dolphins in Shark Bay have also been observed carrying conch
shells. In this behavior, dolphins insert their rostrum into the
shell's aperture. Although this behavior is rare, it appears to be used
for foraging. Dolphins appear to use the conch shells to scoop fish from
the substrate then carry the shell to retrieve the fish near the
surface.
Sea otters
A sea otter using a rock to break open a shell
Under each foreleg, the sea otter (Enhydra lutris)
has a loose pouch of skin that extends across the chest. In this pouch
(preferentially the left side), the animal stores collected food to
bring to the surface. This pouch also holds a rock, unique to the otter,
that is used to break open shellfish and clams.
To open hard shells, it may pound its prey with both paws against the
rock which it places on its chest. Furthermore, sea otters will use
large stones to pry an abalone
off its rock; they will hammer the abalone shell with observed rates of
45 blows in 15 seconds or 180 rpm, and do it in two or three dives.
Releasing an abalone, which can cling to rock with a force equal to
4,000 times its own body weight, requires multiple dives by the otter.
Other carnivores
Wild banded mongooses (Mungos mungo) regularly use anvils to open food items with a hard shell such as rhinoceros beetles, bird eggs, snail shells or pupating dung beetles.
They use a range of anvils commonly including rocks and the stems of
trees, but will also use the side-walls of gullys and even dried
elephant dung. Pups as young as 2 months of age are already showing the
behavioural patterns associated with using an anvil, however, successful
smashing is usually shown in individuals older than 6 months of age.
Honey badgers
both wild and captive have been filmed manipulating various objects to
assist them in making climbs, including making mud balls and stacking
them.
North American badgers (Taxidea taxus) hunt Richardson's ground squirrels (Spermophilus richardsonii).
The most common hunting technique is excavation of burrow systems, but
plugging of openings into ground-squirrel tunnels accounts for 5–23% of
hunting actions. Badgers usually use soil from around the tunnel
opening, or soil dragged 30–270 cm from a nearby mound to plug tunnels.
The least common (6%), but most novel, form of plugging used by 1 badger
involved movement of 37 objects from distances of 20–105 cm to plug
openings into 23 ground-squirrel tunnels on 14 nights.
In 2011, researchers at the Dingo Discovery and Research Centre in Melbourne, Australia, filmed a dingo manipulating a table and using this to get food.
A family of captive Visayan warty pigs have been observed using a flat piece of bark as a digging tool.
In birds
Tool use is found in at least thirty-three different families of birds. According to Jones and Kamil's definition, a bearded vulture
dropping a bone on a rock would not be considered using a tool since
the rock cannot be seen as an extension of the body. However, the use of
a rock manipulated using the beak to crack an ostrich egg would qualify the Egyptian vulture as a tool user. Many other species, including parrots, corvids and a range of passerines, have been noted as tool users.
Many birds (and other animals) build nests.
It can be argued that this behaviour constitutes tool use according to
the definitions given above; the birds "carry objects (twigs, leaves)
for future use", the shape of the formed nest prevents the eggs from
rolling away and thereby "extends the physical influence realized by the
animal", and the twigs are bent and twisted to shape the nest, i.e.
"modified to fit a purpose". The complexity of bird nests varies
markedly, perhaps indicating a range in the sophistication of tool use.
For example, compare the highly complex structures of weaver birds to the simple mats of herbaceous matter with a central cup constructed by gulls, and it is noteworthy that some birds do not build nests, e.g. emperor penguins.
The classification of nests as tools has been disputed on the basis
that the completed nest, or burrow, is not held or manipulated.
Lead Section: Prey-dropping behavior is seen in many
species of birds. Species of crows such as Carrion, Northwestern,
American, and New Caledonian crows exhibit this behavior using different
prey.
Gulls, particularly Kelp, Western, Black-Headed and Sooty gulls are
also known to drop mussels from a height as a foraging adaptation.
This behavior is demonstrated by dropping prey from a height onto a
hard substrate in order to break the prey's shell open. Several
variables such as prey size, substrate type, kleptoparasitism, etc. can
influence the behavior of prey dropping in various species.
Finches
Perhaps the best known and most studied example of an avian tool user is the woodpecker finch (Camarhynchus pallidus) from the Galápagos Islands.
If the bird uncovers prey in bark which is inaccessible, the bird then
flies off to fetch a cactus spine which it may use in one of three
different ways: as a goad to drive out an active insect (without
necessarily touching it); as a spear with which to impale a slow-moving
larva or similar animal; or as an implement with which to push, bring
towards, nudge or otherwise maneuver an inactive insect from a crevice
or hole. Tools that do not exactly fit the purpose are worked by the
bird and adapted for the function, thus making the finch a "tool maker"
as well as a "tool user". Some individuals have been observed to use a
different type of tool with novel functional features such as barbed
twigs from blackberry bushes, a plant that is not native to the islands.
The twigs were first modified by removing side twigs and leaves and
then used such that the barbs helped drag prey out of tree crevices.
There is a genetic predisposition for tool use in this species,
which is then refined by individual trial-and-error learning during a
sensitive phase early in development. This means that, rather than
following a stereotypical behavioural pattern, tool use can be modified
and adapted by learning.
The importance of tool use by woodpecker finch species differs
between vegetation zones. In the arid zone, where food is limited and
hard to access, tool use is essential, especially during the dry season.
Up to half of the finches' prey is acquired with the help of tools,
making them even more routine tool users than chimpanzees. The tools
allow them to extract large, nutritious insect larvae from tree holes,
making tool use more profitable than other foraging techniques. In
contrast, in the humid zone, woodpecker finches rarely use tools, since
food availability is high and prey is more easily obtainable. Here, the
time and energy costs of tool use would be too high.
There have been reported cases of woodpecker finches brandishing a twig as a weapon.
A New Caledonian crow showing sequential tool use in the laboratory
Corvids are a family
of birds characterised by relatively large brains, remarkable
behavioural plasticity (especially highly innovative foraging behaviour)
and well-developed cognitive abilities.
Carrion Crows
Carrion
crows were observed on Eden estuary in Scotland between February and
March 1988 to investigate their dropping strategies with mussels.
Carrion crows selected larger mussels and dropped them from a height of
~8m onto hard substrate. The height of mussels dropped were lower than
researchers, Whiteley, Pritchard, and Slater expected which may be due
to difficulty locating prey post dropping as well as trying to prevent
kleptoparasitism (stealing of food by other scavengers). Behavior of
prey dropping seen in Carrion crows suggest that the size of prey,
substrate surfaces, and height drop influence their behavior. Therefore,
it can be inferred that other species may exhibit different behavior
strategies based on their prey, and environment.
Northwestern Crows
Different
variables such as, prey size, shell breakability, predators, substrate,
and height affect the behavior of prey dropping for different species.
For instance, selection of prey may depend on substrate used in that
environment.
Northwestern crows are another example of birds that drop prey from a
height onto the ground. Northwestern crows flew vertically up, releasing
whelks and immediately diving after it. Similar to the Carrion crows,
Northwestern crows also preferred larger whelks over smaller ones and
selected sizes by sight and weight by picking whelks up with their bill.
Unlike Carrion crows, Northwestern crows exhibited a unique response
upon releasing prey. After releasing whelks, Northwestern crows
instantly dove after it whereas Carrion crows were not as diligent in
following and immediately retrieving prey. This behavior is likely due
to Northwestern crows minimizing and potentially avoiding
kleptoparasitism.
Therefore, why do Carrion crows not display the same response after
releasing prey that Northwestern crows do? It is unknown for sure why
Carrion crows have a different response to prey being released than
Northwestern crows, however, these differences in behavior could
potentially be due to higher predation in areas that Northwestern crows
inhabit, or increase in food sources in areas inhibited by Carrion
crows.
American Crows
American
crows are another of several species of birds that possess prey
dropping behavior. When performing the study of prey dropping in
American crows, the number of drops to crack a walnut decreased as the
height of prey dropped increased and crows had more success when
dropping walnuts onto asphalt compared to soil. Prey loss almost always
occurred through kleptoparasitism however, there is a lack of evidence
that shows kleptoparasitism being directly affected by height of
prey dropped.
Caledonian crow
New Caledonian crows (Corvus moneduloides) are perhaps the most studied corvid with respect to tool-use.
In the wild, they have been observed using sticks as tools to extract insects from tree bark.
The birds poke the insects or larvae until they bite the stick in
defence and can then be drawn out. This "larva fishing" is very similar
to the "termite fishing" practised by chimpanzees. In the wild, they
also manufacture tools from twigs, grass stems or similar plant
structures, whereas captive individuals have been observed to use a
variety of materials, including feathers and garden wire. Stick tools
can either be non-hooked—being more or less straight and requiring only
little modification—or hooked. Construction of the more complex hooked
tools typically involves choosing a forked twig from which parts are
removed and the remaining end is sculpted and sharpened. New Caledonian
crows also use pandanus tools, made from barbed leaf edges of screw
pines (Pandanus spp.) by precise ripping and cutting although the function of the pandanus tools is not understood.
While young birds in the wild normally learn to make stick tools from elders, a laboratory New Caledonian crow named "Betty" was filmed
spontaneously improvising a hooked tool from a wire. It was known that
this individual had no prior experience as she had been hand-reared.
New Caledonian crows have been observed to use an easily available
small tool to get a less easily available longer tool, and then use this
to get an otherwise inaccessible longer tool to get food that was out
of reach of the shorter tools. One bird, "Sam", spent 110 seconds
inspecting the apparatus before completing each of the steps without any
mistakes. This is an example of sequential tool use, which represents a
higher cognitive function compared to many other forms of tool use and
is the first time this has been observed in non-trained animals. Tool
use has been observed in a non-foraging context, providing the first
report of multi-context tool use in birds. Captive New Caledonian crows
have used stick tools to make first contact with objects that were novel
and hence potentially dangerous, while other individuals have been
observed using a tool when food was within reach but placed next to a
model snake. It has been claimed "Their [New Caledonian crow]
tool-making skills exceed those of chimpanzees and are more similar to
human tool manufacture than those of any other animal."
New Caledonian crows have also been observed performing tool use
behaviour that had hitherto not been described in non-human animals. The
behaviour is termed "insert-and-transport tool use". This involves the
crow inserting a stick into an object and then walking or flying away
holding both the tool and object on the tool.
New Caledonian crows also demonstrate prey dropping behavior The
first recorded evidence of this species of crow demonstrating prey
dropping behavior on the snail Placostylus fibratus in a 2013 study.
New Caledonian crows would drop snails from a particular height onto
rocky beds and investigation observed that they would be so four times
at the same height. These observations may be evident that the snails
shell is harder to break which requires more dropping attempts, but may
also reflect variation in the substrate, which can also affect the
number of drops required to access the food reward.
Hawaiian crow
Captive individuals of the critically endangered Hawaiian crow (Corvus hawaiiensis)
use tools to extract food from holes drilled in logs. The juveniles
exhibit tool use without training or social learning from adults. As 104
of the 109 surviving members of the species were tested, it is believed
to be a species-wide ability.
Others
Other corvid species, such as rooks (Corvus frugilegus), can also make and use tools in the laboratory, showing a degree of sophistication similar to that of New Caledonian crows. While not confirmed to have used tools in the wild, captive blue jays (Cyanocitta cristata) have been observed using strips of newspaper as tools to obtain food.
Various corvids have reached for stones to place in a vessel of
water so as to raise the surface level to drink from it or access a
floating treat, enacting Aesop's Fable of The Crow and the Pitcher.
A wild American crow (Corvus brachyrhynchos) has been observed to modify and use a piece of wood as a probe. Green jays (Cyanocorax yncas) have been observed using sticks as tools to extract insects from tree bark. Large-billed crows in urban Japanhave been filmed using an innovative technique to crack hard-shelled nuts
by dropping them onto crosswalks (pedestrian crossings) and letting
them be run over and cracked by cars. They then retrieve the cracked
nuts when the cars are stopped at the red light. In some towns in America, crows drop walnuts onto busy streets so that the cars will crack the nuts. Hooded crows (Corvus cornix) use bait to catch fish. Individuals (who may have observed fish being fed bread by humans) will place the bread in the water to attract fish.
Common ravens (Corvus corax) are one of only a few species who make their own toys. They have been observed breaking off twigs to play with socially. A corvid has been filmed sliding repeatedly down a snow-covered roof while balancing on a lid or tray. Another incidence of play in birds has been filmed showing a corvid playing with a table tennis ball in partnership with a dog, a rare example of tool use for the purposes of play. Blue jays, like other corvids, are highly curious and are considered intelligent birds.
Young blue jays playfully snatch brightly coloured or reflective
objects, such as bottle caps or pieces of aluminium foil, and carry them
around until they lose interest.
The tailorbird (genus Orthotomus)
takes a large growing leaf (or two or more small ones) and with its
sharp bill pierces holes into opposite edges. It then grasps spider
silk, silk from cocoons, or plant fibres with its bill, pulls this
"thread" through the two holes, and knots it to prevent it from pulling
through (although the use of knots is disputed). This process is repeated several times until the leaf or leaves forms a pouch or cup in which the bird then builds its nest.
The leaves are sewn together in such a way that the upper surfaces are
outwards making the structure difficult to see. The punctures made on
the edge of the leaves are minute and do not cause browning of the
leaves, further aiding camouflage. The processes used by the tailorbird
have been classified as sewing, rivetting, lacing and matting. Once the
stitch is made, the fibres fluff out on the outside and in effect they
are more like rivets. Sometimes the fibres from one rivet are extended
into an adjoining puncture and appear more like sewing. There are many
variations in the nest and some may altogether lack the cradle of
leaves. It is believed that only the female performs this sewing
behaviour. The Latin binomial name of the common tailorbird, Orthotomus sutorius, means "straight-edged" "cobbler" rather than tailor. Some birds of the genus Prinia also practice this sewing and stitching behaviour.
Brown-headed nuthatches
Brown-headed nuthatches (Sitta pusilla) have been observed to methodically use bark
pieces to remove other flakes of bark from a tree. The birds insert the
bark piece underneath an attached bark scale, using it like a wedge and
lever, to expose hiding insects. Occasionally, they reuse the same
piece of bark several times and sometimes even fly short distances
carrying the bark flake in their beak. The evolutionary origin of this
tool use might be related to these birds frequently wedging seeds into
cracks in the bark to hammer them open with their beak, which can lead
to bark coming off.
Brown-headed nuthatches have used a bark flake to conceal a seed cache.
Crested lark
A Crested lark (Galerida cristata) has been photographed apparently holding in its bill a stone chip it was reportedly using to dislodge prey from paving joints.
Parrots
Kea,
a highly inquisitive New Zealand mountain parrot, have been filmed
stripping twigs and inserting them into gaps in box-like stoat traps to
trigger them. Apparently, the kea's only reward is the banging sound of
the trap being set off. In a similarly rare example of tool preparation, a captive Tanimbar corella (Cacatua goffiniana) was observed breaking off and "shaping" splinters of wood and small sticks to create rakes that were then used to retrieve otherwise unavailable food items on the other side of the aviary mesh. This behaviour has been filmed.
Many owners of household parrots have observed their pets using
various tools to scratch various parts of their bodies. These tools
include discarded feathers, bottle caps, popsicle sticks, matchsticks,
cigarette packets and nuts in their shells.
Hyacinth macaws (Anodorhynchus hyacinthinus)
have been repeatedly observed to use tools when breaking open nuts, for
example, pieces of wood being used as a wedge. Several birds have
wrapped a piece of leaf around a nut to hold it in place. This behaviour
is also shown by palm cockatoos (Probosciger aterrimus).
It seems that the hyacinth macaw has an innate tendency to use tools
during manipulation of nuts, as naïve juveniles tried out a variety of
objects in combination with nuts.
Egyptian vultures
When an Egyptian vulture (Neophron percnopterus)
encounters a large egg, it takes a stone into its beak and forcefully
throws it at the egg until the shell is broken, usually taking a few
minutes. This behaviour, first reported in 1966,
seems to be largely innate and is displayed by naïve individuals. Its
origin could be related to the throwing of eggs; rounded (egg-like)
stones are preferred to jagged ones.
In a small population in Bulgaria, Egyptian vultures use twigs to
collect sheep wool for padding their nests. Although both twigs and
wool can serve as nesting material, this appears to be deliberate tool
use. The birds approached bits of discarded wool with a twig in their
beak, which was then either used as a rake, to gather the wool into
heaps, or to roll up the wool. Wool was collected only after shearing or
simulated shearing of sheep had taken place, but not after wool had
simply been deposited in sheep enclosures.
Fire-foraging raptors
In Australia the black kite (Milvus migrans), whistling kite (Haliastur sphenurus) and unrelated brown falcon (Falco berigora)
are not only attracted to wildfires to source food, but will variously
use their beaks or talons to carry burning sticks so as to spread fire,
complicating human efforts to contain fires using firebreaks.
Owls
Burrowing owls (Athene cunicularia) frequently collect mammalian dung, which they use as a bait to attract dung beetles, a major item of prey.
Gulls
Gulls
have been known to drop mollusc shells on paved and hard surfaces such
as roads. Their dropping habits are similar to corvids in the sense that
repeated drops allow for gulls to have easier access towards their
prey. Certain species (e.g. the herring gull) have exhibited tool use behavior, using pieces of bread as bait to catch goldfish, for example.
Kelp Gulls
Kelp gulls are one of the well-known gulls that have displayed prey-dropping.
These gulls are known to learn their prey-dropping skills by studying
other gulls around them, and are able to refine this behavior to benefit
themselves. They commonly break their prey on hard surfaces, such as
rocks, asphalt, and even roofs of houses and cars. Kelp gulls normally
drop black mussels, and drop-sites are normally chosen based on how well
it would break the prey as well as the amount of kleptoparasites that
are in the area, as other gulls may take the opportunity to steal an
individuals’ prey. Dropping behavior occurs at any time of year but is
more prevalent in the winter during low-tide hours, most likely due to
having more access to larger mussels. Kelp gulls will fly over 0.5 km to
a preferred substrate on which to break their prey. Height from which
the prey is dropped will increase after each drop of the prey. Once the
prey is dropped, a gull will descend as quickly as possible to recover
its prey. This is likely to prevent kleptoparasitism, which is very
common in prey-dropping. On average, a kelp gull will descend at an
average of 4 m/s in comparison to the prey’s fall of 5 m/s, which allows
the gull to reach the ground about 0.5 seconds after the prey has
landed onto the surface. Adult kelp gulls have a higher success rate of breaking and obtaining their prey while prey dropping than juvenile kelp gulls.
Western Gull
Western gulls are one of the many species of gulls that have been observed to drop their prey on the ground.
A study observed that a major factor influencing dropping behavior in
these gulls had to do with the mass and size of the prey being dropped.
When performing a study using different sizes of Washington clams,
smaller clams were normally pecked at. The larger clams however were
dropped unless they were too heavy to carry, usually exceeding 268 grams
in weight.Drop behavior differs between adult and immature western
gulls. All adult western gulls that have been studied displayed prey
dropping behavior, and dropped from an average off 118 meters away from
where they were originally retrieved. In the study, dropping occurred
either over mudflats or a parking lot, which correlated with weight of
the clams, which average clam weights were 106.7 g and 134.3 g
respectively. Immature gulls meanwhile are much more clumsy with their
dropping, and only 55% of juvenile western gulls that were observed
displayed this behavior. Juvenile gulls also did not seem to have a
correlation between the weight of the clam and the height the clam was
dropped at, though it is noted that the younger gulls seemed to drop
their prey at much lower heights than their older peers. This could be
evident that juvenile gulls are learning this behavior through trial and
error. The low height at which the clams are dropped may also result in
the number of times the younger gulls had to drop their prey. Immature
western gulls tend to drop their prey more frequently than the older
gulls do, most likely due to inconsistency in drop height as well as the
height of the drops.Unlike most birds who drop their prey, western
gulls actually seem to prefer softer substrates over larger substrates
when dropping their prey, and only seem to drop their prey on hard
surfaces if their prey is heavier.
Black-Headed Gull
In
observations made in Central Europe, a two-year-old black-headed gull
was seen taking a small swan mussel about 60 feet up into the air to
drop on an asphalt road.
It is unknown how successful the gull was seeing as a nearby crow stole
the mussel. This was the first time prey-dropping was recorded in this
species of gulls. It is likely that this behavior is not common in this
species of gull, as there is no other evidence of black-headed gulls
dropping prey. It is more likely that this observation was due to the
fact that there was a large group of hood crows during this study, and
it may be that the gull observed was mimicking the prey-dropping
behavior of the hood crows nearby. This may be evident seeing as after
the gull had dropped the mussel, it made no move to try and grab it for
another drop. However, due to the fact that it was not only a single
black-headed gull that was observed, but also a young bird, it is
possible that successful prey-dropping may occur in other members of
this species.
Sooty Gull
In
2009, two sooty gulls near Hamata, Egypt, were seen using prey-dropping
behavior on a strip of coral reef. Unlike other gulls, the gulls only
flew up about 6 m and broke molluscs in one drop. All drops were
successful.
Herons
The green heron (Butorides virescens) and its sister species the striated heron (Butorides striata)
have been recorded using food (bread crusts), insects, leaves, and
other small objects as bait to attract fish, which they then capture and
eat.
In reptiles
Tool use by American alligators and mugger crocodiles
has been documented. During the breeding season, birds such as herons
and egrets look for sticks to build their nests. Alligators and
crocodiles collect sticks to use as bait to catch birds. The crocodilian
positions itself near a rookery, partially submerges with the sticks
balanced on its head, and when a bird approaches to take the stick, it
springs its trap. This stick displaying strategy is the first known case
of a predator not only using an object as a lure, but also taking into
account the seasonal behavior of its prey.
Several species of wrasses have been observed using rocks as anvils to crack bivalve (scallops, urchins and clams) shells. It was first filmed in an orange-dotted tuskfish (Choerodon anchorago)
in 2009 by Giacomo Bernardi. The fish fans sand to unearth the bivalve,
takes it into its mouth, swims several metres to a rock which it uses
as an anvil by smashing the mollusc apart with sideward thrashes of the
head. This behaviour has been recorded in a blackspot tuskfish (Choerodon schoenleinii) on Australia's Great Barrier Reef, yellowhead wrasse (Halichoeres garnoti) in Florida and a six-bar wrasse (Thalassoma hardwicke) in an aquarium setting. These species are at opposite ends of the phylogenetic tree in this family, so this behaviour may be a deep-seated trait in all wrasses.
It has been reported that freshwater stingrays use water as a tool by manipulating their bodies to direct a flow of water and extract food trapped amongst plants.
Prior to laying their eggs on a vertical rock face, male and female whitetail major damselfish
clean the site by sand-blasting it. The fish pick up sand in their
mouths and spit it against the rock face. Then they fan the area with
their fins. Finally they remove the sand grains that remain stuck to the
rock face by picking them off with their mouths.
Banded acara, (Bujurquina vittata), South American cichlids,
lay their eggs on a loose leaf. The male and female of a mating pair
often "test" leaves before spawning: they pull and lift and turn
candidate leaves, possibly trying to select leaves that are easy to
move. After spawning, both parents guard the eggs. When disturbed, the
parent acara often seize one end of the egg-carrying leaf in their mouth
and drag it to deeper and safer locations.
Archerfish
are found in the tropical mangrove swamps of India and Australasia.
They approach the surface, take aim at insects that sit on plants above
the surface, squirt a jet of water at them, and grab them after the
insects have been knocked off into the water. The jet of water is formed
by the action of the tongue, which presses against a groove in the roof
of the mouth. Some archerfish can hit insects up to 1.5 m above the
water surface. They use
more water, which gives more force to the impact, when aiming at larger
prey. Some triggerfish (e.g. Pseudobalistes fuscus) blow water to turn sea urchins over and expose their more vulnerable ventral side.
Whether these later examples can be classified as tool use depends on
which definition is being followed because there is no intermediate or
manipulated object, however, they are examples of highly specialized
natural adaptations.
In invertebrates
Cephalopods
A small octopus (4-5 cm, c. 2-inch diameter) using a nut shell and clam shell as shelter
At least four veined octopus (Amphioctopus marginatus)
individuals were witnessed retrieving coconut shells, manipulating
them, stacking them, transporting them some distance (up to 20 metres),
and then reassembling them to use as a shelter.
The octopuses use coconut shells discarded by humans which have
eventually settled in the ocean. They probe their arms down to loosen
the mud, then rotate the shells out. After turning the shells so the
open side faces upwards, the octopuses blow jets of mud out of the bowl
before extending their arms around the shell—or if they have two halves,
stacking them first, one inside the other. They then stiffen their legs
and move away in a manner which has been called "stilt-walking". The
octopuses eventually use the shells as a protective shelter in areas
where little other shelter exists. If they just have one half, they
simply turn it over and hide underneath. But if they are lucky enough to
have retrieved two halves, they assemble them back into the original
closed coconut form and sneak inside. This behaviour has been filmed.
The authors of the research article claimed this behaviour falls under
the definition of tool use because the shells are carried for later use.
However, this argument remains contested by a number of other
biologists who state that the shells actually provide continuous
protection from abundant bottom-dwelling predators in their home range.
Octopuses deliberately place stones, shells and even bits of
broken bottle to form a wall that constricts the aperture to the den, a
type of tool use.
In laboratory studies, Octopus mercatoris, a small pygmy species of octopus, has been observed to block its lair using a plastic Lego brick.
Smaller individuals of the common blanket octopus (Tremoctopus violaceus) hold the tentacles of the Portuguese man o' war, to whose poison they are immune, both as protection and as a method of capturing prey.
Insects
Ants of the species Conomyrma bicolor
pick up stones and other small objects with their mandibles and drop
them down the vertical entrances of rival colonies, allowing workers to
forage for food without competition.
Several species of ant are known to use substrate debris such as
mud and leaves to transport water to their nest. A study in 2017
reported that when two species of Aphaenogaster
ant are offered natural and artificial objects as tools for this
activity, they choose items with a good soaking capacity. The ants
develop a preference for artificial tools that cannot be found in their
natural environment, indicating plasticity in their tool-use behaviour.
Hunting wasps of the genus Prionyx
use weights (such as compacted sediment or a small pebble) to settle
sand surrounding a recently provisioned burrow containing eggs and live
prey in order to camouflage and seal the entrance. The wasp vibrates its
wing muscles with an audible buzz while holding the weight in its
mandibles, and applies the weight to the sand surrounding its burrow,
causing the sand to vibrate and settle. Another hunting wasp, Ammophila, uses pebbles to close burrow entrances.
Some species of crickets construct acoustic baffles from the leaves of plants to amplify sounds they make for communication during mating. It was in 1975 that scientists first observed Oecanthus burmeisteri [sv] and two other species of South African chirping crickets doing this.
Insects can also learn to use tools. A study in 2017 showed that bumblebees of the species Bombus terrestris learned to move a small wooden ball to the goal in order to get sucrose reward.
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