Social Learning in Tortoises

In a previous post, AnimalWise saluted the red-footed tortoise (Geochelone carbonaria) for its Ig Nobel Prize achievements but, in doing so, may have unfairly maligned the tortoise’s cognitive capabilities. To atone for any past disparagement, this post is dedicated to an impressive, and perhaps surprising, red-footed tortoise intellectual accomplishment.

Many social animals are able to solve problems and shortcut the costly process of trial and error learning by simply observing the behavior of their peers. While some have speculated that this type of observational learning is an adaptation for social living that may be unique to animals who live together in groups, a research team led by Anna Wilkinson of the University of Vienna wanted to see whether a decidedly non-social animal, the red-footed tortoise, could also learn by observing others. Wilkinson specifically hoped to test the hypothesis that social learning abilities may simply be a reflection of an animal’s general learning capacity, and that non-social animals may be able to learn by observing peer behavior in fundamentally the same way as they use other environmental stimuli to learn.

Finally – respect for my brains as well as my dashing good looks!

The red-footed tortoises were perfect subjects for this study. The natives of Central and South American forests are naturally solitary, receiving no parental care (once the eggs hatch, it’s every little tortoise for himself and herself!) and, unless presented with a mating opportunity, living apart from other tortoises.

For Wilkinson’s study, eight young (juvenile or sub-adult) tortoises – four randomly assigned to the “non-observer” condition and the other four assigned to the “observer” condition – participated in a series of trials in which they needed to navigate around an obstacle to achieve a food reward. All trials took place in a square arena in which a 40 cm high V-shaped fence separated the tortoise from the desired food:

First, the tortoises in the non-observer groups were each given 12 trials (one per day) in which they were allowed two minutes to solve the task. Between trials, the bark flooring in the arena was redistributed to prevent the tortoises from being able to latch onto any scent trails from prior trials.

Next, the observer group tortoises had their turn. Their trials were identical except that, before each test, they were able to observe a specially-trained tortoise who invariably detoured around the right side of the obstacle and ate the food prize.

The results were unambiguous. While none of the non-observer tortoises ever solved the puzzle (they went up to the fence by the food, but never figured out how to go around the obstacle), all of the observer tortoises succeeded at least twice, with two of them correctly navigating around the barrier on the first attempt.

In other words, the red-footed tortoises have another addition for their trophy room. Not only are they the first red-footed and hard-shelled recipients of the Ig Nobel Prize, they are also the first non-social reptile to display social learning skills, revealing that group living is not necessarily a prerequisite for social learning.

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ResearchBlogging.orgWilkinson, A., Kuenstner, K., Mueller, J., & Huber, L. (2010). Social learning in a non-social reptile (Geochelone carbonaria) Biology Letters, 6 (5), 614-616 DOI: 10.1098/rsbl.2010.0092.

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Setting His Own Dinner Table: Spontaneous Tool Use by a Dingo

The name tags kept disappearing, and the staff at Melbourne’s Dingo Discovery and Research Centre was mystified. After romping around the grounds of the dingo sanctuary, Sterling, an 18 month old sub adult male, and his two canine companions spent time in an indoor enclosure that had a name tag posted on the outside of the steel mesh wall. The tag was positioned 1.7 meters above the ground, well out of dingo-reach. Still, it kept vanishing.

As reported in a paper published online last week in Behavioural Processes,1 the caretakers decided that it was time solve the mystery. First, they hung a small plastic envelope filled with food near the name tag and watched to see what the dingoes would do. The dingoes were having none of that, however – as long as observers were around, the dingoes studiously ignored both the name tag and the envelope of food. Since the direct approach clearly wouldn’t work, the staff resorted to sneakiness, rigging up a video camera and then leaving the dingoes to their own devices.

Success! When the staff returned to the enclosure, they found that the food was gone and, more importantly, that the videotape reflected perhaps the first documented instance of tool use by a member of the Canid family. As described in the Behavioural Processes paper:

Big deal, Lassie; when Timmy fell down *my* well, I hoisted him out using a system of pulleys. (Sterling at Dingo Discovery and Research Centre, photo by Dingo Lyn)

[A]fter several unsuccessful attempts at jumping for the envelope, Sterling “solved” the task by first moving and then jumping up onto a trestle table (1.2 m × 0.6 m × 0.73 m) which allowed him to gain the additional height necessary to reach the food item. To move the table, Sterling clamped his mouth onto the strut between the legs of the table. He then walked backwards, dragging the table approximately 2 m, until it appeared that either his back leg or tail touched the enclosure mesh. He then jumped onto the table, but as he was still at least a body-length away from the envelope, he had to span the gap between the table and the enclosure mesh by propping his front paws onto the mesh gradually moving them towards the envelope. At full stretch, he reached the envelope on his second attempt.

While this account of Sterling’s actions may sound impressive, it’s even more striking when seen on video:

Bradley Smith of the University of South Australia and his colleagues noted in their paper that Sterling’s behavior appeared to be spontaneous – he had never been trained or encouraged to position the table in order to reach food (or name tags) – but they cautioned that they had to rely on information provided by the sanctuary’s staff regarding Sterling’s (lack of) relevant training in the past.

No problem, just bring me a socket wrench, a crow bar and three sticks of gum... (Sterling at Dingo Discovery and Research Centre, photo by Dingo Lyn)

Sterling, for his part, was no one-hit wonder. According to sanctuary staff, from an early age Sterling was adept at manipulating his environment to serve his purposes. For example, during one breeding season he used his front paws to roll a barrel to a wall, jumped up on the barrel, scrambled over the wall, and approached a female dingo in another area of the sanctuary. Also, the staff and research team later videotaped separate occasions in which Sterling used his mouth to drag a plastic dog kennel to differing locations around his enclosure, allowing him to stand on the kennel and peer over walls into neighboring dingo enclosures.

Thus, while the researchers couldn’t exclude the possibility that Sterling’s problem-solving abilities were the result of observational learning or that they had somehow been reinforced when he was younger, they rightly recognized that he appeared to be engaging in “high order behaviour” in using tools within his environment to solve complex problems. (Indeed, on the face of it, Sterling’s problem-solving is quite very reminiscent of Kandula the elephant’s insightful use of a box within his yard to solve an out-of-reach food challenge.)

So, now that you know what canines are capable of, please feel free to ask your dog Barkley when he’s going to get around to assembling that futon you bought at Ikea. No more excuses.

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ResearchBlogging.org1Smith, B., Appleby, R., & Litchfield, C. (2011). Spontaneous tool-use: An observation of a dingo (Canis dingo) using a table to access an out-of-reach food reward Behavioural Processes DOI: 10.1016/j.beproc.2011.11.004.

2As we’ve noted in previous posts (see, for example, the post on the poison rat and the tuskfish tool post), scientific authorities have defined the concept of “tool use” in various ways. In the Beck and Shumaker treatise discussed in the poison rat post, the authors describe a couple of anecdotal instances that may qualify as canid tool use under their broad definition, including an account of a wolf mother who used meat as a “baiting” and “enticing” tool to distract her young pup. Fox, M. (1971). Possible Examples of High-Order Behavior in Wolves Journal of Mammalogy, 52 (3) DOI: 10.2307/1378613.

Rise of the Planet of the Ants

These days, we’ve been hearing quite a bit about a future in which humans find their dominion over the planet suddenly challenged by a group of super intelligent apes. This may make for an exciting Hollywood movie plot and some stunning visual effects, but I wonder whether we really need to look to humanoid science fiction in order to feel a shiver of doubt regarding our supremacy as a species.

Maybe all we need to do is to look at the world the way it is, a world that could well be called … The Planet of the Ants!

So, why is it that we should feel just a wee bit threatened by these small six-legged colonizers? Here are just a few reasons.

Quadrillions of Ants

Burning Man seems more crowded every year, doesn't it? (photo credit: Mehmet Karatay)

Like us, ants thrive just about anywhere, with the exception of Antarctica and a few isolated islands. Moreover, while there are approximately seven billion of us on the planet, conservative estimates put the number of ants at between one and ten quadrillion.1 That’s between 150,000 and 1,500,000 ants for each and every one of us. At the higher figure, this means that, if you were to put all the world’s ants onto a giant scale, they would weigh about as much as all of the humans on the planet put together.2 In fact, on average, it has been estimated that ants make up 15–20% of the terrestrial animal biomass on Earth (and more than 25% of the animal biomass in tropical regions).3

Our tendency as humans is to unquestioningly assume that we are far and away the most successful species that has ever been. If we take a step back, though, and simply consider the above numbers and the possibility that an animal’s success is most properly measured by the degree to which it has been able to thrive in various environments, perhaps we should already be feeling a pang of doubt about how incontestable our supremacy really is.

Ants Teach

While many animals are able to learn through imitation, ants are the only non-mammal known to engage in interactive teaching.4 In at least one species of ant, knowledgeable workers actively teach inexperienced nest mates where to find food through a process known as “tandem running,” in which the lead worker ant recruits an inexpert follower, and then makes sure that the follower stays on track, slowing down when it lags and speeding up when it gets too close.

Ants Learn

Ants are also able to engage in so-called latent learning, whereby they memorize information that they cannot use at once, but that may be useful later on – a behavior that’s been labeled as “planning.”5 Specifically, ants have been shown to be able to reconnoiter potential new living spaces, retaining information about relative desirability and tailoring their choices based on how urgently the need to move is.

Ants Can Learn to Navigate Mazes

Ants can be trained to remember multiple visual patterns presented in a fixed sequence, enabling them to navigate mazes.6 Ok, I’m not sure how exactly this leads to world domination, but it is definitely pretty cool.

Ants Practice Agriculture

Approximately 50 million years ago (and, accordingly, approximately 49+ million years before Homo Sapiens first arose as a species), ants began engaging in agriculture.7 Today, different species of leafcutter ants have adopted a purely agrarian lifestyle, feeding exclusively on gardens of fungus that they actively weed and cultivate, feed with fresh-cut leaves, and keep free from parasites and other pests.8 Here’s a video of some fungus farming ants:

Ants Engage in Animal Husbandry

Some ants raise aphids and feed on the sugary honeydew the aphids secrete when “milked” by the ants’ antennae. The ants are careful with their herds, keeping predators and parasites away, moving the aphids from one feeding location to another, and often bringing the aphids with them when they migrate.9 Here’s a video of ants tending to their aphids:

Ants Sometimes Enslave Other Ants

Certain types of ants are incorrigible slave-makers, raiding other colonies of ants and making captured slaves perform all routine tasks for their masters, including brood care, foraging, and even feeding slave-maker workers who are unable to feed themselves.10 Obviously, this isn’t a particularly attractive ant characteristic, but unfortunately it is one that may seem all too familiar to us humans.

Ants Use Tools

That’s right, tools. For example, some ants transport liquid and other non-solid food by dropping bits of leaves, sand or mud pellets or pieces of wood into a pool of food and, after the food has soaked in, using these objects to carry the meal back to their nests.11 Other ants use pebbles and soil pellets as weapons, dropping them on other ants or ground-dwelling bees, and then attacking and killing their competitors.12

Ants Build Cooperative Solutions

Hey, watch your foot! You're stepping on my head! (photo: Mlot, Tovey & Hu)

Ants, including army ants, are known to self-assemble into living bridges or ladders that allow them to cross gaps while on the move. When a single ant cannot make it across alone, other ants will successively grab on, steadily lengthening the bridge until it’s long enough to reach the destination. These structures, which can span significant distances and can even cross water, are then used by the rest of the colony and may stay in place for hours, until traffic dies down.13 Comparably, fire ants self-assemble into waterproof rafts to survive floods. These rafts can be made up from anywhere from a few hundred to many thousand ants and are incredibly durable, allowing ants to sail for months at a time as they migrate.

Ants Have “Collective Intelligence”

The concept of collective intelligence has been hot lately, with a number of books and articles describing how groups can make collectively make sophisticated decisions and solve complex problems, even where each individual in the group knows very little, collectively a g (think of the analogy of each individual acting as a neuron, and the group as a whole acting as a collective brain). Collective intelligence is a topic unto itself, one we may address in future posts, but for now suffice it to say that if ants truly can make wise decisions as a group, we humans may really have something to envy!

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ResearchBlogging.org1Holldobler, B & E. O. Wilson (2009). The Superorganism: The Beauty, Elegance, and Strangeness of Insect Societies. New York: W. W. Norton. p. 5. ISBN 0-393-06704-1.

2Ibid.

3Schultz, T. (2000). In search of ant ancestors Proceedings of the National Academy of Sciences, 97 (26), 14028-14029 DOI: 10.1073/pnas.011513798.

4Franks, N., & Richardson, T. (2006). Teaching in tandem-running ants Nature, 439 (7073), 153-153 DOI: 10.1038/439153a; Richardson, T., Sleeman, P., McNamara, J., Houston, A., & Franks, N. (2007). Teaching with Evaluation in Ants Current Biology, 17 (17), 1520-1526 DOI: 10.1016/j.cub.2007.08.032.

5Franks, N., Hooper, J., Dornhaus, A., Aukett, P., Hayward, A., & Berghoff, S. (2007). Reconnaissance and latent learning in ants Proceedings of the Royal Society B: Biological Sciences, 274 (1617), 1505-1509 DOI: 10.1098/rspb.2007.0138.

6Chameron, S., Schatz, B., Pastergue-Ruiz, I., Beugnon, G., & Collett, T. (1998). The learning of a sequence of visual patterns by the ant Cataglyphis cursor Proceedings of the Royal Society B: Biological Sciences, 265 (1412), 2309-2313 DOI: 10.1098/rspb.1998.0576; Reznikova, Z. 2008: Experimental paradigms for studying cognition and communication in ants (Hymenoptera: Formicidae). Myrmecological News 11: 201-214.

7Schultz, T., & Brady, S. (2008). From the Cover: Major evolutionary transitions in ant agriculture Proceedings of the National Academy of Sciences, 105 (14), 5435-5440 DOI: 10.1073/pnas.0711024105.

8Ibid.; Schultz, T. (1999). Ants, plants and antibiotics. Nature, 398 (6730), 747-748 DOI: 10.1038/19619.

9Nielsen, C., Agrawal, A., & Hajek, A. (2009). Ants defend aphids against lethal disease Biology Letters, 6 (2), 205-208 DOI: 10.1098/rsbl.2009.0743; Styrsky, J., & Eubanks, M. (2007). Ecological consequences of interactions between ants and honeydew-producing insects Proceedings of the Royal Society B: Biological Sciences, 274 (1607), 151-164 DOI: 10.1098/rspb.2006.3701.

10Pohl, S., & Foitzik, S. (2011). Slave-making ants prefer larger, better defended host colonies Animal Behaviour, 81 (1), 61-68 DOI: 10.1016/j.anbehav.2010.09.006; Brandt M, Foitzik S, Fischer-Blass B, & Heinze J (2005). The coevolutionary dynamics of obligate ant social parasite systems–between prudence and antagonism. Biological reviews of the Cambridge Philosophical Society, 80 (2), 251-267 PMID: 15921051; Hölldobler, B. & Wilson, E.O., 1990. The Ants, Harvard University Press.

11FELLERS, J., & FELLERS, G. (1976). Tool Use in a Social Insect and Its Implications for Competitive Interactions Science, 192 (4234), 70-72 DOI: 10.1126/science.192.4234.70.

12See, e.g., Pierce, J. (1986). A Review of Tool Use in Insects The Florida Entomologist, 69 (1) DOI: 10.2307/3494748.

13Mlot NJ, Tovey CA, & Hu DL (2011). Fire ants self-assemble into waterproof rafts to survive floods. Proceedings of the National Academy of Sciences of the United States of America, 108 (19), 7669-73 PMID: 21518911.

Elephant Insight

With each passing week, it seems like we’re finding out more and more about how smart elephants are. Now, in addition to their other cognitive abilities, it turns out that elephants can have “aha!” moments of insight as they face puzzling dilemmas. [No, not a-ha as in 1980s synth-pop from Norway; if you're looking for an early MTV a-ha moment, you should probably go here!]

Elephants have the largest brains and the greatest volume of cerebral cortex of all terrestrial mammals. They live in elaborate matriarchal societies that include long-lasting relationships, close family bonds, and complex social groupings that change over time. They squabble and negotiate with each other over travel directions; they flirt, show empathy towards one another and solve problems cooperatively. They are one of the very few animals that can recognize themselves in mirrors (more about self-recognition testing here and here). True to their reputations, they have terrific memories, are adept at making and using tools, are logical thinkers, and even appear to mourn their dead in a “ceremonial” manner suggesting they may have a real awareness of the separate lives and experiences of other elephants.

Until now, however, on the few occasions when elephants have been tested for insightful problem solving abilities, they have been performed poorly. In these previous tests, the elephants failed to use their trunks in order to gain access to food treats that had been placed just beyond reach (for example, by using a stick grasped in the trunk to reach out for the food, or by pulling on a retractable cord with their trunks in order to reel in the food reward).

In a paper just published online on August 18th in PLoS ONE, a research team led by Preston Foerder and Diana Reiss of the City University of New York reported on its own revelation that led to a breakthrough in tests for elephant problem-solving insight. The researchers surmised that the problem with prior testing was not that elephants were incapable of insight, but rather that the tests had called for the elephants to act in ways that undermined their ability to use their trunks as effective sense organs during the task:

We believe that the problem in previous studies has been in treating the elephant trunk as a grasping appendage analogous to a primate hand. Although the trunk is a highly manipulable appendage, in food foraging its function as a sensory organ may take precedence. The elephant has an extraordinary sense of smell, and the tip of the trunk is as highly enervated as a human fingertip…. When a stick is held in the trunk, the tip is curled backwards and may be closed, prohibiting olfactory and tactile feedback…. We posit that previous failures to observe insightful problem solving in elephants is not indicative of a lack of cognitive ability but rather is due to the reliance on problem solving tasks that precluded the use of the trunk as a sense organ.

To address this issue, the researchers set up a series of experiments designed to allow elephants to keep their trunks free while facing problem-solving challenges. They tested three Asian elephants (Elephas maximus), two adult females and a 7-year-old juvenile male, at the Smithsonian National Zoo in Washington, DC, with the juvenile male, Kandula, soon emerging as the rock star problem-solver.

In the first experiment, the researchers dangled enticing fruit rewards from a cable they had placed across the elephant yard, including from positions that were just beyond trunk-reach. After leaving a large plastic cube and some other objects in the yard, they let Kandula into the yard for sessions to see whether he would figure out how to obtain the dangling food reward. While Kandula had previously played with the cube as an enrichment toy, he had no prior training in pushing large objects or in standing on them to reach for things.

During an initial six sessions, each lasting 20 some minutes, Kandula showed interest in the food dangling above his reach, played with the cube, moved it on several occasions, and once even stood on it briefly, but never tried to reach out for anything while standing on the cube.

Then, during the seventh session, Kandula suddenly had his moment of epiphany: he rolled the cube into position beneath the hanging food, stood on the cube with his front two feet, stretched out his trunk, and grabbed his prize.

Kandula - Insightful and Now Less Hungry Elephant

From then on, Kandula was off to the races. In the next session, he not only rolled the cube over and stood on it to reach the fruit again, he also started using the cube as a tool to reach other objects: e.g., standing on it to explore the inside of an enrichment object and, after rolling it to the edge of the yard, using it as a platform to reach for blossoms on an overhanging tree branch.

Moreover, Kandula showed he was able to apply his insight to new situations. For example, in a second experiment, the researchers used the same general setup, but began moving the cube around from place to place, including behind fences and in locations that Kandula couldn’t see as he entered the yard. In each case, Kandula found the cube and rolled it over to capture his food reward. Here’s a video of Kandula retrieving the cube from behind a fence:

Next, the researchers replaced the cube with a large tractor tire – in three of four sessions Kandula used the tire as a tool, rolling it to the proper place, and then standing on it to obtain the food reward.

In a final experiment, the researchers replaced the cube and the tire with a variety of other objects, including large plastic balls, discs, cones, a barrel lid and three cutting boards that would have to be stacked to form a platform for Kandula to reach the food. While Kandula didn’t stack all three boards (he did stack two, though), he experimented with various approaches such as standing with one foot on separate objects. Ultimately, he reached the food by standing on a plastic ball, a solution that surprised the researchers since he had never placed his weight on a similarly unstable platform before.

So, to summarize, Kandula demonstrated sudden insight – using a tool to solve a problem in a novel and spontaneous fashion, without evidence of prior trial and error learning. Further, he showed that he could repeat, transfer and extend his technique in subsequent sessions.

If you’re an elephant, please feel free to give yourself a pat on the back. Job well done!

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1Foerder, P., Galloway, M., Barthel, T., Moore, D., & Reiss, D. (2011). Insightful Problem Solving in an Asian Elephant PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023251.

Sheep: Barnyard Brainiacs

It turns out that sheep are far more intelligent than their reputation for barnyard slowness would lead one to believe. In recent research published in PLoS ONE1, Professor Jenny Morton of the Department of Pharmacology at the University of Cambridge and her colleague Laura Avanzo reported that domestic sheep can perform extremely well on tests of designed to measure cognitive abilities, possibly as well as any animal other than primates.

Professor Morton, who had been studying Huntington’s disease, wanted to find out whether transgenic sheep with a specific genetic defect might be useful in preclinical research regarding potential treatments for this neurodegenerative disease. Because Huntington’s is characterized by cognitive deterioration, Morton was particularly interested in seeing how well sheep would perform cognitively, since suitable research subjects for neurologic disorders like Huntington’s inevitably must undergo systematic cognitive testing relevant to the disease.

Accordingly, Morton and Avanzo devised a series of tests that they gave to seven female Welsh Mountain sheep, six of whom completed the whole study. No word on why all of the ungulate volunteers were female, although my guess is that the males were off rollicking around with male bottlenose dolphins who were avoiding sponge fishing duty.

Welsh Mountain ewe: wool-giver and five-time Jeopardy champion (photo credit: Vertigogen)

The Tests

The tests were designed to measure the ability of the sheep to perform in three areas (discrimination learning, reversal learning and “attentional set-shifting”), which are relevant to what the researchers refer to as executive function – that is, the “ability to learn associations between stimuli, actions and outcomes, and to then adapt ongoing behavior to changes in the environment.” While the sheep took a large number of very specific tests, the tests fell into the following general categories:

  1. Simple discrimination tests. Sheep must choose between two feed buckets that are identical except one is blue the other is yellow. One color contains a food reward; the other is empty. Later “retention tests” repeat the original tests after time has passed to see how well the sheep remember.
  2. Simple discrimination reversal tests. Sheep must relearn the correct answer after sneaky researchers reverse the color of the bucket containing the food reward. (Note: we encountered this type of testing in the earlier AnimalWise post about the clever Anole lizards). Again, later “retention tests are given.
  3. Compound discrimination tests. The rewarded color is the same as in 1 above, but the relevantly-colored objects are now “perforated sports cones” rather than buckets. Additional buckets of irrelevant colors (one black, one green) are placed next to the sports cones, with the food reward in whichever bucket happens to be next to the correctly-colored sports cone.
  4. Intradimensional shift tests. Now, the sheep are presented with new shapes (rhomboids and cones) and new colors (purple and green). The sheep must still make a correct choice based on color, but need to learn the new color to apply.
  5. Intradimensional shift reversal tests. Same as 4, but sheep must relearn correct answer after the researchers change the rewarded color.
  6. Extradimensional shift tests. Again, the sheep are presented purple or green cones or rhomboids, but this time they must figure out now that the reward is based on choosing the correct shape, rather than a particular color.
  7. Extradimensional shift reversal test. Same as 6, but sheep must relearn after researchers swap which shape is rewarded.

Of the above tests, 1 & 3 measure “discrimination learning”; 2, 5 & 7 measure “reversal learning”; and 4 & 6 measure “attentional set-shifting.”

The Results

In a nutshell, the sheep did amazingly well.

They very quickly learned to pass the initial simple discrimination test (within seven sets of eight discriminations). When presented with the first reversal test, their performance initially dropped off, but they learned the new correct answer within three days of testing (11 sets of discriminations). For the compound discrimination testing, their performance again dropped slightly at the outset, but within two days they had this new puzzle figured out as well. Moreover, the retention tests showed that the sheep were able to remember the correct answer after time had passed (six weeks in the case of the simple discrimination test; two weeks for the simple reversal test).

At first, the sheep performed no better than chance on the more difficult intradimensional shift test, but they soon were performing at over 90% correct. They also experienced a large drop off in performance on the extradimensional shift test, but improved gradually until they reached 80% correct on the fourth day of testing. The sheep learned also were able to learn the reversals (within eight sets of discriminations for the intradimensional reversal and within 10 sets for the extradimensional reversal).

Morton and Avanzo summarized the results as follows:

We show that not only can normal can sheep perform discrimination reversal learning tasks, but they can also perform attentional set shifting tasks that test executive function. To our knowledge, this is the first time that these executive functions have been demonstrated in any large animal, apart from primates.

They were surprised by this success, conceding that they hadn’t been expecting the sheep to do well on the more difficult tests and indicating that they were “driven more by curiosity than expectation” in even giving the tests to them.

So, given these results, sheep seem to have gotten a bum rap for intelligence. There are relatively few studies on ovine intelligence, although research has shown that they can learn and remember how to navigate complex maze2 and that they are very good at remembering faces3.  And then there’s my favorite, that they’ve learned to roll their way across hoof-proof metal cattle grids in order to raid villagers’ valley gardens4!

One reason for the mistaken impression about sheep cognition may be that we have a bit of a blind spot when it comes to intelligence. We expect it in ourselves and a few other select animals, but even scientists can be quite surprised when it pops up elsewhere. Perhaps the main lesson here is that we should do our best to remain open to finding intelligence in unexpected places – if nothing else, this sort of a mental stretch will be a good test of our own cognitive abilities.

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1Morton, A., & Avanzo, L. (2011). Executive Decision-Making in the Domestic Sheep PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0015752.

2LEE, C., COLEGATE, S., & FISHER, A. (2006). Development of a maze test and its application to assess spatial learning and memory in Merino sheep Applied Animal Behaviour Science, 96 (1-2), 43-51 DOI: 10.1016/j.applanim.2005.06.001.

3Kendrick, K., da Costa, A., Leigh, A., Hinton, M., & Peirce, J. (2007). Sheep don’t forget a face Nature, 447 (7142), 346-346 DOI: 10.1038/nature05882.

4See, e.g., BBC News, “Crafty sheep conquer cattle grids,” July 30, 2004.

Female Dolphins Sponge Their Way to Success

After 27 years, scientists finally appear to have unraveled most of the mystery surrounding a very enterprising group of (primarily) female bottlenose dolphins (tursiops aduncus) who live in Shark Bay, off the coast of Western Australia.

Why are those dolphins looking at me like that? (photo credit: Eric Patterson, Shark Bay Dolphin Project)

The story opens in 1984, when observers first noticed that some of the Shark Bay dolphins were breaking off conical marine basket sponges and wearing them over their beaks (rostra). Because only a small percentage of the dolphins in the area engaged in this behavior and it was very difficult to see what they were doing with the sponges, especially when they were underwater, the first research on this behavior wasn’t published until over a decade later.

Preliminary Findings: Tool Use by a Few Females

In a 1997 article in Ethology1, a team of researchers led by Janet Mann of Georgetown University described their initial findings: five female dolphins were regularly seen with sponges, and four additional dolphins (only one of which was a male) were each seen carrying sponges on a single occasion. The regular sponge users were relatively solitary, tended to use the sponges in a deep water channel area, and did not participate in the group feeding and social aggregations to which other dolphins in the group were attracted.

The researchers weren’t sure what the dolphins were doing with the sponges, but they assumed that there had to be some sort of functional advantage, since the sponges were often quite large, covering a large portion of the dolphin’s face, interfering with normal use of the mouth, contributing to hydrodynamic drag, and potentially impacting the ability to engage in echolocation. They considered three possibilities: that the dolphins were playing with the sponges, that the sponges contained some medicinal or other useful compound, or that the dolphins were using the sponges as a tool to aid in foraging.

They concluded that it wasn’t likely that the sponges were being used as toys, as the spongers were relatively solitary, used the sponges methodically for hours at a time, year after year, and didn’t engage in typical play postures, splashing or vocalizations as they carried the sponges. Similarly, they determined that medicinal or similar uses were unlikely, since, among other things, the regular sponge users all seemed healthy and there were no indications that they were ingesting the sponges (although the researchers conceded that this could be difficult to observe).

Hi ho, hi ho, it's off to sponge I go! (photo credit: Eric Patterson, Shark Bay Dolphin Project)

On the other hand, it did seem likely that the dolphins were using the sponges to help them forage for prey: they were seen eating fish when engaging in sponging behavior; they invested an amount of time in carrying sponges similar to that invested by other foraging dolphins; and they made sounds and generally behaved in ways consistent with foraging. The researchers speculated that sponges might be used to protect the dolphin’s face, either from spines or stingers of prey animals or from the abrasive sea floor as they flushed out burrowing prey. In either case, they believed that this would constitute “tool use,” something that had been reported in captive dolphins but never before in the wild.

Finally, the researchers drew no conclusions on why males didn’t engage in sponging, except to note that perhaps it required a degree of solitary living that was at odds with their need to form and maintain cohesive and cooperative alliances.

Additional Findings: A Cultural Tradition of Tool Use among a Related Group of Females

Next, in 2005, Mann’s researcher team expanded on its findings in a paper published in the Proceedings of the National Academy of Sciences2, with salient points of the research including the following:

  • Sponges Are Foraging Tools. By this time, the researchers had found 15 adults in the community who regularly used sponges, only one of whom was a male. Although not a focus of the paper, it appears that the researchers had concluded by this time that the dolphins were indeed using the sponges as tools to protect their rostra as they foraged for prey on the sea floor.
  • “Sponging Eve.” The researchers tested the mitochondrial DNA of the regular spongers and found that sponging had been passed on mainly along a single matriline (line of descent from mother to daughter) and that, due to the high degree of genetic relatedness, all spongers likely descended from one recent “Sponging Eve.”
  • Female Social Culture. After considering in detail whether the sponging behavior could have resulted from either a genetic propensity or some unique aspect of the deep-water channels where the most of the sponging occurred, the researchers found the evidence for these alternatives lacking and concluded that by far the best explanation was that the sponge use was being socially learned and transmitted from mother to daughter. The researchers weren’t overly surprised by this finding, given that studies had already shown that dolphins have uncommonly complex cognitive and imitative skills and the ability to excel at vocal and social learning.
  • Uncommon Cultural Diversity. It was particularly rare to see this sort of cultural phenomenon in a small subset of the overall population (a single maternal line comprising only about 10% of the females in the group). In other studies (for example, involving apes), this type of culturally learned behavior is seen across the entire population.
  • Can’t Explain Males. Once again, the researchers surmised that perhaps males didn’t engage in sponging because they had to associate at high levels with alliance partners, but they left this point open.

The Story Continues: Spongers Are Fit

The story continued to unfold in 2008, when Mann and her team published a paper in PLoS ONE3 that focused in more on whether sponging was an advantageous behavior, or whether the spongers were in some fashion subordinate or less competitive and were making the “best of a bad situation.”

I don't know what you mean, it's no more elaborate than the other hats at the Royal Wedding... (photo credit: Eric Patterson, Shark Bay Dolphin Project)

By this point, recurrent sponging had been seen in 41 of the dolphins and a few more of them were male (29 were females, 6 were males, and 6 were of unknown sex). This still represented a small percentage (about 11% of adult females were spongers) and, although it now appeared that more than one matriline was involved, the data continued to show that the behavior was consistently passed down from mother to daughter, and less frequently from mother to son: there were no instances observed where a calf adopted the behavior if its mother wasn’t a sponger, and of 19 offspring born to sponger females who could be observed and whose sex was known, 91% of the daughters (10 of 11) and 25% of the sons (2 of 8) adopted sponging.

Further, the researchers found that the spongers were highly specialized, not using other hunting techniques and spending approximately 96% of their foraging time using sponges. In fact, the researchers concluded that, due to their lifestyle and specialization, spongers actually used tools more than any non-human animal.

So, was the sponging advantageous or a way of coping for not particularly well-adapted dolphins? Well, the researchers did find that spongers were more solitary and spent more time foraging at deeper depths and on longer dives, but noted that they really didn’t seem to suffer from any kind of fitness cost, as their calving success was equivalent to that of other females in the population.

Since there was no evidence that any kind of competition for food was relegating the spongers to their strategy, the research concluded that sponging simply seemed to be an “all-or-none phenomenon,” that required a specialized approach and a commitment to a single foraging type, but that most likely opened up a particular hunting niche in a diverse environment. While other dolphins could theoretically adopt the strategy, the researchers noted that daughters in particular tend to adopt their mothers’ foraging strategy, and unless the mother was a sponger, a daughter might simply not have had sufficient exposure to develop this highly specialized technique while a calf.

Once again, the team hypothesized about the males, stating: “Male offspring are exposed to sponging as often as female offspring, but do not seem to adopt the behaviour early, if at all. … [M]ales likely range more widely post-weaning, focus on establishing long-term alliances, and cannot afford to adopt foraging tactics that both demand extensive effort and specialization and limit their range and access to females.”

The researchers offered no opinions about whether the male dolphins were simply slow on the uptake or whether they associated sponges with housework to be avoided.

The Latest Chapter: Explaining the Purpose of Sponging

While all of this research had answered many questions and shed light on a fascinating example of tool use in wild female dolphins, one fundamental question remained. Dolphins are great at using echolocation to detect prey (even prey that is buried), so why do the Shark Bay spongers probe the debris-covered sea floor with their noses, risking injury (even with the protection afforded by the sponges) instead of minimizing sea floor contact by simply echolocating for buried prey as they do in other locations (for example, the Bahamas)?

What a mess! This sea floor needs a good sponging! (photo credit: Eric Patterson, Shark Bay Dolphin Project)

This is the question is answered in the latest chapter, a research paper published last week in PLoS ONE4. Mann’s research team had fun with this one, grabbing poles and going sponging themselves. What they found, aside from the fact that dolphins are far more graceful than people, was that the nature of the prey turned up by sponging helps explain the dolphins’ behavior.

It turns out that most of the bottom-dwelling fish that hide in Shark Bay the sea bottom lack swim bladders, gas-filled chambers used by fish to control their buoyancy as they swim up and down. Because they lack the major characteristic that distinguishes their density from sea water, they generate relatively weak acoustic signals and are difficult to detect with echolocation. In addition, the debris (rock, shell and coral) on the sea floor in the area seemed likely to cause “interfering reverberation and echo clutter,” which would further reduce the effectiveness of echolocation.

Moreover, it’s worth it to go after these swim bladderless fish. They are attractive targets, as they are reliably present on the sea floor and exhibit consistent, predictable behavior when rousted out of their hiding places, allowing the dolphins to adopt a single efficient technique as they sponge. Further, bladderless fish tend to have a relatively high fat content, providing hungry dolphins with a particularly energy-rich meal.

So, the sponging female dolphins of Shark Bay really are quite remarkable. They have established a mother-daughter subculture of tool use in the wild, successfully devising a highly specialized way of exploiting an attractive niche in their diverse environment.

You go girl(s)!

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1Smolker, R., Richards, A., Connor, R., Mann, J., & Berggren, P. (2010). Sponge Carrying by Dolphins (Delphinidae, Tursiops sp.): A Foraging Specialization Involving Tool Use? Ethology, 103 (6), 454-465 DOI: 10.1111/j.1439-0310.1997.tb00160.x.

2Krutzen, M. (2005). Cultural transmission of tool use in bottlenose dolphins Proceedings of the National Academy of Sciences, 102 (25), 8939-8943 DOI: 10.1073/pnas.0500232102.

3Mann, J., Sargeant, B., Watson-Capps, J., Gibson, Q., Heithaus, M., Connor, R., & Patterson, E. (2008). Why Do Dolphins Carry Sponges? PLoS ONE, 3 (12) DOI: 10.1371/journal.pone.0003868.

4Patterson, E., & Mann, J. (2011). The Ecological Conditions That Favor Tool Use and Innovation in Wild Bottlenose Dolphins (Tursiops sp.) PLoS ONE, 6 (7) DOI: 10.1371/journal.pone.0022243.

Portia, Queen of Spiders

Do you think that spiders are mindless machines, driven by pure instinct to make their webs and then attack intruders? Well, it’s time you met Portia:

The formidable Portia! (photo credit: Akio Tanikawa)

In an emerald rainforest of northeastern Australia, a sunbeam pierces the canopy, touches broad green leaves on the way down, and beams onto a lichen-spotted rock surface. In the beam’s circle, the slow, careful motions of a brownish jumping spider are illuminated. The jumping spider belongs to the genus Portia and it is stalking its prey, a different species of spider sitting in its own web. Portia steps cautiously from the rock surface out onto the web and stops. Delicately, Portia begins to pluck the web with its palps and legs, making signals that mimic the struggles of a trapped insect. When the prey spider ignores Portia’s plucking, Portia varies the characteristics of the signals, generating a kaleidoscopic of what appears to be a random selection of signals. Eventually, in response to one of these signals, the prey spider swivels toward Portia. Immediately, Portia backtracks to that particular signal and repeats it again and again. There being no further response from the prey, Portia eventually reverts to broadcasting a kaleidoscope of signals. When the prey spider still moves no farther, Portia adopts another ploy.

Now Portia slowly and carefully stalks across the web toward the resident spider, intermit­tently making a variety of signals. From time to time, a soft breeze blows, ruffling the web. The ruffling creates background noise in the web, and Portia exploits these moments, during which the resident spider’s ability to detect an intruder is impaired, by stalking faster and farther during these periods than when the air is still. Nearing the resident spider, Portia makes a signal that elicits from the resident spider a sudden, rapid approach. However, the spider advances very aggressively, and Portia scrambles to the edge of the web, then turns around to look over the scene. Soon Portia moves away from the web and undertakes a lengthy detour, first going away from the prey and around a large projection on the rock surface, losing sight of the prey spider along the way.

About an hour later, Portia appears again, but now is positioned above the web on a small overhanging portion of the rock. After anchoring itself to the rock with a silk dragline, Portia next slowly lowers itself down through the air, not touching the web at all. Arriving level with the resident spider, Portia suddenly swings in, grabs hold of the unsuspecting spider, and sinks its poison-injecting fangs into the hapless victim.

I’m going to leave the light on tonight, too.

This rather dramatic account is from a chapter in The Cognitive Animal written by Stim Wilcox (Department of Biology, SUNY Binghamton) and Robert Jackson (Department of Zoology, University of Canterbury, New Zealand)1.

For those of you who like visuals, here’s a brief video of Portia:

Clearly, you don’t want to mess with Portia.

In their essay, Wilcox and Jackson note how tricky it is to discuss cognition in animals, with almost as many definitions of the term as people using them. Rather than trying to choose a single definition, they instead apply a framework designed to raise questions about six separate cognitive properties: reception (taking in information), attention (focusing on particular tasks), representation (maintaining a mental image or cognitive map), memory (retaining information), problem solving (deriving pathways to the achievement of goals), and communication language (influencing other individuals by manipulating symbols).

They then run through these properties point by point, in the process illustrating the cognitive abilities of Portia.

Reception: In this area, Wilcox and Jackson emphasize Portia’s amazing eyesight, which apparently is more acute in distinguishing spatial features than that of any known animal of comparable size and even rivals that of primates: “Portia can precisely locate and identify spiders from a distance of 30–40 body lengths away, monitor the spider’s orientation and behavior during the course of a predatory sequence, and in general quickly gain critical information for predatory decisions during complex interactions with a dangerous prey.” For an in-depth article on Portia eyesight, you can check out this piece2 by Jackson and Duane Harland (I love the title: “‘Eight-legged cats’ and how they see”).

Attention: Wilcox and Jackson highlight the extraordinary, prolonged attention paid by Portia as she hunts, especially as she singles out and zeros in on a prey spider in an extended bout of stalking that involves multiple tactics and focused flexibility over time. They note how she must be particularly attentive, given the extreme sensitivity of her prey’s own web to movement and weight, and describe how she manipulates the signals she sends across the target’s web (aggressive mimicry) and opportunistically takes advantage of wind-caused background noise and vibration to move more quickly across the web than she does when the air is still (smokescreen tactics).

Representation, Memory, Problem Solving: For these areas, Wilcox and Jackson point to her planned detours, which demonstrate problem-solving and suggest mental maps and prolonged memory. They observe that, by planning ahead and formulating a solution before executing her maneuver, Portia comes particularly close to what we might typically call “thinking.”

Communication: Finally, while acknowledging that Portia clearly does not have any sort of verbal language or use symbols with arbitrarily assigned meanings, Wilcox and Jackson describe the way in which Portia strings together series of signals as she engages in aggressive mimicry, noting how this involves a complex, flexible and dynamic sequence of interactions between her and her target. As they put it, “Studying Portia’s signal-making strategy from this perspective may bring us closer than we initially expected to something like the cognitive implications of verbal language.”

I don’t have much to add here.  Hail Portia!

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1Wilcox, S. and Jackson, R. (2002). Jumping Spider Tricksters: Deceit, Predation, and Cognition. In M. Bekoff, C. Allen & G. Burghardt (Eds.). The cognitive animal: Empirical and theoretical perspectives on animal cognition. pp. 27–33. Cambridge, MA: MIT Press.

2Harland, D. and Jackson, R. (2000). ‘Eight-legged cats’ and how they see – a review of recent research on jumping spiders (Araneae: Salticidae). Cimbebasia 16: 231–240.

Lizards Shed Reputation as Slow Learners

A new study has shown that anoles (Anolis evermanni), a tropical tree-dwelling lizard found in Puerto Rico, are surprisingly good problem-solvers who have cognitive abilities that rival those of birds known for their highly flexible behaviors.

Manual Leal, a professor at Duke University, led a study in which six anoles were given a series of challenges designed to test their behavior flexibility, cognitive abilities and memory.  In these experiments, the lizards were presented with a platform containing two wells, one containing a food reward and the other empty. The wells were covered with tight-fitting opaque discs of differing colors and patterns, and the lizards were given 15 minutes to obtain the reward.

Anole Lizard: will you quit messing with my dinner if I drop that whole GEICO thing? (photo credit: Manuel Leal, Duke University)

According to Leal’s research paper, which was published online on July 13, 2011, in the Journal of the Royal Society: Biology Letters1, two-thirds of the lizards were able to solve the puzzle and find the food reward, a “completely unexpected” result since:

The correct response required major changes to what has previously been considered highly stereotyped foraging behavior, which consists of scanning the environment for moving prey items and striking them from above. In our experiment, motion cues were absent and striking from above was ineffective at dislodging the disc. Lizards used multiple strategies to remove the disc. The first was a modified strike, laterally biting the disc and lifting it away from the reward. The second strategy required the lizard to advance on the disc with its head held against the substrate, using its snout as a lever to push the disc out of the way…. This strategy is not a natural foraging behaviour that has at least been witnessed, and may demonstrate an entirely novel solution, which is one of the main criteria used to recognize behavioural flexibility.

Here’s a video from the New Scientist2 that shows one of the lizards in action:

When the tests were repeated with the disc colors associated with the reward reversed, two of the lizards continued to flip the original disc in an unsuccessful search for the reward, but the remaining two, nicknamed Plato and Socrates by Leal’s team, figured out that the discs had been changed and solved the problem again, reversing their previously learned color associations. (This sort of test is known as a “reversal learning” test.) Although there haven’t been many studies of cognition in reptiles, Plato and Socrates’ success appears to be particularly notable since prior evidence had suggested that reptiles do better at solving puzzles involving location change than ones involving altered visual cues.

Finally, Leal and his team were surprised to discover that the anoles were able to solve the challenges presented in these experiments in only one-third the attempts needed by birds given similar tasks in comparable experiments. While the researchers did not draw any definitive conclusions about this, they did note that, due to the slower metabolisms of the cold-blooded anoles, they could be tested only one time a day, and that the tempo at which the tests were performed might have some bearing on the number of attempts required.

Perhaps because people don’t expect displays of cognitive flexibility in reptiles, Leal’s research has generated a fair bit of media attention, including articles in The Economist3, ScienceNOW4MSNBC5, BBC Nature News6 and LiveScience7. Enjoy!

Now, after a long week, I think I’m going to go out and lie on a warm rock and then get some dinner.

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1Leal M, & Powell BJ (2011). Behavioural flexibility and problem-solving in a tropical lizard. Biology letters PMID: 21752816.

2New Scientist, “Smart lizard solves a problem it’s never seen before,” July 13, 2011.

3The Economist, “Cold Blooded Cunning,” July 14, 2011.

4ScienceNOW, “Tropical Lizards Get Brainy,” July 12, 2011.

5MSNBC, “Don’t underestimate the brainpower of a lizard,” July 13, 2011.

6BBC Nature News, “Lizard has problem solving skills,” July 13, 2011.

7LiveScience, “Lizards Are Wizards At Solving Food Puzzle,” July 12, 2011.

Did You Hear the One About the Traveling Salesman and the Bumblebee?

Last fall, bumblebees enjoyed their moment in the sun, as a series of headlines proclaimed that they were mathematical geniuses:

“Tiny Bee Brains Beat Computers at Complex Math Problems”
Fox News1

“Bees Solve Complex Problems Faster Than Supercomputers”
The Daily Galaxy2

“Bees’ brains more powerful than computers”
Natural News3

Bumblebee solving quadratic equations (photo: U.S. Fish & Wildlife Service)

What was all the fanfare about? Are we about to enter a new era in which paparazzi stalk bees rather than reality TV stars? (We won’t complain if this is the case.) PhysOrg.com4 summarized the context as follows:

Scientists at Queen Mary, University of London and Royal Holloway, University of London have discovered that bees learn to fly the shortest possible route between flowers even if they discover the flowers in a different order. Bees are effectively solving the ‘Travelling Salesman Problem’, and these are the first animals found to do this.

The Travelling Salesman must find the shortest route that allows him to visit all locations on his route. Computers solve it by comparing the length of all possible routes and choosing the shortest. However, bees solve it without computer assistance using a brain the size of grass seed.

Professor Lars Chittka from Queen Mary’s School of Biological and Chemical Sciences said: “In nature, bees have to link hundreds of flowers in a way that minimises travel distance, and then reliably find their way home – not a trivial feat if you have a brain the size of a pinhead! Indeed such travelling salesmen problems keep supercomputers busy for days. Studying how bee brains solve such challenging tasks might allow us to identify the minimal neural circuitry required for complex problem solving.”

In actuality, the bumblebees’ achievements, while impressive, were a bit more modest than publicized.

Bumblebees (Bombus terrestris) do indeed visit flowers in predictable sequences called “traplines,” and the UK research team wanted to learn more about whether these sequences simply reflect the order in which flowers are discovered or whether they result from more complex navigational strategies enabling bees to optimize their foraging routes. Accordingly, the researchers set up an array consisting of four (not hundreds of) artificial flowers, which they introduced to bumblebees in sequence.

The researchers observed that over time the bees tended to stop visiting the artificial flowers in their discovery order and, through a process of trial and error, began reorganizing their preferred routes to minimize total flight distance. In general, the bumblebees adopted a primary route and two or three less frequently used secondary routes, with the primary route typically being the shortest distance route. The bees also did a (reasonably) good job of remembering the most efficient route after an overnight break.

Even though the bees gravitated toward the shortest route, they did continue to experiment with novel routes, a behavior that – the researchers hypothesized – might allow them to fine tune their behavior as new sources of food were found over time.

Now, in their research paper5, the UK team did note that the bees’ search to find the shortest path among flowers is analogous to the traveling salesman problem, and did state that “Our findings suggest that traplining animals can find (or approach) optimal solutions to dynamic traveling salesman problems (variations of the classic problem where availability of sites changes over time) simply by adjusting their routes by trial and error in response to environmental changes.” These observations are, however, just a tad less dramatic than the “triumph over supercomputers” celebrated in the popular media reports on the research.

So what are the morals of this story?

  • While all too often animals are derided as “dumb beasts” and the like, sometimes we go in the opposite direction, overstating what animals are capable of accomplishing in order to create a sensation.
  • Even without the hyperbole, bumblebee route optimization behavior is noteworthy. There are often multiple ways to solve difficult problems, and sometimes the efficient approaches developed by animals who do not boast large brains can be surprisingly effective.
  • Insects, both in collective groups and as individuals, seem to be particularly adept at finding rational solutions that have an almost mathematical feel to them.
  • Bumblebees can sure generate a lot of buzz.

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1Fox News, “Tiny Bee Brains Beat Computers at Complex Math Problems,” October 25, 2010.

2The Daily Galaxy, “Bees Solve Complex Problems Faster Than Supercomputers,” October 26, 2010.

3Natural News, “Bees’ brains more powerful than computers,” October 27, 2010.

4PhysOrg.com, “Complex mathematical problem solved by bees,” October 25, 2010.

5Lihoreau M, Chittka L, & Raine NE (2010). Travel optimization by foraging bumblebees through readjustments of traplines after discovery of new feeding locations. The American naturalist, 176 (6), 744-57 PMID: 20973670.

Tooling Around Underwater

Tool Time For Tuskfish

As reported last week in ScienceNOW1, a professional diver exploring the Great Barrier Reef off the coast of Australia recently snapped the first photos of a fish using tools. The diver, Scott Gardner, came across a blackspot tuskfish (Choerodon schoenleinii) that was hovering over a sandy area near a rock with a clam in its mouth. The tuskfish rolled on its side and, with a repeated cracking noise, slammed the clam against the rock until the shell fractured. Here’s one of the photos that Gardner took of the industrious (and hungry) tuskfish:

Tuskfish cracking open clam (photo credit: Scott Gardner)

While there have been anecdotal accounts of other fish using tools, this is the first time that this type of behavior has been caught on film.

What Is Tool Use, Anyhow?

In an interesting aside, this incident has brought to the forefront some of the ways in which it is difficult to define, and reach agreement upon, exactly what constitutes “tool use” in animals.  As noted in the ScienceNOW article, there has been previous debate over whether stingrays and archerfish targeting jets of water to capture prey constitutes tool use (is a solid external object necessary for there to be a tool?), as well as whether tool use “requires the animal to hold or carry the tool itself, in this case the rock.”

The research paper regarding this tuskfish behavior, which was published in the most recent issue of Coral Reefs2, the official Journal of the International Society for Reef Studies, argues that the tuskfish using the rock as an anvil to open the clam conforms to a definition of tool use first formulated by Jane Goodall back in 1970, that tool use is “the use of an external object as a functional extension of mouth or hand in the attainment of an immediate goal.” The paper adds: “The use of a rock as an anvil rather than a hammer could be considered a sign of intelligence considering the ineffectiveness of manipulating a freely suspended tool in water. The images certainly provide an interesting starting point for further comparative studies on tool use in fishes.”

The ScienceNOW article describes how Culum Brown, a behavioral ecologist at Macquarie University in Sydney, Australia, and a co-author of the Coral Reefs paper:

argues that it’s not logical to apply the same rules to fish as to primates or birds. For one thing, fish don’t have anything but their mouths to manipulate tools with, and for another, water poses different physical limitations than air. ‘One of the problems with the definition of tool use as it currently stands is it’s totally written for primates,’ he says. ‘You cannot swing a hammer effectively underwater.’

Those of you who pay close attention may already have noted that the definition of tool use can stir controversy. For example, beginning at the 10:34 mark in her video presentation relating to the awesome octopus, Maggie Koerth-Baker describes two very divergent definitions that might lead to different conclusions about whether the octopus engages in tool use: (a) a stricter definition that requires that an animal use a solid object to solve an “immediate problem,” rather than just to provide defense, and (b) a broader definition holding that tool use occurs whenever an animal modifies an object so as to alter some aspect of its environment.

Food For Thought

In considering tool use by animals, here are some things you might want to ponder:

  • Which of the above definitions makes the most sense to you?
  • Does it matter whether the behavior is performed by a captive animal (like the New Caledonian crow) or in the wild?
  • Are definitions of tool use inherently anthropocentric and subjective? That is, are we trying to come up with a definition that basically requires the behavior to look like something a human would do (if it really is a tool, then I should be able to see the Craftsman logo) before we accept it?
  • Is it significant whether the behavior is widespread? That is, if the behavior is only observed once or twice, is it a fluke? If the behavior is widespread, is it mere instinct?
  • Is nest building by birds an example of tool use?

Conclusion

There will undoubtedly be more AnimalWise posts about tool use. In the meantime, if you run across any tuskfish, you should look very closely to see if you can see their very small, teeny-tiny tool belts. They really are quite cute.

Here are some more photos (note, the following pictures may not be suitable for small children and clams):

More Scenes from "Crouching Tuskfish, Hidden Clam" (photo credit: Scott Gardner)

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1ScienceNOW, “Diver Snaps First Photo of Fish Using Tools,” July 8, 2011.

2Jones, A.M., Brown, C., Gardner, S. Tool use in the tuskfish Choerodon schoenleiniiCoral Reefs. DOI:10.1007/s00338-011-0790-y.

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