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.


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.


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., “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.

Spotted Hyenas: Clever Carnivores, Not Simply Comedians

Underestimated by many, spotted hyenas (Crocuta crocuta) are providing insight into the roots of human intelligence.

Far from being clownish buffoons, spotted hyenas – also known as laughing hyenas – live in large, complex matriarchal communities, or clans, in which social intelligence is critical. They are fascinating animals – although they look something like dogs, they are more closely related to cats, and closer still to mongooses and civets. Female spotted hyenas are the true clan leaders: they are larger and more aggressive than males, socially dominant, and have even evolved to have male-like external features, including a pseudopenis that is extremely similar in appearance to the male’s sexual organ.

Spotted hyenas enjoying the water (photo credit: K. Holekamp)

Kay Holekamp, a professor of zoology at Michigan State University, has been studying these gregarious carnivores for many years, and is particularly focused on how they can help us gain a better understanding of why certain animals, including humans and other primates, have developed high intelligence and large brains (which, from a metabolic standpoint, are extremely expensive to maintain). More specifically, she has been looking at spotted hyena society as a means of probing the “social complexity” theory of intelligence, which posits that brainpower provides a significant edge to animals living in complex social groups, where individuals need to be able to anticipate, respond to and manipulate the social behavior of other group members.

The majority of intelligence research in this area has been performed on primates, but Holekamp notes in recent research1 that social complexity theory predicts that “if indeed the large brains and great intelligence found in primates evolved in response to selection pressures associated with life in complex societies, then cognitive abilities and nervous systems with primate-like attributes should have evolved convergently in non-primate mammals living in large, elaborate societies in which individual fitness is strongly influenced by social dexterity.”

In this research, Holekamp acknowledges that much remains to be learned about social cognition in spotted hyenas, but concludes:

Work to date on spotted hyenas has shown that they live in social groups just as large and complex as those of cercopithecine primates [AW: a subfamily of Old World monkeys], that they experience an extended early period of intensive learning about their social worlds like primates, that the demand for social dexterity during competitive and cooperative interactions is no less intense than it is in primates, and that hyenas appear to be capable of many of the same feats of social recognition and cognition as are primates.

While the paper includes much more detail, the following are among Holekamp’s observations regarding spotted hyena social knowledge and skills:

  • Individual recognition. Spotted hyenas possess a rich repertoire of visual, acoustic and olfactory signals, which other hyenas can use to discriminate clan members from alien hyenas, to recognize the other members of their social units as individuals and to obtain information about signalers’ affect and current circumstances.
  • Kin recognition.Hyenas can distinguish vocalizations of kin from those of non-kin, with intensity of responses increasing with degree of relatedness between vocalizing and listening animals, and kin recognition potentially occurring among hyenas as distantly related as great-aunts and cousins.

    Basking spotted hyena cub (photo credit: K. Holekamp)

  • Imitation and behavior coordination. Although hyenas have not been observed to engage in true imitation (that is, replicating a novel act performed by a species member) the way some primates do, they do appear to modify their behavior after observing goal-directed behavior of other hyenas. In addition, they engage in cooperative hunting involving complex coordination and division of labor among hunters. This cooperation, which enables them to capture prey many times their size, involves – at a minimum – communicating by simple rules of thumb (e.g., “move as necessary to keep the prey between you and another hunter”), if not the operation of higher mental processes.
  • Social rank and social memory. Spotted hyenas are intensely aware of social rank, and they learn quickly where they and their relatives fit into their clan’s dominance hierarchy. They are able to remember previous interactions they have had with other individuals, and appear to remember the identities and ranks of their clan mates throughout their lives. They apply their knowledge of social ranks in many ways, including to avoid conflict, figure out feeding priority, help them choose appropriate mates, determine which social relationships are desirable to establish and maintain, and when to reconcile after conflicts have occurred.
  • Flexible problem-solving. Similar to certain primates, it appears that spotted hyenas are able to achieve short-term goals through a variety of different tactics. As stated in the Holekamp’s research article, “For example, a hyena can avoid aggression by leaving the aggressor’s subgroup, exhibiting appeasement behavior or distracting the aggressor. A hyena can potentially use greeting ceremonies to reconcile fights, reintroduce itself to conspecifics [AW: members of their own species] from which it has been separated, or increase conspecifics’ arousal levels in preparation for a border patrol or group hunt.”
  • Tactical deception. One sign of social cleverness, which should be familiar to all humans, is tactical deception. It appears that hyenas may share this sophisticated behavior as well, as anecdotal accounts of hyena deception include a low-ranking hyena noticing an unprotected meal but ignoring it until higher-ranking group mates were out of range, and other low-ranking individuals similarly emit alarm vocalizations in what appear to be deceptive attempts to gain access to food.

Finally, here’s a brief video in which Holekamp shows one of the ways she and her colleagues have been assessing the puzzle-solving skills and memories of spotted hyenas:

So, hats off to laughing hyenas: they may sound comical, but they are seriously smart!


1Holekamp, K., Sakai, S., & Lundrigan, B. (2007). Social intelligence in the spotted hyena (Crocuta crocuta) Philosophical Transactions of the Royal Society B: Biological Sciences, 362 (1480), 523-538 DOI: 10.1098/rstb.2006.1993.

Memory Superstar Eats Like a Bird

How has your memory been lately? You’ve been a little absent-minded, haven’t you? (Your keys are on the dining room table, right where you left them.)

If you don’t have a border collie to help you remember things, you may want to see if there are any Clark’s Nutcrackers in the neighborhood.

Clark's Nutcracker thinking about eating 30,000 pine nuts (photo: US Fish & Wildlife Service)

Clark’s Nutcrackers are medium-sized birds in the corvid family (the same family as jays, crows and ravens) that live in the Western United States and that rely on their memory to relocate stored food during the long winter months.  Every year, they can harvest more than 30,000 seeds from pine cones, which they then hide in thousands of separate places within a 15 mile or so radius.

Their memories for these locations are pretty incredible.  As one researcher, Brett Gibson, described it in a ScienceDaily1 article:

Nutcrackers are almost exclusively dependent upon cache recovery for their survival so if they don’t remember where they’ve made those caches, then they are in trouble. During winter, their cache locations are covered with snow so many of the small local features in the landscape during fall are no longer available to them. What’s clear is that they are using spatial memory to recover these caches. They are remembering these caches based on landmarks and other features of the terrain.

Another biologist, Russell Balda, who has studied Nutcrackers for a number of decades, is even more effusive in National Wildlife2 magazine:

How these birds find their caches looked like an incredible feat when we began studying them. We soon found out that the Clark’s nutcracker is the spatial memory superstar of the avian world, and possibly of the vertebrate world.

These two articles note that there is still some uncertainty about exactly how the Nutcracker is able to have such an astonishingly good memory. Regardless of how they do it, though, I think we all can be impressed by – and a little jealous of – these birds and their brains.


1ScienceDaily, “Researcher Uncovering Mysteries Of Memory By Studying Clever Bird,” October 12, 2006.

2National Wildlife, “THE BIRD THAT NEVER FORGETS – The unassuming Clark’s nutcracker has one of the most remarkable memories in the animal kingdom,” October 1, 2000.

My Border Collie Is Smarter Than Your Honor Student

Or so the bumper sticker says.

On this Fourth of July, it seems appropriate to salute man’s best friend in a brief holiday post. Meet Chaser, a true canine linguistic champion.

Chaser understands more than 1,000 words, along with simple sentences. Her vocabulary includes the names of 1,022 objects, including 800 stuffed animals, 116 balls and 26 “Frisbees,” any of which she can fetch on command.

Chaser, resting after studying for the bar exam (photo credit:

In addition, if a new toy is placed among her playthings, she is able to retrieve it when given its unfamiliar name, inferring its identity by a process of exclusion. She also has been studying her verbs, demonstrating that she knows how to “find,” “nose” and “paw” each of her toys. I assume that next she will be working on her gerunds and finishing her mastery of the subjunctive mood.

Happy Fourth, Chaser!

You can read more about Chaser and see her in action in this ABC News1 story.


1ABC News, “World’s Smartest Dog? Meet a Border Collie Whose Memory Astounds,” February 9, 2011.

Memory: Chimp is Champ!

It didn’t sound like a fair contest: the memory champion of the UK against a lowly chimpanzee. In one corner, Ben Pridmore, a man capable of memorizing all of the cards in a shuffled deck in less than half a minute; in the other corner, Ayumu, a seven year old hairy primate wearing no clothes.

No, it wasn’t fair at all.

As reported in the UK Daily Mail1, both chimp and man watched a computer screen on which five numbers flashed up at various positions before being obscured by white squares, and then had to touch the squares in order of the numbers they concealed, from lowest to highest.

Ayumu hard at work (photo credit: Primate Research Institute Kyoto University)

By the time the competition heated up and the numbers were shown for a mere fifth of a second, the results weren’t even close: while the winner was able to order the numbers correctly almost 90% of the time, the loser couldn’t even manage 33%.

Fortunately, NaturalNews.com2 notes that the loser was gracious in defeat: “It is extremely impressive for anybody,” Pridmore said when asked about Ayumu’s performance. “He is doing something which I think is a really great performance even by human standards, so I’m sort of forgetting he is not a human being. When I bring that into the equation, it makes it overwhelmingly impressive.”

(If you wish to try to avenge Mr. Pridmore’s loss, the good news is that there’s a website3 where you can watch a video of Ayumu in action and then take the memory test yourself. Good luck, our species is counting on you.)

You may be thinking that this is a meaningless fluke, a highly specific area where a chimpanzee just happens to excel, a parlor trick that is not at all indicative of true intelligence. Well, maybe so, but don’t we as humans like to point to these sorts of unique abilities as precisely what set us apart from the rest of the animal kingdom? Are we tilting the playing field by giving inordinate weight to the mental gifts that we enjoy, downplaying others and defining intelligence to suit ourselves and our abilities? Perhaps we should ask Ayumu what he thinks…


1The Mail Online, “I’m the chimpion! Ape trounces the best of the human world in memory competition,” January 26, 2008., “Chimpanzee Beats Human Memory Genius in Memorization Competition,” August 3, 2008.

3lumosity games website, visited June 28, 2011.

Udderly Intelligent

While you might be willing to acknowledge that a cow can be out standing in its field, I’m willing to bet that you don’t typically think of Bessie as leading a rich intellectual and emotional life.  You might want to think again.

According to The Sunday Times1, “cows have a secret mental life in which they bear grudges, nurture friendships and become excited over intellectual challenges.” Moreover, cows don’t have a monopoly on farm animal intelligence, as the article reports similar findings for sheep, pigs, goats, chickens and other livestock.

Notable feats of barnyard intellectual prowess include:

  • Cows form friendship groups and spend most of their most of their timing licking, grooming and generally hanging out with a few other like-minded bovines.  They can also form dislikes and hold grudges “for months or years.” (Note to self: don’t get on the wrong side of a cow.)
  • Cows have become so excited in solving intellectual challenges such as figuring out how to open a door to get some food that their “brainwaves showed their excitement; their heartbeat went up and some even jumped into the air.” (Ok, that alone made this post worthwhile – I would pay to see a cow jump into the air as it solved a puzzle!)
  • Sheep can recognize up to 50 other sheep simply by looking at their profiles, and can remember the other sheep even after a year apart.  (Admit it, you can’t do that.)
  • Sheep can form strong affections for particular humans, become depressed when separated from their human friends, and greet them enthusiastically … even after three years.

So, a little additional respect for livestock is definitely in order.  While it may suit our purposes to think of farm animals as dumb, unfeeling beasts who exist only to serve us, this simply is not the case.  They are complex emotional beings that lead active intellectual lives filled with strong memories, friendships, dislikes, fears and great achievements.  Next time a cow turns its large head towards you and looks at you with those big brown eyes, remember that it just may leap with excitement if you tell it that it’s your friend.


1The Sunday Times (UK), “The secret life of moody cows,” February 27, 2005.

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