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Happy World Turtle Day! Turtles Can Learn From Each Other

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Admittedly I don’t know much about turtles. So when I found out today is World Turtle Day, it was the perfect opportunity for me to dig around for some interesting research on these aquatic creatures.

A few years ago, two scientists from the University of Tennessee, Knoxville did a clever experiment and discovered that one type of turtle, the Florida Red-bellied Cooter (Pseudemys nelsoni), can learn from each other.

A Florida Red-bellied Cooter. Source: iNaturalist.
A person holding a Florida Red-bellied Cooter to show its size. Source: iNaturalist.

The scientists came up with the idea because not a whole lot is known about whether turtles are social or not–you can sometimes see them basking in the sun together and they get together to mate, but do they actually “hang out” together? The scientists saw some behaviour in a group of turtles that looked like they were behaving socially. They also witnessed turtles copying one turtle who tried to get a yummy leaf that was hanging over the surface of the water. Maybe turtles are more social than we think? The second observation in particular led to the question: Can turtles learn from each other?

In their laboratory, the scientists had six Florida Red-bellied Cooters. These turtles had hatched in their lab and lived in captivity in a big tank of water. The scientists set up a tank where at one end there were two bottles sitting above the water surface on bricks. One bottle was white and the other was black. Under one of the bottles was a food pellet. The scientists trained two of the six turtles how to knock one of the bottles over to get the food pellet: for one turtle, the pellet was always under the white bottle, and for the other turtle, the pellet was always under the black bottle. Interestingly, one turtle always knocked the correct bottle over by swiping at it with its front legs, whereas the other turtle knocked the bottle over by biting at it. (The scientists swapped the positions of the bottles every so often so that the turtles had to learn the colour of the correct bottle, rather than its position.)

The set-up the scientists used in their experiment. On the left you can see the top of the white bottle and the top of the black bottle. Underneath one of the bottles is a food pellet, and the turtle had to learn which colour bottle to knock over to get it. Here a turtle is climbing up toward the black bottle. It has paint on its shell so the scientists could tell the turtles apart. Source: Journal of Comparative Psychology.

Soon the two turtles learned to knock over the correct bottle to get the food. These turtles were called the Demonstrators. The scientists then put the remaining four turtles, one at a time, with one of the Demonstrators, so they could watch as the Demonstrator knocked over a bottle to get the food pellet. These four turtles were referred to as the Observers. Then the scientists placed each Observer alone with the bottles to see what they would do. Did they learn how to get a food pellet simply by watching a Demonstrator?

When tested on their own, all four Observer turtles chose the correct bottle: if their Demonstrator had to knock over the black bottle, the Observer chose the black bottle; if their Demonstrator had to knock over the white bottle, the Observer chose white. But the funny thing is that the Observers simply approached the correct colour of bottle or just touched it with its snout. They did not attempt to knock over the bottle, like their Demonstrator had done. I wonder why? The scientists aren’t sure either. Maybe the Demonstrator turtles’ big shell blocked the view of the Observers so they couldn’t see exactly what the Demonstrator did to knock over the bottle? More research could perhaps provide an answer.

The cool thing is that turtles learned from other turtles which bottle to choose. And I think it’s neat that the Demonstrators had their own way of knocking over the bottles. This research scratches the surface of what is going on in those reptilian brains. What else is waiting to be discovered? Maybe turtles have more of a “social life” than we think.

Two Florida Red-bellied Cooters. I wonder if they are communicating with each other somehow? Source: iNaturalist.

Reference

Davis, K. M., & Burghardt, G. M. (2011). Turtles (Pseudemys nelsoni) learn about visual cues indicating food from experienced turtles. Journal of Comparative Psychology, 125(4), 404-410. DOI: 10.1037/a0024784

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Baby Long Legs! And a First Look into the Mind of the Giraffe

By Posted on 5 min read 516 views

A baby giraffe was born the other day at the Toronto Zoo! I’m so excited. Her name is Baby Long Legs. Take at look at her here.

Welcome to the world, Baby Long Legs!

I’ve been meaning to talk about a really cool research study that was done with giraffes so now is the perfect time, to celebrate Baby Long Legs!

We know quite a bit about giraffe biology, their behaviour, and their interactions with their surroundings, but as far as I know, nothing is known about their cognition: what goes on inside their head. Until now!

A group of scientists from Spain and Germany noticed that like chimpanzees, giraffes live in fission-fusion societies and eat quite a variety of plants. A fission-fusion society is where animals come together into groups, but over time separate, perhaps come back together, or form different groups. For example, a large group of animals may form smaller groups while they are eating or sleeping throughout the day.

Chimpanzees are well-known for being quite intelligent. (I’ll have to write a blog or two about them some time. They are amazing.) So if giraffes are similar to chimpanzees in certain ways, could they be intelligent too? The scientists decided to design some experiments to find out if they could get a glimpse into giraffe cognition.

Where to start? Well, one of the most basic things we can do is realize that the world is made up of objects that are separate from our own bodies, and that these objects exist in time and space. Taking this a bit further, we can also realize that objects continue to exist even if we can no longer see them. Scientists call this object permanence. Object permanence develops gradually in humans when we are babies, but it also occurs in other primates and birds such as corvids and parrots. Are giraffes capable of object permanence?

One way object permanence is tested is by showing the animal an object that it really likes (such as a piece of food), then hiding it under one of several identical opaque containers, and allowing the animal to choose which container the food or object is hiding under. If the animal picks the correct container on its first choice, it has passed the test of object permanence.

This is what the scientists did with three giraffes from the Barcelona Zoo and three giraffes from the Leipzig Zoo. They separated each giraffe inside their indoor enclosures. An experimenter approached each giraffe with two containers. The giraffe watched as the experimenter placed a piece of apple or carrot (depending on what that particular giraffe liked best) in one of the containers. The experimenter then closed both containers and presented the containers to the giraffe to make a choice. If the giraffe chose the container that held the apple or carrot, this was evidence of object permanence.

An experimenter showing the contents of the container to a giraffe before closing the lids and allowing the giraffe to make a choice. One of the containers holds apples or carrots. Source: Journal of Comparative Psychology.
A giraffe choosing one of the containers. Look at that beautiful tongue! Source: Journal of Comparative Psychology.

So, how did the giraffes do? They overwhelmingly chose the container with the food! They showed evidence of object permanence.

(I should note a couple of things before moving on. It is important that the giraffes did not choose the correct container simply because they could smell the food inside. The experimenters did a test where they hid the food in one of the containers and the giraffes didn’t see which container the food was placed in–they were just presented with two closed containers. In this case, the giraffes chose the container with the food only half the time, which is what we would expect if they were just choosing containers randomly. This means the giraffes could not choose the correct container based on smell. The other important point is that whether they mean to or not, the experimenter could give subtle cues to the giraffe about which container to choose. To prevent this, the experimenter closed their eyes when they presented the giraffes with the containers. The experimenter could tell which container the giraffe chose because they could feel the giraffe bunt it with its nose or touch it with its tongue (see photo above).)

But the scientists did not stop there. Next they gave the giraffes a memory test. After closing the lids of the containers, the experimenter waited 30 seconds, 60 seconds, and then 120 seconds, before allowing the giraffe to make a choice. (In the experiment described above, the delay between closing the lids and allowing the giraffes to choose was only 2 seconds.) In this case, giraffes still correctly chose the container with the food after a 30 second delay, again showing object permanence. But for the 60 second and 120 second delays, they chose the correct container only half the time. This suggests that maybe giraffes have limits to their memory or attention.

For their last experiment–and this is really cool–the scientists wanted to see if giraffes could choose the container with the food based on sound cues. The experimenter turned their back on the giraffes while putting the food in one of the containers, so the giraffe couldn’t see which container held the food. With both containers closed, the experimenter turned around to face the giraffe and shook the container that held the food, which made a loud rattling sound. The giraffes chose the container with the food!

Then, instead of shaking the full container, the experimenter shook the empty container. In this case, the giraffe would have to figure out that the container that was shaken did not contain anything, so they could have to choose the other container, which contained the food. Unfortunately, the giraffes had a hard time with this situation and did not choose the correct container very often. As the scientists point out, the giraffes might not have been using sound cues at all but instead chose the container that was shaken. This would result in the correct choice when the full container was shaken, but not when the empty container was shaken.

A clever thing the scientists did was keep track of the giraffe’s body position throughout the testing. After seeing which container was full, did the giraffes simply turn their body towards the full container as a trick to remember which container to choose? Turns out sometimes the giraffes did this, but they did not use this tactic consistently. The most successful giraffe, Ashanti, never seemed to use her body position at all. Whether or not giraffes adjusted their body position to ensure they chose the correct container, I think the results of these experiments show that giraffes are quite clever! And also, given that giraffes were successful participants in these experiments, this paves the way for more discoveries to be made about giraffe cognition.

Which makes me marvel at what must be going on in Baby Long Legs’s mind as she explores this big new world around her. Welcome, Baby Long Legs!

Baby Long Legs and her mom. Source: blogTO.

Reference

Caicoya, Á. L., Ensenyat, C., Amici, F., & Colell, M. (2019). Object permanence in Giraffa camelopardalis: First steps in giraffes’ physical cognition. Journal of Comparative Psychology, 133(2), 207-214. http://dx.doi.org/10.1037/com0000142

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Sharks and Music

By Posted on 5 min read 304 views

Animals that live under water can use sound to find prey, escape from predators, and find their way around. For example, a fish in distress who is thrashing around can alert a bigger fish that a tasty morsel is nearby.

Sharks are one type of fish that can rely on sound to catch their next meal. As far as we know, sharks don’t make any sounds themselves (unlike, for example, dolphins, who communicate using clicks and squeaks and other sounds. Which is incredibly cool. I’ll have to blog about dolphins some time). Sharks do have an inner ear, though, and tests have shown that they can detect certain frequencies.

A couple of scientists in Australia decided to see whether sharks can learn where to get food based on music cues. Scientists have studied the behaviour of sharks for a long time, often using things that the sharks can see, rather than hear. These two Australian scientists realized that we don’t know much about how flexible sharks can be in terms of learning things about sound cues. So, they designed an experiment with Port Jackson sharks–a species of shark that we know relatively little about when it comes to cognition, or mental processes.

Some info about the sharks: Port Jackson sharks (we’ll call them PJs for short) live along the coast of Australia. Here is a map with orange dots showing where these sharks have been sighted:

PJs are benthic sharks, which means they hang out around the ocean floor. They eat sea urchins, molluscs, crustaceans, and fishes. As you can see from the photo below, PJs don’t have the big, ferocious-looking teeth that sharks are usually known for. But their bite can still pack a punch!

Source: iNaturalist.

On the smaller side of sharks, male PJs generally grow to only 75 cm in length, and females grow 80-95 cm. (75 cm is roughly the length of a grown man’s arm.) PJs are pretty harmless to humans, as you can see from this short, up-close video that a scuba diver took of several PJs:

So, back to the music experiment. The scientists used eight young PJs (four male, four female) that had been raised at the Sydney Institute of Marine Science (SIMS) from wild-caught eggs. (Click here to learn more about SIMS.) The sharks lived in huge seawater tanks and once the scientists’ experiment was finished, all of the sharks were released into the wild where their eggs had been found.

The scientists put a special arena into a tank of seawater:

A diagram of the arena the scientists used in their music experiment. Source: Animal Cognition journal.

Only one shark was ever in the arena at a time, and they gave the PJs lots of opportunities to swim around the arena to get used to it. The scientists actually gave each of the eight PJs a “boldness score”: They placed the shark in the start box with the sliding door closed, and when they opened the door to give the shark access to the rest of the arena, they timed how long it took for the shark to come out and explore. It turns out the male PJs were more shy than the female PJs: they took longer to come out of the start box.

So, where does the music come in? As you can see in the diagram above, there was a speaker at the opposite end of the arena. The scientists played a 20-second clip of a jazz song after the shark was let out of the start box. (They were careful to select a clip that had sound frequencies that were within the sharks’ hearing range.) For half of the sharks, if they swam to the far right-hand corner of the tank when they heard the music, then they got a prize: a tasty piece of squid (the sharks’ favourite food!). For the other four sharks, if they swam to the far left-hand corner of the tank when they heard the music, they got some squid. So, the sharks had to learn that the music was a cue to swim to a specific corner of the arena.

(Click here to listen to the jazz music that the sharks heard.)

As a test, the scientists played the music a few times and did not give the sharks any squid, to see if the sharks would swim to the correct corner. Five of the eight sharks passed the test: they learned to swim to a specific corner of the tank when they heard the jazz music.

Next, the scientists added classical music to the mix. Again, they chose a 20-second clip that had sound frequencies that the sharks would be able to hear. This time, if the PJs heard the jazz music they were to swim to the same corner as before to get some tasty squid. However, if the heard the classical music, they had to swim to the opposite corner to get squid. In other words, the type of music that was played to the sharks told them which corner to swim toward.

(Click here to listen to the classical music that the sharks heard.)

Interestingly, the sharks did not do well at this task. They kept swimming to the far right corner of the tank, regardless of which music was played. Even the five sharks who, in the previous task, learned to swim to the left when jazz music was played, swam to the right. In other words, the five sharks who were successful before did worse in this task. Why did all the sharks favour the right side of the tank so much? We’re not sure.

So there was no evidence that the PJs were able to tell the two types of music apart. Or, if they could tell them apart, their behaviour certainly didn’t show it. And remember how the scientists scored the “boldness” of each shark at the beginning of the experiment? Well, it turns out “boldness” did not have an effect on the sharks’ learning ability (or lack thereof).

It is possible that the five PJs who originally swam to the correct corner of the tank learned the simple rule of “swim to the right (or left) corner of the tank,” and basically ignored the jazz music. They figured out how to get a squid meal using the simplest way possible. They didn’t need any music. Pretty bright if you ask me.

To learn more about PJs, click here to check out the Australian Museum.

Reference

Vila Pouca, C., & Brown, C. (2018). Food approach conditioning and discrimination learning using sound cues in benthic sharks. Animal Cognition, 21, 481-492. https://doi.org/10.1007/s10071-018-1183-1

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Self-Control in Crows: Can They Wait for a Better Prize?

By Posted on 0 Comments 5 min read 498 views

In a now-famous experiment, researchers placed a marshmallow in front of a child and told them that they could eat the marshmallow now, or, if they waited 15 minutes, they could have two. The researcher then left the room. If the child couldn’t wait for 15 minutes they could ring a bell to alert the researcher, and then they could eat the marshmallow. But if the child held out for the full 15 minutes, the researcher returned and gave them a second marshmallow.

Photo courtesy of ScienceNews.

Fifteen minutes is a heck of a long time to stare at a marshmallow you’re trying not to eat. I don’t know about you, but I’d fail this test! The researchers kept in touch with the kids who participated in the experiment. They found that kids who were able to endure the torturous 15 minutes in order to get two marshmallows instead of one, tended to do better in school and show success in other areas as well.

Psychologists use the fancy name delayed gratification to refer to this ability to wait for a better result. Delayed gratification is a form of self-control, and it is an important building block for things such as decision making and future planning. Kids tend to get better at delayed gratification as they grow older: 5-year-olds are generally better at waiting for two marshmallows compared to 3-year-olds.

Are other animals, besides humans, capable of delayed gratification? It might be no surprise that monkeys and great apes like chimpanzees are able to wait for a better result. In some cases, they even held out longer than adult humans! One species that shows great potential for delayed gratification is New Caledonian crows. They are impressive little tool-users, often using twigs to fish grubs out of logs. Given their incredible problem solving abilities, are they also able to wait for a better prize?

New Caledonia is an island off the coast of Australia:

Photo courtesy of Encyclopedia Britannica. For more information on New Caledonia, look here.

A group of scientists travelled there and caught nine wild New Caledonian crows using nets. The scientists kept these crows in a large aviary during the experiment. The crows were given the names Jupiter, Mars, Triton, Neptune, Io, Mercury, Venus, Uranus, and Saturn. Then, once the experiment ended, they set all the crows free where they were originally caught.

First, the scientists had to find a prize for the crows that the crows really liked. It turns out that they don’t mind apple slices but they really like pieces of meat. The scientists kept this in mind for their experiment. (The scientists didn’t feed the crows marshmallows. Do crows even like marshmallows? I’m not sure…but marshmallows would be a terrible thing to feed crows anyway! Much better to offer them food similar to what they would find in the wild.)

The contraption that the scientists used was quite cool. It was a large, round platform that rotated by remote control. The scientists placed the platform in a clear plastic box with an opening on one side, so the crows could only grab something off the platform if it was right in front of them.

The platform that was used to test delayed gratification in New Caledonian crows. It is enclosed in a plastic box, and crows can only grab something from the open end. In this photo are two objects to show where the food was placed. In this instance the crow could access the object in front, but could not access the object in the back until the platform rotated. Bottom centre of the photo is a large stick that was a perch for the crows. Photo courtesy of Animal Cognition journal.
A crow waiting to snatch something off the platform. Photo courtesy of Animal Cognition journal.

For the test, the scientists placed one piece of meat in one spot on the platform, and a pile of several pieces of meat in a second spot on the platform. They then left the aviary to let the crow swoop down to investigate. (The crows were very shy of people. They only checked out the platform if no one else was in the aviary with them.) When the crow was perched on the branch in front of the platform, a scientist activated the platform by remote control. After five seconds, the one piece of meat appeared in front of the crow, ready to be snatched up. However, if the crow waited fifteen more seconds, then the one piece of meat would have passed by and instead, the pile of meat would be there for the taking. The crow could only make one choice: grab the one piece of meat that was immediately available, or wait and grab the pile of meat. Once the crow made its choice, a scientist entered the aviary, the crow was spooked and flew away, and the experiment ended.

Remember how crows preferred meat over apple slices? Well, in a second test, the scientists put apple slices in position 1 and pieces of meat in position 2 (which rotated past, 15 second later). So the crows could take the less-liked food right away, or they could wait for the better-liked food.

So, what happened? In every case, the crows could pick one of two choices: the food immediately in front of them, or the food that took longer to arrive. If the crows just chose at random, we would expect them to choose the food immediately in front of them 50% of the time, and the food that took longer to arrive the other 50% of the time. It turns out, crows picked the bigger pile of food, and the meat over the apple slices, well above 50%. They certainly showed the ability to delay gratification. Interestingly, they were “better” at delaying gratification during the test with the apple slices versus meat, compared to the test where one piece of meat was pitted against a pile of meat. In other words, they were better at choosing between quality versus quantity. We’re not sure why that is.

Monkeys have also been tested with a similar set-up, where if they wait fifteen seconds, they can grab a better prize off the platform. These crows seem to be in league with those primates! And also, arguably, with humans. What would happen if the delay was increased? Are crows able to hold out longer for more meat, just as the kids did for their marshmallows? It remains to be seen!

Want to learn more about the amazing things that crows can do? Check out this fantastic book:

Reference

Miller, R., Frohnwieser, A., Schiestl, M., McCoy, D. E., Gray, R. D., Taylor, A. H., & Clayton, N. S. (2020). Delayed gratification in New Caledonian crows and young children: Influence of reward type and visibility. Animal Cognition, 23, 71-85. https://doi.org/10.1007/s10071-019-01317-7