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Lizards learn from their elders too!

Social learning—the ability of an animal or human to acquire information by learning from the actions of others is a short-cut to solving many of life’s problems or simply acquiring information more quickly. Just think back to when you got your first video recorder all those years ago, or satellite TV, with a remote with more functions than a space shuttle. Who wants to spend hours poring over an instructional manual when an older person can show you what you need to know in a matter of a few minutes? That way you can get to watching and recording your favourite programs in no time.

Social learning was always thought to be the hallmark of highly intelligent primates and birds. And indeed, we see chimps and crows learning to use tools by watching group members in action. More recently, social learning has been documented in a much wider range of species including insects, turtles, fishes and tadpoles. This should not be all together surprising, because natural selection should select for animals capable of rapidly acquiring essential information that will ultimately give them the edge over rivals.

Martin and I teamed up with Richard Byrne from the University of St. Andrews in Scotland, to conduct the first test of social learning in a lizard which has recently been published the the Royal Society journal Biology Letters. We used our favourite lizard, the Eastern Water Skink (Eulamprus quoyii), since we have been working with them since 2010 and we have previously shown that they can learn quite rapidly. We used two groups of lizards based on their age: ‘old’ lizards that were about 5 years old and ‘young’ lizards that were 1.5-2 years. We began by training a group of demonstrators to solve a task that involved them having to flip a lid off a dish in order to acquire a nice juicy mealworm. We then randomly allocated lizards either to a social learning treatment where they would see a demonstrator conduct the task, or to a control, where they would see another lizard but without them doing the task. The lizards were separated from each other by a piece of see through plastic. Both young and old lizards were put through two different tasks differing in their complexity. Check out the video at the bottom of the post to see a lizard in action!

A lizard with the two food dishes

A water skink with the two food dishes it had to choose from.

Our favourite water skink...enjoying the beach!

Our favourite water skink…enjoying the beach!

 

 

 

 

 

 

 

 

 

 

 

 

 

The results were somewhat surprising. Old lizards did not appear to use social information in any significant way and learnt to solve the tasks at much the same speed as the control group. Young lizards on the other hand, did pay attention to social information and learnt to solve the second task faster than both the control group, and old lizards. There may be several reasons for this interesting result. Young lizards may stand to benefit more than older lizards by paying attention to the life lessons of other lizards. Alternatively, they may also have more opportunity for social learning because adults are less tolerant of rivals and more likely to chase adults away than they would a juvenile. Lizards can now be added to the growing list of animals capable of social learning. Furthermore, they can also be added to the much smaller list of animals in which we know that social learning is age-dependent.

If you’re interested in reading more about our paper you can access it from my publications page HERE or visit the link below:

Age-dependent social learning in a lizard, Biology Letters 2014, Daniel W. A. Noble, Richard W. Byrne and Martin J. Whiting, http://dx.doi.org/10.1098/rsbl.2014.0430

 

 

Athletic lizards: Sex, hormones, and physical performance

When it comes to animal athletics lizards have been model systems for exploring the relationships between ecology and physical performance. Our two recent papers, one in the Biological Journal of the Linnean Society and the second in Behavioral Ecology add to the growing list of studies looking at functional performance in lizards.

Cover_image_Biology_Letters

Water skink basking on a log (Eulamprus quoyii)

Water skink basking on a log (Eulamprus quoyii)

In our first study, we explored the proximate underpinnings of physical performance in lizards and tested what might drive differences in performance between the sexes. Sex-dependent performance is found in many animals, including humans. Males tend to excel in activities such as running and jumping. The same is true for many lizards. But why are males better athletes than females? This is actually a very difficult question to answer because males differ from females in a number of different ways. For example, aside from hormone differences between the sexes, males are often larger than females and as a result differences in size can allow males to dominate in performance related activities.  One way to get around this is to control for size, but how can we do this? Well we could explore functional relationships in species that are not strongly sexual dimorphic because physiological traits that scale with size should be much more similar between the sexes. This provides a unique opportunity to explore how proximate mechanisms, such as hormones, affect the physical abilities of males and females and whether such physiological traits drive performance differences between the sexes.

Measuring lizard biting

Measuring lizard biting

Measuring lizard endurance on a human treadmill.

Measuring lizard endurance on a human treadmill.

Measuring lizard speed from a lizards eye view

Measuring lizard speed from a lizards eye view

 

 

 

 

 

 

 

 

In our recent paper published in the Biological Journal of the Linnean Society we tested whether a key hormone, thought to be different in males and females, was a driver of performance differences using our familiar and charismatic lizard species, the Eastern Water Skink (E. quoyii). The cool thing about E. quoyii is that males and females are of similar body size (at least in length). The notorious hormone I speak of above was testosterone. Testosterone is known to be an anabolic (build up) hormone, promoting muscle and body growth. It also affects a whole suite of other physiological parameters. We predicted that differences in circulating testosterone may be one reason why performance may vary between individuals and possibly explain any sex differences in performance. In our study we collected over 200 lizards and took measurements of their androgen levels (testosterone-like hormones) and tested whether: a) it varied between the sexes and b) whether it was positively related to performance in males and females. What we found was interesting. First, as expected males and females did not differ in body length, but did differ in mass and head size with males being heavier and having larger heads. We also found that males were far better performers than females. They ran faster, longer and bit much harder than females. However, surprisingly, we found no differences at all in the levels of circulating hormone concentrations between males and females and also found that it was not related to any of the performance traits. Despite this, we found huge variation in hormone levels, from individuals with virtually non-detectable levels to ones having orders of magnitude higher concentrations. We also found that androgen concentrations may not be related to performance in a simple linear way in males (although much more work needs to be done on this front). The jist of our results are that despite no differences in androgens males and females still differ substantially in their athletic abilities and that body size (at least length) and testosterone don’t seem to be the main reasons. However, we suggest that these differences may arise as a result of the development of different limb and head sizes, which contribute to running and biting performance that are likely organized differently among the sexes as they develop. This may have been a result of different sensitivities to androgens at key periods of growth of the limbs and muscle. The differences in the shape between the sexes suggest that differential selection on performance traits occurs between males and females. However, that is another story and for selection to result in evolutionary change these traits need to be heritable. But are they?

In our second study published in Behavioral Ecology, we explored whether running speed and endurance had additive genetic variance and showed evidence of being heritable (traits can be passed on from one generation to the next). Interestingly, we found weak evidence that sprint speed was heritable, but rather it appears to be strongly controlled by the phenotype of the mother. When a mother’s phenotype affects the phenotype of their offspring beyond their genetic contribution, this is called a maternal effect.  These can have very interesting effects on trait evolution. In contrast, running endurance showed reasonably high heritability suggesting that, if selection were to act on endurance, this trait has the potential to respond to selection.

You can read more about our work in the Biological Journal of Linnean Society and Behavioral Ecology by going to my publications page and clicking the relevant links.

 

 

Filming at the Lizard Lab!

It’s been a very busy few months. Martin and I just got back from a great ASH (Australian Society of Herpetology) conference that was hosted by folks at ANU (Thanks Scott Keogh and Mitzy Pepper). Upon our return we were greeted by a Dutch film crew who were interested in learning about our research and filming some cool herps! Freek Vonk is a Dutch scientist and host of a very popular documentary. They were wrapping up there first season of “Freek in Australia” and featured various animals that the lizard lab is currently working on including Cane Toads and Water Dragons. It was a fun day catching and talking about our work.

Martin has all the photos of our adventures catching Dragons in lane Cove National Park with the film crew. You can read all about it and see some really cool pictures HERE! It’s a must see.