Hot off the press! Roommates are not all they’re cracked up to be (if you’re a lizard)

Recently, myself and collaborators published our study that found – social experience has a crucial role in development of a family-living lizard. We also discovered that despite their social nature, the Australian tree skink (Egernia striolata) does not necessarily thrive in a ‘share-house’ environment.

Egernia striolata from Gluepot, South Australia


Group- and family-living animals, like humans, birds, and mammals, tend not to cope well if they have to grow up alone. Individuals seem to require particular social experiences that appropriately guide their development. If instead, they grow up alone, individuals tend to be more fearful, more anxious, and less social. These differences in behaviour can also greatly impact an individual’s survival and mating success.

Despite a lot of interest in the role of social experience in the behavioural development of birds and mammals, there has been limited research on how early experience influences later social behaviour in reptiles. Although, research on hatchling veiled chameleons (Chamaeleo calyptratus) found that offspring raised in isolation were more submissive during social interactions and had lower performance in a foraging task, which could indicate reduced sociability and boldness. Also viperine water snakes (Natrix maura) that were incubated in isolation were less social than water snakes incubated in contact with other eggs. These studies found that the presence/absence of social cues during development affected reptile behaviour, but the nature and degree of social interactions with others can also affect juvenile development (e.g., bronze anole, Anolis aeneus). Yet, none of these reptiles are known to live in stable, family groups with parents and siblings. In fact, currently there are only a few documented cases of family-living in lizards, so tree skinks offer a unique opportunity to study how early social experience influences development of a family-living reptile.

In this study, just published in Royal Society Open Science, we raised tree skinks alone or paired with another juvenile and then we repeatedly measured their behavioural traits (exploration, boldness, sociability, and aggression) 4 times across their first year of life. This was a lot of work, and involved watching over 1500 hours of behavioural videos after the 2 years of data was collected!!! We also quantified the type of relationship that each skink formed with its ‘roommate’.

Personality in tree skinks from The Lizard Lab on Vimeo.

The behavioural assays procedures we used in this study

We expected that growing up alone would negatively affect tree skink behavioural development. However, the skinks who were raised alone were not affected negatively in the way that often affects family-living birds and mammals.

Interestingly, within the social environment a dominant-subordinate – or ‘bullying’ – relationship formed, and this relationship affected both the physical and behavioural development of the skinks. Tree skinks grew more slowly in a social environment, as well, the subordinate member of a pair lost their tail more often than any of the other skinks (likely due to aggressive encounters with their ‘roommate’).




Socially-reared skinks grew faster, and subordinate skinks had a higher rate of tail loss

In terms of behavioural differences – the dominant skinks became bolder as they aged, perhaps because as they grew larger or ‘won’ in more social interactions they were more likely to exhibit risky behaviour. In contrast, subordinate skinks were the least social and increased in aggression over time, perhaps suggesting that after aggressive encounters with their roommate these skinks may have learnt to avoid social interactions and react aggressively to fellow lizards. These findings show that feedback in social relationships affects juvenile development – and particularly subordinate tree skinks within a pair appeared to pay the price of living with a dominant roommate.

Interestingly, our study was also able to tell us a little bit about how consistent juvenile tree skink behaviour may be. If an individual’s behaviour is consistent over time, this is often referred to as ‘personality’ in the field of animal behaviour. Yet, our study found that the repeatability of tree skink behavioural traits was quite low over their first year of life – perhaps individuals are more sensitive to change while a juvenile than an adult. Currently, only a few studies have examined the development of personality traits, and our results corroborate previous work that found juvenile personality is not temporally stable.




Tree skink behaviour was not consistent across their first year of life

All in all, our study showed that a tree skink’s early social experience – either positive or negative – affects its physical and behavioural development. This is an important insight into the life and biology of reptiles, an under-studied taxon in regards to social behaviour.

We hope that our findings will be informative for reptile conservation and management projects, as well as ethical considerations a zoos and aquaria – as we show that isolation rearing does not consistently impact behaviour across all social taxa. In fact, tree skinks appeared cope well in isolation rearing, perhaps due to existing social variation within wild rearing conditions.

Finally, we hope this study adds to our understanding of behavioural development across all social taxa. Environmental factors (e.g., predation pressure, incubation temperature, nutrition) are known to impact development and cause behavioural divergence. Our study highlights that both a lack of social interaction and the nature of social interactions are other factors that can potentially drive change and divergence across behavioural development.

Article reference: Riley, JL., Noble, DWA., Byrne, RW., Whiting, MJ. 2017. Early social environment influences the behaviour of a family-living lizard. Royal Society Open Science. (doi:10.1098/rsos.161082)

Link to the Macquarie University press release: http://www.mq.edu.au/newsroom/2017/05/03/roommates-not-all-theyre-cracked-up-to-be-if-youre-a-lizard/ (there is some repetition between this article and blog)

Hot off the press! Toads at the invasion front are more prone to explore and take risks

By Jodie Gruber

The cane toad (Rhinella marina) has been spreading rapidly across northern Australia since its introduction to control sugar cane beetles in 1935. While toads have been the focus of considerable research, we still have a poor understanding of how behavioiural traits vary across the range, particularly with respect to traits that . . . → Read More: Hot off the press! Toads at the invasion front are more prone to explore and take risks

Julia Riley interviewed on ABC radio!

Take a listen to Julia Riley discussing our latest publication on the influence of social environment on learning in tree skinks (Egernia striolata). The interview was with Marc Fennell on ABC radio.

This work, led by Julia, has been published in Animal Cognition:

Riley, JL., Noble, DWA., Byrne, RW., Whiting, MJ. 2016. Does social . . . → Read More: Julia Riley interviewed on ABC radio!

Skinks and Ladders: A family-living lizard’s learning ability is not affected by their home environment

By Julia Riley

A family-living lizard’s ability to navigate through a complex maze is not linked to how they were raised

We have found that the learning ability of the Tree Skink, a lizard that lives with family, is not linked to growing up with others. These lizards were . . . → Read More: Skinks and Ladders: A family-living lizard’s learning ability is not affected by their home environment

Dispatches from the field: frogging at the DMZ

After attending the 8th World Congress of Herpetology in China, I had a night and a day in South Korea before flying on to my next destination, the US. What to do? As it turned out, I had a windfall (thanks Julia). I met Amaël Borzée, a PhD student from Seoul National University. Amaël . . . → Read More: Dispatches from the field: frogging at the DMZ

The 8th World Congress of Herpetology

Note: the following post is by Julia Riley and also posted on her web page.

On 14 August 2016, a small contingent of the Lizard Lab headed from Sydney, Australia to Hangzhou, China for the 8th World Congress of Herpetology. Our fearless leader, Martin Whiting, as well as James Baxter-Gilbert and I were the Lizard . . . → Read More: The 8th World Congress of Herpetology

The Slow Professor: Challenging the Culture of Speed in the Academy

Book Review

A Riley & Whiting Collaboration

Julia Riley’s Review:

First, I would like to say as an expat Canadian researcher, I am happy to say that two Canadian professors wrote this book! Woot!

This book proposes a means to tackle the effect corporatization of higher education has on universities. Their ‘Slow’ Professor Manifesto . . . → Read More: The Slow Professor: Challenging the Culture of Speed in the Academy

Why do winners keep winning?

by Fonti Kar

Animals often find themselves in direct competition with other individuals for resources and mates. Because fighting is costly, many species honestly signal their fighting ability to avoid injury (non-escalated fights). For example, in flat lizards (Platysaurus broadleyi), males can resolve dominance status by displaying their UV-reflective throats to their opponent. . . . → Read More: Why do winners keep winning?

Awesome new mini-documentary on Julia Riley’s PhD and social lizards!

Lizard Lab associate and honorary member Dr. James O’Hanlon has produced a fantastic mini-documentary about Julia Riley’s PhD work on tree skinks (Egernia striolata) and family living.

The documentary offers some great views of our Albury study site and the amazing lizards! It asks the question why are animals social, and talks about what . . . → Read More: Awesome new mini-documentary on Julia Riley’s PhD and social lizards!

Lizard Lab word cloud

Lizard Lab word cloud based on titles and key words from about 35 recent papers. Martin made this instead of working on an important research grant. It somehow seemed much more fun at the time. It does nicely sum up the research in the lab . . . → Read More: Lizard Lab word cloud