Surprising Science: A Look Into the Lives of Red-footed Tortoises

This article was written by Animal Welfare Scientist Shannon O’Brien, who is with Lincoln Park Zoo’s Animal Welfare Science Program.

Four male red-footed tortoises reside at Regenstein Small Mammal-Reptile House. However, during the warm summer months you may only find two of these tortoises indoors; this is because the tortoises also have a private outdoor yard to explore.

On days when weather is appropriate, Animal Care staff transport two of the tortoises to their outdoor space, where they exercise, graze on grass, and bask in the sunshine. Curator Dan Boehm says, “Time outside gives the tortoises exposure to natural sunlight with the full spectrum of ultraviolet light,” which is important for their health and welfare. Animal Care staff rotate which tortoises go outside each day, ensuring that each gets plenty of time outside.

Since the tortoises are transported to their outdoor yard in pairs, Animal Care staff and scientists from the Animal Welfare Science Program were interested in whether certain pairs of tortoises got along better than others, as indicated by fewer dominance-related behaviors such as mounting and more friendly, prosocial behaviors such as resting near one another. Additionally, the team wanted to see whether the tortoises’ activity budgets—how the tortoises spend their time—differed when they were outside versus inside.

Time With Tortoises

To answer these questions, intern Addie Diaz, with the mentorship of Animal Welfare Scientist Shannon O’Brien, Ph.D., collected data on the tortoises’ behavior and space use patterns using the ZooMonitor app. Together, Diaz and O’Brien observed the tortoises for 24 days in both their indoor space and their outdoor yard. All four of the tortoises were observed each day, but the pair combinations differed as Animal Care staff randomly selected which two tortoises to transport outside on a given day.

Each tortoise varies in size and coloration, which makes them easily identifiable, and this allows Diaz and O’Brien to assess their individual behaviors and the interactions between individuals. Simply observing the tortoises for extended periods of time also allows their unique personalities to shine. “It was fun getting a sense of the tortoises’ personalities. I felt like I was getting to know them on a personal level,” Diaz says.

What Zoo Scientists Learned

This study revealed that the tortoises tended to engage in more dominance-related behaviors when they were in their indoor space compared to their outdoor yard. Interestingly, dominance-related behaviors decreased when only two tortoises were present in the indoor space, compared to the typical four. Our scientists think that having more space available per tortoise may influence the frequency of dominance-related behaviors.

Additionally, the researchers found that certain pairs of tortoises do seem to get along better, and that size may play a role in their interactions. The two smaller tortoises and the two larger tortoises, respectively, had fewer instances of mounting and greater instances of resting near each other, suggesting that tortoises of a similar size get along better than mixed-size pairs. Zoological Manager Lou Keeley says, “This study will help us decide which pairs to put together based on which were more compatible with one another.”

Reptilian Research

Many species, including popular animals such as tortoises, are understudied in science, but this research highlights the fact that tortoises have complex social lives and may even have preferences for who they spend their time with.

To add to the growing body of knowledge, the Animal Welfare Science Program has conducted multiple studies on reptile welfare that help inform how the zoo cares for these species—and plans to continue its work in this area. Each new study helps zoo staff make evidence-based decisions that support and enhance animal welfare.

Next time you visit the zoo, be sure to check out the red-footed tortoises and other reptiles in Regenstein Small Mammal-Reptile House. Take the opportunity to observe each animal and see their unique personalities shine through their behavior!