August 02, 2017
By Evan Emmel, Institute for Conservation Medicine Intern
My name is Evan Emmel, and I am a fourth year veterinary student at the University of Illinois at Urbana-Champaign. I have been passionate about conservation and zoological medicine since I began volunteering at the Brookfield Zoo while in high school. Since that first exposure 10 years ago, I have seen first-hand the diverse roles that zoological veterinarians have in the conservation of both captive and wild animals; sparking my serious pursuit of a career in zoological medicine. As a component of my veterinary education, I am working with the Saint Louis Zoo’s Institute for Conservation Medicine under the direction of Dr. Sharon Deem. Our work this summer is part of the larger Galapagos Tortoise Movement Programme (GTMEP) of which ICM is one of the collaborating partners. This program focuses on better understanding the health and movements of wild tortoises in the Galapagos.
Like many reptiles, Galapagos tortoises experience temperature-dependent sex determination. This means that the temperature at which each egg is incubated dictates whether the hatchling will be a male or a female. For most turtle species, warmer temperature during incubation is associated with an increased proportion of female hatchlings, while cooler incubation temperatures are associated with a higher proportion of males. (Just remember cool dudes and hot babes and you will be fine!) As global temperatures rise from climate change, reptile populations may develop an imbalanced ratio of male to female individuals. These demographic alterations may threaten population sustainability if environmental temperatures continue to increase as predicted.
The relationship between temperature variation and hatchling sex ratios had not previously been investigated in wild Galapagos tortoises, so our work this summer aimed at identifying the sex of juvenile Galapagos tortoises on Santa Cruz Island. The juveniles are part of the population that the GTMEP has been studying for eight years. The GTMEP has acquired extensive environmental data for this population, including nesting temperature data for these hatchling tortoises. Unfortunately, juvenile tortoises do not have external features that allow them to be distinguished as male or female. The only way to definitively know the sex of these young tortoises is by visualizing the internal gonads through a procedure called laparoscopic coeloscopy. This procedure involves inserting a small endoscope into the coelom (body cavity) of each individual so that the reproductive organs can be identified. This technique is used in zoological institutions to identify the sex of hatchlings, and we adapted the procedure so that it could be performed in the field on wild tortoises.
While veterinarians played a large role in our project this summer, collaboration with biologists, social scientists and local policy makers is essential for conservation of the Galapagos tortoises. Dr. Deem and Dr. Samuel Rivera, a veterinarian from Zoo Atlanta, lead all of the medical procedures performed in this study. Both Dr. Deem and Dr. Rivera are board certified by the American College of Zoological Medicine and are prime examples of how zoological veterinarians can impact conservation in both in situ (wild)and ex situ (captive) settings. I have been incredibly fortunate to participate in this project and receive training from these outstanding veterinarians. I hope to incorporate similar projects into my future career and follow in the footsteps of zoo veterinarians who work to conserve threatened species.
For now, the data obtained through this summer study will be combined with environmental and nesting temperatures to begin understanding how temperature variations may impact the sex demographics of Galapagos tortoises. This could help guide captive breeding programs and provide early insight into how increased global temperatures may affect Galapagos tortoise populations. When combined with data from the GTMEP projects investigating the migration patterns, ecology, and health of adult tortoises, the information from this study contributes to a large-scale understanding of Galapagos tortoises that will be necessary for developing effective conservation strategies.