Cownose rays (Rhinoptera bonasus) are commonly displayed in touch pool exhibits at accredited zoos and aquariums across the country, but there has been little research to explore how these practices might affect the health of the animals. That was the motivation behind a newly published study in the Journal of Zoo and Wildlife Medicine, which compared health parameters of cownose rays in a public-facing touch pool with those of cownose rays that remained in a larger system off-exhibit. The results found that, despite the difference in habitat and visitor engagement levels, both groups of animals remained clinically healthy.
“Understanding the health differences in animals in living in different aquarium habitats is important for creating and maintaining optimal environments for them to thrive,” said Dr. Jimmy Johnson, DVM, MS, CertAqV, DACZM, the study’s lead author, staff veterinarian at the Columbus Zoo and Aquarium and adjunct assistant professor at the Ohio State University College of Veterinary Medicine. “The results of this study signify that, within the measured health parameters, the cownose rays in the outdoor touch pool remained in comparable planes of health with the rays in the indoor habitat behind-the-scenes.”
The comprehensive, comparative study looked at 58 cownose rays, all living at Chicago’s Shedd Aquarium. 40 of the rays lived in a seasonal outdoor touch pool, while the other 18 were kept off-exhibit in a separate habitat. Throughout the study, researchers looked at 38 different health parameters to identify any changes that might indicate how the rays might be affected by living in the touch pools and engaging with guests. This included physical examinations to determine body condition, ultrasounds to view internal organs, blood gas analysis, blood cell count, plasma protein and cholesterol electrophoresis parameters.
“We recognized a gap in scientific knowledge in this area and looked at nearly every measurable indicator of health to better understand how touch pool exhibits might be impacting the health of these rays,” said Dr. Bill Van Bonn, DVM, vice president of animal health at Shedd Aquarium. “This study is important for maintaining optimal environments for animals to thrive, animal health and welfare is our top priority, so we are proud to have taken the lead on this type of research. We are also happy to report that the rays in our touch pool exhibits remained clinically healthy.”
The research indicated only three statistically significant differences in the health parameters between the two groups of cownose rays:
- Heart rate: The first is that the cownose rays living in the outdoor touch pool had a lower heart rate when compared to the cownose rays living off-exhibit. This can likely be attributed to the fact that the animals habitually engage with guests at the aquarium and have been desensitized to this type of interaction. Water volume and the shape of the habitat may also have played a role.
- Blood Lactate: The levels of lactate in the outdoor touch pool rays was higher than their off-exhibit counterparts. If the lactate levels were associated with a stress response, it was considered minimal, because there were no other differences in other indicators of acute stress such as pH, pCO2, or HCO3between the two groups. The lactate levels were comparable to in-house reference ranges for cownose rays.
- Low-density lipoproteins (LDL): Previous studies have noted that stress or changes in salinity can increase cholesterol levels in elasmobranchs; however these differences were not observed in the present study population. While LDL did increase in the touch pool animals over time, it was still within the published reference range from a clinically normal population of cownose rays living in an aquarium setting.
This study lays the foundation for future research into the wellness of animals in touch pool exhibits, including additional parameters for health and immune stimulation. Other environmental factors, including considering the microbial environment in various habitats, may also provide insights into potential health implications.