Assessing post-release success of rehabilitated odontocete cetaceans

Jan 17, 2012 No comments By and


Important questions have been raised regarding the relative risks and benefits of rehabilitating and releasing stranded odontocete cetaceans, but until recently few data have been available to support an appropriate evaluation.

In the early years of cetacean rehabilitation, success in getting the animals to the point of release was infrequent, but success rates have improved markedly in recent years thanks to increased experience and knowledge and improved diagnostics and facilities.

Concurrently, safe and practical techniques for monitoring rehabilitated cetaceans post-release have become available, especially involving radio telemetry, providing the potential for assessing the success of the animals released back into the wild. Decreased tag size and increased experience with attachments lasting for periods of months have helped to allay concerns about safety risks from the tags themselves.

Recognizing that rehabilitation can be a very expensive undertaking, requiring extended allocations of limited medical, facility, and staff resources, increasing effort has been made in recent years to monitor rehabilitated cetaceans post-release in order to be able to evaluate the success of the treatments.

With support of the NOAA John H. Prescott grants program and collaborative efforts involving Dr. Forrest Townsend, Dr. Frances Gulland, and Rob DiGiovanni, we engaged in a systematic review of post-release success relative to initial cause of stranding, aspects of rehabilitation, treatments, or life history parameters.

We compiled and reviewed 69 cases from 1986-2010 involving 10 species of small odontocete cetaceans.

Of these, 41 cases involved single strandings or rescues, while 28 of the cases involved mass strandings. Thirteen of the bottlenose dolphin cases and all 38 of the cases involving other species were strandings with subsequent rehabilitation efforts. Eighteen bottlenose dolphin cases were rescue captures brought about by entanglement, out-of-habitat, or maternal death situations. Seven of these interventions led to rehabilitation, while the remaining 11 rescues involved on-site examination, treatment if necessary, and release without rehabilitation.

A final report for this review is currently being prepared. Among the preliminary findings is a definition for release success: following release, the cetacean exhibits ranging patterns, habitat use, locomotion, behavior, and social interactions typical for the species, stock or individual, and/or at least does not exhibit abnormal behavior, for a minimum of six weeks. Not all of these data will be available in all cases. To obtain these data, direct visual observations are best, but in the absence of observations, some of these data may need to be inferred from radio-telemetry.

Based on this criterion, 80% of cases were identified as successful or unknown but likely to have been successful. In general, interventions prior to stranding led to higher success rates than did stranding with rehabilitation. Mass stranded individuals demonstrated greater success than single stranders. Young calves without their mothers, old animals, and animals with hearing deficiencies exhibited poor success post-release. In all cases, the importance of post-release monitoring was noted.



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About the author

Randall Wells, PhD, is the Director of the Chicago Zoological Society’s Sarasota Dolphin Research Program (SDRP). He began studying bottlenose dolphins in Sarasota as a high school volunteer at Mote Marine Laboratory in 1970. He received his BA in Zoology from the University of South Florida in 1975, a Master’s in Zoology from the University of Florida in 1978, a PhD in Biology from the University of California, Santa Cruz in 1986, and a Post-doctoral Fellowship in Biology from the Woods Hole Oceanographic Institution in 1987. Employed by the Chicago Zoological Society since 1989, he is a Senior Conservation Scientist, and in this capacity he also manages Mote Marine Laboratory’s Dolphin Research Program. As a Professor of Ocean Sciences (adjunct) at the University of California, Santa Cruz, he serves as major advisor for MS and PhD students, and he is an adjunct Professor with the University of North Carolina, Wilmington, Duke University, and the University of Florida’s College of Veterinary Medicine. Wells was President of the Society for Marine Mammalogy (2010-2012).

About the author

Deborah Fauquier, DVM, PhD, MPVM works with NOAA’s Marine Mammal Health and Stranding Response Program, based in Silver Spring, MD, and she is an Adjunct Scientist at Mote Marine Laboratory in Sarasota, Florida. She also serves as the lead veterinarian for Chicago Zoological Society’s Sarasota Dolphin Research Program’s dolphin health assessments in Florida. She has over 10 years experience working with live and stranded marine animals, and she received her Veterinary and Master’s degrees from the University of California-Davis, and PhD from the University of California, Santa Cruz. Her research interests include investigating the impacts of disease and environmental changes including harmful algal blooms on marine organisms. Her Ph.D. research investigated the effects of red tide on sea birds in Florida.
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