Risk Mitigation Strategies and Health Management in Reptile Reintroduction Programs
Captive breeding, headstarting, translocation, and reintroduction are valuable tools to augment conservation efforts for endangered and threatened reptiles. Potential risks of these conservation strategies include inadvertent introduction of novel diseases to free-ranging populations and challenges in achieving high standards of management and husbandry in low resource locations. To maximize success and mitigate potential risks in these projects, attention should be focused on both medical and the non-medical considerations. Risks commonly recognized by veterinarians and herpetologists experienced with range country recovery programs include infectious diseases, suboptimal nutritional plane, and adverse consequences of inappropriate management and husbandry. The following examples from projects conducted by the Wildlife Conservation Society (WCS) and our partners illustrate risks and mitigation strategies.
One effective and efficient approach to minimize potential risks associated with parasitic and infectious diseases are to locate propagation and holding facilities within the species natural range, and only include individuals from within the natural range in these programs and facilities. These straightforward biosecurity measures limit the risk of novel disease introduction. Housing animals outside their natural range also potentially exposes these animals to vectors (e.g., hematophagous insects and arachnids) that can transmit novel pathogens like hemoparasites or other infectious organisms. Any infectious organism can be pathogenic if introduced to naïve populations. Incorporation of animals that originate from outside the captive population’s natural range are potentially of greater risk, including when those animals originate within zoos or private collections. Those settings are more likely to expose animals to pathogens from a range of species or vectors originating in other geographic regions, which can have devastating impacts if introduced to novel hosts. The projects described herein are all within the species natural ranges and with rare exceptions that occurred before these protocols were developed are composed entirely of individuals from within the range.
A long-term commitment to these programs and periodic health assessments are valuable to both enhance individual and population level health. It is important to perform individual health evaluations of release candidates to ensure the individual is healthy before release, perform diagnoses of ill animals, and perform necropsies of those that die, to determine causes and patterns of morbidity and mortality. Compilation of individual health results also provides health information at the population level. Consistent long-term health monitoring by the same team provides a relationship with those managing the program, and a base for comparison of health and disease over time. An example of this is the veterinary support that WCS has provided since 2001 for the National Trust for the Cayman Islands Blue Iguana Recovery Programme in Grand Cayman. The program’s success resulted in significant augmentation of the wild population due to release of captive animals and subsequent sustained reproduction in the wild. In 2015 a novel Helicobacter spp. infection caused morbidity and mortality of captive and free ranging Grand Cayman iguanas (Cyclura lewisi) on Grand Cayman. Because of the longstanding WCS health dataset for this population, we could confidently determine that this disease had not been previously recognized as a cause of morbidity or mortality in these populations. Molecular analysis demonstrated the causative Helicobacter sp. was a novel species most closely related to other reptilian Helicobacter spp., likely harbored by an unknown local host, and investigations are underway to determine its source.
Pathogen spillover to wild populations is generally recognized as significant potential risks for reintroduction and headstarting programs. Ideally and when possible, infectious disease screening of the wild populations should serve as the gold standard for comparison with captive populations in both the range country and other locations. Unfortunately, some wild populations are so depleted that this is not possible, such as in the case of the Burmese star tortoise (Geochelone platynota) in Myanmar that went functionally extinct in the wild before disease screening could be conducted. A joint WCS/Turtle Survival Alliance (TSA)/Myanmar Forestry Department captive breeding program was established within Myanmar resulting in recovery of a robust captive population and subsequent successful reintroduction. Pathogen screening of this captive population was conducted, much of it using portable molecular testing performed in Myanmar. The results clearly demonstrated that a number of infectious diseases that had been observed in this species at zoos and private collections in North America and Europe were absent in Myanmar. The recognition that pathogens found in captive populations in other countries are absent from the Myanmar population clearly indicates an inherent risk of novel disease introduction posed by tortoises from outside the country to this captive breeding population. Similar infectious disease screening is underway for captive populations managed by WCS and TSA for Southern river terrapins (Batagur affinis edwardmolli) in Cambodia and Burmese roofed terrapins (Batagur trivittata) in Myanmar. Baseline infectious disease status of wild populations and range country captive colonies serve as useful comparisons to mitigate risks posed by populations from outside the range.
Optimal management and husbandry is critical to ensure animals are in ideal condition for growth, survival after release, and reproduction. In some low resource locations within the natural range of species, provision of appropriate expertise, facilities, and resources can be challenging. In addition to infectious disease screening and health assessments, results can provide insights to the population’s nutritional plane and general fitness and condition. Health screening of Burmese roofed terrapins in Myanmar and Southern river terrapins in Cambodia revealed lower than expected blood total protein values indicating a suboptimal nutritional plane. Diet adjustments are underway to resolve the hypoproteinemia that will result in turtles that are healthier for both captive breeding and release to the wild.
When properly managed, captive breeding, headstarting, translocation, and reintroduction programs can make valuable contributions to reptile recovery programs. Veterinary involvement can enhance the success, and mitigate the risks, in these valuable conservation programs.
The authors thanks the Wildlife Conservation Society veterinarians, veterinary technicians, and field conservation staffs who contributed to these projects. Throughout we worked closely with our partners, the Turtle Survival Alliance and the Blue Iguana Recovery Programme, without whom these programs and procedures could not have been accomplished. Wildlife Reserves Singapore kindly shared Batagur sp. hematology data from their zoo collection for comparison with the results from Batagur sp. in these range country facilities.