Another milestone was reached this month in our efforts, in partnership with the Wildlife Conservation Society, to reestablish a population of wild Burmese star tortoises (Geochelone platynota) in Myanmar. On 4 January 2015 at a wildlife sanctuary in central Myanmar, 300 captive-bred and headstarted subadult tortoises (3-5 years old) were moved from an assurance colony into three expansive holding pens, each encompassing 2 ha (about 5 acres) of natural scrub forest and grassland enclosed within a bamboo fence. Our plan is to hold the tortoises in the pens for varying periods before releasing them later this year.
The idea behind our approach is simple; by penning tortoises for several months, we hope to instill in them some degree of site fidelity, making it less likely they will wander (and perhaps leave the sanctuary) after being released. This “soft-release” strategy draws heavily on research conducted on gopher tortoises (Gopherus polyphemus) in the southeastern United States, which demonstrated that post-release wanderings were negatively correlated with penning period; in other words, those tortoises held for the longest time moved the shortest distances after being liberated. This is a critical consideration in our efforts because the wildlife sanctuary is in effect, an “island” of natural habitat surrounded by a “sea” of agriculture. Should a tortoise wander into the surrounding farmland, it risks being captured by poachers or killed by the ubiquitous free-ranging domestic dogs.
A great deal of fanfare accompanied the transfer of the tortoises into the holding pens. We timed the event to coincide with Myanmar’s Independence Day, and a bevy of local dignitaries showed up to participate in a ceremony presided over by Buddhist monks who dwell in a monastery that sits atop a nearby promontory overlooking the sanctuary. Tortoises figure prominently in local belief systems and we view the involvement of Buddhist clergy as critical to the long-term success of our efforts. As a finale to this ceremony, a local shamaness enjoined the Nats (Earth spirits) to watch over the tortoises and protect them from future harm.
Shortly after the ceremony concluded, we carefully packed the 300 tortoises into wicker baskets and carried them to the holding pens in the bed of a small truck. Dr. Tint Lwin, the project veterinarian gave each tortoise a cursory medical exam (tortoises selected for release were screened for infectious diseases by a veterinary field team led by the Bronx Zoo in October 2014), and then it was weighed and measured before being allowed to amble off into the pen. Although we provide supplemental food for the first few days, many tortoises begin feeding on wild plants within minutes of being liberated. Our plan is to maintain the tortoises in the pens for the next 6-18 months. During this period, each tortoise will be located monthly (no easy task given the size of the enclosures and density of the vegetation), and weighed and measured to monitor body condition and determine growth. The first group is slated for release in June 2015 and transmitters attached to many tortoises will allow us to closely follow their movements. These tortoises will join 150 other captive-bred tortoises that have already been released – or will be shortly – in the sanctuary. Encouragingly, a radio telemetry team following these released tortoises recently came upon two young females (one released in May and the other in November 2014) depositing eggs, an event that marks the first documented reproduction by free-living Burmese star tortoises in more than a decade!