Interventions & adaptive management
In 2001, the Frégate Island Tortoise Conservation Project was initiated by the Frégate Island Private. We cover this recovery project, although it is not the only effort that has been made, because it seems to have been the most successful at restoring the surrounding ecosystem. According to Gerlach et al, the project was launched in a dual attempt to:
The conservation program primarily involves population monitoring and a juvenile rearing program. In the program, juvenile tortoises are collected and raised until the age of 3 years, after which they are released. The program houses around 200-400 juveniles per year and releases occur about once per year (Gerlach et al, 2013). There is no recorded number of juveniles released although it is thought to be around 150 tortoises (Gerlach et al, 2013).
The program has made various attempts at monitoring species, however all data previous to 2010 was deemed unreliable due to non-methodical data recording (Gerlach et al, 2013). Recently, due to increased attention to endangered species, a census was done in 2010 and it was found that there were 191 +/- 10.8 tortoises on the island (Gerlach et al, 2013). The study also looked at population gender distribution (Figure 1), and the percent recovery per ecosystem. Gaps in age distribution can provide insight into events or factors such as temperature exremes, flooding, etc. that would have led to tortoise death or spike in abundance.
Perhaps the most pertinent issue is the monitoring of which ecosystem is preferred by the Aldabra tortoises. A re-capture program was done over a two week period and the results can be seen above (Figure 2). It can be seen that the tortoises much preferred the “Exotic scrub” habitat. This raises one of the on-going challenges of restoration and adaptive management. One of the key characteristics of restoration is that it must be target driven. Generally, the propagation of exotic scrub is frowned upon – however, in this case if the target of conservation and restoration was to create suitable habitat for the Giant Tortoises, it may be worth looking into introducing more exotic scrub. Whether or not this idea has any merit is dependent on the objectives identified by conservation managers. The Frégate Island Private (FIP) continues to monitor the existing individuals and ensure the survival of the population (FIP, 2015). Conservationists on Frégate Island would most likely benefit from looking at a wider range of factors that could contribute the success of the species.