Wild Conservation – A Houston Zoo Blog

In November 2009, a group of veterinarians including the Houston Zoo’s Director of Veterinary Services Dr. Joseph Flanagan, working with the Galapagos National Park (GNP), prepared 39 hybrid tortoises slated to be the pioneer group to initiate the return of tortoises to Pinta Island.  Project Pinta is a multi-year project aimed at the restoration of the island following the successful eradication of goats on Pinta in 2003.  While complete island restoration will require the eventual repopulation of Pinta with a reproductive tortoise population, scientists and managers are awaiting the final results from genetic analyses of a massive sampling of tortoises before making the final selection of which tortoises to use.  To initiate the return of tortoises, critical ecosystem engineers during this important period of vegetative recovery, a special group of tortoises will be released onto Pinta.  To ensure that this group of hybrid tortoises will not compromise any future efforts to reestablish a reproductive population, veterinarians sterilized them.   

Research on giant tortoises in Galapagos during the last 40 years has demonstrated many ways in which tortoises play a major role in Galapagos ecosystems.  Given their size, movement patterns, and use of resting forms (hollowed-out beds created by tortoises for resting), tortoises can affect both the pattern and structure of vegetation.  In addition, grazing by tortoises can help maintain open areas within forests.  Studies of the Galapagos tomato and other plant species have shown a marked increase in germination rates following passage through the gut of tortoises.  Besides scarification of seeds, tortoise scat can provide a rich substrate for germination and growth.  Studies have shown that seeds consumed by tortoises may take from a few days to weeks to be deposited, allowing for seed dispersal over distances of several kilometers.  Probably more than any other native species in Galapagos, tortoises have a major impact on the structure and composition of their environment.   

Tortoises are needed back on Pinta.  With the eradication of goats in 2003, vegetation grew back quickly but without tortoises to engineer the recovery.  Shade-loving plant species are becoming more and more abundant, reducing the available habitat for native and endemic sun-loving species.  Pinta needs a natural habitat engineer, the giant tortoise, to ensure a balanced recovery and to fully restore the island to its near pristine condition.  

While awaiting the final results of the genetic survey, conservation managers took steps to initiate the return of tortoises to Pinta through the use of sterilized adult hybrid tortoises currently held in captivity.  This is considered the best short-term solution to initiate a more balanced recovery. 

Watch our http://www.houstonzoo.org/conservation website in the coming week for more detalis on this project.

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