Iguanas: Why Move?

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Turks & Caicos iguana

Late 2011 marked the first in a series of experimental iguana translocations on Big Ambergris Cay in the Caribbean’s Turks & Caicos designed to determine the conservation value of moving these large, endangered lizards out of areas slated for development to areas on the island that will not be developed. At first glance you may find it difficult to question the value of moving animals like this. Then again, why wouldn’t you move animals out of the bulldozer’s path? Well, what if the translocated animals simply return home? Or what if their survival in their new habitat is very low? Both of these outcomes are actually quite possible.

Iguanas are territorial animals with small home ranges, and they live a long time. They know their territories well and have invested a lot of time and energy establishing themselves in these areas. This means that animals moved away from their home areas may be highly motivated to return. It also means that iguanas moved to a new area may find they are not welcome by the iguanas already living in that area.

To test these ideas, we moved adult and juvenile animals of both sexes and attached radio transmitters to them to follow what they did. Five out of 12 adults moved (3 males, 2 females) successfully returned to their home areas, and all of those that didn’t return home had tried to. All of the adults moved also lost weight, an indication that they were stressed by the move.

In contrast, none of the 12 juveniles moved returned home, although some did make movements in that direction. The juveniles also lost less weight than the adults, suggesting they may be better candidates for such translocations. To determine if these conclusions are valid, we will need to repeat this experiment to increase our sample sizes. In the end, we will be able to implement a conservation management strategy that makes the best use of limited resources and has the best probability for success.

Glenn Gerber is head of the San Diego Zoo’s Caribbean Regional Program. Read his previous post, Turks Island Boas.