San Esteban & Rasa Islands
Iftecool, “the island of the big lizards” in Seri language, or simply San Esteban Island, has been the scenario of remarkable evolutionary events, like speciation of the native (and endemic) “piedbald” or “giant” chuckwallas. These vegetarian lizards are allies of the common green iguana, and are restricted to the desert areas of northewestern Mexico and southwestern United States. In the Gulf of California islands they have gotten their most important diversity and speciation levels, with at least four endemic insular forms. San Esteban is the one that holds the largest chuckwalla species. We walked in a beautiful arroyo and found them basking under the sun or under chollas and other bushes, with their beautiful, well-camouflaged contrasting yellow-black, bulky bodies and relatively short and fat tails. A cousin of theirs, the spiny-tailed iguana, called garrobo in parts of Mexico, was also seen during our hikes. We were really fortunate in watching both species so close and in such numbers. Iftecool has also been historically occupied by a branch of Seri indians who lived there for almost two centuries, but now they have vanished.
The Sea Voyager moved later to Rasa (that means “flat”), another ecologically important island since it is the nesting site for Heermann’s gulls and elegant and royal terns. Our group was allowed to walk among the nesting pairs or individuals, that at this time have chicks about half of the adults’ size. A very busy and noisy island, Rasa represents a real sanctuary or a type of Noah’s ark (with the “seeds” for repopulation) for these species. The associated researcher, Lety, and a volunteer filmaker, Sara, came up to the ship and told us about the projects and daily living on this tiny remote and isolated island.
With these visits we realized how important remote islands are as evolutionary laboratories, but also how fragile they can be. Introduction of non-native species can be catastrophic for the entire insular biota. Now we have the feeling that we have to contribute to their preservation and for the enjoyment of the following generations. The Gulf of California has started to unveil its secrets and jewels to us.
