"House" Day Geckos
We have spent most of the day hiking in the jungle. Land leeches reach up from the ground trying to hitch a ride like earthworms standing on their tippy toes. Exhausted, we stop to rest in an abandoned shelter with maps of the reserve's trails on the walls. I rest my arms across the table and a bright green gecko approaches me. It begins to lick my hands that are sticky from snacking on lychee fruits all day. I have a couple left, so I slowly pull a red fruit from my pocket and peel off its skin. I hold the juicy fruit out to the gecko and it climbs right up.
There seem to be those animals that have learned to survive in human alterd environments. They find shelter in the cracks between tiles of the wall. They eat crumbs off the floor and steal from the table when you aren't looking. For some of us, those animals are rats and pigeons. In Madagascar, several species of day geckos have adapted to the human life. They roam the walls of the restaurants, licking sweets being sold in baskets.
Madagascar is home to about 70 species (and subspecies) of day geckos. Each different region of the island has its own species that are adapted to the area's unique conditions, with the species of geckos in human dwellings varying from region to region.
Lined Day Geckos (Phelsuma lineata) are found throughout the humid forest on the east side of the island. They run behind the toilet when you walk into the bathroom, and catch moths by waiting for them next to lights. These are behavioral adaptions that has helped them succeed in the human environment.
In Ranomafana rainforest region, Lined Day Geckos are joined by two species of Peacock Day Geckos (P. quadriocellata & P. parva) sharing the same buildings. The two peacock day geckos have been separated into two distinct species. P. parva is smaller and has red stripes along it's side and is more readily found in the human environment than in the jungle.
In the hot, dry southwest region, the Thick Tail Day Gecko (P. mutabilis) is the "house gecko." They are not a brightly colored day gecko, but grey to brown, occasionally with a bright blue tail. The range of their natural habitat is huge, extending across most of the west side of the island.
In the Spiny Forest, there are three species of day geckos taking shelter on human made structures: Standings Day Geckos (P. standingi), Modest Day Geckos (P. modesta) and Thick Tail Day Geckos (Phelsuma mutabilis).
Although Standings Day Geckos are commonly found in buildings, their populations aren't thriving. They are listed as Vulnerable, meaning that their population is small enough that extinction is highly likely if conservation actions aren't taken (1).
Why haven't Standing's Day Geckos been able to grow their populations, even though they seem to have adapted to the human environment? They are more than twice the size of any other Phelsuma "house gecko," meaning they require more food. Does this lead to more competition and perhaps there aren't sufficient resources to support populations of these larger geckos?
In captivity, they pair bond. Does this somehow affect their ability to reproduce in the wild?
Most animals aren't able to modify their habitat or behavior to successfully live in altered environments. Species are going extinct every day. What behavioral changes do animals make to live with humans? What traits have allowed them to thrive? Leave a comment with your thoughts.
(1) Raxworthy, Christopher. "Extinction and extinction vulnerability of amphibians and reptiles in Madagascar." Amphibian and Reptile Conservation. December 1997: 15-23.