However, we believe that it is actually a combination of genetic and environmental effects that ultimately determine island boa size. He recently told me, “we determined that there is some genetic component to dwarfism on islands. You can easily imagine how the two processes would work together, perhaps with environmental effects working initially but genetic changes accruing over time.īoback did eventually come to a conclusion about the small size of the island boas. If so, the genes involved in growth would be shaped by natural selection and over time the island snakes would be small because they are genetically different. Alternatively, it could be that snakes that grow slowly or nearly stop growing as they approach a certain size survive longer or reproduce more effectively (probably owing to food supply being limited). It would take them so long reach a large size that somewhere along the line they would have met their demise. Perhaps there is a limited food supply on the islands, so snakes grow slowly, and thus there are few or no large ones. ![]() The most likely explanations for size differences would seem to be either diet or other features of the environment, or genetics. Scott Boback is an expert on these animals, and from the time he was a graduate student at Auburn University, he’s been trying to answer the question “ how and why are these snakes small?” Image provided by Dickinson News and Events Something like this may happen with snakes as well.Īllison Hall (left) says “It’s a normal thing to be a little afraid of snakes, but you really get into the project and come to love the animals.” Amanda Hayes is on the right. Medium and larger mammals like deer tend to be smaller on islands, small mammals like rodents tend to be larger. It is common for animal populations that live on islands to exhibit differences in size from those on the mainland. This is small compared to the mainland boas of the same species, which can reach 4 meters (13 feet) in length. When I say “miniature” I mean that they range in length from 30 cm to about 2 meters (1 to 6 feet). This is the miniature boa of Snake Cayes, a group of islands off the coast of southern Belize. ![]() All of them kill their prey by wrapping around it and squeezing it to death.Īmong the boas there is an island-dwelling form in Belize that is the subject of interest to conservationists, ecologists and, lately, behavioral biologists. Boas (family Boidae) are found in the New World (North, Central and South America including some Caribbean islands). Pythons are found in the Old World (Africa and Asia) as well as Australia. They are close relatives that diverged millions of years ago. ![]() Let’s start with the snakes.Īmong the many different kinds of snakes are the constrictors: boas and pythons. This is a story of snakes, islands and students. note: We welcome back guest blogger Greg Laden for a two-week blogging tour on Surprising Science.
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