Running out of reptiles
provided by Savannah River Ecology Lab
ational attention has been riveted on the issue of amphibian declines for years and has intensified with each new report of vanishing populations or deformities. However, according to an article in the latest issue of the journal BioScience, reptiles are in even greater distress worldwide than their better known cousins.
These two vertebrate classes are collectively referred to as the herpetofauna, but the focus of general concern has been almost exclusively on amphibians. Now, however, scientists are hoping that the general public will recognize what they have long known: that reptiles across the globe are affected by many of the same forces as amphibians but with even greater impact.
The article's lead author, Dr. Whit Gibbons, a herpetologist and professor of ecology at the University of Georgia, said, Although the amphibian decline problem is a serious threat, reptiles appear to be in even greater danger of extinction worldwide. He said that while studies on both amphibians and reptiles have not been as rigorous as scientists would like, the existing documentation points to a coming crisis situation.
The problem is multifaceted. Habitat loss and degradation may be the largest single factor in reptile loss. For even when part of a habitat is protected, such as a wetland, the surrounding terrestrial habitat needed by semiaquatic reptiles often is not. Conservation biologists hold as a basic tenet of ecology that intact habitat is necessary for species persistence and well-being. But habitat destruction is just the beginning of the problem.
Invasive species introduced to new areas can spell real danger for reptiles. One example is the Galapagos tortoise, now near extinction due largely to introduced rats that destroy the tortoise eggs. Other problems include environmental pollution, disease and even the simple presence of humans among a fragile population. Cars kill animals; predators are attracted by human food wastes; cats and dogs hunt and people remove interesting animals or handle them incorrectly.
The commercial use of reptiles is also cited as a cause for declines. The harvesting of reptiles for pets, food and for use in folk medicines can result in overcollection. This kind of use affects reptiles more than amphibians.
Human use is not universally bad, according to Gibbons, but such use should be sustainable, that is, the population from which individuals are harvested should be able to rebound to at least the same population level. This is especially difficult for long-lived species, which may take years to reach maturity. Global climate changes may also present problems for reptiles, according to the BioScience article, and some population declines have been noted for which a cause cannot be discerned.
Many populations thought to be in decline simply have not been monitored over long periods of time, making evaluation of the problem difficult. Additionally, the clandestine nature of many reptiles and their large home ranges may allow a population to decline without notice.
Gibbons believes the best course for conservation initiatives is to assume the worst for all herpetofauna while gathering more data.
The disappearance of reptiles from the natural world is genuine and should be a matter of concern, according to Gibbons. Current evidence suggests that these declines constitute a worldwide crisis.