Declining frog populations
Declining Frog Populations
Conservation of Frogs
All animals are affected by parasites, and amphibians are certainly no exception. In fact, because they live in moist, humid conditions conducive to life in general, they may catch more than their share. Certainly, many parasites such as the platyhelminth flatworms, leeches and insects prefer or may only to be able live and/or breed in such conditions. More recently, polluted waters have meant amphibians have been more likely to get bacterial infections form water.
An example of an obvious parasite on local frogs is provided by the endemic Australian genus of Batrachomyia flies. It seems quite common in the Green Eyed Tree Frog Litoria genimaculata of Wet Tropics streams. The adult lays an egg under the skin. This then hatch into a larva that is relatively large compared to the frog host, thus resulting in a hideous looking lump on the back or shoulder. The larvae poke a breathing hole through the amphibian's skin. It eventually emerges, often killing the frog host in the process. From there, it pupates in the ground.
Population crashes and extinctions in frogs
A fungus has also been implicated in some of the declining and disappearing frog populations around the world. The fungus has been identified as Batrachochytrium dendrobatidis and has dermal and systemic effects on the infected frogs. The fungus may have actually already been naturally present in the frog populations, with a particular stress may have bringing it up to such threatening levels. A cooperative study between James Cook University and NASA suggested there was a correlation between the time just before the population crashes, and certain climate extremes. There were also suggestions that the disease may have spread from captive specimens. The stress in the populations of these frogs may have been previous to the crashes and indicated by disabilities or abnormalities in individual frogs. By incredible scientific fortune, surveys of amphibians were actually being undertaken before, during, and after the `crash'. The surveys measured limbs of the caught frogs and found evidence of asymmetry. This is a technique often utilized in the analysis of insect ecology to detect population stress.
Of the amphibians, only the frogs are found in Australia. Frogs can be simply defined as tailless amphibians. They have two shorter front limbs and two very long hind limbs. This body plan facilitates jumping very effectively and this design has obviously been successful as it has changed little over million of years. Like other amphibians, frogs skins are relatively permeable; that is many liquids and gases can pass through into their body. Frogs thus require a moist environment for this reason and for reproduction, and are also thus sensitive to environmental conditions.