Because surveys have been used only since the 1980s, researchers are challenged to discern trends and causes of declines. Mossman comments, Cricket frogs were abundant 50 years ago in Wisconsin, but hardly any of those are left now. They disappeared in about 30 years. It is hard to know exactly what conditions led to the demise of the cricket frog, because systematic data were not collected until the mid-1980s. Conditions may not be optimal for breeding one year, so a population may have a short-term decline.
Amphibians also experience very high mortality.
Predators such as fish and snakes devour amphibians at various stages of their lifecycle. Thus, amphibian populations can vary dramatically from year to year, depending on reproductive success and the number of predators in an area. However, as data are collected across the state every year, it may be possible to compare sites where populations are in decline against sites where declines are not occurring, to isolate causes, states Mossman. Possible Causes of Declines Casper states that historically most of the declines could be due to habitat loss. Wisconsin has lost more than half of its wetlands since settlement.