This is not true of amphibians. While enthusiasts have maintained amphibians in limited numbers, no amphibian, except the axolotl, Ambystoma mexicanum, has a history of mass culture for repeated generations. B. THE NEED 1. The Demand Factors that stimulate a demand for amphibians are their utility for current research problems, the increased cost of avian and mammalian research animals, and the increased use of living material in high school and college instructional laboratories. Only rodents exceed this figure.
Birds exceed it only if the number of incubated eggs are included in the tally.
This heavy use of amphibians escapes the casual observer, because these animals are either used within days of their arrival in a research laboratory or lost prior to the completion of experiments due to inadequate maintenance. The Supply a. American amphibian dealers find it increasingly difficult to identify high-density pop populations that permit economical collection of animals. Informal surveys among herpetologists and others interested in amphibians suggest that in recent times American amphibian populations have decreased significantly. Amphibian populations fluctuate drastically in response to cataclysmic environmental factors such as food shortage, drought, and early winter.