This is not true of amphibians. While enthusiasts have maintained am- phibians 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 ani- mals, and the increased use of lining 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. Informal surveys among herpetologists and others interested in amphibians suggest that in recent times American amphibian populations have decreased significantly. However, no clear evidence exists that the survival of any of the amphibian species commonly used for investigative purposes is endangered by collection practices. The high reproductive potential of these amphibians assures that, given optimal environmental and climatic conditions, the popula- tions rapidly regenerate.