The Management of Amphibian and Reptile Populations: Species Priorities and Methodological and Theoretical Constraints

Abstract

Many reptile and amphibian populations either are pests, are harvested, or are declining towards extinction; however, relatively few are managed. This neglect can be traced to many causes, chief of which is the lack of sympathy that many people have for reptiles and amphibians, especially life-threatening forms such as large or poisonous snakes and large crocodilians. A few reptiles and amphibians are pests, especially some introduced forms such as the brown tree snake (Boiga irregularis) on Guam and the cane toad (Bufo marinus) in many tropical areas. Many reptiles and amphibians are on the U. S. list of endangered and threatened species because of uncontrolled harvest and habitat degradation. International trade in amphibian and reptilian products amounts to hundreds of millions of U. S. dollars annually. Management priorities are often set by nonbiological criteria, such as economic importance and the size and appeal of the animal. Sea turtles and crocodilians receive the most attention. However, priorities set in this manner ignore economically less valuable and less glamorous species that may become endangered by neglect. Common management measures include the protection of species from illegal exploitation, the establishment of harvest quotas, and the captive rearing of endangered species. Management protocols are often hastily implemented without adequate testing for effectiveness. As a group, crocodilians are probably the most effectively managed reptiles. By partially controlling the international market, illegal harvest has been greatly reduced and many formerly threatened populations are recovering. Legal harvest and ranching projects provide the impetus (and often the funds) for high priorities being placed on the research and management of crocodilians. Placing a value on wild crocodilian populations helps conserve wetlands for the benefit of other species of wildlife. Sea turtles are also the recipients of massive management efforts. However, positive results are not easily demonstrated. The huge effort in saving eggs and hatchlings on sea turtle beaches seems to be largely misplaced; long-lived, highly fecund species such as sea turtles are most effectively managed by controlling the mortality of large juveniles and adults. Recently, the reduction of mortality in Kemp’s ridley turtle (Lepidochelys kempi) resulting from the killing of nesting females and drowning in shrimp nets seems to have reversed the plunge towards the extinction of the world’s rarest sea turtle. Management-oriented research on reptiles and amphibians is unevenly distributed among taxa. Crocodilians and sea turtles are the subjects of much research, but reliability of much of it is difficult to judge as it does not undergo the peer-review process of scientific literature. Research is especially needed to identify the critical life stages of sea turtles, in order to better direct management. Because of their ecothermic physiology, the life history and ecology of amphibians and reptiles often differ markedly from those of traditionally managed game species. Amphibians and reptiles can survive long periods without food, have extended periods of inactivity (often including long periods of hibernation), and exhibit strong seasonal changes in habitat utilization. When compared to endotherms, amphibians and reptiles have low rates of parental care and viviparity, high rates of neonate mortality, low frequencies of reproduction, extended age at sexual maturity, and long generation times. These traits suggest that appropriate management of amphibians and reptiles should focus more on protecting subadults and adults than protecting juveniles and neonates. However, most current management practices protect juveniles and neonates, and allow adults to be harvested. Many reptiles and amphibians are difficult to study and require specialized techniques. There is a need for standardized monitoring techniques to allow comparison of different studies and years. Herpetologists could more often choose their organisms and design their studies to better meet the informational needs of wildlife managers. Wildlife management training needs to include reptiles and amphibians, along with birds and mammals, so that managers in the future will consider all taxa in their plans.