Hybridization as a Means of Preserving Endangered Species

Abstract

{Editor's Note: Tbe author is a graduate student at the University of California, Davis in the Avian Sciences Department where her primary areas of study are consertation and genetics. She is currently working on her thesis which is investigating the fate of confiscated smuggled birds and is also engaged in a special project with the School of Veterinary Medicine related to the anatomy, physiology and nutritional needs of the 20 members of the Musophagidae family (turacos, plantaineaters and go-away birds). In her spare time, she tends a large flock of her own and practices law on a part-time basis. S.L.DJ

Abstract

Endangered species, including nearly 1000 species of birds, are in need of human intervention if their long term survival is to be assured. Methods such as habitat conservation, captive propagation and cryopreservation have been the standard conservation methods employed to date. Now, because so many bird species are at critically low population levels, more extreme methods such as hybridization need to be considered if extinction is to be avoided.

Introduction

Each year, there is an increase in the number of plant and animal species whose populations have declined to a critically low level, endangering their continued survival. Birds are not exempt from this phenomenon and at least 1,000 species, ten percent of all the bird species in the world, are facing the threat of extinction in the next century (Perrins 1990). Science and humanity at large have developed various plans for coping with the problem

of endangered bird species but have achieved relatively minimal success. Creative approaches to the situation may, in the end, be the only means of protecting these threatened species.

Protection of Endangered Species

As stated above, the problem now facing ecologists, wildlife conservationists, and other scientists is preservation of many species1 whose populations are dwindling rapidly due to a number of factors including loss of habitat, poaching, human encroach-. ment on their territories, and the introduction of diseases, predators and competing species. These problems have led to the creation of various legislative programs such as the U.S. Endangered Species Act CESA) and CITES plans designed to identify and protect species whose numbers and habitats have been depleted to the point of threatening their long term survival. Interestingly enough, the listing of certain animals as endangered has caused researchers to investigate the molecular genetics and field ecology of those species, often leading to information which contradicted previously held ideas about the species' integrity or taxonomic distinctions.

Historical Means of Preservation.

To date, there are three established methods for preserving endangered bird species which have been designated as threatened or endangered. The first involves habitat preservation and related conservation practices. While this method has worked as a stopgap measure, conservation efforts have also backfired by significantly modifying the evolutionary course of a given species.

An example of this can be seen in a project carried out by officers of the U.S. Fish and Wildlife Service who collected a number of members of a

Hawaiian finch species on the atoll of Laysan in 1967. The birds had become endangered in their own habitat due to the presence of human introduced rabbits and rats. The USFWS moved the finches to Pearl and Hermes Reef, islands more than 300 miles from their · home. Over the next 20 years, the birds adapted to their new habitat and different food supply by changing first their eating habits and ultimately the configuration of their beak. "As more and more species are endangered, well-meaning attempts to save them involve introducing them to new homes or reintroducing them to their old homes. Conservationists may be frustrated to find that by moving a species, instead of helping it to survive, they have helped it evolve into a new form." (Weiner 1992; see also Grant and Grant 1988).

The second method is captive cooperative breeding programs, which have been taken on primarily by zoos around the world. As an example, the American Zoos and Aquariums developed Species Survival Plans tor a num-

ber of different vertebrate species including many birds. These Plans include the development of stud books to keep track of the genealogy of captive animals so that inbreeding will not occur, cooperation with and education of citizens and government agencies in the native countries of the species to increase awareness of the need for habitat conservation for the target species, and sponsorship of fieldresearch programs to increase populations of a given species in the wild (Cohn 1992).

A third method of conservation and repopulation which has proved virtually unworkable for bird species involves the cryopreservation of sperm, oocytes, primordial germ cells, and/or early embryos for later revitalization. This conservation method is predicated on the assumption that at some future date science will have developed methods not now available for taking the genetic material contained in the frozen samples and using it to "recreate" the species a new.