CAPTIVE BREEDING & SPECIES REINTRODUCTIONS
Corresponding Readings in Primack, Richard B. Essentials of Conservation Biology.
Chapter 14: pages 361-393
Introduction:
Captive breeding and subsequent re-introduction of a threatened species is an important and in some cases very successful tool for species conservation. Critics point to the need to conserve/restore habitat, list examples of failures, decry the cost, and argue we should rescue species before they are on the brink of oblivion. Fair enough. But, captive breeding saved the bison. Wolves roam Yellowstone and the Upper Peninsula of Michigan, the Peregrine Falcon is off the endangered species list, golden-lion tamarins thrive in the Brazilian forests, whooping cranes perform their mating dances along river banks in the west, and many more species might similarly be rescued. Zoos, botanical gardens and aquaria have found new purpose and direction, providing a safety net when other protective measures have failed.
Terms:
Ex situ conservation: captive breeding, gene and seed banks, zoos and aquaria and all other forms of maintaining species artificially and off-site. Contrasts with in situ methods such as parks and habitat management.
Introductions: releasing animals (captive or wild born) where they never existed. Usually because old habitat is gone or degraded, not available, but the new habitat is considered suitable
Reintroductions: releasing captive born animals where they once existed. Only successful after you have corrected the cause(s) of the original population decline.
Translocations: moving wild-born animals from one place to another. This is done when the wild population is in imminent danger of extinction due to habitat alteration. One of Michigan's three populations of endangered redside dace (Clinostomus elongatus) was about to be wiped out by the installation of a new sewage treatment plant which would discharge lethal levels of ammonia into the section of the small creek where the fish live. In a last-ditch effort, a few concerned scientists gathered some fish and translocated them to Flemming Creek in the Botanical Gardens, where a small population established successfully.
Captive Breeding Programs:
These programs arose out of the coincidence of two forces -- unplanned parenthood by zoo animals raised the issue of what to do with surplus (zoos often had to destroy surplus animals); and concern for extinctions in the wild.
Although some species can be very hard to breed, captive breeding has a high success rate.
Criticisms of Captive Breeding
Despite these statistics, captive breeding has its critics.
Rules For A Successful Reintroduction (based on Kleiman article)
- enough breeding stock to provide a surplus. For big animals, this requires a lot of space
- good genetic management.
2. REQUIRE A SUITABLE AMOUNT OF ADEQUATE AND PROTECTED HABITAT
- conduct field studies to determine the amount and type of habitat required by new population
- a "wild" model is necessary to establish suitable conditions for release
- population must be protected from whatever caused its previous decline
3. EFFECTIVE TECHNIQUES TO PREPARE ANIMALS FOR REINTRODUCTION
- train re-introductees prior to release in predator, ability to find and process, how to interact properly with conspecifics; how to find/construct shelter.
4. POST-RELEASE MONITORING AND EVALUATION
- constant monitoring provides opportunity to evaluate and modify program
5. PROFESSIONAL AND PUBLIC EDUCATION
- partnerships with US can provide opportunities for education of professionals
- conservation education can create local support to sustain the reintroduction efforts.
6. SUFFICIENT LONG-TERM FUNDING POTENTIAL
- Long-term money is necessary, and long-term commitment by individuals/agencies
7. SIDE BENEFITS
- can be substantial. include (a) habitat restoration required to allow successful reintroduction (b) public education, public pride (GLT examples) (c) basis for continued habitat protection.
8. SUCCESSFUL EXAMPLES
whooping crane, bison, American condor, perigrine falcon, golden lion tamarin, wolves, and many more.
Major Players in Ex Situ Conservation:
Zoos -Once places for people to stare at "curiosities", Zoos today are centers of captive breeding and opportunities for public education to heighten awareness about endangered species.
Game Farms - Viewed as repugnant by some, these propagate game species in semi-natural captive settings and reduce hunting pressure on wild populations. Excess animals produced may be source of genetic material for other breeding programs or may be candidates for re-introductions.
Aquaria - Fish and marine mammals. Mammals trained to perform for entertainment of public help to bring in money, prevents boredom in these intelligent animals, and today aquaria are important for public education. Some success with captive breeding of fishes, smaller marine mammals (esp. dolphins, manatee), less success with others (Orcas, sea lions and seals).
Captive breeding programs - set up specifically for the captive breeding of target species; animals not for public view. Smithsonian maintains a wildlife game farm inVirginia countryside.
Botanical Gardens - focus on ornamental and/or horticultural species.
Arboreta - traditionally focused on all sorts of trees, many ornamental and/or exotic. Problems is few trees of each species per arboretum.
Seed Banks - originally for the preservation of unique cultivars of horticultural and agricultural species. Primarily started for preserving unique, local cultivars of corn, rice, wheat, and potatoes during the "green revolution", when farmers started to abandon traditional, local cultivars in favor of high-yield hybrid strains.
some new tricks boost genetic variability, increase the effective population size, and improve reproductive success.
1. Cross - fostering - Some animals can breed successfully in captivity, but are not able to raise their own young. In these cases, the young are raised by another (closely-related) species. Typical of birds. An example is Asiatic jungle fowl chicks incubated and reared (taught to forage, peck, scratch, and drink) by domestic hens; eggs of whooping cranes placed in nests of wild, closely-related sandhill cranes and raised by them.
2. Artificial Incubation - Also called the "head start program", used extensively with aquatic organisms and some birds which experience extremely high mortality during the critical hatchling period. Eggs are collected, incubated under artificial conditions, and reared to beyond the critical size or stage prior to release. (esp. useful for turtles, some fish).
3. Artificial Insemination - Sperm is collected from donor males, processed, and frozen for long-term storage and for worldwide distribution to inseminate females.
4. Embryo Transfer (mammals) - A single female can only have a limited number of offspring during her lifetime - eg, a milk cow with high production can only have about ten calves during her lifetime, even though she has thousands of egg follicles in her ovaries. The solution: 1. female is superovulated (hormonal induction of release of multiple eggs), and the eggs are collected via a surgical procedure called laparoscopy 2. Eggs are fertilized in a test tube with sperm from any of several donor males. 3. Embryos can be frozen for long-term storage, or immediately (or eventually) implanted into the uterus of a closely-related but non-endangered species for full-term development, birth, and subsequent foster rearing by the surrogate mother.
Fish Hatcheries: an "evil" twin and a "good" twin?
There is a long history of propagation of fishes in hatcheries for commercial and recreational fisheries, of course, and many view the success of these efforts from a conservation perspective as decidedly mixed. Hatcheries typically are used to supplement natural production of harvested species, and their goal usually is mitigation of other human activities that have led to declines in natural production (NRC 1996). Our appreciation of the negative aspects of hatchery propagation have been greatly clarified by examination of the health of the 7 species of Pacific Salmon occurring in western North America. The fact that many valuable stocks are in decline, despite rising output of hatchery-reared juveniles, shows that hatcheries alone cannot compensate for the problems of habitat loss, over-fishing, and dams and other barriers. Furthermore, because of lack of attention to genetic concerns, and the over-fishing of native populations in mixed fisheries of wild and reared fishes, hatcheries have done actual harm.
Consideration of ex situ conservation reminds us that genetics is of fundamental importance to the long-term conservation of species. Healthy species normally contain much genetic diversity, both within local breeding populations (demes) and between demes (NRC 1996). Genetic diversity represents the basis for adaptive evolution, and is evidence of adaptation to local conditions by individual populations. Loss of this diversity, through extirpation of local populations, fragmentation of previously inter-connected populations, and careless selection of breeding stock for hatcheries represent serious threats to long-term species survival (NRC 1996).
Genetic risks associated with hatchery propagation can be grouped into four classes: loss of within-population variability, loss of among-population variability, domestication, and extinction (Busack and Currens 1995). Loss of genetic variability within populations stems mainly from using too small a hatchery broodstock and from inappropriate mating protocols, potentially resulting in inbreeding depression, genetic drift, and artificial selection (National Research Council [NRC] 1996). These problems are almost certain to confront efforts to culture threatened species as well. Hatchery propagation contributes to loss of among-population variability mainly through the release of reared fish from nonindigenous broodstock into areas where local populations may persist, a practice now much less common (NRC 1996). Domestication, or genetic adaptation to hatchery conditions, can result from nonrandom selection of broodstock as well as from differences between hatchery and natural environments. Ironically, these effects of hatchery propagation together can contribute to the extinction of populations they are design to rescue.
Despite these considerable concerns about fish hatcheries, they potentially could play an important role in the conservation of threatened species. The hatchery infrastructure of the USA, and accumulated knowledge of scientists and hatchery operators, represents a formidable infrastructure for the propagation of threatened and endangered species. Re-direction of hatchery efforts towards the culture of imperiled species is a relatively recent change that holds the potential to aid in the recovery of many species, provided that it takes place within a holistic program that includes habitat protection. At present, 33 National (USA) Fish Hatcheries (out of a total of 74) are working with 28 federally listed fish species and 11 State-listed species in accordance with recovery plans and to prevent further declines and listings.
Dexter National Fish Hatchery, a warmwater facility in New Mexico, has been at the center of intensive efforts to protect native fishes of the southwestern USA; to date, some 24 taxa of mainly riverine and spring-dwelling poeciliids, cyprinodontids and cyprinids have been held at this facility (Johnson and Jensen 1991). In addition, several rare taxa of salmonids in the genera Oncorhynchus and Salvelinus are held at coldwater facilties. The Dexter facility has pioneered a number of hatchery methods that may be less important in rearing sports fish, but are important when dealing with native species. These include once-through rather than recirculated water, to minimize diseases, strict measures to prevent mixing of populations, with the possibility of interbreeding, and extra attention to minimizing escape of fishes into nearby waters, which might establish non-native populations (Johnson and Jensen 1991).
An augmentation plan for the razorback sucker Xyrauchen texanus in the Upper Colorado River Basin (Modde et al. 1995) is a good example of how ex situ conservation efforts can aid in the recovery of an Endangered Species (USFWS 1991). At present only older (mostly 30-40-year-old individuals), non-recruiting adults persist in isolated segments of the fish's historic range. (Minckley et al. 1991). Artificial propagation, along with habitat rehabilitation and flow management, form the basis of a multi-agency plan to reconcile water development and razorback sucker recovery (Wydoski and Hamill 1991). Previous releases of fingerling razorback suckers (lower Colorado River: 1981-87; middle Green Riber (1987-89) were unsuccessful and indicate that stocking alone is likely to be insufficient. The present plan makes use of careful analyses of local riverine stocks (termed genetic conservation units, or GCUs), a cross-breeding strategy to maintain genetic diversity, along with flows to inundate bottomlands and better management of these nursery sites.
Development of rearing facilities for the razorback sucker exemplify the potential for innovative approaches to the propagation of endangered species. Initially fingerlings were reared in earthen ponds (Minckley et al. 1991). More recently, seasonally occurring backwaters along Lake Mohave's shoreline have been utilized and then made more permanent, and water heaters have been added to cold-water trout hatcheries to make them suitable (Mueller 1995).
Future Need for a Millenium Ark
Michale Soule likens our situation to Noah's. A catastrophic extinction event is imminent, driven by the rise in human population and technology, and the usurping of wildlands. Perhaps 20 - 25 % of the world's species will go extinct. How can we use captive breeding programs as the equivalent of Noah's ark ? Let's break this down into three questions: how long a voyage, how many staterooms, how many passengers ?
How long a voyage: how long will it be before habitat in the tropics begins to increase rather than decrease ? Best guess if plus or minus 500 years, barring catastrophes such as nuclear warfare. However, we can hope that cryogenic and similar technologies will be operational within 200 years -- so that is the time line.
How many staterooms: how many species will require captive maintenance and propagation ? Best guess is about 2,000, excluding fish, and probably plus or minus 500. { This is roughly 10% }
This will place great demands on available space and resources, given that we must maintain large enough Ne to maintain essential genetic variation.
How many passengers: What population size is necessary to prevent the decay of genetic variation and ensure the future survivability of populations ? For animals that are very long-lived, an Ne of about 40 should do; for short-lived species we need more. Detailed genetic and demographic analyses are needed for each species to be maintained.
Links:
1. American Zoo and Aquarium Association:
Excellent source on zoos and aquariums. Make sure to check out
"Conservation Programs" to learn about Species Survival Plans
and other website links to any zoo or aqaurium in
the world.