|Biodiversity and Conservation|
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Przewalski Horse: photograph courtesy of the
Foundation for the Preservation and Protection of the Przewalski Horse
|GENETIC PROBLEMS WITH SMALL POPULATIONS
Loss of genetic variability
EMBRYO STORAGE AND TRANSFER
When wild populations reach extremely low levels and are in imminent danger of extinction, the only way to save them is to bring them into captivity, build up their numbers, and try to re-establish the wild population. This is being tried with many endangered species, but it involves many challenges, both biological and political.
Several problems arise when a species reaches a very small population size:
Loss of Genetic Variability. When a population gets below about 500 breeding individuals, the amount of genetic variation is reduced, and this can eventually diminish the species' capacity to adapt to environmental changes. An example is the cheetah, a member of the cat family. There are 37 species in the cat family, and all except the domestic cat are considered threatened or endangered.
Cheetahs are genetically extremely uniform. This has been shown in two ways: first, protein patterns as seen by gel electrophoresis (slide). None of 52 genes tested showed variation in the cheetah whereas between 8% and 31% of the same group of genes showed variation in other mammals including other cats. Second, skin grafts between cheetahs are not rejected, indicating that they are genetically identical as far as histocompatibility genes are concerned; these are the most variable genes in other mammals. Cat House
Inbreeding. Populations that fall below about 50 breeding individuals are forced to breed with close relatives - a pattern of breeding called inbreeding which can lead to depression of fitness called inbreeding depression - this includes problems such as decreased fertility, high juvenile mortality and birth defects, already well known from human populations. Captive populations of endangered species such as the California condor, which was down to less than 30 individuals, have to be managed very carefully in order to minimize inbreeding effects. The chart shows how, with most species, the offspring of related parents ("inbred") show higher juvenile mortality than offspring of unrelated parents ("noninbred").
In the cheetah, there is high juvenile mortality in both sets of offspring; this is presumably because even unrelated parents are genetically very similar, just like related parents. Cheetahs show other reproductive problems including very low sperm counts and high incidence of abnormal sperm; these are also thought to be due to genetic uniformity.
The number of cheetahs in the wild is not known precisely; it is estimated at between 1,500 and 25,000. This is not a small enough population in itself to show loss of variability and inbreeding effects. Rather, it is thought that the cheetah population went through a very small bottleneck in the recent past, leaving the present population exceptionally uniform.
Inbreeding also leads to the expression of specific genetic defects, that are masked by dominant normal alleles in outbred populations. For example, inbreeding has apparently caused a high incidence of a genetic defect of the diaphragm in the endangered Golden lion tamarin, and kinky tail in the Florida panther.
Inbreeding was probably one of the factors responsible for the extinction of the heath hen. This bird was once widespread in the eastern United States, but it was reduced by overhunting, disease, and bad weather to a population of less than 100 birds on Martha's Vineyard. By 1920, the population had become so small that genetic deterioration resulting from inbreeding caused the population to die out in 1932.
There are some examples of populations that have been reduced to very low levels and appear to have recovered quite well. The Northern elephant seal was reduced to a population of less than 100 but is now thriving with over 30,000 individuals.
All of the pet golden hamstersin the world are descended from one female caught in Syria in the 1930s, and the species has not been found in the wild since. It is not known why some species are more sensitive to inbreeding than others.
Hybridization seems to occur more often when species are reduced to very small numbers. This can be a significant problem because species hybrids cannot be protected under the Endangered Species Act. For example, a large fraction of both red wolves and gray wolves have turned out to be wolf/coyote hybrids.
The 50 or so Florida panthers include some that are the products of hybridization with a South American subspecies (because some hybrid panthers were released into the Everglades between 1957 and 1967). This may be beneficial to the Florida panther, which shows significant reproductive problems, probably due to inbreeding. But the current status of the Florida panther as endangered could be revoked under a strict interpretation of the Endangered Species Act. What You Can Do to Save the Florida Panther.
The present-day population of Przewalski's horse occasionally produces an individual with an unusual coat color, probably because the species has hybridized with the domestic horse at least once in its history.
Hybridization between subspecies has led to a major problem in buffalo conservation in Canada. Most of the wood buffalo in Wood Buffalo National Park in Alberta are hybrids resulting from interbreeding with plains buffalo (a different subspecies) that were removed from cattle country in southern Alberta. But there is still a small herd of pure wood buffalo. The biologists are considering killing or at least removing all the hybrids and allowing the park to be taken over by the pure wood buffalo.
The "hybrid policy" of the Endangered Species Act has often been questioned. It has been argued that hybrids between species should not be given protection because this destroys the integrity of the species, but that hybridization between subspecies is a natural process that helps prevent loss of genetic diversity and inbreeding depression. Therefore, hybrids between subspecies should be given protection under the Act.
Selective breeding. With long periods in captivity there is a danger that unintentional selective breeding will result in the establishment of traits that are desirable in captivity but not in the wild. There is a danger that animals may gradually become domesticated because of their dependence on human caretakers. A possible example is the golden lion tamarin, where the first animals released in Brazil failed to respond to danger or a predator. More releases are being tried.
The maintenance of species in captivity in zoos, aquaria, and botanic gardens is sometimes called ex situ conservation. It is the only hope for the survival of some species where the threat to their existence in the wild is now extreme. This conservation method, however, serves many other purposes such as allowing more control over breeding in order to avoid inbreeding, increased reproductive rate, providing educational and public awareness programs and providing materials for basic and applied research.
The technology for management of captive populations of endangered species in zoos is primitive but rapidly improving. There are roughly 500,000 mammals, birds, reptiles and amphibians in captivity in zoos throughout the world. 500,000 is equal to about 1% of the number of cats in American households.
Not all attempts at captive propagation have been successful. Only 26 of 274 species of rare mammals in captivity are self-sustaining. Giant pandas, cheetahs, elephants, penguins, humming birds, killer whales, and vicunas have been very difficult to breed. Only one species of bats (gray headed flying fox) has ever been bred in captivity. Only about 10% of reptile species in zoos have reproduced.
Improved management of the genetics of small captive populations is beginning to make propagation more successful by eliminating some of the problems associated with inbreeding. The International Species Inventory System now keeps genealogical information on individual animals of 2,500 species of mammals and birds kept in 326 zoos in Europe and North America. This makes it possible to arrange matings by computer in order to minimize problems caused by inbreeding.
Molecular methods are also being used to obtain more definitive information on the relationships between endangered species and their close relatives. Lack of this type of information has already caused problems in endangered species conservation. For example, in the early 1980's the five remaining male individuals of the dusky seaside sparrow were crossed with what was thought to be their closest relative, the subspecies Scott's seaside sparrow, to produce hybrids that, theoretically, could be interbred to give back a strain that was close to 100% dusky. But subsequent mitochondrial DNA analysis show that Scott's seaside sparrow was actually a distant relative while there were four other subspecies that were much closer to the dusky. Thus DNA analysis can be a useful source of information in desperate situations such as this.
The potential role of zoos for species conservation is limited by space and expense. In the U.S., zoos contain self-sustaining populations of a total of only 96 species. The cost of maintaining a herd of about 100 herbivores is up to $250,000 a year, much more than the cost of maintaining the same number in the wild.
It is estimated that if existing zoos were used exclusively for captive propagation of threatened species, a maximum of about 900 species of vertebrates could be kept alive in captivity. But at least 2000 mammals, reptiles and birds would have to be bred in captivity in the near future in order to escape extinction. Of course, the ultimate hope is that zoos will serve as facilities for the temporary recovery of species prior to their return to the wild within a few generations.
Most captive propagation programs in zoos focus on large birds and mammals, partly because they face greater extinction threats than do most small animals, but also because these are more successful in attracting customers. This has also led to some problems. The World Wildlife Fund recently sued the Fish and Wildlife Service for providing the Toledo Zoo with a permit to import two Giant pandas, a species close to extinction (fewer than 1000 animals) in the wild in China. Pandas are listed as endangered under the U.S. Endangered Species Act and are on CITES Appendix I. The zoo was planning to set up a special exhibit of the pandas, charge a special fee, make about $3 million for a three-month exhibit, and pay about $300,000 to China for the loan. The WWF argued that the exhibit was primarily for commercial gain and that issuing the permit would therefore violate the ESA and CITES, both of which prohibit commercial trafficking in endangered species. This case was especially troublesome because the two animals were of breeding age and were taken from a captive breeding facility in China, in violation of China's policy to loan only non-breeding animals. Thirty other zoos were negotiating with the Chinese to borrow pandas when this case went to court.
Because of concerns about short-term exhibition loans and how the demand for such loans might impact pandas in the wild, the U.S. Fish and Wildlife Service imposed a moratorium on live panda import permit applications from 1993 to 1998. In 1998 they announced a new policy under which the service has to make the following determinations before it can issue a permit:
the import cannot be for primarily commercial purposes;
the purpose for the import must not be detrimental to the survival of the species in the wild;
the importer must have facilities and the expertise to care for the panda;
the import must enhance the survival or propagation of the species as outlined under the ESA, meaning that scientific research or the propagation of the species must benefit wild pandas; and
the import must not jeopardize the continued existence of giant panda populations in the wild.
Aquaria have been much less successful than zoos in propagating threatened species, in spite of the fact that there are threats to large numbers of freshwater species and that many of these fish take up very little space. The captive breeding specialist group of IUCN is mounting a major effort to develop captive breeding programs for endangered fish species, such as the cichlids of Lake Victoria, the desert fishes of North America and Appalachian stream fishes. Some of these will need to be propagated in aquaria for many generations in view of the difficulty in solving the exotic predators and/or acid rain problems.
River dolphin. The Dallas World Aquarium has filed for a permit with National Marine Fisheries Service (NMFS) to capture and import four Amazon River dolphins from South America to Dallas. These animals do not do well in captivity, the Aquarium has no plans to breed or reintroduce them, and the species in the wild is likely to be listed as endangered in the near future.
At present, zoos are not able to deal with the hundreds of thousands of insects and other invertebrates threatened with extinction by habitat loss. However, some zoos and independent operations are developing the technology for captive propagation of these other kinds of organisms. For example, there are now 47 butterfly houses in England, three in the U.S., and two in Australia. These operations could attempt captive propagation of endangered species of insects (but they have not done so yet).
It is much easier and cheaper to maintain captive populations of plants than of animals. Hundreds of species of plants can be kept in a small botanic garden. They require less care, they do not require cages, mating can be arranged more easily, they can be vegetatively propagated and they can easily be stored during their dormant seed stage. The world's roughly 1500 botanic gardens together contain at least 35,000 plant species or more than 15% of the world's flora. Seeds of many plant species, especially those with dry, small seeds, can be stored at low temperatures for long periods with little loss of viability. They are usually maintained at 5% humidity and -20oC. A small seed storage facility can easily store thousands of species. Unfortunately, there are some plant species that do not survive well in storage, and there are some plants that can only be propagated vegetatively (not via seeds). The role of botanic gardens in conservation is growing very rapidly with research into storage techniques, better data collection and better coordination.
The UCI Arboretum, directed by Dr. Peter Bowler, has a collection of 4,000 species, mostly from Africa, of which more than 200 are endangered and 76 are grown nowhere else.
Techniques for embryo transfer and artificial insemination, which have been developed for laboratory animals and farm animals, are potentially very useful for improving the reproductive potential of captive populations of endangered species. These kinds of techniques have been worked out mainly for mammals.
In this technique, fertilized eggs or early embryos (usually about the 8- cell stage) are removed from the reproductive tract of a donor female and transferred into the tract of a surrogate mother, who carries the embryos to term and produces live young. This can all be done non-surgically, at least with cattle. What makes it useful is that the donor and recipient can be of two different species (although they must be of the same genus); successful transfers have been carried out from guar (endangered species) into domestic cow, Grant's zebra into horse, Przewalski's horse into domestic horse, macaque into rhesus monkey, and several others.
One technique for enhancing reproduction is superovulation; treatment of the donor with fertility hormones such as follicle-stimulating hormone causes the release of large numbers of eggs (up to 31 in eland), all of which can potentially be fertilized, transferred and carried to term in surrogate mothers. This method works well in cattle (and humans!), but not so well in other mammals so far. Another method of increasing the reproductive rate is embryo bisection to give identical twins or triplets; this has so far been demonstrated only with laboratory and domestic animals (slide: sheep twins).
Embryo transfer is useful in several ways, not all obvious:
It increases the number of progeny per female (potentially increases the yield per ovulation and increases the number of ovulations that are productive).
It prevents disease transmission between populations (embryos are almost always free of disease agents that may have been present in the donor).
The offspring acquire passive immunity from the surrogate mother via placental blood supply or milk, and this makes them as resistant to local diseases as the surrogate mother. This method therefore potentially gives better survival than transporting the animals themselves to a new location.
Animals can be transferred from one place to another as embryos in test tubes, implanted into foster mothers and then, when they have grown, they can be used in breeding programs. This is much cheaper and safer than transferring full-grown animals. This technique is being considered for the tiger, which lives on 18 tiger reserves in India with no wildlife corridors connecting them. Moving embryos from one site to another will allow the transfer of genes that is important for maintaining fitness and adaptability of populations.
The embryos can be frozen before transfer into the recipient female. Embryos of the eland have been frozen for 1.5 years then successfully transferred and carried to term. Thousands of mouse embryos are kept frozen as a method of preserving genetic stocks. For mice, rabbits and cows, 80-90% of the embryos develop after freezing and thawing. This raises the possibility of long-term cryopreservation of embryos of many different species in a "frozen zoo", and of large numbers from individual species so that genetic variability can be maintained at fairly low cost. Cryopreservation may also be important when insufficient surrogate mothers are available or are not yet synchronized.
Artificial insemination is another technology that may be useful. Sperm can be frozen and used later, or transferred to another breeding facility to increase genetic diversity. Sometimes, the sperm can be added to the eggs in a dish and fertilization will occur. In other cases (for example, horses) the sperm has to be injected into the egg. A few years ago, the black-footed ferret was down to six individuals, but artificial insemination has now been used to produce 16 kittens. Elephants and cheetahs have conceived, and a live cheetah cub has been born following artificial insemination. Elephants have not bred naturally in captivity, so this method may be useful simply to make captive breeding possible.
|Somatic Cell Cloning holds some promise for propagating from one or a few survivors of an almost-extinct species. This was first done with domestic sheep at the Roslin Institute in Edinburgh (see panel, from University of Virginia) but has since been done with other mammals. It has already been used to rescue a rare breed of cattle that had been reduced to a single old female ("Lady") and some frozen sperm. Granulosa cells (somatic cells in the ovary) from Lady were fused with enucleated eggs (lacking DNA) from a different breed, and the resulting eggs were implanted into an Angus cow (a common breed). The first calf born from these cells ("Elsie", =LC, =Lady's Clone) is genetically identical to Lady, as expected, although her markings are slightly different.|
Trans-species Somatic Cell Cloning is being proposed for propagation of the Giant Panda (Nature, 30 July 1998). Scientists at China's National Academy of Sciences are hoping to transfer nuclei from an adult giant panda cell into the egg of another species, perhaps a black bear. They are hoping to have the eggs carried in a foster mother. A major advantage would be that the technique would not require panda eggs, which are very difficult to obtain. Similar nuclear transfer methods are being proposed to help the recovery of the Northern Hairy nosed wombat, Australia's rarest mammal. Nuclei from ear cells will be implanted into egg cells from the more Common Wombats, and any embryos will be transferred into surrogate mothers. Sheep, monkey, rat, and pig embryos have been successfully produced by fusing somatic cells from these species with cow eggs. However, many of these embryos were lost by miscarriage and none has given rise to a living animal.
Some scientists are even working on using cloning techniques to bring extinct species back to life. For example, they hope to find some intact nuclei preserved in 20,000 year-old carcasses of woolly mammoths frozen in the permafrost in Siberia. The nuclei would be implanted into elephant eggs, and if development occurred the embryos would be implanted into surrogate mother elephants. If a calf was produced it would be an authentic woolly mammoth.
The proposal to clone an animal from tissue that has been dead for 20,000 years seems like science fiction. But Japanese scientists have already used the technique of Polymerase Chain Reaction (PCR) to amplify (accurately replicate many times) small pieces of DNA from a woolly mammoth muscle fragment. They were able to amplify and determine the nucleotide sequence of DNA segments of 1-200 base pairs in length, but were not able to amplify fragments of 1000 base pairs, suggesting that the DNA had been degraded into fragments smaller than 1000 nucleotides. This means that the chances of finding a nucleus with its entire DNA intact are very remote indeed (also, to support development the nucleus would need to have not just the DNA intact, but also many proteins and other molecules that are required for the DNA to function). However, the Japanese group was able to reconstruct the DNA sequence of two entire genes (~1000 base pairs each) by piecing together the sequence from many smaller fragments. They used the information from these two genes to show that the woolly mammoth was genetically closer to the African elephant that to the Asian elephant - the opposite to what had been concluded based on comparative anatomy. In fact, they showed that the mammoth was more closely related to the African elephant than is the Asian elephant. African and Asian elephants have been hybridized in a zoo, and a hybrid calf was born although it did not live long. This makes the biologists wonder whether hybridization might be used to bring the mammoth back from the dead. If they are able to find sperm in a frozen mammoth carcass, they will try to take the nucleus from mammoth sperm and use it to fertilize an elephant egg in vitro. If the egg were to develop, it would be an elephant-mammoth hybrid. Unfortunately, it would probably be sterile, like other species hybrids (the mule, for example), so it would be difficult to resurrect the species this way.
In contemplating these far-fetched ideas, it is important to remember that new techniques in molecular and developmental biology are being developed at an incredibly rapid rate. Even though we can't do it today, some time in the future we may be able to produce an animal starting only from information about its DNA. And we now know that we can get this kind of information from woolly mammoth carcasses! We have a long way to go though - two genes have been analyzed, out of a total of about 140,000.
Scientists in New Zealand are hoping to use trans-species cloning to bring back the recently extinct Huia bird.
Many egg-laying animals (i.e. birds and reptiles) are capable of producing many more eggs than they can rear. This raises the possibility of collecting the extra eggs and hatching and rearing the animals in captivity with a foster parent, then using them to supplement wild populations. It has worked extremely well with some birds, particularly the peregrine falcon, which is now doing so well that the fostering program is being phased out. Rearing of whooping cranes has also been successful, and the species recovered from a population of 21 birds in 1941 to over 300 in 1996. But the other part of the whooping crane program, in which the young were to be reared by the much more numerous sandhill cranes, has not been successful - the fostered animals have not yet reproduced in the wild.
A major problem with fostering programs is that the young animals learn crucial behaviors in the wild but not in captivity. Captive bred animals sometimes bond to their human keepers instead of their own species, and this makes reproduction difficult. An ornithologist who had helped to raise a whooping crane had to perform the bird's courtship rituals in order to get a female crane to reproduce. In the wild, the cranes will not produce eggs without having formed a bond with a male. Now the trend is to keep the keepers away from the animals as much as possible in order to prevent this kind of occurrence, and to use mirrors, puppets, etc. in order to keep the animals focused on their own species.
At least 19 species have been reintroduced into the wild after captive propagation. In at least seven cases (Pere David's deer, Arabian Oryx, American bison, Red wolf, Guam kingfisher, Guam rail, and the California condor) the species were extinct in the wild at the time of reintroduction.
Numerous other species not completely lost from the wild such as the peregrine falcon, the bald eagle, the gray wolf and the alpine ibex have been successfully reintroduced to portions of their range from which they had been lost. Reintroduced peregrine falcons are now established in many places (there is one living in Upper Newport Bay), and reintroduced bald eagles are doing well on Catalina Island.
Nene. One of the first examples of successful reintroduction was the Nene or Hawaiian goose. The population was reduced (by exotic rats and mongooses eating the eggs) from about 25,000 in the year 1700 to only 43 on the big island by 1940. It was totally gone from Maui. It was bred at the Wildfowl Trust in England until enough were available for reintroduction to Maui. The wild population in Hawaii is up to about 800, but there is a high rate of male infertility, apparently because of inbreeding.
Spix's Macaw, the rarest bird in the world, is now the subject of a "last-ditch" captive breeding and reintroduction effort. Prior to 1990 the species had been decimated by a combination of habitat loss and capture of birds for the pet trade, and was considered extinct in the wild. But then a single wild male was discovered. At that time there were, fortunately, also eleven Spix's Macaws in captivity. The wild male is still alive and the number in captivity has (3/00) increased to 60. The committee responsible for saving the species decided early on not to capture the last wild bird, because they felt he might have learned vital facts and behavior patterns (for example, about how to avoid capture by poachers, and where to find food) and that he could teach survival skills to other birds after they were introduced to the wild.
One difficulty has been that this kind of bird bonds for life, and when the single wild male was discovered in 1990 he had already bonded with a female of a different though related species, Illiger's Macaw. These two birds have different roosting sites, probably part of their different inherited behavior patters. The male roosts on a large cactus and the female sleeps in a hole in a tree. The pair solved this problem in an interesting way. They fly together during the day, then in the evening the male escorts the female to her tree, then goes home to his cactus.
Monitoring of the last wild Spix's macaw and the attempts to get him to breed have captured the imagination of the locals. An entire village is involved in watching and guarding him, and they keep detailed notes on his behavior. Four full-time observers are employed to watch the birds. The story provides a wonderful example of how the local community can get deeply involved in and committed to a conservation project. The project has also brought enormous benefits to the community.
A female Spix's was released near the male in 1995, and for a while she and the male kept company as a threesome with the Illiger's. But after a month the Spix's female was found dead. Now the biologists are hoping to introduce some Spix's eggs from captive birds into a nest made by the cross-species couple, and hope to get them fostered in the wild.
Articles on Spix's Macaw | Macaw survival project takes flight
Iguana Farming - A Source of Food and a Method of Tropical Forest Preservation
Pere Davids Deer. In the case of Pere David's deer, an Asian deer with a tufted tail and big feet, the species had been extinct in the wild for 800 years before it was reintroduced. It originally lived in swamps in northeast China, and became extinct in nature when these swamps were drained for agriculture during the Shang dynasty (1766-1122 B.C.). They were discovered by Pere David in the Hunting Park in Beijing. Pere David had 18 of them sent back to some European zoos. This was quite fortunate because the stock in China was subsequently (in 1894) completely lost. Herds have been established in several countries, and the zoo population is now up to over 1400, all descended from Pere David's 18 animals. In 1964 the London zoo sent four of the deer to the Peking zoo, after the species had been gone from China for almost 50 years. In 1985, more were sent and released into a park, where they are now breeding successfully.
Przewalski horse (Mongolian wild horse). This is the only remaining really wild horse, never having been domesticated. It has a stiff mane and no forelock. It had been known to exist for only 87 years when it became extinct in the wild in 1968. From 13 captive animals, over 1400 now exist in captivity. Eventually they will be reintroduced to Mongolia, China and the Soviet Union.
Golden lion tamarin. One of the world's smallest monkeys (less than one foot long); lives in the Atlantic forest in eastern Brazil. The total wild population has decreased from 400 in the mid-1970s to 100-200 today. There are about 300 in captivity in the U.S. and Europe. Since 1984, 89 captive bred animals have been released and about 35 are still alive. The tamarin is the first primate bred in captivity with the goal of reintroducing it into the wild. The remaining habitat has to be restored and the fragments reconnected in order for the reintroduced population to become self-sustaining.
The Arabian oryx was extinct in the wild in 1972 but reintroduced after captive breeding in the Phoenix and San Diego zoos. Now there are wild herds in special reserves in Oman, Jordan, Israel and Saudi Arabia.
Endangered antelope returning to Tunisia
Marine Mammals. Sea World, in San Diego, has an active program for rescuing stranded marine mammals (not necessarily endangered species), rehabilitating them, and releasing them into the wild. They have even tried this with a stranded gray whale ("J.J."). Unfortunately, J.J. has not been sighted recently.
The Oregon Coast Aquarium in Newport, Oregon, rehabilitated a killer whale, Keiko, and has tried to release him in appropriate habitat near Iceland. He is being kept in a netted pen in a sheltered cove while he builds up enough strength and skills to be released into the same area where he was captured in 1979 as a two-year-old calf. Unfortunately, several attempts to release him into the wild have ended in failure as he has always returned to the boat carrying his handlers.
Reintroduction has also been tried as a way of boosting the small California population of Southern Sea Otters. Because of the California population's small size, limited range and vulnerability to oil spills, in 1987 the US Fish and Wildlife Service decided to try to establish a second population at San Nicolas Island, one of the southernmost of the Channel Islands that once had a natural population. 139 otters were translocated over a three-year period. However, the biologists were surprised when many of the otters left, probably to return to the Mainland (70 miles away). About 20 remain and there has been some reproduction, so the plan may succeed eventually. But the program has now run into trouble because about 150 otters are seasonally visiting the island and feeding on the sea urchins that are the target of a commercial fishery.
A lynx immediately after release in the San Juan Mountains around May 1, 2000. Photo by Michael Seraphin, courtesy Colorado Division of Wildlife.
Lynx. Since February 1999, the Colorado Division of Wildlife has released 96 lynx brought from British Columbia, Canada to rebuild the Colorado population that was nearly eliminated by hunting and habitat destruction. The program is a huge success, with the cats finding appropriate prey, and very few losses. The lynx released this year are being tracked with satellite collars.
Swift Fox Reintroduction on Blackfeet Reservation
Red Wolf. The historic range of the red wolf was in the southeastern U.S., but generations of hunters had almost completely exterminated the species by 1970. In the recovery program for this species, the last 400 wolves were captured (in Louisiana and Texas) in the mid-1970's. All but 14 of these, upon genetic testing, turned out to be gray wolf/coyote hybrids, and could not be used to rescue the wolf (hybrids are also not protected under the Endangered Species Act). But the original population of 14 has now increased to about 240. The red wolf became extinct in the wild in 1980. Since 1986, the wolves have been gradually returned to wild habitats including some areas, like Roanoke Island in North Carolina, where the wolves had been extinct for several hundred years. Coyote-free habitats have been chosen for most of the introductions. The five wild populations now contain a total of approximately 60 animals, and there are about 180 red wolves in 31 captive-breeding facilities in the United States.
Gray Wolf. Before European settlers arrived, gray wolves once roamed all over North America, their population in the millions. After hunters depleted many of their large prey animals (bison, elk), the wolves turned to livestock and became a hated enemy of farmers, ranchers and their representatives the U.S. Farm Bureau. Wolves were shot, trapped and poisoned in huge numbers by individual settlers, fur traders, hunters and government employees in organized predator-control programs. A favorite technique was to lace bison carcasses with strychnine, a practice that was finally outlawed on federal lands by President Richard M. Nixon. Wolves were eradicated in Montana and Idaho by the late 1920's, leaving the main populations in Minnesota (a few hundred animals) and Alaska (7000 animals) where there was a government-sponsored wolf control program until 1995. The gray wolf was one of the first species to be listed as endangered under the first federal endangered species law in 1967. It is now listed as endangered throughout its historic range in the lower 48 states, except in Minnesota where it is listed as threatened.
Gray wolves from Canada are now being used in a reintroduction program in two areas in the U.S.: Yellowstone National Park, Montana and the mountains of Idaho.
The first fifteen wolves (captured in Canada) were released in the mountains of central Idaho in January 1995 and another 14 were released in Yellowstone in March 1995 after being held in acclimatization pens for 6 weeks. Twenty wolves were reintroduced in central Idaho and 17 in Yellowstone National Park in 1996. They have been surviving and multiplying rapidly - Yellowstone now has about 121 wolves in 12 packs, after 50 pups were born in 1997 and 42 in 1998. They have taken their place in the ecology, feeding on elk, mountain lions, and coyotes. The carrion left behind by these kills has provided food for foxes and raptors, whose populations have rebounded. The project has been so successful that no new releases were planned in either area in 1997.
The U.S. Fish and Wildlife Service (USFWS) is the primary agency responsible for the recovery and conservation of endangered species in the U.S., including the gray wolf. They tried to work with the Idaho Department of Fish and Game but the Idaho legislature is dominated by "wise use" anti-environmentalists who prohibited Idaho Fish and Game from helping with wolf reintroduction. Instead, the USFWS contracted with the Nez Perce Indian tribe to manage the wolves, and this has been quite successful. The goal of the wolf recovery process in the northern Rocky Mountains is to remove the species from the Endangered Species List. This will be done when ten breeding pairs of wolves (about 100 wolves), become established in each of three recovery areas (northwest Montana, central Idaho, and the area in and near Yellowstone National Park) for three consecutive years.
Wolves kill livestock, and this has led to opposition to the reintroduction programs. But the non-governmental organization Defenders of Wildlife has established a fund, which is used to compensate ranchers for kills by either wolves or grizzly bears. Through June 2000 the introduced wolves in all three areas have killed 319 sheep and 159 cattle, so this kind of predation is a significant problem. The owners of the livestock are being reimbursed by Defenders of Wildlife (over $120,000 paid out so far). 64 of the wolves have had to be killed, and 83 moved to prevent further livestock damage. New reintroduction programs must include much more involvement of the local communities affected by them.
Mexican Gray Wolf. The Mexican subspecies of gray wolf was listed as endangered in 1976; and in 1998 the subspecies was down to 175 animals, all in captivity. A federal program to reintroduce the wolf in the American southwest has run into problems similar to those in Yellowstone. The wolves are being released in the Blue Range of the Apache National Forest within the Gila Headwaters Ecosystem along the Arizona - New Mexico border. Of 11 wolves released in January 1998, one was shot by a threatened camper, three were shot by unknown individuals, one disappeared and three had to be recaptured because they did not adjust well to life in the wild. The remaining three were all males. The second release involved nine wolves in two packs released in March 1998, of which four are still in the wild (update). Two more were released in November 1998 and four more in March 1999.
Following the Yellowstone example, the livestock industry has used a lawsuit to try to stop the Mexican gray wolf recovery program. The industry claims that the wolves should be removed from the Gila Headwaters Ecosystem, because wild wolves already exist there, and because the introduced wolves are coyote/wolf hybrids. Federal and academic scientists dispute both claims.
Grizzly Bear. Grizzly bears in the lower 48 States were almost wiped out by predator control programs over the past 100 years - from an estimated 50,000 before European settlement, to 800-1,000 living in about 2% of their historic range in Montana, Idaho, Wyoming, and Washington. They are listed as threatened in the lower 48 states, but are much more abundant in British Columbia and Alaska (distribution map). The Great Bear Rainforest of British Columbia is a major stronghold for the remaining grizzlies, yet in 2001 the B.C. Premier announced he would reinstate grizzly bear hunting in that province.
Because of the bear's threatened status, USFWS is planning to reintroduce the bear to appropriate but no longer occupied habitats. Grizzly bear reintroduction is politically even more difficult than wolf reintroduction, because grizzly bears are much more likely than wolves are to kill people. The reintroduction is being planned for the Selway-Bitterroot area of Idaho and Montana, an area that now has no grizzly bears but could support about 200. The plan is different from other reintroduction plans in that the animals would be established as an experimental population to be managed by a local Citizen Management Committee. There are strong feelings both for and against the reintroduction of grizzly bears, but 76.6% of over 20,000 signatures on petitions received in response to the plan were in favor of the reintroduction. In spite of this, in June 2001 Secretary of Interior Gale Norton proposed to withdraw the program. Then in June 2001 a wild grizzly was spotted in the Bitterroot area, suggesting that a viable population might still exist there. If confirmed, this discovery would mean a lot more protection for the area under the Endangered Species Act. The bear was shot. (Grizzly bear photograph by Barbara Jordan)
Trumpeter Swan. Reintroduction of migratory species can be especially difficult. The Trumpeter Swan, the largest waterfowl species in North America (weighing up to 35 pounds) was originally very abundant - every winter, hundreds of thousands migrated from their breeding grounds in New York state and Canada to their wintering areas further south, especially on the shores of the Chesapeake Bay. But by 1932 it was reduced to about 70 individuals because of drainage of marshes and over-exploitation for meat, skin, and feathers, which were used for making hats, powder puffs and quill pens. The haunting trumpetings, which were once heard over the entire continent, were silenced and the trumpeter was the rarest swan in the world. It was extirpated from California.
Conservation measures allowed the Trumpeter to increase to 3000 animals in the northern parts of the U.S. and Canada. The birds on the Pacific Flyway have re-established their original migration pattern, but the swans east of the Rockies no longer fly south for the winter; instead they live in the warm-water waste pools of power plants. Apparently they used to learn their migration route from the previous generation. Attempts have been made to reintroduce the swans into formerly inhabited marshes, but when they are released they fly off in all directions, and do not fly south for the winter.
Biologists have decided that they need to teach the swans how to migrate. Their project is based on a very famous discovery by the Austrian naturalist Konrad Lorenz. While breeding a captive colony of Greylag Geese, Lorenz discovered that the newly hatched goslings would form a permanent bond with their mother. But if she is not around they will bond with the first moving thing they see, and follow it around until they are mature. It can be a different species of bird (raising the possibility of fostering programs) or a moving cardboard box, or a nearby human. This phenomenon is called imprinting. Lorenz imprinted a whole gaggle of greylags on himself.
Biologists are now trying to get birds to imprint on boats and airplanes, so they can be taught to migrate. In a pilot (?) project, Sladen and Lisman imprinted a small flock of Canada Geese on an ultralight aircraft and taught them a migration route. In 1997 they removed eggs from a trumpeter swan nest prior to hatching. They imprinted them on on the ultralight, and eventually led them on their first migration - a 103-mile journey from Virginia across the Chesapeake Bay to its eastern shore. Three birds became the first trumpeter swans to winter on the Eastern Shore in over 200 years and they all found their way back to their starting point in Virginia. In the next phase of the project, the birds will be taught a longer route from western New York to the Chesapeake Bay. Hopefully, the pioneers will train the migration routes to their young, so the training by humans would only be necessary with one generation. In 1998, four swans followed an ultra-light aircraft from Canada to southern Indiana, and at least one made the return trip without help.
Similar tests are being done with Whooping Cranes.
A colony of European storks has been established in France in which the annual migration to West Africa has been deliberately suppressed, so that they can be protected even if the rest of the species suffers from habitat problems in the other part of their range.
Kemp's Ridley Sea Turtle. Migratory species are difficult to manage because nobody really knows how they learn their migration routes or how they navigate. Kemp's Ridley Sea Turtle is an example. In the 1940s about 40,000 of these turtles were seen nesting at one time on a beach in northeastern Mexico. In 1987 the number was down to 500 over the course of the entire year. In 1985 the species was reduced to less than 200 nests at a single nesting site (Rancho Nuevo, Mexico). In 1994, the number of nests at this site had risen to 580.
The depletion of Kemp's Ridley is due to poaching and to turtles getting caught in shrimp nets (at least 11,000 each year, perhaps four times that many, of which at least 500 are ridleys). Now the shrimp nets are required to have turtle excluder devices on them, which let the turtles out without losing the shrimp. Since 1977 USFWS has been taking turtle eggs from nests in Mexico, raising them in captivity for the first nine months in order to protect them from predators, then releasing them to the open sea. They have spent $4 million on this "headstarting" program, and released over 18,000 turtles (as of 1996). Some of them were released briefly into the water off Padre Island National Seashore in Texas, in the hopes that they would get imprinted on to that area and return there when grown.
The main problem with the headstarting program is that there is no way to know whether it is working or not! If the turtles do return to the beach where they started out, it would not be until they were ten years old, and there is no way to tag them for that long. So there is no way to tell if any of the headstarted turtles are surviving, and if they are, whether they are returning to the right beach and whether they are breeding. Certainly they are not breeding at Padre Island. The headstart organizers have cited, as evidence for survival, the fact that some tagged turtles have been found stranded on European coasts. If this is evidence for survival, it is also evidence that they are wandering far away from their normal migration routes, since wild turtles have not been seen there before.
Another ironic twist to this story is that the scientists involved as well as several major environmental groups are now against the program, and are arguing that the resources should go into proven conservation measures such as protecting the nests. But the program is strongly supported by the USFWS, and by the Gulf shrimp fishermen who are trying to avoid having to use turtle excluder devices that, they believe, reduce their catch. Representatives of Louisiana, Mississippi and Texas have introduced turtle "stocking" bills before Congress that would provide for a tenfold expansion of the headstarting program!
By the early 1980's it was clear that the only hope for the California Condor, the largest north American bird, was captive breeding. These giant birds have a wingspan of over nine feet and a weight of up to 25 pounds. In prehistoric times ranged from California to Florida, from Baja California to British Columbia. They probably fed on the carcasses of giant Pleistocene mammals like mammoths, ground sloths and camels.
By 1980 the population of California Condors was down to 27 birds in the coast range behind Santa Barbara. In the winter of 1984-85 the population in the wild plummeted from 15 to nine, and the decision was made to bring the remaining birds into captivity. The last nine wild condors were captured, leaving the animal extinct in the wild in 1987. Two of the captive birds successfully mated and produced the first captive-bred condor chick the following year. California Condors are now being produced at the Los Angeles Zoo, The World Center for Birds of Prey in Boise, Idaho, and the San Diego Wild Animal Park (where live condors are on public exhibit). One technique that helped, as with peregrine falcons, is double clutching - taking the first egg from the nest to induce the mother to lay a second one. The population has been managed very carefully in order to minimize inbreeding effects, and in October 2002 consisted of 126 birds.
Beginning with the first reintroductions in 1992, 13 condors have been reintroduced into the wild at the Sespe Condor Sanctuary in Los Padres National Forest, Santa Barbara County. However, they have had several problems. Four have died due to collisions with power lines and one due to poisoning by ethylene glycol (a component of antifreeze). One got sick after it visited a campground where campers fed it hot dogs and popcorn. Another five were recaptured because they were showing some behaviors that were too risky (like perching on power lines). The biologists tried to move them to more remote areas, but they flew back to their original release area.
Some of the captive-bred condors have been getting into trouble because they have no fear of people. The recovery team has therefore set up a condor preschool where the birds are given "aversion therapy". They let the chick loose in a large flight pen, move a person into its line of sight, then a group of biologists grab the bird and turn it upside down. They hope this will make them fearful of humans. They are also giving them a power line to perch on where they get a small shock, in order to teach them power line aversion.
California Condors have also been released at Lion Canyon in Kern County, Castle Craig in San Luis Obispo County, and the Vermilion Cliffs area in the Grand Canyon, Arizona. In October 2002 there were 75 living in the wild in California, Arizona and Baja California, Mexico.
The released condors have reproduced in the wild but unfortunately all of the chicks hatched since 1984 have died.
The primary goal of the Condor reintroduction project is to change the bird's status from "endangered" to "threatened". The U.S. Fish and Wildlife Service has established the following criteria that must be met for the status to be changed:
1. At least two non-captive populations
(one in California, one in Arizona) and one captive population must be established.
2. Each population must consist of at least 150 birds and contain at least 15 breeding pairs.
3. Each population must have a positive growth rate and must contain individuals descended from each of the 14 founding birds to ensure maximum genetic diversity.
4. The non-captive populations must occupy separate territories and not interact with each other.