Population Viability, Nature Reserves, and the Outlook for Gray Wolf Conservation in North America

Population Viability, Nature Reserves, and the Outlook for Gray Wolf Conservation in North America

S. H. Fritts & L.N. Carbyn

1995

Abstract

Theoretical work on population viability and extinction probabilities, empirical data from Canis lupus (gray wolf) populations, and expert opinion provide only general and conflicting conclusions about the number of wolves and the size of areas needed for conservation of wolf populations....We estimate that a population of 100 or more wolves and a reserve of several thousand square kilometers may be necessary to maintain a viable population in complete isolation....In most cases, management intervention is probably necessary to assure the viability of relatively small, isolated populations. Because most reserves may be inadequate by themselves to ensure the long-term survival of wolf populations, favorable human attitudes toward the species and its management must be recognized as paramount....

Any attempt to foretell the future is risky. Nonetheless, if history teaches us anything at all, it seems safe to predict that human attitudes and values will continue to be the ultimate factor limiting the number and distribution of wolves in North America. These factors, combined with conflicts over land-use priorities will shape the laws, policies, and human behavior that will determine the fate of wolves in different parts of the continent throughout the twenty-first century....Reintroduction programs and natural repopulation will re-establish wolves in parts of their former range and potentially create the situations that concern population viability theorists the most -- that is, relatively small populations that are isolated or semi-isolated from other populations.

A viable wolf population requires an area of some minimum size and with adequate prey and security from excessive human exploitation....In some regions, wolf populations may be able to survive only in parks, designated wilderness areas, wildlife refuges, and wildlife management areas, where conflict with human economic enterprise in minimal. Generally such areas...are not now essential to the survival of the species on a continent-wide basis. They are the most secure places, however, to which the range could collapse in future decades or centuries...and the result may be a complex subdivision of the species' range.

Accordingly, it becomes important to ask what minimum population levels and types of areas are necessary for wolf population survival. How much genetic exchange between and among populations is necessary to maintain genetic variability and viability? What does it take to preserve wolves in special places, and what should be the size and characteristics of those areas?....

We synthesized information pertaining to the estimation of the minimum viable population (MVP) size for wolves, examined case histories of wolf populations, especially the performance of isolated or semi-isolated populations of various sizes, and solicited the opinions of wolf biologists to develop insight into the minimum population size and land area requirements for wolf conservation....

What is the Potential Role of Nature Reserves in Wolf Conservation?

....Large carnivores are particularly vulnerable by virtue of their low numbers and wide-ranging movements. Often people living closest to wolves have negative perceptions about them. Therefore, it is especially challenging to protect these animals against anthropogenic effects that operate outside of nature reserves. In Canada and the U.S. national parks and preserves, national wildlife refuges, ecological reserves and wilderness areas are the best examples of such places, but none is free of human impacts. National parks are more likely to be free of practices such as livestock grazing and hunting that could conflict with the presence of wolves. Even within parks, factors such as tourism and roads may compromise the ability to protect certain wildlife, especially in temperate areas where human population is higher....Nature reserves may be buffered by surrounding lands that provide habitat (for example, Yellowstone National Park surrounded by national forests) or may have no buffer (for example, Riding Mountain National Park surrounded by agricultural lands). The adequacy of even the largest reserves to protect viable populations of carnivores over the long term is questionable. To date, nature reserves have not played a critical role in gray wolf survival in the U.S. and Canada, although they have been important regionally. Most such reserves in the contiguous U.S. were established after the wolf was virtually extinct and certainly not with wolf conservation in mind. In considering potential nature reserves for wolves, we need to recognize that places with minimal human influence are not necessarily required. Although people have come to associate wolves with undisturbed wilderness, wolves are able to survive in highly altered landscapes and near humans as long as food is available and they are not unduly persecuted.

The availability of additional lands that could be occupied by wolves in combination with those currently occupied generally sets the upper limit to continent-wide population recovery. In Canada, wolves remain on about 86% of their former range....Wolves still occupy at least 85% of Alaska.

In the U.S., the areas with the greatest potential to afford protection to wolves and their prey are under federal ownership, including national parks, designated wilderness, national wildlife refuges, and possibly some tribal and military lands. Federal land in the U.S. totals 2,679,671 km2, or 29% of the land area, with the percentage in most inter-mountain states ranging from 28% to 82%; federal land in Alaska totals 68%....It is heartening that 85% of lands adjacent to national parks is in public ownership. Nine units of the national park system exceed 10,000 km2, and those...are in Alaska. Yellowstone National Park, at 8992 km2, is the largest in the lower 48 states....

Wildlands in the U.S. and Canada are owned and managed by a variety of agencies under widely differing mandates. Large carnivores, including wolves, are thought to require tracts of land larger than the jurisdiction of a single agency or landowner. Both in Canada and the U.S., cooperation between adjacent national parks, wildlife refuges, and other wildlands as conservation networks has been advocated as a means of greatly increasing the effective size of areas for large species. Salwassar et al. (1987) identified 10 potential networks in the U.S., most in the western states, ranging from 925 km2 to 12,373 km2....

National parks also provide the most secure areas for carnivore conservation in Canada....In 1993 Canada contained 36 national parks, of which 18 supported wolf populations....Wood Buffalo National Park, at 44,800 km2 is the largest in Canada and the second largest park in the world.

As is true for the U.S., the effectiveness of the Canadian National Parks System in protecting carnivores has been questioned, and one solution being proposed is to establish "Carnivore Conservation Areas." Five candidate areas were identified in western Canada, ranging in size from 6500 to 40,000 km2. The concept was to identify protective core areas -- critical areas with the highest protection -- and secondary areas around the core in which resource extraction and the use of renewable resources could occur in the most appropriate manner to minimize effects on wildlife populations in core areas....The concept of Carnivore Conservation Areas has attracted little political support, although some progress is being made within the Canadian Rocky Mountain Parks complex.

Concept of Minimum Viable Populations

The relationship between the size and design of nature reserves and long-term wolf conservation is inextricably related to the concept of minimum viable population. The estimation of MVP has been widely applied to wolves, mainly because some 60,000 to 70,000 gray wolves survive over a broad area of the continent.

Population viability analysis addresses the likelihood of a population's persistence over a specified period under specified conditions. The minimum viable population is a population large enough to permit "long-term" persistence despite genetic, demographic, and environmental uncertainties. Discussions of MVPs are predicated on the availability of a minimum secure space, sometimes referred to as a minimum area requirement, that has a specified probability (such as 95% or 99%) of supporting a population for an arbitrarily chosen period (such as 100 or 200 years). Parameters applicable to MVPs include genetic diversity, demographic stochasticity, environmental stochasticity, long-term stages in plant succession, natural catastrophes, and social dysfunction. Genetic heterozygosity is thought to be positively correlated with the reproductive vigor needed for population growth and adaptation to changing environments. Demographic factors affect population size and persistence and include such parameters as sex ratio, litter size, survival rates, age distribution, and age at first reproduction. Variance in individual reproductive performance is a major component of both demographic and genetic stochasticity and thus is a major component of the analysis of population viability. Changes in climate and other unpredictable aspects of the environment affect the availability of key resources, especially vulnerable prey in the case of wolves. Similarly, long-term changes in plant succession can cause major shifts in prey availability, thus affecting a wolf population.

The genetic variation of closed populations may be affected if the gene pool is small....Debates have centered on the impact of inbreeding within a mammalian population. Small, isolated populations are theoretically more likely to become extinct within a specified period than large, contiguous populations because of loss of genetic variability, demographics, and unpredictable events. Small populations lose genetic variability much faster than larger populations, but the problem evidently can be offset with only one or a few migrants per generation. Wolf dispersal can be very extensive, up to 886 km, and wolves can cross large expanses of open area and interstate highways, so complete isolation and problems of genetic variability would likely be rare. Actually...no wild population has been demonstrated to have declined because of inbreeding.

The development of the concept of minimal viable population has been highly theoretical and has generally followed two separate tracks. Community ecologists have focused on minimum areas for system viability, drawing on concepts from island biogeography, whereas population biologists have focused on the minimum population sizes or densities for target species. The process of population viability analysis (PVA) was developed in the 1980s to examine how stochastic factors interact to influence the persistence of small populations....[D]evelopment of an accurate model to predict population survival is still elusive. An MVP is yet to be confidently calculated for any species....

Existing Information on the State of the Art

....Theberge (1983)...anticipated loss of genetic variability in small or isolated populations of wolves and the loss of vigor and fecundity that could result. Based on the minimum...of 50 wolves, he calculated that a minimum of 13,000 km2 would be necessary to support a population in Canada, owing to the low densities of wolves, assumed at 1 wolf/260 km2, in his calculations. He warned against actions that would create an increasingly patchy distribution, including regional prey depletion and long-term wolf control....

Estimating MVP from models is difficult for a variety of reasons, a major one being environmental stochasticity. Boyce (1992) reviewed five empirical studies on extinction for different vertebrate taxa on oceanic and habitat islands, which revealed that populations below 50 consistently show a high probability of extinction, whereas populations above 200 are often reasonably secure, given protected habitat. Soule and Simberloff (1986) observed that thoughtful estimates of MVP for many animal species are rarely lower than...a few hundred, and this lower limit would often correspond to an actual population of about 1000. Soule (1987) guessed that MVPs...would often be in the low thousands for vertebrates. If this were the case, long-term conservation for many wolf populations in a specific regional setting would be impossible.

Thomas (1990)...pointed out, however, that populations that occupy habitat fragments far too small to hold thousands of individuals sometimes have strong conservation potential. If isolation is not complete, if variability in population size is low, and if the environment is stable, geometric mean values of 500 may allow long-term persistence.

The only PVAs done on wolves to date have been on Canis lupus baileyi, the Mexican wolf, Canis lupus spp., the gray wolf in Italy, and Canis rufus, the red wolf....The PVA for the Italian wolf was unique in that it examined an existing wild population (280-300 individuals)....This PVA depicted an extreme sensitivity of the Italian population to any increase in adult mortality. The analysis suggested a fairly high probability of extinction within both 100 and 60 years for the two presumably isolated subpopulations if any increase in adult mortality occurred, even in the absence of any environmental instability or inbreeding depression....Assessment of the accuracy of this model should consider that the population(s) recently rebounded from around 100 wolves for several decades to its present size, that it has been isolated for 100-200 years, and that it has been increasing.

The PVA for the red wolf concluded that it would not be possible to maintain a single, contiguous wild population of the hundreds or thousands that were determined necessary for viability. The chosen approach was to manage it as a metapopulation, with intensive migration management to preclude genetic and demographic problems. Establishment of 220 red wolves in the wild and 330 in captivity is the goal. The original founder population of the red wolf was 15 wild individuals.

The draft PVA for the Mexican wolf, which exists only in captivity, recommends that to recover the subspecies biologically a metapopulation of at least 1000 free-ranging wolves will be needed, although no justification for this number is provided. In addition, a population of 300-500 Mexican wolves in captivity was recommended to preserve 90% of the original genetic diversity for 200 years....The entire population is based on four founders.

Discussion and studies about the reintroduction of wolves into Yellowstone National Park (8992 km2) have addressed whether the park alone is an adequate reserve for wolves. Estimates of the number of wolves that would occupy the park range from 50 to 150, with the general conclusion that the park could support a self-sustaining population....[T]he security of a Yellowstone wolf population could be increased by expanding the recovery zone outside of Yellowstone National Park, which was assumed to increase population size.

....There appears to be general consensus among conservation biologists that U.S. reserves are too small to support large vertebrate species for long periods. Newmark (1985) examined eight parks and park assemblages in western North America and concluded that only one could support populations of wolves and other wide-ranging mammals....Simberloff (1988) suggested, however, that Newmark may have greatly overestimated the insularization of American parks and rates of mammalian extinction....

....Goodman (1987) believed that a series of reserves, equal in total area to one large reserve, would have fewer extinctions from environmental perturbation than a large one, so long as there was migration among them (all other factors assumed to be equal)....Many species, including wolves, in reality often exist as a population of populations, termed a metapopulation. Allendorf's (1983) recommended management strategy of one successfully reproducing migrant per generation among isolated nature reserves would presumably occur naturally in a true metapopulation, maintaining genetic viability. Shaffer (1987) pointed out that metapopulation arrangements can aid significantly in reducing the size requirement of any particular reserve, so long as animals can move among reserve units. Wolves have a strong advantage in this regard because of their tendency to travel long distances....

....American recovery plans for the gray wolf contain area and number requirements arrived at by consensus of recovery team members familiar with the species. The Northern Rocky Mountain Wolf Recovery Plan mentioned a minimum contiguous area of 7770 km2, or a lesser area if adjacent available lands that could support wolves exceed 7770 km2 in the aggregate of lands. The Mexican Wolf Recovery Plan recommended reestablishing a "viable, self-sustaining population of at least 100 Mexican wolves in the middle to high elevations of a 12,950 km2 area within the Mexican wolf's historic range". Areas being considered for release of Mexican wolves contain 2000-3000 kmn2 and 13,000-18,000 km2 of habitat thought to be suitable for wolves....An evaluation of areas suitable for wolves in Colorado identified a complex of 98,000 km2 of public land...that is contiguous. The area was estimated to be capable of supporting 1128 wolves.

The revised Eastern Timber Wolf Recovery Plan specified the need for two "viable" populations, Minnesota's plus one other. For a population outside of Minnesota to be considered viable, (1) if isolated, it must average at least one wolf per 128 km2 (self-sustaining, >200 wolves) distributed within a minimum of 25,600 km2 over five consecutive years, or (2) if located within 160 km of a self-sustaining wolf population, it must average at least one wolf per 128 km2 or consist of 100 wolves in an area of at least 12,800 km2 over five consecutive years. The recovery team believed that a population of at least 200 wolves located more than 322 km from the Minnesota population (for example, in northern New York or northern Maine) was large enough to be viable, as well as to have sufficient genetic diversity to exist indefinitely in isolation. The team also believed that a smaller population (>100) in Wisconsin/Michigan would remain viable and retain necessary genetic diversity via immigration from Minnesota. Overall, the team believed that a healthy, self-sustaining population should include at least 100 interbreeding wolves.

Survey of Biologists

In November-December 1992, 43 American and Canadian biologists familiar with wolves were surveyed about whether a scenario as in the Northern Rocky Mountain Wolf Recovery Plan would equate to a viable population. Recovery goals set in the plan were 10 breeding pairs (assumed to be about 100 wolves) living in each of three separate areas for at least three consecutive years....Fourteen of the 23 who responded (61%) believed that 10 breeding pairs sustaining themselves for three consecutive years at least met the minimum standards of a viable population, whereas five believed this number was too low....Eleven volunteered the comment that an isolated single population would likely face future difficulty, but exchange among three subpopulations would greatly enhance viability of subpopulations. Relatedness of founders was another frequently mentioned consideration.

Case Histories

....Isle Royale National Park, Biosphere Reserve, Michigan -- 544 km2. The best information on the dynamics of a small, isolated wolf population is from Isle Royale in Lake Superior. The Isle Royale wolf population was probably founded in 1949 from a single gray wolf pair immigrating over the ice from mainland Minnesota, a distance of 24 km. The population has numbered as high as 50, but from 1988 to 1993 it declined to about a dozen animals, and then increased to 17. Wayne et al. (1991) calculated that the Isle Royale population may have only about 50% of the heterozygosity of mainland wolves. Both the founder effect and genetic drift were believed instrumental in reducing genetic variability, which may have been responsible for the population decline via poor reproduction....An advantage of this island as a nature reserve is that it is completely surrounded by water and relatively free of most negative human influences. But absence, or near absence, or immigration is a clear disadvantage.

Riding Mountain National Park, Man and Biosphere Reserve, Manitoba -- 2978 km2/6700 km2. This Biosphere Reserve consist of the park (2978 km2) and surrounding agricultural area. Wolves colonized the area during the early 1930s, probably from the Duck Mountains, a distance of about 35 km. The population has fluctuated between 40 and 120 wolves and has persisted some 60 years. About 70% of the packs are vulnerable to human exploitation, with considerable turnover in the population. The surrounding agricultural zone affords no protection, so the effective zone for wolf conservation is the park area. A high prey biomass and lack of obvious clumping of prey seem to be important factors. The population appears secure in the short term....

Jasper National Park, Alberta -- 10,878 km2. Wolf extermination and recolonization in this park has occurred twice in the 20th century. The area has supported 40 to 80 wolves in recent years....[A] large proportion of wolves leaves the park in winter. The population has undergone wide fluctuation due, at least in part, to predator control outside the park. Even though the Canadian Rocky Mountain National Parks cover large areas, the effective zones for wolf conservation are limited to areas of high ungulate concentrations. These areas are limited, often to valley bottoms. Areas that are also used as human transportation corridors render wolves vulnerable to vehicular and train mortality.

Kenai Peninsula, Alaska -- 26,000 km2. This peninsula is essentially an island connected with the Alaska mainland by a narrow neck of land and ice only 16 km wide. About 14,278 km2 on the Kenai are considered wolf habitat. Wolves were extirpated by about 1915; natural recolonization began during the 1960s. During the 1970s the population expanded rapidly and became established throughout the peninsula, with about 186 wolves present in 1981. Currently, the population is stable at 150-180 wolves, with substantial regulated human harvest.

Alexander Archipelago, Alaska. Wolves occupy a 540-km long complex of islands of various size and degree of isolation off the coast of southeastern Alaska. Island sizes range from less than 30 km2 to more than 6700 km2 (Prince of Wales Island), and distance between islands range from less than 1 km to 12 km. The overall population is estimated at about 750-1500 animals. The wolves occupying these islands, considered in some taxonomic treatments as Canis lupus ligoni (the Alexander Archipelago wolf) may have been isolated for centuries or even millenia by open water. The Alexander Archipelago wolf is currently being proposed by the U.S. Fish and Wildlife Service for listing as threatened under the Endangered Species Act of 1973, as amended. Historical data suggests that only a few islands are sufficiently large to maintain persistent wolf populations completely within their boundaries. Preliminary simulations...indicated that an island size of 2500-3500 km2 was needed for a population persistence of 250 years. Smaller islands may represent ephemeral sink populations maintained by dispersal from stable sources on larger islands....The smaller body size and skull dimensions of Alexander Archipelago wolves compared to Alaska mainland wolves supports the notion that they have indeed been isolated for long periods.

Coronation island, Alaska -- 73 km2. This island is part of the Alexander Archipelago discussed above and historically was not inhabited by wolves. Four wolves were introduced in 1960 by the Alaska Department of Fish and Game. Wolves increased to 13...in four years, declined to one wolf by 1968, and went extinct within 10 years of introduction. The conclusion from the experiment was that the island was too small to sustain a prey base for a population of wolves and that immigration of wolves was not possible.

European wolf populations. Various parts of Europe support wolves...and circumstances there shed light on the tenacity of wolf populations. Wolves on the Italian and Iberian peninsulas have survived long periods of isolation at greatly reduced population sizes.

In Italy, wolves were widespread until the second half of the nineteenth century. They have apparently been isolated from other European wolves for 100-200 years and are distributed in two apparently isolated populations in central and southern Italy. As a result of legal protection, populations have increased from 100-200 in 1971-1973 to 300-400 in 1990-1991, and distribution has expanded....This population seems to be viable in every sense, appears limited only by killing by humans, and is believed to still be increasing as human attitudes toward the species become more positive.

The wolf population in Spain has been progressively reduced in number and distribution by human activities. Blanco et al. (1990) estimated a total population of 1500-2000 individuals, primarily in the northwest portion of the country, with small isolated groups of 40-56 individuals surviving in the south. Some 150 wolves remain in northeastern Portugal adjacent to the Spanish population. Wolves in Spain and Portugal have been isolated from continental populations for at least several decades and appear to be depressed only by human persecution.

The population in Poland numbered about 1000 wolves at the end of World War II, but subsequently they were considered pests and deliberately reduced to about 100 after the 1950s. After 1976, when their game-animal status was resumed, wolves increased steadily and were estimated at 858 by the spring of 1991.

At least 23 immigrant wolves, apparently from Poland, were killed in Germany between World War II and 1992. Reproduction occurred in the country in 1992 for the first time in 150 years. The wolf was eliminated from France, but now a pack has become established in the French Alps, likely via dispersal from Italy.

Wolves were widespread in Sweden and Norway until they were heavily persecuted and essentially eradicated by the beginning of the nineteenth century. Remnants survived for a long time with a surprisingly small population base in northern Scandinavia. The last wolf was killed in Sweden in 1966. Legal protection was granted in Sweden and Norway in 1973. Since then a population has become reestablished, probably via dispersal from Finland; although isolated from the nearest population by at least 500 km, this population has grown dramatically in the past two years, increasing to a total of 20-25 wolves in the two countries....

Reserve Considerations

The overall size and configuration of nature reserves is important in providing adequate space for the protection of wolves, but prey biomass and prey distribution in the system are also critical. For example, the clumping of prey on winter range in mountain/valley systems tends to negate the value of large areas because the distribution of wolves is affected by the availability of prey. Areas may be large in absolute terms, but their effectiveness is reduced if they are long and narrow, thus increasing the probability that wolves will spend time outside the reserves and be exposed to harmful human activities. Ideally, relatively few wolf pack territories should traverse or border the reserve edge, depending on conditions outside. However, in all of North America there are probably fewer than half a dozen wolf packs living exclusively within parks that are not potentially vulnerable to exploitation, or that would be vulnerable except for legal protection in the surrounding area....

The seasonal migration or movement of wolves in response to prey migration is well known, primarily from tundra and mountainous areas. In some U.S. and Canadian national parks, prey populations regularly emigrate across park boundaries to areas not under park jurisdiction. Forbes and Theberge (1994) reported that extensive excursions by several Algonquin Park wolf packs to a deer yard outside the park resulted in a high rate of human-caused mortality. Consequently, wolves from half of the packs in one of the few officially protected wolf populations in Canada were vulnerable. Seven of nine Yellowstone elk herds migrate out of the park in winter (40% of Yellowstone elk leave the park), causing concern that some wolf packs may follow them and be vulnerable to human taking, although most wolves are expected to remain on the high-density elk winter range within the park. The availability of ungulate winter habitat appears to limit the abundance of wolves in Glacier National Park. The 2-3 wolf packs that have used the park occupy the western edge because of prey distribution....

Productivity manifested as prey biomass per unit area is also important. This factor affects wolf density, which affects total wolves supported within a given area....Early indications in the northern Rockies of the U.S. are that more remote and pristine areas will often be avoided by wolves because of high elevation, steep terrain, deep snow, and poorer habitat quality for seasonal use by ungulates....Generally, more northerly reserves will have to be larger because overall prey biomass density is lower.

....Of primary importance to wolf conservation within nature reserves are the attitudes and density of humans living around the reserves....The presence or absence of livestock adjacent to nature reserves and the degree of hunting of large ungulates are important factors in the human response to wolves when they leave a reserve....This is one of the most important factors of all, because deliberate killing of wolves by humans can reduce or eliminate populations....

Wolf populations should not be totally isolated. Dispersal corridors connecting populations for occasional or regular gene flow theoretically would allow greater persistence of the populations, although we have previously pointed out that wolves are excellent dispersers and that the presence of discrete dispersal corridors per se seems to be less important to them than to most other species. Nonetheless, connectivity between reserves can enhance wolf colonization of adjacent areas and movement between reserves. The colonization pattern and movements of wolves within the Rocky Mountain chain in southwestern Canada and Montana are examples. At population lows and where exchange of individuals among populations does not occur, loss of genetic variability is possible and may in the long run be detrimental to wolves living in isolation. But this result remains to be documented for wild wolves.

Discussion and Conclusions

....Riding Mountain National Park, Manitoba, appears to be large enough at 3000 km2 to accomplish the objective of total ecosystem protection, and some exchange of wolves between this area and populations to the north likely occurs. We conclude, given the appropriate prey base and types of land uses around the area, that 3000 km2 may be an adequate area to protect a core wolf population. It should be noted that farming around Riding Mountain National Park is largely for grain production. In areas with cattle ranching, the human pressures are greater, particularly if areas surrounding nature reserves contain mosaics of forest and open range land.

In the absence of experimentation (opportunities are limited, but some work is possible), the next best approach to learning about wolf population viability is long-term monitoring of isolated or semi-isolated wolf populations to determine their persistence times. The upcoming re-establishment and long-term monitoring of wolves in Yellowstone National Park and central Idaho and in the Southwestern U.S., as well as long-term data from the red wolf program in North Carolina, will significantly increase understanding of these processes and enhance wolf conservation. Similarly, natural re-establishment of wolf populations in certain areas of Europe (France, Germany, Sweden, and Norway) will enhance the understanding of wolf population survival in a modern and changed human landscape....

Clearly, no one really knows the MVP of wolves or the size and design of reserves that can guarantee long-term survival. Theories about the viability of populations and extinction probabilities need to be tailored more appropriately to wolves and continually refined....Efforts to build on existing theory should benefit from data derived from the long-term monitoring of key populations over long periods....The extraordinary dispersal capability of the species -- hence a large degree of "metapopulation connectedness" -- may be a major reason that small, local populations can survive and why simple theoretical models are not adequate for wolves....

According to existing theory, few individual U.S. and Canadian parks would be able by themselves to support viable populations over long periods if extermination took place outside the park areas. The field data available, however, suggest that wolf populations may be considerably more resilient than suggested by the theoretical MVP calculations to date. Furthermore, most wolf biologists replying to our survey view the wolf as less vulnerable than indicated by existing theory, at least if not extirpated by humans. We see the fate of wolves in most of North America as more a function of human tolerance than of nature reserve availability, although reserves may provide insurance of some base population level.

Even under the bleakest of fragmentation scenarios, we view the long-term future of wolves over much of the continent to be as a metapopulation in which one unit can augment or even repopulate others via dispersal. A wolf population that was truly in danger of extinction could be artificially augmented with wolves from another area, unless introducing genetic material from another area is not desirable. Overall, very little genetic differentiation has been found in gray wolves in North America. Metapopulation arrangements can aid in reducing the size requirement for any particular reserve, so long as wolves can move or be moved among reserve units.

In conclusion, we believe that wolf conservationists should not be daunted by theoretical treatments of population viability to date. Moreover, the lack of wolf reserves of sufficient size to satisfy population viability theorists should not alone negate resotration efforts....For the foreseeable future, the most challenging wolf conservation efforts will involve fringe populations -- especially those located in the southern part of the species' range -- and rare subspecies, such as the Mexican wolf. Since single jurisdictions will rarely support the number of wolves necessary for theoretical viability, joint efforts of different jurisdictions should be stressed. We strongly agree with others...who argue that the conservation of relatively small numbers of a species in small reserves may be worthwhile for ecological or social reasons, even though these populations may add little or nothing to the theoretical viability of the species as a whole....

INCLUDES

References: 108