A second silent spring awaits the wolves at Isle Royale, a tacit death knell for the struggling inbred population. There were no puppies born in 2012 and last summer when the puppies should have undenned and filled the island with their distinctive yips, none were heard to mark the presence of another generation. This last winter no new wolves were counted during the yearly census confirming the fears that 2012 would be the first year in 50 that no new wolf life would grace the island; this year could be the second.
June marks the earliest that scientists would expect to hear the vocalizations if a litter was born this year. None reported so far. The possibility for pups remains as researchers believe that half of the 8 wolves on the island are female and although the population now is as low as it has ever been in the half-century of study, the balance of males and females means that regrowth is possible. Some females were spotted out of their dens earlier in the spring which signals that they likely didn’t have a litter.
Beyond the spinal malformations you’re probably aware of, additional inbred diseases are becoming apparent in the population. Some wolves are being spotted with clouded eyes and a female wolf was found dead in her den during the 2009 winter having birthed only one of her litter, the first time a failure to whelp causing death has been observed in a wild wolf. The population has fallen every year since.
The Isle Royale wolves were once central to the debate over how significant inbreeding is in wild wolves and just how detrimental inbreeding depression could be. Amazingly some wolfaboo scientists were inbreeding depression denialists, although history and re-examination of their studies has not helped their position. The debate now is shifting to what should be done, if anything to remedy the situation on the island which few believe will turn itself around.
I’ve written before about how inappropriate it was that inbreeding apologists were using the Isle Royale wolf population as an example of animals that are either adapted to or unaffected by high levels of inbreeding. The wolves are on the brink of extinction, so time has bolstered this observation.
It’s an open question if and how much the influx of new genes has changed the bone deformities which had come to define Isle wolves. Surprisingly, before the results of the bone study were published, Isle Royale was used as an example of a wild population that was thriving and unharmed by inbreeding and isolation. This is why I’m cautious of anyone who argues from ignorance regarding their ability to inbreed and avoid disease. This is the third lesson: don’t assume that inbreeding can exist in high levels without detriment and don’t cite wild populations if no one has ever done a detailed health study to document the true health of the population.
Professor Linda Laikre in the Division of Population Genetics at Stockholm University prechoed* this sentiment over a decade ago:
Several misconceptions exist regarding inbreeding and the conclusions that can be drawn from the kind of studies of captive animals presented here, and unfortunately these misunderstandings appear to be fairly widespread. I discuss a few of these misconception in some detail because of their importance in practical conservation management.
The view that carnivores, and particularly wolves, regularly reproduce with close relatives in the wild still seems to be common. It is surprising that this notion is so difficult to change because it is based on weak argumentation.
First, it has been speculated that the effective population sizes of carnivore species in general are small (WATHEN et al. 1985; CHEPKOSADE et al. 1987), that the social structure of many carnivore species such as that of the wolf promotes close inbreeding (MECH 1970, 1987; SHIELDS 1982; HABER 1996), and that inbreeding does not pose a problem to wild wolves (SHIELDS 1983; MECH 1995). As pointed out by RALLS et al. (1986) there are no empirical data supporting these speculations. For instance, in their extensive literature review RALLS et al. (1986) could only find one occasional observation of a mating between wolves identified as close relatives (grandfather-granddaughter) in the wild (PETERSON et al. 1984).
Second, the results of a computer simulation study performed by WOOLPY and ECKSTRAND (1979) have been taken as evidence that wolf packs are highly inbred. The weakness of this study is also discussed by RALLS et al. (1986).
Third, the situation at the Isle Royale (Lake Superior, USA), where a single wolf pair is believed to have founded a population which has persisted for five decades is frequently referred to as an example indicating that wolves are adapted to inbreeding (MECH 1995; SWEDISH ENVIRONMENTAL PROTECTION AGENCY 1997a). Wolf numbers at Isle Royale increased during the first three decades to a maximum of approx. 50 individuals, but has dropped considerably on several occasions during the last 20 years (PETERSON 1997). For instance, the winter 1997-98, 13 of a total of 24 animals died (ENVIRONMENTAL NEWS NETWORK 1998). To consider the Isle Royale case as a proof of wolves being adapted to close inbreeding disregards several facts: i) the effects of inbreeding on various traits have not been studied in this population, ii) it is not clear that the repeated drops in population size are not coupled with genetic factors (WAYNE et al. 1991), iii) even if the wolf population at Isle Royale should prove to be insensitive to inbreeding this observation cannot be used to conclude that wolves in general are adapted to close inbreeding.
The occurrence of inbreeding depression in a wild animal species bred in captivity provides clear indications that this particular species is not adapted to close inbreeding. This conclusion is obvious to a geneticist, but is frequently questioned by, for instance, wildlife managers and behavior specialists, who express the idea that genetic studies on animals in captivity are not relevant to those in the wild (e.g., SWEDISH ENVIRONMENTAL PROTECTION AGENCY 1997a).
This misconception may stem from the fact that conclusions regarding behavior of animals in the wild may not be possible to draw from behavior observations of captive animals. In contrast to behavior, however, the genes are the same whether the animal is free or held in captivity. Of course, it is not certain that the same type of inbreeding effects occur in every population.
If and how inbreeding depression is expressed depends on the particular genes that the individuals which are inbred carry. For instance, in a recent study of two captive populations of Mexican and red wolves no effect of inbreeding on juvenile survival and litter size could be detected (KALINOWSKI et al. 1999). This does not mean, however, that other characters in these populations are not affected by inbreeding, or that other wolf populations are not sensitive to inbreeding. As a parallel to the skeptic question “even if inbreeding is harmful in captivity, how can we be sure that inbreeding will have the same effects in the wild?” one may consider a query like “this chemical substance has proven toxic in laboratory animals, but how can we be sure it will cause damage in nature?”.
Laikre, L. 1999. Conservation genetics of Nordic carnivores: lessons from zoos. – Hereditus 130: 203-216. Lund, Sweden.
Inbreeding apologists in the dog world love invoking the notion that wolves inbreed all the time and are just fine and not harmed. As is clear from the scientific evidence, this once common refrain is nothing more than an unsupported meme that is not backed up by empirical or observational evidence.
Scientists are fighting against this misconception because it has major implications on the structure and success of wildlife conservancy programs. Dog breeders should take note as these same principles are vital for the maintenance and rejuvenation of our breeds as well.
past participle, past tense of prech·o
Statement of an idea prior to another source, especially when the existence of the first source is unknown to the second or less prominent. e.g. Archibald Carey prechoed Martin Luther King when he ended a civil rights speech with “from every mountainside, LET FREEDOM RING!”
Chepko-Sade BD and Shields WM, Berger J, Halpin ZT, Jones WT, Rogers LL, Rood JP and Smith AT, (1987). The effects of dispersal and social structure on effective population size. In: Mammalian dispersal patterns. The effects of social structure on population genetics (eds. BD Chepko-Sade and ZT Halpin) The University of Chicago Press, Chicago and London, p. 287-321.
Haber GC, (1996). Biological, conservation, and ethical implications of exploiting and controlling wolves. Conserv. Biol. 10:1068-1081
Kalinowski ST, Hedrick PW and Miller PS. No evidence for inbreeding depression in Mexican and red wolves. Conserv. Biol., 1999.
Mech LD, (1970). The wolf: the ecology and behavior of an endangered species. The Natural History Press, Garden City, New York.
Mech LD, (1987). Age, season, distance, direction, and social aspects of wolf dispersal from a Minnesota pack. In: Mammalian dispersal patterns. The effects of social structure on population genetics (eds. BD Chepko-Sade and ZT Halpin) The University of Chicago Press, Chicago and London, p. 55-74.
Mech LD, (1995). The challenge and opportunity of recovering wolf populations. Conserv. Biol. 9:270-278.
Ralls K, Harvey PH and Lyles AM, (1986). Inbreeding in natural populations of birds and mammals. In: Conservation biology. The science of scarcity and diversity (ed. ME Soule) Sinauer Associates, Sunderland, Massachusetts, p. 35-56
Shields WM, (1982). Philopatry, inbreeding, and the evolution of sex. State University of New York Press, Albany.
Shields WM, (1983). Genetic considerations in the management of the wolf and other large vertebrates: an alternative view. In: Wolves in Canada and Alaska: their status, biology and management (ed. LN Carbyn) Canadian Wildlife Service Report Series 0069-0031, 45. Ottawa, p. 90-92
Swedish Environmental Protection Agency, (1997a). Forslag till itgardsprogram-Varg (Canis lupus, Linnaeus 1758). (Suggested action program-Wolf (Canis lupus Linneaus 1978 (In Swedish), Stockholm, Sweden
Wathen WG, McCracken GF and Pelton MR, (1985). Genetic variation in black bears from the Great Smoky Mountains National Park. J. Mamm. 66:564-567.
Wayne RK, Lehman N, Girman D, Gogan PJP, Gilbert DA, Hansen K, Peterson RO, Seal US, Eisenhawer A, Mech LD and Krumenaker RJ, (1991). Conservation genetics of the endangered Isle Royale gray wolf. Conserv. Biol. 5:41-51
Woolpy JH and Eckstrand I, (1979). Wolf pack genetics, a computer simulation with theory. In: The behavior and ecology of wolves. Proceedings of the symposium on the behavior and ecology of wolves held on 23-24 May 1975 at the annual meeting of the Animal Behavior Society in Wilmington, NC (ed. E Klinghammer) Garland STPM Press, New York and London. p. 206-224.
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