Isle Royal wolf Vertebrae at right.
Prior to the atomization of wilderness, is was very rare for wolves, leopards, lions, etc, to inbreed very deeply for the simple reason that males were generally driven from their natal territories as they matured.
The "lone wolf" story is not a myth -- it is merely a very young or very old male wolf pushed out to try its luck finding a new territory ... or die trying. Much the same occurs with red fox, as I have noted in the past.
Wolves may travel many hundreds of miles looking for a space -- and a mate -- to call their own.
In very rare occasions, however, very isolated wolf populations have developed. The most famous of these is on the 206-square mile Isle Royale in Lake Superior, where two or three wolves crossed over on the ice in the 1940s in order to prey on a booming moose population that had established itself on the island around 1900.
The latest news is that an examination of Isle Royale wolves has found that the two dozen or so gray wolves on the island are suffering from backbone malformations caused by inbreeding, and that the abnormalities cause pain and partial paralysis while limiting the range of motion necessary for the wolf population to remain viable predators.
A full 58 percent of the wolves on Isle Royale have a congenital malformation in the lumbosacral region or lower back. This malformation is identical to the lumbar sacral deformities seen in German Shepherds. Other malformed vertebrae problems are also evident. Scientists note that while only 1 percent of noninbred wolf populations have malformed vertebrae, all of the Isle Royale wolf bone remains examined in the past 17 years have shown vertebrae problems.
As the Isle Royal Wolf web site notes:
Domestic dogs with LSTV malformities tend to suffer from cauda equina syndrome (CES), which involves injury to the spinal cord and associated nerve roots. The consequences of CES are variable and include partial paralysis; deficits in placing reactions when walking; deficits in voluntary movement of the tail; loss of muscle tone causing weakness of the hind limbs and flaccidity of the tail, low back pain and incontinence.
Dead Isle Royale wolf with tracking collar still on.
- Congenital bone deformities and the inbred wolves (Canis lupus) of Isle Royale
- Severe inbreeding depression in a wild wolf (Canis lupus) population (Sweden)
Inbred wolves have smaller litters which are less likely to survive.
- Selection for Heterozygosity Gives Hope to a Wild Population of Inbred Wolves (Sweden)
The least inbred wolves in a population were most likely to mate.
- Congenital defects in a highly inbred wild wolf population (Canis lupus) (Sweden)
Congenital malformations of the lumbosacral transitional vertebrae were found.
The probability that an Isle Royale wolf will be born with malformed vertebrae has increased dramatically over the past 50 years (dotted line). Source