Small wolf population faced with danger of inbreeding

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By Tapio Mainio in Oulu
     
      The reduction in the size of the wolf population in Finland is threatening the animal’s genetic diversity, says Jouni Aspi, senior curator at the Zoological Museum of Oulu University.
      The nightmare scenario is the situation already being faced in Sweden, where a highly inbred population of around 120 wolves is known to be suffering from a range of congenital bone disorders.
      “One in ten Swedish wolves has some form of skeletal problem”, says Jannike Räikkönen from the Swedish Museum of Natural History.
      Swedish wild wolves have been shown to have development anomalies in their spine, which have even led to paralysis of the back legs. In 1999, a paralysed male wolf was found in Sweden.
     
Wolves suffering from something resembling a kind of lupine scoliosis could start to turn up in Finland, too, according to Räikkönen, if a dwindling wolf pack takes to breeding among close relatives.
      The Finnish wolf population has been seen to have declined of late from around 300 to 200.
      Such congenital faults in the vertebrae of Finnish wolves have thus far been found only in just over 1% of animals.
     
“The Finnish wolf population has regularly got new bloodlines from Russia, but the recent evidence seems to suggest that the arrival of wolves from across the eastern border has declined”, says Jouni Aspi.
      The downward trend in the health of Swedish wolves was first noticed more than a decade ago at the Kolmården Zoo in Sweden, where it was found that some of the wolves had gone blind. The wolves in captivity had been studied by Linda Laikre.
      Zoos make a special effort to exchange animals in order to limit the risk of inbreeding.
     
“The wolf is extremely sensitive to the adverse effects of excessive inbreeding, because it has a very large territory”, says emeritus professor Erkki Pulliainen.
      Pulliainen first observed congenital blindness caused by inbreeding in studies he made in the 1960s.
      Sweden’s original wolf population was hunted to extinction back in the ‘60s.
      “The wolf made a return to Sweden in 1983, when the population was restarted through a pair of wolves that had wandered across from Finland. The male wolf later mated with some of its own offspring, because the mother wolf died”, says Aspi.
     
“Sweden would need migration of wolves from Finland. At least a dozen or so wolves have crossed the western border in this decade, but with just one exception, all have been hunted down and killed illegally in the Swedish reindeer herding areas”, says Räikkönen.
      A she-wolf gives birth to an average of four pups or cubs a year.
      There can be several mature females in a wolf pack. They will come into season, but only the alpha female, coupling with the alpha male, will actually have a litter of pups.
      A pack cannot usually support more than a single litter, hence the restrictive behaviour.
     
“There should be at least 50 females reproducing in Finland in order for the population’s genetic diversity to be maintained”, says Jouni Aspi.
      The Finnish wild wolf population should be at least 250 in order that there would be enough mating pairs, but a recent survey indicated that the numbers had mysteriously declined, over and above the numbers culled legally.
     
Helsingin Sanomat / First published in print 13.4.2008

More on this subject:
 BACKGROUND: The wolf still evokes fears

Previously in HS International Edition:
  Scientists baffled by disappearance of wolves from Finnish forests (7.4.2008)
  European Court of Justice ruling will not change Finland´s wolf population management plan (15.6.2007)

TAPIO MAINIO / Helsingin Sanomat
tapio.mainio@hs.fi