WILDLIFE scientists are not to blame for outbreaks of disease that have
helped push the African wild dog onto the endangered list, according to a new
study. But the research has not ended the controversy raging around a suggestion
that dogs handled by biologists get so stressed that they readily succumb to
deadly viruses.
There are now fewer than 5000 wild dogs, Lycaon pictus, on the
plains of Africa. Some estimates put the figure as low as 3000. To help save the
remaining animals, scientists have fitted some dogs with radio collars to track
their movements, and have vaccinated many of them against rabies. Unfortunately,
for both procedures the dogs must be darted with anaesthetic and handled.
This has been the centre of a bitter controversy since Roger Burrows of the
University of Exeter suggested that handling the dogs contributed to an outbreak
of disease that nearly wiped them out in Tanzania鈥檚 Serengeti National Park in
1991. In a series of papers, Burrows argued that handling the dogs boosts levels
of stress hormones that suppress the immune system, leaving the dogs unable to
fight off dangerous viruses (see 鈥淲ild at Heart鈥�, 快猫短视频, 19
November 1994, p 34).
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Until now, no one had compared levels of stress hormones in dogs that were
handled and those that were not. But Scott Creel and Nancy Creel of Rockefeller
University in New York and Steven Monfort of the US National Zoological Park鈥檚
Conservation and Research Center in Fort Royal, Virginia, have done just that
for dogs in the Selous Game Reserve, also in Tanzania.
As part of the Frankfurt Zoological Society鈥檚 Selous Wild Dog Project, the
Creels and Monfort measured levels of the stress hormone corticosterone in
samples of the dogs鈥� faeces collected over two years. They found no differences
between dogs that had never been handled and those that had been darted,
vaccinated against rabies and fitted with a radio collar.
Dogs handled during the study also showed no obvious jump in corticocosterone
levels. And there was no relationship between levels of corticosterone in the
faeces of dogs wearing collars and the time that elapsed since they were handled
(Conservation Biology, vol 11, p 544). 鈥淲e detected no effect of
collaring,鈥� says Scott Creel.
Burrows is not convinced, however. He argues that the Selous researchers
selected 鈥渧igorous individuals鈥� for collaring. This would mask any effects of
handling, Burrows claims, because strong, healthy dogs will be less prone to
stress.
Burrows points to studies by his group which suggest that dogs that leave
their own pack and join another鈥攎ost of which tend initially to be low
down the pecking order鈥攔espond badly to handling. 鈥淪urvival of those
handled after joining a new pack is significantly reduced,鈥� he says.
However, the Selous researchers counter that their research shows that it is
the top dogs, not those as the bottom of the social pile, that are more stressed
(鈥淪tressed out鈥�, 快猫短视频, 5 October 1996, p 38).
Wildlife biologists hope that a definitive ruling on the merits of collaring
will come from an action plan to protect wild dogs commissioned by IUCN, the
World Conservation Union. Rosie Woodroffe of the University of Cambridge, the
plan鈥檚 author, says that she will not comment until details of her scheme are
made public later this year.