Tranquilizer darts do serious damage to bears, scientist finds

Researcher criticizes bear drug-dart survey methods


Inuit hunters aren't happy about a Government of Nunavut research scheme that would tranquilize, tag and collar 300 polar bears from the Foxe Basin because the hunters say this procedure harms the bears and renders them unfit for use.

Now a scientist who has studied research methods on bears, also supports their views, saying mark and recapture methods hurt bears' ability to move and damage their overall condition.

Marc Cattet of Saskatchewan's Western College of Veterinary Medicine, said the capture and handling of bears in their natural habitats can affect them for many weeks, in an article published last week in the Journal of Mammalogy.

And with repeated captures, the bears' condition deteriorates.

Cattet says the capture and handling of bears may affect how they reproduce and grow, especially bears recaptured many times.

Drugs are only one part of the equation, Cattet said.

"We have to look at it as the cumulative effect of a number of stressors, which include drugs, method of capture and handling procedures. You add all that stuff together and it equals a significant amount of stress which some animals can cope with and others can't," he said.

The effects of captures may also distort the results of scientists' research.

For example, descriptions of activity patterns or the determination of bears' home ranges may be inaccurate if scientists don't take the time after capture into account as a potential factor.

The effects of the mark and recapture methods may even interfere with results attributed to environmental causes or climate change, such as low body weight or poor condition.

"Repeated captures could contribute to that effect, but I would not want to dismiss the potential effects of global warming," Cattet said.

For the recently-published study, Cattet compiled data from two studies: on grizzly bears in Western Alberta and American black bears in the Pisgah Bear Sanctuary of North Carolina.

Cattet found that the blood from six of every 10 captured bears showed abnormally high values for muscle enzymes.

The presence of these enzymes indicates muscle injury, which could be caused by the stress of bears struggling to escape capture.

Injury was particularly common in bears captured by leg-hold snare. Enzymes were also high in one in every five grizzly bears darted from helicopters and in one in every five grizzly or black bears captured by culvert trap.

Regardless of the capture method used, bears moved less through their territory after capture, with effects lasting three to six weeks on average after capture, the study found.

Cattet said the findings are more broadly applicable to other bears and animals.

Cattet would like to see researchers to seek out other methods such as hair capture, which is currently being used in a Kitikmeot survey of wolverines and grizzlies.

For collecting tissue samples, Cattet proposes using a dart on bears that collects skin sample and then drops off – with no tranquilizing required.

"The bear goes off on its way and you retrieve the dart and you have your skin sample in it," he said.

He also recommends the use of GPS positioning collars over the more commonly-used satellite collars because the GPS devices are more accurate.

In an earlier study, published in the Wildlife Society Bulletin, Cattet looked at the effect of darting bears with tranquilizers.

The study recommends against using darts "because of their potential to cause deep, chronic wounds."

In another 2002 paper in Science, Cattet evaluated polar bear tranquilizers, including Lozetil (also called Telazol), which is used in Nunavut.

This tranquilizer carries risks to bears because the doses, administered by darting, are often either too powerful or not powerful enough.

In spite of the evidence against the use of darting and tranquilizers, Cattet said the capture of animals will remain a necessity for wildlife management and research.

"But saying that, I think we can reduce the number of animals we capture. I think we can also put effort in finding alternative ways of finding information from animals without capturing," he said.

Cattet's research findings haven't made him popular with some scientists, who accuse him of being a tree-hugger or animal rights activist. He's also experienced difficulty in having his research studies published.

But Cattet hopes the "solid science" of his latest study will convince more scientists to develop and use non-invasive methods to study wildlife, if only because they want more accurate results.

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