Harvesting male polar bears may lead to population collapse

November 21st, 2007 - 4:20 pm ICT by admin  

London, Nov 21 (ANI): Researchers at the University of Alberta in Canada have warned that the Canadian policy of hunting mainly male polar bears could result in the collapse of the entire population.

Peter Molnar and his colleagues said that precisely when such a collapse may take place would depend on the density of each population.

Their findings are the result of a modelling study designed to predict how successfully polar bears are mating.

Canadian government hunting quotas insist on killing male polar bears over female ones because females rear the bear cubs, therefore losing one female polar bear will have a more serious impact on the population’s ability to sustain its number.

As a result, at least two thirds of polar bears killed in Canada each year are male, according to a separate study that will appear in a forthcoming issue of the journal Wildlife Biology. Research has shown that the policy has significantly reduced the ratio of males to females in polar bear populations across the Canadian Arctic.

A population that is not hunted would normally have two or three males for each female not taking care of a cub. But research carried out in the late 1990s showed that Canadian bear populations had at best even numbers of males and females, while some had more females than males.

The research team has been studying the effects of Canada’s male-specific hunting policy on the long-term sustainability of polar bear populations.

They developed a computer model to describe how male polar bears seek out females after collecting data from polar bears numbers and distribution around Lancaster Sound in the Canadian Arctic, between 1993 and 1997. The model predicts the way males locate females, mate with them, and then separate in order find other females.

The idea was to create a model that could predict how many pairs could be formed with a given population density and distribution.

The Lancaster Sound population has roughly as many males as it has females. Despite this depleted ratio, their model predicts that 99 percent of available females will be fertilised. However, they warn that once the population drops below about three females for every male, it may collapse.

Moreover, the model revealed that the point at which a population of polar bears collapses depends on the density of the bears. In a less dense population, females need more males in order to reproduce successfully. In this case, the collapse of a bear population can begin when there are less than one male for every two females.
“Our results indicate that not isolated populations but low density populations would be the most endangered, as in low-density populations it takes males and females longer to find each other during the mating season,” New Scientist quoted Molnar, as saying. (ANI)

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