Wild plains bison remain a species-at-risk
Thursday, Dec 05, 2013 06:00 am
Despite the fact that Canada is home to over 250,000 plains bison living on ranches and farms, their wild cousins are still staring down the barrel of extinction.
Plains bison were re-listed as a threatened species in Canada following the Nov. 24-29 meeting of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in Ottawa.
Plains bison, the species of bison Parks Canada is considering restoring to Banff National Park, were first assessed as threatened in 2004. According to COSEWIC, a threatened species is likely to become endangered, or facing “imminent extirpation or extinction” if action is not taken.
Canada’s population of wild plains bison has grown by 36 per cent since 2004. There are, however, only 1,200 to 1,500 mature, breeding individuals in five wild subgroups in Canada. These herds inhabit a mere fraction of their former territory: only 0.5 per cent.
The bison in domestic or commercial herds are not included in the COSEWIC assessment as those animals, according to Graham Forbes, a spokesman for COSEWIC, who works at the faculty of forest and environmental management at the University of New Brunswick, are not considered as wild animals.
Wild bison experience predation, starvation and competition between bulls for the right to mate. While fenced conservation herds, such as in Grasslands National Park, may not experience predation, they do face the other pressures.
“Some of them are quite wild and they’ve got predation occurring and that’s a selective pressure. They’re not being given antibiotics. They’re not being supplementary fed. The breeding is by their own selection as opposed to the difference in some commercial operations there’s a controlled breeding program. We recognize, and we call this ‘wild by nature.’ There’s a level of wildness and natural selection in certain herds, so those are the ones we used in our assessment,” Forbes said.
Wild plains bison, also unlike commercial herds, continue to face threats that could tip the balance taking the species in the wild from threatened to endangered, Forbes said.
The overall population of wild plains bison is still “quite low” and the opportunity to increase that number is also low, he added. Society has in effect decided where it will allow wild plains bison and those areas are limited due to widespread use of the land for agricultural or other commercial/industrial use.
“So there isn’t really an opportunity to allow the populations to expand too much because we are keeping them in these fairly small fenced in areas or isolated areas and the numbers are managed so they don’t get too large in order to minimize our impact on agricultural practices,” he said.
With a shortage of land to roam, the small, dispersed herds are more at risk of die-offs due to disease and severe weather.
COSEWIC has projected wild plains bison will see its current population decline as fragmented or unsuitable habitat is curtailing the establishment of new herds.
Along with plains bison, COSEWIC also re-assessed wood bison, North America’s second subspecies of bison and also the continent’s largest land mammal.
Wood bison, found primarily in Canada with a herd in Alaska, has seen some success in recent years and as a result COSEWIC upgraded its status from threatened to special concern.
“The wood bison is a good news story, with some caution that there are mortality factors that make you still somewhat concerned with saying everything is fine,” he said.
This past winter, 75 to 100 of roughly 400 to 600 bison in the Hay-Zama herd died of starvation during severe weather, leading the province to suspend the annual hunt.
Last summer, the Mackenzie herd of Fort Providence, NWT dropped dramatically when anthrax killed 53 per cent of the herd
Despite setbacks in the Hay-Zama and Mackenzie herds, Forbes said the population of mature, breeding wood bison still ranges between 5,136 to 7,172.
Wood bison were listed as endangered when the species was first assessed in 1978. It was later upgraded to threatened in 1988 after the new wild herds were established outside of Wood Buffalo National Parks.
“In the case of wood bison the feeling was there has been some improvements and some good populations established and we recognize the value in these and that places some confidence that the species is becoming more secure. That is the main reason for the status of special concern,” Forbes said.
He added, however, that even though the number of wood bison has increased, the committee felt the species was not ready to be taken off the at-risk list.
Even though wild plains and wood bison continue to face threats, Forbes said bison conservation is a success story. Overhunting nearly wiped out both species by the mid-to-late 1800s. Wood bison were reduced to about 300 animals, while plains bison were essentially extinct in Canada and down to a population of roughly 81 in the U.S. –from an estimated population of 30 million.