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How Do Bison Get Anthrax?
Spores of Bacillus anthracis, commonly known as anthrax, are long-lasting and highly resistant. They can remain dormant in the earth for decades, especially in areas with alkaline, calcium-rich soils such as those found in the Mackenize Bison Sanctuary. Under normal conditions, the spores are buried beneath the surface, but if periods of heavy rain and flooding are followed by extremely dry weather, they can become exposed in “pockets” of parched soil.

The bison are infected by the anthrax-laced pockets as they graze; the spores enter their bodies through ingestion, inhalation and skin abrasion (eating, breathing and cuts or scratches). Anthrax can be spread even further when scavengers feed on the carcasses of infected bison, exposing the spores to the air. In the Mackenzie Sanctuary, bison are closely monitored during anthrax season (July and August) and contaminated carcasses are incinerated.

The Mackenzie Bison Sanctuary is located in one of Canada’s “anthrax zones,” which include the western Prairies, northern Alberta and the Northwest Territories.

Characteristics of the Mackenzie Wood Bison

• Both wood bison and plains bison have curved black horns, shaggy brown/black hair around their heads and necks, and short tails with tassels. But wood bison are taller, heavier and longer-legged than plains bison (3.8 metres in length, 1.8 metres tall, 500 –1,000 kilograms in weight). They have a more pronounced shoulder hump, and a less developed beard than plains bison.

• Wood bison roam less than plains bison. They move only short distances between open meadows and surrounding forests.

• Like plains bison, wood bison are herbivores. They feed on grasses, sedges, willow leaves and twigs. In winter, they find food by swinging their massive heads from side to side to sweep the snow away.

• Wood bison live up to 20 years in the wild. Causes of mortality in the Mackenzie Bison Sanctuary have included an outbreak of soil-transmitted anthrax, predation by wolves, flooding of feeding areas, and drowning. The tendency of bison to herd together for safety reasons can be fatal during spring ice break-up, when melting ice gives way. In 1989, 177 bison of the Mackenize Herd died when they broke through thin ice.


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