Deer, moose and caribou
In the Bras d'or Lake Biosphere Reserve
September marks the beginning of the rutting season for moose (in Mi’kmaq: tia’m) in the Bras d’or Lake Biosphere. This time is exciting for the amorous moose and the hunters! The noisy antics of the excitable males may be one of the reasons that the September moon is called Wikumkewiku’s, or matecalling time, in Mi’kmaw culture. Another important ungulate (hoofed animal) that may have played a part in the naming of the September moon was the reindeer, or caribou (in Mi’kmaq: qalipu). Although we have none in Cape Breton now, they played a significant role here in the past.
The caribou is one of the main characters in a story that includes the closely-related moose and white-tailed deer. When Europeans first joined the Mi’kmaq in Cape Breton (in Mi’kmaq: Unama’ki) moose were the largest members of the deer family here. According to information from Nova Scotia’s Department of Natural Resources they successfully co-existed with one other ungulate, the mainland caribou, until the 1920s. The demise of caribou in Cape Breton was then blamed on over-harvesting and habitat loss. However, the last caribou was seen at about the time that a new species, the white-tailed deer (in Mi’kmaq: lentuk), became established on the island. Timing is everything, isn’t it?
A successful release of white-tailed deer in the Digby and Halifax areas during the mid 1890s was documented in the book “Deer of Nova Scotia’ by Benson and Dodds (N.S. Dept. of Lands and Forests, 1977). The herd thrived and was reported in all mainland counties by 1904. It first reached Cape Breton around 1911. The healthy deer population was rapidly growing just as the caribou population disappeared from the island. It may be coincidental. However, scientists propose that moose, caribou and white-tailed deer can’t co-exist in close quarters because of a tiny brain worm with the scientific name of Parelaphostrongylus tenuis. This parasite is common in deer and they usually show no adverse symptoms. However, P. tenuis is fatal for many other ungulates such as caribou and moose. Caribou are now out of the picture in Cape Breton and the moose seem to be keeping a healthy distance between their populations and those of the colonizing white-tailed deer. Currently we seem to be at an impasse in the Biosphere.
So, why is the tiny brain worm tolerated by whitetailed deer and not moose and caribou? And, why has it been more of a problem in recent times? Well, white-tailed deer and P. tenuis have co-existed for thousands of years and evolution has enabled the deer to adapt to this parasite. For the moose and caribou it is a relatively new threat and they haven’t had time to adapt.
Brain worm fatalities in moose and caribou are becoming more of a problem as the climate warms. Warmer winters allow the populations of white-tailed deer and their tiny passengers to move further north across North America invading traditional habitats of moose and caribou. Another factor related to climate change is increased rainfall, which affects another player in this complex drama. The lifecycle of P. tenuis depends on the presence of certain species of snails and slugs which are the intermediate hosts in the brain worm’s lifecycle. So, moist ecosystems with warmer winters have enabled the white-tailed deer and their tiny brain worms to thrive and that may have contributed to the loss of the Biosphere’s caribou herds. What will happen in the future in the snail and wormmediated impasse between the deer and the moose? Although we may place an educated guess, it is hard to predict. In nature, everything is connected and the nature of those connections is often very complex!
Dr. Annamarie Hatcher is an adjunct professor at Unama’ki College, Cape Breton University, and a board member of the Bras d’or Lake Biosphere Reserve Association. For more information about the Bras d’or Lake Biosphere Reserve Association, please visit our Facebook page or http://blbra.ca/.
A white-tailed deer seen in the wild. File photo.