The largest of the caribou subspecies, the woodland caribou is widely distributed throughout the boreal forest, from the island of Newfoundland to British Columbia. Despite its vast range, the boreal population of woodland caribou is listed as threatened by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and endangered in British Columbia. One of the main reasons numbers are dropping is that fewer calves are surviving their first year of life. The main cause is predation. More calves are being preyed on by wolves and black bears than ever before.
The Canadian Wildlife Federation’s Endangered Species Fund recently gave $30,000 over three years to researchers Craig DeMars and Dr. Stan Boutin of the University of Alberta’s Biology Department for a new study that will help find ways to reduce the risk of predation during the calving season.
The increase in caribou predation is linked with industrial activity. Forestry, agriculture and mining have destroyed or fragmented caribou habitat into small patches. In a fragmented landscape, where the habitat is broken up by roads, clear-cuts, pipelines, and oil and gas wells, it is harder for pregnant cows to isolate themselves from predators during the calving and neonate (newborn) period. Linear corridors (like roads and pipelines) also make it easier for predators to reach their prey. In BC, the survival rate for newborn calves has been particularly low — less than 30 per cent over the last seven years.
Gotta Keep ‘Em Separated
Woodland caribou require large tracts of relatively undisturbed, older forest habitat so they can spread out. This makes it harder for predators to find them. This is especially important for cows. Caribou cows usually begin bearing young in their third year, giving birth to one calf a year in May or early June. Females leave the herd before they calve to find an isolated place like a lakeshore, island, or peat land to give birth. This spatial separation maximizes their distance from predators and reduces the risk of calves being preyed on while they are still dependent on their mothers.
Where the Research Fits In
DeMars and Boutin will fit female caribou, as well as black bears and wolves — the caribou’s main predators — with radio collars, then track their movements with weekly fly-overs during the calving and neonate period. This will allow them to count the surviving calves and survey the features of calving sites, like size, distance to nearest water source, and shortest distance to the nearest road or other linear feature. They will also track the wolves’ and bears’ movements to see how predators use the same habitat during this period. They will use their results to develop recommendations for reducing predation risk to caribou. Habitat managers will then be able to direct resources and actions to the factors with the greatest influence on calf survival.