A new study from the University of Alberta says the Qamanirjuaq caribou herd, with calving grounds in Nunavut, is adapting to early spring, and the earlier “green-up” that comes with it.
The study tested the hypothesis in a Greenlandic study regarding caribou arriving at their calving grounds before spring green-up. According to what’s known as the trophic mismatch hypothesis, reindeer were missing “the flush of high nutrient vegetation that occurs right at the early green-up stage,” said Mark Boyce, a University of Alberta professor and ecologist who co-authored the study with government of Nunavut researcher Conor Mallory.
As a result, the reindeer didn’t get the nutrition necessary to support calving and went into decline. But with the Qamanirjuaq herd, that hypothesis doesn’t hold up.
“The caribou are adapting. They’re following that green-up and so the timing of their migration coincides almost perfectly,” Boyce said.
“We don’t see any support, based on our data, for this trophic mismatch hypothesis, which is that the time of green-up and the timing of migration are off-kilter.”
Caribou responding to range snow cover
The University of Alberta study used satellite collar data on the Qamanirjuaq herd collected from 2004 to 2016.
It found that female barren-ground caribou respond to environmental cues, such as snow cover on the late-winter and migratory ranges, and adapt to a premature spring.
Over the last decade, spring green-up started a week earlier on average. The Qamanirjuaq herd is leaving its winter grounds two weeks earlier, and ending their migration six days earlier.
Their peak for calving started an average of nine days earlier.
Insects, global warming, industry possible sources of decline
The Qamanirjuaq herd has recently declined, from 496,000 animals in 1994 to 348,000 animals in 2008, and down to 288,000 animals in 2017, according to recent surveys.
Boyce said there are other potential culprits for the declining herd, such as insect harassment.
As a result of global warming, “mosquitoes, bot flies and warble flies, some of the really nasty pests that harass the caribou are moving farther north,” he said.
Other studies point to development, said Boyce.
The early stages of regenerating deforestation creates excellent habitat for moose and deer. Those conditions become unfavourable for caribou, because an increase in other ungulates supports wolf populations.
The Qamanirjuaq herd migrate into the boreal forest for their winter range. Changes like industrial development and wolves may well be the key to the decline of many migratory caribou herds, Boyce said.