A new study by biologists has attributed the decline of Caribou calves in West Greenland to global warming.
The study was conducted by Eric Post, a Penn State associate professor of biology, in collaboration with Mads Forchhammer at the University of Aarhus in Denmark.
Post, who believes that caribou may serve as an indicator species for climate changes including global warming, based his conclusions on data showing that the timing of peak food availability no longer corresponds to the timing of caribou births.
Caribou, which are closely related to wild reindeer, are dependent on plants for all their energy and nutrients.
Throughout the long Arctic winter, when there is no plant growth, they dig through snow to find lichens. However, in spring, they rapidly switch to grazing on the new growth of willows, sedges, and flowering tundra herbs.
As the birth season approaches, they are cued by increasing day length to migrate into areas where this newly-emergent food is plentiful.
But this routine, which has worked for millennia, is faltering because caribou are unable to keep pace with certain changes that have occurred as a result of global warming.
When the animals arrive at their calving grounds now, pregnant females find that the plants on which they depend already have reached peak productivity and have begun to decline in nutritional value.
According to Post, the plants - which initiate growth in response to temperature, not day length - are peaking dramatically earlier in response to rising temperatures.
"Spring temperatures at our study site in West Greenland have risen by more than 4 degrees Celsius over the past few years," said Post. "As a result, the timing of plant growth has advanced, but calving has not," he added.
The phenomenon, called trophic mismatch, is a predicted consequence of climate change, in which the availability of food shifts in response to warming, whereas the timing of demand for those resources does not keep pace.
Though trophic mismatches have been documented in birds, the phenomenon had not been observed in terrestrial mammals till now.
"Our work is the first documentation of a developing trophic mismatch in a terrestrial mammal as a result of climatic warming," said Post. "And the rapidity with which this mismatch has developed is eye-opening, to say the least," he added.