After migrating to their wintering grounds, the animals move as little as possible to conserve energy
In the fall, reindeer migrate from their northern grazing areas to the south. During the winter, they move much less than in the summer. Since they find only meager lichens, mosses and mushrooms under the snow, they have to be particularly economical with their energy during the cold season. They avoid energy-sapping activities, especially when the snow is closed. This is shown by studies collected in the "Arctic Animal Movement Archive" on the Movebank platform at the Max Planck Institute for Behavioral Biology in Konstanz. In 2020, researchers from Germany and the United States launched the archive to make studies of animal migration in the Arctic more easily searchable and accessible.
Reindeer occur in several subspecies around the Arctic on the American and Eurasian continents. In America, the animals, which belong to the deer family, are referred to as caribou. Reindeer usually commute between their summer pastures further north and their southern winter pastures over the course of the year. On these migrations, they can form huge herds of several hundred thousand individuals. Some summer and winter ranges are up to 5,000 kilometers apart. Reindeer migrations are among the longest of any mammal.
Experienced adults pass on knowledge of the migration routes to the next generation. Reindeers usually travel one behind the other, forming extended lines. On the way, they apparently orient themselves to the migratory direction of neighboring individuals. According to a study from the Arctic Animal Movement Archive, caribou rely on the directional decisions of certain neighbors more than on others on their way from Victoria Island in northern Canada to the mainland.
Ecological impact
The movement of such a large number of animals is not only an impressive spectacle, it also has an enormous impact on Arctic ecosystems. Researchers are tracking the behavior of reindeer and other species in the Arctic using GPS transmitters, drones and aircraft. The data collected in this way can then be added to the Arctic Animal Movement Archive.
According to a study from the archive, caribou and other species in the Canadian Arctic react differently to temperature and precipitation fluctuations: moose, wolves, black bears and caribou, for example, all travel less in winter than in summer. Black bears and wolves travel less in warm summers, while moose are particularly active then. Snow slows down all four species except from barren-ground caribous, while rain in summer does not affect any of them.
Habitat destruction
Reindeer are protected worldwide. Still, their numbers are still declining worldwide. While humans decimated the animals in the past centuries mainly through hunting, today they are threatened mainly by the development and destruction of their habitat. Oil and other resource extraction sites, as well as dams, destroy their grazing areas, while roads cut through their migration routes. One example is the construction of the Kárahnjúkar dam in eastern Iceland. Researchers are investigating the consequences of the reservoir's destruction of pastures for the local reindeer population.
Added to this are the changes caused by climate change. A study shows that reindeer are already feeling its effects. By analyzing the movement data of over 900 caribou in northern Canada, researchers found that the northern herds are giving birth earlier and earlier in spring. By contrast, the birthing period of the more southern populations has remained constant.
Prime example of global ecological collaboration
The Arctic Animal Movement Archive aims to connect scientists and promote collaboration. Researchers from over hundred universities, government agencies, conservation groups, andd indiginous groups in 17 countries are involved. "To detect changes in the behavior and habitat of animals in the Arctic, we need to work together to gain insights across decades and populations," says Sarah Davidson, a data curator at the Max Planck Institute of Animal Behavior who leads the NASA-funded global data archive.
The archive currently contains nearly 300 research projects with the movement data of more than 15,000 marine and terrestrial animals from 1991 to the present. "The Arctic Animal Movement Archive is a prime example of global ecological collaboration: at the moment, researchers at the Max Planck Institute are working on global consortia for animal observations in drylands, southern Africa and the Galapagos," says Martin Wikelski, director at the Max Planck Institute of Animal Behavior.
