Global-scale View of Animal Behavior Shows Climate Change's Impacts

From when they give birth to the timing of their migrations, animals are responding in unexpected ways to changes in their environment, an international team including University of Maryland biologists found using a new large-scale archive of animal movement studies.

The collection contains data from studies from 1991 to the present across the global Arctic and sub-Arctic, vast areas experiencing some of the most dramatic effects of global warming, including animal declines. The researchers used the archive to conduct three case studies that revealed surprising patterns and associations between climate change and the behavior of golden eagles, bears, caribou, moose and wolves.

This work, published today in the journal Science demonstrates both the feasibility and importance of studying animal ecology on extremely large scales.

“(T)his is an early example of what we might call global animal movement ecology,” said Elie Gurarie, an associate research scientist in UMD’s Department of Biology and a co-author of the paper. “We’re increasing our ability to monitor the pulse of animal populations across the Earth and ask big picture questions about what it means.”

Gurarie and members of his lab analyzed the movements of more than 900 female caribou from 2000 to 2017. They found that the iconic long-distance migrating mammals are giving birth earlier in the spring, roughly tracking rates of warming.

But among the non-migratory mountain and lowland woodland caribou, only the northern sub-populations are showing similar changes. While the drivers of these differences remain a mystery, understanding their behavior is critical to anticipating how they will respond as the Arctic continues to warm and many populations continue to shrink. But predicting how these trends will affect caribou populations is tricky, Gurarie said.

“It can be better to give birth earlier, as it gives the calves more opportunity to grow during the summer season. On the other hand, giving birth too early may mean you literally don’t have time to reach the optimal calving grounds,” he said.

Data analysis tools Gurarie developed to study caribou were also used for another case study led by his collaborators. In an analysis comparing movements of more than 100 golden eagles from 1993 to 2017, Scott LaPoint, a researcher from Columbia University who is now at Black Rock Forest Consortium, found that immature birds migrating north in the spring arrived earlier following mild winters, while adult birds did not.

A third study by Peter Mahoney of the University of Washington looked at the movement speeds of bears, caribou, moose and wolves from 1998 to 2019. His study showed that species respond differently to seasonal temperatures and winter snow conditions. Those differences could influence species interactions, food competition and predator-prey dynamics.

Large-scale monitoring of sea-surface temperature and global forest cover have revealed important information about the response of Earth’s systems to climate change and human activity. But big-picture trends in animal behavior have been difficult to study, in part because animal ecology is not traditionally studied across entire regions of the globe, and also because the necessary data are collected by a variety of agencies and jurisdictions.

To address these issues, Gurarie and his collaborators spent years building relationships with scientists from national, regional and First Nations governments and research groups throughout the Arctic to convey the benefits of sharing data in a global repository that they call the Arctic Animal Movement Archive.

“This work has given us a baseline to understand the large-scale picture so we can get a sense of how animals and environments are really interacting across species and across space as the environment changes,” Gurarie said.