Global study confirms caribou as longest migrator and reveals even greater distances traveled by animals without regular migratory pattern
Caribou are often credited with the longest terrestrial migrations in the world, though without much scientific support. An international team of scientists gathered GPS collar data from around the world to answer the question of which large terrestrial mammal migrates the farthest. Recognizing that not all mammals migrate, the team also determined how far non-migratory mammals moved during the course of a year.
The research team—which includes Eliezer Gurarie, an associate research scientist in the University of Maryland’s Department of Biology; Kyle Joly of the National Park Service; and Mark Hebblewhite of the University of Montana—published its findings on October 25, 2019, in the journal Scientific Reports.
Caribou from numerous populations, were found to have the longest existing migrations with round-trip distances exceeding 745 miles (1,200 km). A few species such as gray wolves and khulan (Mongolian wild ass), while not migrating in a regular manner like caribou, traveled even greater annual distances. A gray wolf from Mongolia captured the title of top terrestrial mover, having traveled 4,503 miles (7,247 km) in a year, the equivalent of a walk from Washington, D.C., to Los Angeles and back.
"What was fascinating about this study is how quickly it escalated,” Gurarie said. “What started as a narrow effort to set the record straight on caribou migration morphed into this globe-spanning survey of long-distance movement, and then touched on all kinds of ecological relationships between predator and prey, habitat features, human impacts."
The team discovered interesting patterns among these big movers. First, not only can predators keep up with their prey, they are often required to move much more in the course of their search for a meal. In Mongolia, gray wolves moved more than their prey, the khulan and Bactrian camel. In Alaska, gray wolves moved more than caribou or moose. Second, small prey animals from the same region tended to move more than larger ones. For example, wildebeest moved more than zebras in the Serengeti, caribou more than moose in Alaska, and khulan more than wild camels in Mongolia.
One possible explanation for this pattern is that large animals are capable of using lower quality food sources which are more abundant, and this allows them to move less overall. Lastly, higher movement rates by herbivores were associated with lower vegetative productivity. The less food that was available, the more they moved, likely to acquire sufficient resources.
The greatest movements were found in areas of very low human disturbance, which according to the researchers, highlights the effects of habitat fragmentation and human development.
“One of the most amazing aspects of this study is the simple fact that large mammals, from around the globe, need so much habitat to move,” Hebblewhite said. “Seasonal migrations, predator-prey dynamics, and the need to obtain food drive these astonishing long-distance movements. Our study builds on a growing body of science that shows human activity can negatively affect animal movements and populations, and our work emphasizes the need to maintain core habitats and connectivity to keep these animals on the move.”
Long-distance migrations are threatened around the world, yet are critical for the conservation of many iconic species. Understanding migration and animal movement through studies like this is key to effective wildlife management and conservation.
This release was adapted from text provided by the National Park Service.
The research paper Who goes the farthest of them all? World’s longest terrestrial migrations and movements, Kyle Joly, Eliezer Gurarie, Mathew S. Sorum, Petra Kaczensky4, Matthew D. Cameron, Andrew F. Jakes, Bridget L. Borg, Dejid Nandintsetseg, J. Grant C. Hopcraft, Bayarbaatar Buuveibaatar, Paul F. Jones, Thomas Mueller, Chris Walzer, Kirk A. Olson, John C. Payne, Adiya Yadamsuren and Mark Hebblewhite, was published on October 25, 2019, in the journal Scientific Reports.
This study was supported by National Park Service, Alaska Department of Fish and Game, U.S. Fish and Wildlife Service, Bureau of Land Management, NASA’s Arctic Boreal Vulnerability Experiment (Award No. NNX15AW71A), NSF LTREB (Award No. 1556248), the Austrian Science Foundation (Award Nos. P14992 and P18634), the Great Gobi B Strictly Protected Area, European Union’s Horizon 2020 research and innovation program African Bioservices (Award No. 641918), the Frankfurt Zoological Society, Lord Kelvin Adam Smith Fellowship, the British Ecological Society, the Wildlife Conservation Society and Sustainability East Asia LLC. The content of this article does not necessarily reflect the views of these organizations.
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