Study finds large animals must learn to migrate and transmit knowledge across generations

The results were reported today Science.

Biologists have long suspected that unlike many migrations of birds, fish and insects driven by genetics, ungulates learn to migrate from their mothers or other animals in the herd. Previous research had hinted that migration was socially learned in ungulates, but a clear test had eluded researchers to date.

The study's authors used a great deal of experience that has taken place in the American West over the past 60 years. Once the hunt and disease caused the loss of American sheep in most of their range, a group of dedicated wildlife managers, hunters and conservationists have were the first to launch resettlement programs. The mouflons of the few populations that persisted continued to migrate; some of these animals were captured and released in landscapes where bighorn sheep were already present. The conservation effort has succeeded in establishing many new herds "transferred".

"The pattern was striking," says lead author Brett Jesmer, a PhD student at UW. "Detailed GPS data revealed that less than 9% of the animals transferred migrated, but 65-100% of animals migrated to herds that had never been lost."

The transferred animals did not migrate because they did not know their new habitat, supporting the idea that migration requires extended periods for the animals to explore, learn the location of the feeds. nutritious and pass this information on to other members of the herd, including their offspring. When migration and other behaviors acquired by society are transmitted from generation to generation, these behaviors are considered part of the culture of the animal, as are the shared cultural knowledge within human societies.

Researchers were also interested in the time needed for animals to learn to migrate. In recent years, ecologists have learned that ungulates migrate to "surf the green waves" of nutritious food, coordinating their movements to graze the plants that grow on the slopes of the mountains. Just as surfers coordinate their movements to ride the waves of the ocean, spring migration allows ungulates to "catch the wave" of young, nutritious plants that grow higher and higher in the spring. This gives them more time to feed on the highest quality foods, helping them survive and reproduce. For some ungulates, the surfing of green waves is very coordinated over vast landscapes, for weeks or months.

Jesmer and his colleagues wanted to quantify how long it would take for animals to learn to surf the green waves of forage plants in their new habitats, a necessary first step to migration. To answer this question, they used GPS tracking data from 267 American sheep and 189 moose. Some of the animals had just been released in unknown landscapes, while others had occupied their territory for decades or even centuries. Researchers have found that long-established herds that have acquired information over generations are better able to find nutritious foods than animals transferred to unknown landscapes.

Perhaps most importantly, the transferred herds learned to surf the green waves better over several decades and those who surfed the best were more likely to migrate. It took nearly 40 years for reintroduced American mouflon herds to become 80% migratory. Moose have not generally become migratory until about 90 years old, living in a new landscape.

"These results indicate that ungulates accumulate knowledge of their landscapes over time, and the cultural transmission of this knowledge is necessary for migration to occur and persist," says Jesmer.

The study is unique in that it indicates that the quality of the habitat is better imagined as the physical landscape that the animals occupy, in combination with the knowledge that they have accumulated on the how to use this landscape. This finding has important implications for the conservation of migration corridors, says Matthew Kauffman, a Jesmer PhD student and wildlife researcher with the Wyoming Fisheries and Wildlife Cooperative Research Unit. United States Geological Survey.

"When the migration corridors are lost, we also lose all the knowledge of the animals on how to make these trips, which will probably take several decades, if not a century, to relearn," says Kauffman. "This study makes it clear that the best way to conserve migration corridors is to protect the landscapes on which these corridors depend, which will also preserve the cultural knowledge that supports abundant herds."

Explore more:
Migration of the mule deer follows the "green waves" of spring forage

More information:
B.R. Jesmer el al., "Is Ungulate Migration Culturally Transmitted? Proof of Social Learning from Transferred Animals" Science (2018). science.sciencemag.org/cgi/doi… 1126 / science.aat0985