By tracking the "surfing" ability of migratory ungulates, researchers have found that the great migrations of Earth's nomadic mammals develop and persist through the cultural exchange of local knowledge. Each year, migratory ungulates, hooved mammals like bison, elk or wild sheep, set off to follow the new growth of tasty, green foliage brought on as spring washes over the landscape. This "green wave" provides a long-lasting source of food that can sustain large herds over great distances, bolstering the fitness of migratory animals. However, human activity has greatly impeded the migratory behaviors of these animals and as a result, many ungulates, like bison, have become sedentary - forgetting how to surf the green waves of forage. While ecologists have speculated about the role of social learning in developing and maintaining migration behavior, it has never been tested. In this study, Brett Jesmer and colleagues evaluated the green-surfing skills (their ability to follow high-quality forage) of GPS-tracked bighorn sheep and moose from native populations, populations re-established for several generations and animals recently translocated into new areas. Jesmer et al. revealed stark differences in each's migratory behavior. Reintroduced populations (those who'd spent at least several generations in a new place) did not migrate as effectively as native herds, while newly relocated animals didn't migrate at all. According to the authors, the longer reintroduced populations have resided in an area, the better their green-surfing ability. The results demonstrate that ungulates accumulate knowledge about how to catch and ride green-waves over time and that social learning allows for cultural transmission of this knowledge. In a related Perspective, Marco Festa-Bianchet discusses the implication of this finding.
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Science