The Last Mile: How to Sustain Long‐Distance Migration in Mammals

Abstract

Abstract: Among Earth's most stunning, yet imperiled, biological phenomena is long‐distance migration (LDM). Although the understanding of how and why animals migrate may be of general interest, few site‐specific strategies have targeted ways in which to best retain such increasingly rare events. Contrasts among 29 terrestrial mammals from five continents representing 103 populations indicate that remnant long‐distant migrants have poor long‐term prospects. Nonetheless, in areas of low human density in the Western Hemisphere, five social and nongregarious species, all from the same region of the Rocky Mountains (U.S.A.), still experience the most accentuated of remaining New World LDMs south of central Canada. These movements occur in or adjacent to the Greater Yellowstone region, where about 75% of the migration routes for elk (Cervus elaphus), bison ( Bison bison), and North America's sole surviving endemic ungulate, pronghorn (Antilocapra americana), have already been lost. However, pronghorn still migrate up to 550 km (round‐trip) annually. These extreme movements (1) necessitate use of historic, exceptionally narrow corridors (0.1–0.8 km wide) that have existed for at least 5800 years, (2) exceed travel distances of elephants ( Loxodonta africana) and zebras ( Equus burchelli), and (3) are on par with those of Asian chiru ( Pantholops hodgsoni) and African wildebeest (Connochaetes taurinus). Although conservation planners face uncertainty in situating reserves in the most biologically valued locations, the concordance between archaeological and current biological data on migration through specific corridors in these unprotected areas adjacent to the Yellowstone system highlights their retention value. It is highly likely that accelerated leasing of public lands for energy development in such regions will truncate such migrations. One landscape‐level solution to conserving LDMs is the creation of a network of national migration corridors, an action in the Yellowstone region that would result in de facto protection for a multispecies complex. Tactics applied in this part of the world may not work in others, however, therefore reinforcing the value of site‐specific field information on the past and current biological needs of migratory species.