Global decline in aggregated migrations of large terrestrial mammals

Abstract

Knowledge of mammal migrations is low, and human impacts on migrations high. This jeopardizes efforts to conserve terrestrial migrations. To aid the conservation of these migrations, we synthesized information worldwide, describing 24 large-bodied ungulates that migrate in aggregations. This synthesis includes maps of extinct and extant migrations, numbers of migrants, summaries of ecological drivers and threats migrants confront. As data are often lacking, we outlined steps for science to address and inform conservation actions. We evaluated migrants against this framework, and reported their status. Mass migrations for 6 species are extinct or unknown. Most remaining migrants (n = 9) occur from 6 locations in Africa, with Eurasia and North America containing 6 and 4 remaining mass migrants, respectively (with caribou/reindeer Rangifer tarandus occurring in both regions). All migrants declined in abundance, except wildebeest and other migrants in the SerengetiMara Ecosystem (SME), white-eared kob and tiang in Sudan, and some caribou populations. Protected areas only contain migrations for 5 species in the SME, chiru on the Tibetan Plateau, and some caribou populations in North America. Most mass migrants track the seasonal and shifting patterns of greening vegetation over expanses of savannahs, steppes, and grasslands. Principal threats include overhunting and habitat loss from livestock, agriculture, and fencing that excludes animals from forage or water. Conservation science overlooks numerous migrations, so many have already disappeared and continue to do so. Key principles for conserving migrants, exemplified by the SME and Greater Yellowstone Ecosystem (GYE), include securing seasonal ranges, resource protection, government support and minimizing fences. This review forms a baseline for initiating conservation action for many ungulate migrations needing attention.

Effects of large‐scale gold mining on migratory behavior of a large herbivore

“…Ungulate migrations are becoming increasingly compromised due to the increases in human population and expansion of anthropogenic disturbances across the western United States (Sawyer et al 2005, Harris et al 2009, Lendrum et al 2012. Increased disturbance within migration corridors has the potential to reduce the size of populations of migratory ungulates and potentially negate the benefits of migration.…”

“…Many populations of ungulates have been identified as long-distance migrants in a variety of ecosystems , and recent research suggests that many of those populations may be in decline (Berger 2004, Hebblewhite et al 2006, Couturier et al 2009, Harris et al 2009). Migratory ungulates use specific paths known as migration corridors, which allow them to traverse to seasonal ranges; usually areas with greater access to higher quality forage (Garrott et al 1987, Nicholson et al 1997, Sawyer and Kauffman 2011.…”

Diverse rates of gene flow and long-distance migration in two moose Alces alces subpopulations in Europe

“…Global analysis performed by Harris et al (2009) revealed that many populations of different species of ungulates have stopped migrating seasonally in recent times due to changes in the environment, climate changes and over-exploitation. Some populations of moose were also reported to have changed their behaviour in historical times.…”

“…Large herbivores are an interesting group of mammals in this respect as they include both sedentary and migratory species (Harris et al 2009). Some species, such as moose Alces alces, also show high intraspecific variation in dispersal and migratory behaviour.…”

A multi-method approach to delineate and validate migratory corridors

“…Long-distance migrations provide large-scale ecological benefits and services such as nutrient transfer, soil fertilization, and seed dispersal (Hamilton et al 1998;Holdo et al 2009;Estes 2014). However, migrations are in precipitous decline globally 35 because of rapid environmental change in many of the landscapes in which they still occur (Bolger et al 2008;Harris et al 2009;Singh and Milner-Gulland 2011). The linear shape of many corridors (Sawyer et al 2009) make migrations particularly sensitive to the effects of habitat loss and fragmentation, particularly in areas that act as natural bottlenecks such as valleys or passes (Morrison and Bolger 2014).…”