Details

Autor(en) / Beteiligte

• Middleton, Arthur D.
• Kauffman, Matthew J.
• McWhirter, Douglas E.
• Cook, John G.
• Cook, Rachel C.
• Nelson, Abigail A.
• Jimenez, Michael D.
• Klaver, Robert W.

Titel

Rejoinder: challenge and opportunity in the study of ungulate migration amid environmental change

Ist Teil von

• Ecology (Durham), 2013-06, Vol.94 (6), p.1280-1286

Ort / Verlag

Washington, DC: Ecological Society of America

Erscheinungsjahr

2013

Link zum Volltext

Quelle

Wiley Online Library All Journals

Beschreibungen/Notizen

• Increasingly, animals that migrate long distances to exploit seasonal habitats must traverse political boundaries capable of altering the very ecological gradients that promote migratory behavior. This transboundary aspect of migration presents many new challenges and opportunities for research and conservation (e.g., Bolger et al. 2008, Taillon et al. 2012). Work to date has often focused on physical barriers to movement (roads, fences, and housing and energy development) that can threaten migratory populations to varying degrees (Holdo et al. 2011, Sawyer et al. 2013). However, even in the absence of conspicuous barriers, political and jurisdictional boundaries can bring dramatic differences in land use and conservation policy. What happens to migratory populations when these boundaries alter the resources and refuges that they seek on their seasonal journeys? It was this subtler question we confronted as we tried to understand the divergent productivity of migratory and resident elk (Cervus elaphus) in a population that occupies relatively undeveloped habitats of the Greater Yellowstone Ecosystem, USA (GYE). Over two decades, the recruitment rate of migratory elk has declined, while that of resident elk has remained stable, and recently increased. Over the same period, resident elk have grown more abundant, and the population's winter distribution has shifted similar to 18 km further away from the wilderness core of the GYE (Fig. 1). These changes have emerged without any physical obstruction of migration, and without migratory individuals"staying behind" to remain resident (Middleton et al. 2013). Gaillard (2013) points out that (1) calf:cow ratios are an imperfect index of recruitment, (2) that we could have failed to detect a low rate of individual switching between the two subpopulations, and (3) that we could not account for the full suite of fitness components in this population. Nevertheless, our comparative approach revealed important contrasts that suggest the population's ongoing transition has been largely brought about by changes in calf recruitment (Middleton et al. 2013), with residents outperforming migrants. Similar patterns have emerged in and around Banff National Park in Alberta, Canada, where wolf (Canis lupus) recovery and agriculture (factors also at play in the GYE) have been associated with declines in the recruitment and abundance of migratory elk (Hebblewhite et al. 2005, 2006). These trends pose challenges for conservation and management. Migratory ungulates can be ecologically and economically important, but are broadly threatened (Bolger et al. 2008), whereas resident ungulates that commingle with domestic livestock can increase risks of disease transmission (Cross et al. 2009), crop damage, and human-carnivore conflict (Nelson et al. 2012).