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Declining fortunes of Yellowstone’s migratory elk
http://www.esa.org/esa/?p=8351[font face=Serif][font size=5]Declining fortunes of Yellowstone’s migratory elk[/font]
[font size=4]Are human choices redefining the fitness of an ancient survival strategy?[/font]
For Immediate Release: Wednesday, 26 June 2013
[font size=3]In the late spring, the 4000 elk of the Clarks Fork herd leave crowded winter grounds near Cody, Wyoming, following the greening grass into the highlands of the Absaroka Mountains, where they spend the summer growing fat on vegetation fed by snowmelt. It’s a short trip (40-60 kilometers) by migratory standards, and by modern standards, uncommonly free of roads, fences, metropolitan areas, and other human-built barriers. But it crosses an important human boundary: the border into Yellowstone National Park.
The costs of migrating to the high green pastures have lately outstripped the benefits, according to a research report in the June issue of the Ecological Society of America's journal Ecology, published last week. Arthur Middleton and colleagues at the University of Wyoming, the Wyoming Game and Fish Department, and the U.S. Geological Survey reported that the migratory Clarks Fork herd has been returning to winter grounds with fewer and fewer calves over the last few decades. Herds that remain in the vicinity of Cody year-round have more surviving calves. Middleton et al. attribute the change in migration fortunes to climate change and a resurgence within the park of predators that hunt newborn elk calves.
Historically, migratory hoofed beasts like elk have outnumbered sedentary members of their species by as much as an order of magnitude. John Fryxell, a Forum contributor, wrote a classic paper on this effect in the American Naturalist in 1988. Migration allows animals to capitalize on seasonal foods and to shelter from predators and the elements. Elk and their hooved brethren have benefited from chasing the spring “green-up” into higher terrain as snow retreats, leaving behind, at least temporarily, their predators, which are pinned down by the needs of young pups and cubs.
Middleton’s observations therefore demonstrate a severe reversal of fortunes. Ecologists have reported troubled times for migrating animals all over the world, and attributed the problems to habitat changes wrought by human development and climate change. Middleton et al. point to the same influences, but draw a subtle distinction which they believe makes this a novel case study.
…[/font][/font]
[font size=4]Are human choices redefining the fitness of an ancient survival strategy?[/font]
For Immediate Release: Wednesday, 26 June 2013
[font size=3]In the late spring, the 4000 elk of the Clarks Fork herd leave crowded winter grounds near Cody, Wyoming, following the greening grass into the highlands of the Absaroka Mountains, where they spend the summer growing fat on vegetation fed by snowmelt. It’s a short trip (40-60 kilometers) by migratory standards, and by modern standards, uncommonly free of roads, fences, metropolitan areas, and other human-built barriers. But it crosses an important human boundary: the border into Yellowstone National Park.
The costs of migrating to the high green pastures have lately outstripped the benefits, according to a research report in the June issue of the Ecological Society of America's journal Ecology, published last week. Arthur Middleton and colleagues at the University of Wyoming, the Wyoming Game and Fish Department, and the U.S. Geological Survey reported that the migratory Clarks Fork herd has been returning to winter grounds with fewer and fewer calves over the last few decades. Herds that remain in the vicinity of Cody year-round have more surviving calves. Middleton et al. attribute the change in migration fortunes to climate change and a resurgence within the park of predators that hunt newborn elk calves.
Historically, migratory hoofed beasts like elk have outnumbered sedentary members of their species by as much as an order of magnitude. John Fryxell, a Forum contributor, wrote a classic paper on this effect in the American Naturalist in 1988. Migration allows animals to capitalize on seasonal foods and to shelter from predators and the elements. Elk and their hooved brethren have benefited from chasing the spring “green-up” into higher terrain as snow retreats, leaving behind, at least temporarily, their predators, which are pinned down by the needs of young pups and cubs.
Middleton’s observations therefore demonstrate a severe reversal of fortunes. Ecologists have reported troubled times for migrating animals all over the world, and attributed the problems to habitat changes wrought by human development and climate change. Middleton et al. point to the same influences, but draw a subtle distinction which they believe makes this a novel case study.
…[/font][/font]
