What is a Population?

2015-10-29. Vultures nearing extinction in Africa. By Reuters.

2013-08-05.  Climate Change Seen as Threat to Iberian Lynx.     Excerpt:  After 20 years and more than $100 million spent, the effort to save the endangered Iberian lynx is at risk because it fails to factor in the effects of climate change, scientists say.  The lynx is a spotted, yellow-eyed feline from Southern Europe that has long faced a dwindling food supply. Its preferred prey, the European rabbit, suffers from disease and over-hunting. Now only 250 lynx remain, mostly in Spain, and conservationists have focused on relocating them to more rabbit-rich habitats in the country. But warming temperatures and drier conditions could drive the European rabbit out of many of those habitats within 50 years, an international team of scientists reports in the journal Nature Climate Change. ...To save the lynx, the scientists say, conservationists should focus on relocating them to higher ground where the European rabbit will be less affected by changes in climate. .... http://www.nytimes.com/2013/08/06/science/weather-seen-as-threat-to-iberian-lynx.html. Douglas QuenQua, New York Times.

2009 November 4. North American Origins for the Falklands Wolf. By Henry Fountain, The NY Times. Excerpt: The Falklands wolf has puzzled evolutionary biologists since Charles Darwin first encountered it during the voyage of the Beagle in the 1830s. It was the only native land mammal on the Falkland Islands, which are 300 miles off the coast of Argentina. No one knew how it got there or what mainland animals it was descended from — and it did not help that the wolf was hunted to extinction by 1876.
But using genetic analysis, Graham J. Slater, a post-doctoral researcher at the University of California, Los Angeles, and colleagues have solved some of the mystery....
The researchers obtained snippets of DNA from five museum specimens, looked at variations among the samples and compared them with DNA from living species. They were able to build a family tree and a timeline of when the various branches diverged.
Earlier studies of the Falklands wolf had suggested it was related to foxes, but the DNA work showed the closest living relative to be another South American canid, the maned wolf....

2009 July 15. Greater Yellowstone elk suffer worse nutrition and lower birth rates due to wolves. By Tracy Ellig, MSU News.Excerpt: Bozeman -- Wolves have caused elk in the Greater Yellowstone Ecosystem to change their behavior and foraging habits so much so that herds are having fewer calves, mainly due to changes in their nutrition, according to a study published this week by Montana State University researchers.
During winter, nearly all elk in the Greater Yellowstone Ecosystem are losing weight, said Scott Creel, ecology professor at MSU, and lead author on the study....
"Essentially, they are slowly starving," Creel said....
With the presence of wolves, elk browse more - eating woody shrubs or low tree branches in forested areas where they are safer - as opposed to grazing on grass in open meadows where they are more visible, and therefore more vulnerable to wolves.
...the change in foraging habits results in elk taking in 27 percent less food than their counterparts that live without wolves, the study estimates.
...Obviously, wolves kill elk, and direct predation is responsible for much of the decline in elk numbers, but the rate of direct killing is not great enough to account for the elk population declines observed.... In addition to direct predation, the decline is due to low calving rates, which are a subtle but important effect of the wolves' presence, Creel said....

29 March 2005. How Foxes in the Aleutian Henhouse Doomed Islands' Plant Life. By CHARLES PETIT. NY Times. Foxes may not graze, but a new scientific study describes how their arrival on Aleutian islands destroyed rich grasslands and left only sparse tundra. The authors of the report, which appeared in Science last week, say this transformation shows how an entire ecosystem may go into a tailspin if just one new top carnivore shows up. The inadvertent experiment began in the late 1700's and continued into the early 20th century as fur traders looking to expand their supply released nonnative arctic foxes and, in some cases, red foxes on more than 400 Alaskan islands. Some died out, but many populations survived.... The botanical impoverishment that has resulted is the reverse of what usually happens when a new meat-eater comes along. "Traditionally, the predator eats the grazer; the grazer no longer eats the green stuff; and the habitat gets more green," said Dr. Donald Croll, a professor of biology at the University of California, Santa Cruz, and the lead author of the report. An example of the more usual routine is in Yellowstone National Park, where returning wolves, preying on sapling-browsing elk and confining the wary survivors to areas where they can see wolves coming, have touched off a resurgence of willow, aspen and other vegetation. The contrary effect in the Aleutians, once sorted out, has a simple explanation. The grazers on these islands were grass- and seed-eating Aleutian geese, which are smaller cousins of Canada geese. The foxes drove the geese near extinction, which would have been a boon for grasses except that the foxes also feasted on the eggs and hatchlings of puffins, auklets and other ocean-feeding seabirds they found brooding in vast numbers almost everywhere. Some islands lost almost all birds except for cliff-nesting species. And as ground-nesting birds faded, so did their nutrient-rich excrement, or guano, which had been a natural fertilizer. The research team concluded that islands with no foxes received an average 361.9 grams per square meter yearly. Fox-infested islands get just 5.7 grams per square meter of guano per year....


 

Articles from 2005–present

Addition to Teacher Guide:
The Population Game From NSTA Science Teacher, April 2004.
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