Wednesday, November 25, 2015

A changing season means a changing diet for bison

North American bison adjust their diet seasonally in order to take full advantage of the growing season when grasses become less nutritious, a new study led by researchers at the University of Colorado Boulder has discovered.

The findings, which were recently published in the journal PLOS ONE, indicate that bison are not entirely reliant on grass for their nutritional needs and can selectively expand their foraging to include woody shrubs and flowering plants during the spring and fall.

The study sheds new light on variations in the large herbivore's eating habits and may have future implications for management and conservation of bison in Colorado and across the American West.

"We wanted to know if bison might change what they eat as the season goes on and how that affects the microbial composition of their gut," said Gaddy Bergmann, a doctoral candidate in the Department of Ecology and Evolutionary Biology at CU-Boulder. "This study shows that it may be beneficial for the species to have other plants, bushes, and trees available to browse from."

The 166-day study conducted in 2011 sampled a herd of roughly 300 bison living in the Konza Prairie Biological Station in the Flint Hills area of northern Kansas. Bison were reintroduced to the protected native tallgrass sanctuary in 1987.

By sequencing the plant and bacterial DNA found in the bison's fecal samples, researchers at CU-Boulder were able to identify the types of plants that the bison were consuming over time. The researchers found that the bison are willing and able to consume higher quantities of woody shrubs in the early spring and in fall when their preferred menu item--fresh grass--is less available.

The researchers then identified benign gut microbes present in the bison's lower digestive tract and traced how the abundance of those microbes changed over time. Some bacteria became more abundant during the growing season as the bison switched to more energy-rich foods in the summer and autumn.

Other grazing animals throughout the world, such as elk and wildebeests, migrate over long distances in order to follow their food supply. Historically, bison did so as well, but are more sedentary in their range today, making them more susceptible to seasonal changes in vegetation.

While an estimated 20 to 30 million bison once roamed the North American landscape, hunting and habitat encroachment reduced the population to just a few thousand by the end of the 1800s.

Tuesday, November 10, 2015

Cougars, aka mountain lions and pumas, likely to recolonize portions of habitat in the middle part of the United States

A groundbreaking new study shows that cougars, also known as mountain lions and pumas, are likely to recolonize portions of habitat in the middle part of the United States within the next 25 years. It is the first study to show the potential "when and where" of the repopulation of this controversial large predator.

The study, led by researchers at the University of Minnesota and Southern Illinois University Carbondale, will be published soon in the international journal Ecological Modelling.

This is the first, large-scale population viability study on cougars. The research examined more than 40 years worth of data on demographics and geographical information on more than 3 million square kilometers to determine possible areas of population establishment. The researchers specifically looked at the female dispersal since population settlement is dependent upon the arrival of females in a given area.

"We didn't just look at where they are now, but where they could go," said study author Michelle LaRue, a University of Minnesota research associate in the College of Science and Engineering's Department of Earth Sciences. "These are predictive models, but we feel that our study could be an important tool for conservation of this species and education about a large carnivore that can sometimes incite fear."

Breeding populations of cougars are already living in the Black Hills of South Dakota, and researchers noted four breeding populations in North Dakota and Nebraska. The new study shows that cougars could be expected in the next two decades in Arkansas, Missouri and Nebraska with the potential to sustain existing populations in the Dakotas and Nebraska.

Historically, cougars were once one of the most widely distributed land mammals on earth, ranging from the Atlantic to Pacific oceans and from northern British Columbia to southern Chile. In the United States, the cougars were pushed back to the American West with the arrival of European settlers. Although they have been extirpated for more than 100 years, cougars have been reported in the middle part of the U.S. over the past two decades with more than 800 instances of confirmed cougar presence from 1990-2015.

"The reason cougars used to exist across the country and now they don't is because of people," said study co-author Clayton K. Nielsen from Southern Illinois University Carbondale's Cooperative Wildlife Research Laboratory and Department of Forestry. "Now that this large carnivore is expected to come back into new areas, we need have a clear plan for education and conservation."

The next step is to examine human acceptance and attitudes toward the repopulation of cougars, said LaRue, who is also the executive director of the Cougar Network, a nonprofit research organization.
"We now have the information necessary for government agencies to plan for ecosystem-based management and societal attitudes toward the recolonization of this predator," LaRue said. "Given that cougars are expected to inhabit areas where they haven't been for more than 100 years, this will pose considerable challenges for wildlife managers and the general public in the future."