Friday, December 21, 2012

Italian wolves prefer pork to venison

Some European wolves have a distinct preference for wild boar over other prey, according to new research.

Scientists from Durham University, UK, in collaboration with the University of Sassari in Italy, found that the diet of wolves was consistently dominated by the consumption of wild boar which accounted for about two thirds of total prey biomass, with roe deer accounting for around a third.

The study analysed the remains of prey items in almost 2000 samples of wolf dung over a nine year period and revealed that an increase in roe deer in the wolf diet only occurred in years when boar densities were very low. In years of high roe deer densities, the wolves still preferred to catch wild boar.

The results are published in the journal PLOS ONE.

The research team related the prey remains in wolf dung to the availability of possible prey in part of Tuscany, Italy - an area recently colonised by wolves. The findings have implications for wildlife conservation as the impact of changing predator numbers on prey species is important for managing populations of both predators and prey.

Lead author, Miranda Davis, from the School of Biological and Biomedical Sciences at Durham University, said: "Our research demonstrates a consistent selection for wild boar among wolves in the study area, which could affect other prey species such as roe deer."

"Intriguingly, in other parts of Europe where red deer are also available, wolves appear to prefer this prey to wild boar, suggesting that they discriminate between different types of venison."

In Europe, the wolf (Canis lupis) is recovering from centuries of persecution and the expansion of wolf populations has the potential to change the ecology of communities of ungulates (hooved animals) by exposing them to natural predation by wolves, according to the researchers.

The preference for boar is in contrast to other areas of Europe where wolves often avoid boar as prey. One factor may be the relatively smaller size of Mediterranean boar, making them less dangerous to wolves in Mediterranean regions, compared to the larger-sized boar that roam other parts of Europe.

Co-author, Dr Stephen Willis, from the School of Biological and Biomedical Sciences at Durham University, said: "Wolves were hunted to extinction in the UK, probably by the end of the 17th century. Our findings from Italy suggest that if they were reintroduced into an area with a healthy ungulate population their impact on livestock could be minimal."

Tuscany's woodlands support populations of both roe deer and wild boar, and are also grazed by sheep, goats and cattle; however, wild boar and roe deer made up over 95 per cent of wolf diet in the study area, with very little evidence of livestock predation.

The scientists identified prey items from fragments of bones and hair in the wolf dung collected in the region. The prey categories included wild boar, roe deer, red deer, hare, small rodents, goats, sheep and cattle.

For more than five years of the study, the percentage of wolf diet made up of wild boar was more than twice that of roe deer. Other prey represented only a very small proportion of the diet.

The researchers believe that further dietary studies are essential for understanding the true impact of wolves on European wildlife over time.

Co-author, Dr Phil Stephens, from the School of Biological and Biomedical Sciences at Durham University added: "Wolves and brown bears are gradually returning to their former strongholds in Europe. Understanding the needs of these species, as well as their potential impacts, is going to be fundamental to managing that welcome return."

Monday, December 10, 2012

Elk bones tell stories of life, death, and habitat use at Yellowstone National Park

Josh Miller likes to call himself a conservation paleobiologist. The label makes sense when he explains how he uses bones as up-to-last-season information on contemporary animal populations.

Bones, he says, provide baseline ecological data on animals complementary to aerial counts, adding a historical component to live observation. In his November cover article for the Ecological Society of America's journal Ecology, he assesses elk habitat use in Yellowstone National Park by their bones and antlers, testing his method against several decades of the Park Service's meticulous observations.

Now an assistant research professor in the new Quaternary and Anthropocene Research Group in the Department of Geology at the University of Cincinnati, Miller located and recorded the elk bone data while a doctoral student in paleontology at the University of Chicago, and finished analyzing the data during a brief stint at the Florida Museum of Natural History at the University of Florida, in Gainesville. His work with modern animals grew out of curiosity about the fidelity of the fossil record in archiving animals and ecosystems of the distant past.

"It turns out that bones are really informative," he said. At Yellowstone, bone and antler concentrations mirror patterns of animal landscape use known from years of aerial surveys. "This opened up a completely unexpected opportunity for studying modern ecosystems, particularly for areas where our knowledge of animal populations is more limited."

Reconstructing animal community structure and habitat use through the bones of past generations is a new idea. Until recently, common knowledge held that, on the landscape, bones just don't last that long. But Miller has found that they can last for hundreds of years. Bones weather in a stereotypical pattern, from fresh to falling apart. He calibrated weathering in the Yellowstone bones through radiocarbon dating, gaining a familiarity that would allow him to pick up a bone and know it had seen a year, 20 years, or 80 to 100 years or more on the open ground.

Bull elk shed their antlers in late winter, when forage is sparse. Too poor in nutrients to interest most scavengers, heavy, and awkwardly shaped for displacement by the elements, antlers tend to stay where they fall. Miller found that, for the most part, the bones of calves don't travel far either, even in the mouths of predators. The bones of calves mark the range where their mothers sought plentiful food to fuel months of nursing, and shelter to hide their vulnerable newborns.

Old bones from past decades outline a range consistent with the living herd. Miller saw only moderate shifts in a few areas, even given the many recent changes at Yellowstone: the prodigious wildfires of 1988, repatriation of grey wolves starting in 1995, and regrowth of willows, aspen, and cottonwoods over the last couple of decades following a long decline during the 20th century.

Because bones can last decades to centuries in the Yellowstone environment, Miller says they can put relatively recent data from direct observation into broader context for managers looking at long-range planning, helping to sort out important changes from the noise of cyclical booms, busts and shifts in landscape use. Bones are a minimally invasive tool for tracking the history of range animals. They are data just lying on the ground, waiting to be collected.

Spatial fidelity of skeletal remains: elk wintering and calving grounds revealed by bones on the Yellowstone landscape (2012) Joshua H. Miller. Ecology 93:11, 2474-2482.