Monday, October 28, 2013
Global warming and forest disturbances may have a silver lining for threatened species of grizzly bears in Alberta, Canada.
In a 10-year study that monitored 112 bears in Alberta's Rocky Mountain region, University of Alberta biologist Scott Nielsen and his colleagues found that warmer temperatures and easier access to food associated with forest disturbances helped the grizzlies to build more body fat, known to increase the chances of successful reproduction for mothers.
The resulting 'silver spoon effect' shows that bears born into these favourable conditions have a head-start in life, said Nielsen, an assistant professor in the U of A Department of Renewable Resources.
"Understanding variations in body size helps us understand what limits grizzly populations," Nielsen said. "We get clues about the environments that most suit grizzlies by examining basic health measures such as body size. A simple rule is, the fatter the bear, the better. Certain environments promote fatter bears.
The findings, published in BMC Ecology, may help influence forest harvest designs to enhance habitat for the Alberta grizzly, which is classed by the Alberta government as a threatened species. Currently there are only about 750 of the bears in the province, half of them adults.
In years when warmer temperatures and less late winter snow brought on earlier spring conditions, the body size of bears as adults was larger. Smaller bears were found in colder and less productive environments or years that were abnormally cool.
"We hypothesize that warmer temperatures in this ecosystem, especially during late winter and spring, may not be such a bad thing for grizzlies," Nielsen said, noting that historically the range for the bears once extended as far south as Mexico and persists today even in the deserts of Mongolia. "That suggests the species won't likely be limited by rising temperatures which would lengthen the growing season and the time needed to fatten prior to hibernation."
As well, bears that used disturbed forest habitats containing a wide variety of stand ages were healthier, Nielsen said.
"The diversity of stand ages in the landscape has a positive influence on body condition because bears are better able to access a wide range of food sources."
Thursday, October 24, 2013
It has long been believed that coyotes were incapable of taking down an adult moose, but researchers have recently discovered that eastern coyotes and coyote × wolf hybrids (canids) have preyed on adult moose in central Ontario. Their findings were published today in the Canadian Journal of Zoology.
Researchers Dr. John Benson, a PhD student in the Environmental and Life Sciences Graduate Program at Trent University when he conducted the research, and Dr. Brent Patterson, a research scientist with the Ontario Ministry of Natural Resources in Peterborough, documented instances where packs of eastern coyotes and coyote × wolf hybrids (canids) were found to have killed moose.
Their study involved live capture of eastern coyotes and eastern coyote × eastern wolf hybrids to deploy Global Positioning System (GPS) radio-collars and take blood samples for DNA analysis. The GPS collars delivered highly accurate locations of the study animals (via satellites or cell towers) so the researchers were able to visit these locations during winter to investigate their activities and document predation patterns. The DNA analysis allowed them to determine whether the animals were coyotes, wolves, or coyote × wolf hybrids.
In the study, four canid packs ranging in size from two to five animals were found to have killed moose. The researchers obtained two accurate ages from moose that were killed by coyotes and/or hybrids: One was very old (20 years) and one was young (20 months). It is believed that younger and older adult moose are probably more vulnerable due to inexperience and deteriorating body condition, respectively.
“Coyotes and coyote × wolf hybrids probably prey on moose opportunistically and only when circumstances are favorable. For instance, when snow is deep and a hard crust forms on top this impedes the ability of moose to travel and gives the lighter coyotes and hybrids an advantage because they can travel on top of the snow,” explained Dr. Benson.
“Additionally, we noticed that some of the moose killed by coyotes and hybrids were on steep slopes that may have slowed the moose and created unstable footing. We also found that some of the moose were killed in areas where medium-sized trees were moderately dense, which may have prevented moose from swinging around quickly to fend off predators attacking from the rear or side.”
“Killing of adult moose by eastern coyotes and coyote × wolf hybrids appears to be relatively rare and probably does not pose a threat to moose populations in central Ontario. However, from the perspective of a pack of coyotes or hybrids, killing even a single moose during a winter is very beneficial and goes a long way towards helping them meet their energetic demands. For instance, a pack of two eastern coyotes spent some or all of 18 days feeding on a moose that they killed.”
The authors do not believe the viability of moose populations in central Ontario is negatively affected by this predation, as recent studies have shown that populations in WMU49 and nearby Algonquin Provincial Park are increasing and that both adult and calf moose survival is relatively high.
This research was a collaborative project between the Ontario Ministry of Natural Resources and Trent University and was conducted in Wildlife Management Unit 49 (WMU49) in central Ontario -- the area between Huntsville, ON and Parry Sound, ON.
The article “Moose predation by eastern coyotes and coyote × wolf hybrids” by John F. Benson and Brent R. Patterson is published today in the Canadian Journal of Zoology.