Saturday, March 24, 2012

Ruminations on Winter Severity

I recently did a phone interview with a reporter about the unseasonably warm temperatures we’ve been having in Minnesota this winter and how that may affect the wolf population in Minnesota. My comments revolved around the challenge of needing more data to conclusively determine if and how this past winter affected wolves in the state at this time.

Anecdotally, we can make some educated guesses based on what we know about wolf and deer ecology and the state’s winter severity index (a tool used by wildlife biologists to estimate the effect of winter conditions on white‐tailed deer populations).

Images: Wolf tracks on Saganaga Lake; Source

For example, research tells us that wolves have a physical advantage over deer in deep snow conditions. Large paws distribute the wolf’s body weight and act like built-in snowshoes whereas the deer’s narrow, pointy hooves poke through the snow to the ground. A chase in deep snow would give the wolf the upper-hand. However, this year’s low winter severity rating did not provide an opportunity for wolves to use that physical tool and may have affected their hunting success overall.

Little snow also means that deer may have had an easier time foraging for food. Less energy used for traveling through deep snow and easier to access food resources logically means better fed deer. However, the quality of the resources is also an unknown factor right now. Warmer winter temperatures also mean less energy used staying warm. Generally, a deer that is well-fed and warm tends to have more strength and energy to fend off or run away from wolves. (Image: Deer burn lots of energy moving through deep snow like this. Unknown Source: email circulation)

Additionally, if more deer are finding more food and more deer survive until summer rather than starving to death or dying from exposure then that means less carrion for wolves to scavenge on in the spring.

It would make sense to ponder the reproductive impact that a warmer winter would have on deer as well or conversely, the impact on wolves. Will more does have twins this spring thus increasing the chance that more fawns will survive the year?

Alternately, we may or may not see an impact on the number of pups born per pack or how many survive their first year.

It will be interesting to see how this low snow, warmer winter plays out for the wolves and deer of Minnesota.

The game’s not over though. I find it hard to believe that we won’t see more white stuff on the ground before May…

This is Ely in March?

For more information on the complexities of predator/prey relationships, I recommend visiting the Isle Royale Wolf/Moose Project Website. Not only is there a variety of scientific articles on the subject but there are also some interesting ruminations on the unexpected connections in nature.

For more information on Minnesota deer herds, I recommend visiting the state’s Website. There are details on deer density, hunter harvest, the effects of climate and much more.

Learn more about winter severity with curriculum from the New Hampshire Education and Environment Team.