Posts Tagged ‘minnesota’

Minnesota Moose Population Crash Possibly Correlated With Climate Change

February 20, 2011

by John Laumer, Philadelphia on 02.19.11 Original article here


aerial view minnesota moose photo
The end is near. Image credit: Mark Lenarz. (excerpted from slide show)

I recently was chided a bit for suggesting (without having provided a link to supporting scientific evidence) that the behavior of a central-Wisconsin black bear emerging from its den in early February might well be attributed to climate change. (See Black Bear, Bummed Out By Climate Change, Falls Asleep In Backyard ….)

Today I feel lucky, having stumbled onto some related science. The population density of northern Minnesota moose has been falling for years and bull moose are decreasing in proportion to cow moose. No, it’s definitely not a poaching problem; nor is it a human hunting or wolf-predation caused fall off (see below for some data). There is, however, a potential correlation of the long term Minnesota moose population collapse with climate change.

Here are some brief (out of context) excerpts from a presentation made recently that summarized research into possible causes of the observed decline in Minnesota’s moose population. Source: Presentation “Minnesota Moose” by Mark S. Lenarz and Erika Butler Minnesota DNR, Division of Fish and Wildlife Wildlife Research Unit.

  • Moose have an upper critical temperature of 14º C in the summer and -5 º C in the winter (Renecker and Hudson 1986).
  • Moose increase their metabolic rate when these thresholds are exceeded in an attempt to maintain core body temperature.
  • Non-hunting mortality was correlated with temperature indices, both seasonally and annually and these temperature indices have been increasing over the last 50 years.
  • If increasing temperatures are the cause for the decreases in survival, the decline of the northeastern population will take place even more rapidly.

From the same presentation, here are summations of mortality causation and population trend.


Note: I am not personally suggesting that Minnesota moose are dying off mainly because they’re too hot, although, not being an expert, I can’t exclude the direct significance of heat stress, nor can I weigh the impacts on moose of changed seasons. The best thing to do if you are interested in understanding this is to dive into the full presentation and give it some consideration before you comment.

What I am saying, in general – regarding surrogate indicators of climate change – is that a bear crawling out of its den after a two-day Wisconsin February warm up is not a behavior that I’ve ever heard of before. There’s no evolutionary advantage for the bear to then fall asleep in the snow where he is vulnerable to predators. Sure…it happens in March or April; but, a February den emergence signals a change in nature.

Back to Bullwinkle.
Moose evolved to live in a boreal-like forest characterized, in part, by their fitness inside a certain band of seasonal temperatures. When these thermal optima shift upward, individual animals may migrate north and/or the overall moose population will decline. It is the nature of living things. Otherwise we’d have tapirs in Oklahoma and alligators in Maine.

So, I’m sticking with my intuition on this subject. What’s good for the Tea Party is good enough for me. Bears should be in their Wisconsin dens in February and Moose should flourish across northern Minnesota, assuming human-caused habitat changes and disease are shown not to be likely causes of the crash, for example.

All there is left to debate is whether and to what extent we humans are causing the climate to change.

If I lived in Minnesota and liked to hunt I would want to get to the bottom of this and would offer what ever support I could to the researchers studying the population crash. Same if I were a company making a rifle capable of downing a bull moose.


Climate a Factor in Decline of Minnesota’s Moose Population

February 14, 2010
ST. PAUL, Minnesota, February 10, 2010 (ENS) – The moose population in northeastern Minnesota declined again this year, according to results of an aerial survey released Monday by the Minnesota Department of Natural Resources. The causes of this decline are not well understood, but some studies suggest a warming climate may be having an impact on Minnesota’s moose.

Survey results revealed lower moose numbers overall and the proportion of cows accompanied by calves continued a 13-year decline, dropping to a record low of 28 calves per 100 cows.

In addition to the decline in the calf to cow ratio, the bull to cow ratio also continued to decline with an estimated 83 bulls per 100 cows.

“These indices, along with results from research using radio-collared moose, all indicate that the population has been declining in recent years,” said Dr. Mark Lenarz, DNR forest wildlife group leader.

A bull moose in Minnesota (Photo courtesy Minnesota DNR)

A study of radio-collared moose in northeastern Minnesota between 2002 and 2008 determined that non-hunting mortality was substantially higher than in moose populations outside of Minnesota. Lenarz indicated that, “combined with the reduced number of calves, the high mortality results in a population with a downward trend.”

Moose populations are estimated using an aerial survey of the northeast Minnesota moose range. Based on the survey, wildlife researchers estimate that there were 5,500 moose in northeastern Minnesota this year compared to the 7,600 estimated last year, reinforcing the picture of a declining moose population.

Aerial surveys have been conducted each year since 1960 in the northeast and are based on flying transects in 40 randomly selected plots spread across the Arrowhead region in the northeastern part of the state.

The Fond du Lac band of Lake Superior Chippewa and 1854 Treaty Authority contributed funding and provided personnel for the annual survey.

The causes of moose mortality are not well understood. Of 150 adult moose radio-collared since 2002 in Minnesota, 103 have subsequently died, most from unknown causes thought to be diseases or parasites.

Nine moose died as a result of highway vehicle accidents. Two were killed by trains. Only six deaths were clearly the result of wolf predation.

Analyses by Lenarz and other scientists have indicated a significant relationship between warmer temperatures and non-hunting mortality.

“Moose are superbly adapted to the cold but intolerant of heat,” said Lenarz, “and scientists believe that summer temperatures will likely determine the southern limit of this species.”

In August 2009, a Moose Advisory Committee convened by the Department of Natural Resources released its report finding that climate change is a threat to moose in the state.

Rolf Peterson, chair of the DNR Moose Advisory Committee, said the committee concluded that “while climate change is a long-term threat to the moose in Minnesota, moose will likely persist in the state for the foreseeable future.”

In northwestern Minnesota, an area of agricultural land interspersed with woodlots, the moose population has declined from 4,000 moose in the late 1980s to fewer than 100 today.

By contrast, the northeastern population inhabits wetland-rich forested habitat which provides thermal cover even in a warming environment.

Peterson, a professor at Michigan Technical University who studies wolf and moose in Isle Royale National Park in one of the world’s longest wildlife study, said committee members are concerned about high mortality among moose from health-related causes. Still, details are poorly understood.

“For example, the connections between parasites, disease and mortality exist but how they interrelate is not clear,” he said. “Managing white-tailed deer at a density of fewer than 10 per square mile would reduce the potential for parasite-mediated impacts on moose.”

Moose Advisory Committee members concluded unanimously that it is inappropriate at this time to designate the moose as either a threatened or endangered species under state law.

After considerable discussion, a narrow majority of committee members who voted supported state-listed status as a Species of Special Concern, which the committee said accurately reflects the animal’s vulnerable status but conveys no additional legal status or protections.

The committee recommended that moose hunting continue in northeastern Minnesota though key harvest and population data must be monitored as part of a strategy to identify when a closure would be appropriate.

The Moose Advisory Committee report will be used in the development of a research and management plan mandated by law. The plan should be ready for release this spring and will be open to the public for comment.

Copyright Environment News Service (ENS) 2010. All rights reserved.

Original article here