Moose: The Tick Threat|
By Kirby Holcombe
Winter travelers in the back country of the Rangeley area, whether by snowmobile, skis, or snowshoes, have probably found moose beds and hoof prints with blood in them. Their first thought is the blood is from an injury. Most likely, however, it was from winter ticks attached to the moose. The blood can be from open wounds where ticks have just dropped off, dried blood in tick feces, and from live ticks crushed as the moose moves.
The unkempt, and blotchy coat of moose observed in the Spring can also be due to ticks. Although moose shed their winter coats in May and June, during the winter the constant grooming and rubbing of their coat in an attempt to dislodge ticks can result in substantial hair loss. In some cases the hair loss is so extreme the moose appears white, and is referred to as a "ghost moose".
Wally Jacubas, mammal group leader for Maine DIF&W, told the Bangor Daily News in October that a young moose with thousands of ticks on it can struggle during harsh Maine winters. "The moose they don't try to git rid of the ticks until it is too late," Jacubas said. "They start rubbing on trees and rubbing a lot of hair off. Of course the hair of a moose is a great insulator, and with that gone, they're going to expend a lot more energy than they would trying to keep warm." Jacubas said moose are affected by winter ticks, not deer ticks that sometimes carry Lyme disease. The winter ticks are not known to cause health problems in humans.
Karen Morris, Maine DIF&W moose specialist, told the Bangor Daily News also in October, "If (ticks are reducing the herd size and keeping it from reaching the State's goals), we're restricting hunting opportunity for no reason, to try to allow a moose herd to increase." Morris said the real thing is to evaluate whether or not the goals for the moose population make sense.
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Winter tick infestation occurs throughout the range of moose except in Alaska and far northern areas of Canada. Canada has a severe problem with winter ticks which have caused periodic large die offs of moose. Consequently, most of the research on this tick problem has been done in Canada, most notably by Bill Samuel, Federation of Alberta Naturalists, who wrote a book on this phenomena, WHITE AS A GHOST.
Minnesota recently reported a decrease in the number of moose in the northeastern part of the state from 4,000 moose in the early 1990s to an estimated total of only 84 moose today. Biologists in that state cite global warming as the biggest factor in that drop. Warmer temperatures in fall and spring lead to greater numbers of ticks on moose. Higher summer temperatures affect the moose directly. Moose are a northern animal particularly adapted to cold temperatures. Moose can develop heat stress when temperatures reach about 57 degrees F and may start to pant at 68 degrees. This stress leads to decreased feeding, loss of weight, and lessened ability to cope with winter. Couple that with the added stress from winter ticks and you have a lethal mix.
In 2001, the New Hampshire Fish and Game Department began a study of moose habitat and mortality. About 100 moose, mostly cows and cow calves, were collared, tracked, and studied over a five year period. The study took place in the Coos County area of the State, an area similar in habitat to that of the Rangeley area. Kat Bagley, N.H. Fish and Game Department, reported in the September/October 2006 issue of WILD LIFE JOURNAL, that forty percent of the study moose died over the five year period. Winter ticks were determined to be the major cause of 41% of these deaths and almost 90% of these tick related deaths occurred in moose younger than one year old. Moose-vehicle collisions caused 26% of the deaths and hunting caused 18% of the deaths.
Katie Andrle , a fourth year wildlife ecology major at the University of Maine at Orono, spoke about winter ticks and moose at the January meeting of the RRG&SA. Katie is a native Mainer who grew up hunting and fishing in the woods of Maine. This summer she hopes to be in Alaska working with waterfowl and seabirds and next Fall she will be furthering her education in ecology at Umea University in Sweden. She has taken up the challenge to learn more about winter ticks in Maine and to assist DIF&W in their research about the effects of these ticks on Maine's moose herd. She explained that winter ticks are one host specific, feeding on blood from a single moose during all of the tick's life stages. The life stages of winter ticks on moose are shown in the accompanying chart.
The number of ticks on moose varies from year to year and are affected by Fall and Spring weather. Katie said tick larvae are sluggish when temperatures are below freezing in September and October as the tick larvae ascend grass and shrubs. If these cold temperatures occur during this Fall period it can greatly decrease the number of ticks successfully attaching to a moose. Deep snow and high winds in Fall can also decrease the transmission rate. Katie added that in the Spring, when engorged females drop from moose, deep snow can prevent the ticks from reaching the ground.??Katie assisted DIF&W in counting ticks on moose in the Eustis area during this past Fall's hunt. A moose can tolerate 10,000 to 30,000 ticks over winter without serious health effects. But tick loads of over 50,000 cause lethal health effects leading to probable death. They found the number of ticks on moose this past Fall to be on the low side probably due to last year's hard winter.
She is pursuing a project with DIF&W's moose biologist Lee Kantar to look at weather patterns and other factors which could affect tick populations and moose mortality. Their goal is to be able to predict tick densities on moose and to estimate moose mortality for the following year. This is an excellent example of an energetic college student volunteering time and talent to help a cash strapped State agency (MDIF&W) to pursue its goals and serve the public. Thank you Katie Andrle for your contribution to wildlife management and to Lee Kantar for accepting this assistance and using it effectively.
Kirby Holcombe lives in Oquossoc, ME, is a Registered Maine Guide and a director of the Rangeley Regions Guide's and Sportsman's Association.
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