Tuesday, May 31, 2016
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In the last week or so, the Idaho Department of Fish and Game (IDFG) Panhandle office has taken several calls about odd looking moose. Some have been reported in and around towns, others out in more wild places. The moose appear to be partially white; or, as one caller described 'ghost-like' in appearance.
Moose can experience tick infestations that start in mid-September but the problem is not clearly visible to people until late in the following winter. The ticks are called "moose ticks". Less commonly they are referred to as "winter ticks".
The infestations become visible when moose scratch and paw at their own skin enough to cause large patches of hair to break or fall out. That is when IDFG begins to get reports of sick looking moose.
Many times these patches are on the withers where moose are able to reach and scratch with their hooves. The skin exposed by the hair loss is light colored and from a distance the exposed skin makes the moose appear to be white in color.
Moose tick larvae hatch from eggs laid on the ground in April. They climb vegetation during the late summer and early fall. Stimulated by the carbon dioxide exhaled by a moose, they interlock their legs and wait. When a moose contacts the brushy vegetation covered by interlocked tick larvae, strings of thousands of tick larvae cling onto the hair of the moose and crawl toward the skin. (These tick larvae can also cling to deer, however, deer appear to be able to scratch them off.)
Infested moose can have tens of thousands of ticks. One dead moose was documented to have over 100,000 ticks. Pity the biologist who had to do that necropsy and count them!
Moose ticks take a blood meal from their host in November, January, March and April to mature from larvae to adults. In April, the adult female ticks drop off to lay their eggs on the soil surface, starting the tick life cycle over again.
Thousands of feeding ticks are potentially fatal to moose. While some moose survive until the ticks fall off, some moose die. The cause of mortality can be loss of blood, hypothermia due to loss of hair, or starvation when the severe itching causes them to forage less than is necessary to maintain themselves.
Mortality is highest in calf moose. Their smaller body mass loses heat more readily and is more vulnerable to blood loss. A National Geographic video program on moose ticks reports that calves can potentially lose half of their blood to the attached ticks.
Ticks are absent from moose by late May and into September, when new larvae may attach again.
Fortunately for us, moose ticks do not use humans as a host. This particular tick will not attach to a human. However, a moose infested with them can become so agitated that the moose becomes aggressive toward people and poses a potential danger. If you see a ‘ghost moose', stay away. The stressed and irritated moose may become aggressive and could cause severe injury or death to a person.