''Dermacentor albipictus'', the winter tick, is a species of hard tick that parasitizes many different mammal species in North America. It is commonly associated with cervid species such as
elk (''Cervus canadensis''),
white-tailed deer
The white-tailed deer (''Odocoileus virginianus''), also known as the whitetail or Virginia deer, is a medium-sized deer native to North America, Central America, and South America as far south as Peru and Bolivia. It has also been introduced t ...
(''Odocoileus virginianus''),
mule deer
The mule deer (''Odocoileus hemionus'') is a deer indigenous to western North America; it is named for its ears, which are large like those of the mule. Two subspecies of mule deer are grouped into the black-tailed deer.
Unlike the related whi ...
(''O. hemionus'') and
caribou (''Rangifer tarandus'') but is primarily known as a serious pest of
moose
The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult ma ...
(''Alces alces'').
As early as 1909,
Ernest Thompson Seton described the winter tick as a greater enemy of the moose than were "wolves, bears, and cougars."
The tick can be found all across North America, and has a large geographic distribution. While it can be found in several different habitats, it is often located in areas with a presence of moose.
Some evidence indicates that increasing populations of the winter tick may be responsible for a steep decline in the
eastern moose
The eastern moose (''Alces alces americana'') is a subspecies of moose that currently ranges throughout Eastern Canada, New England and northern New York State. It inhabits boreal forests and mixed deciduous forests. It is the third largest North ...
population throughout the southern half of their range.
In recent years, heavy infestations up to 75,000 ticks have been seen on single moose, and can lead to the death of the animal.
Description
The winter tick is
sexually dimorphic
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
, with adult females larger than the males. The adult female is mostly reddish-brown, but with a white dorsal shield behind the head. The smaller adult male is dark brown with some white markings.
Female ticks become unusually large toward the end of winter, measuring up to .
Lifecycle
The lifecycle of ''D. albipictus'' lasts for about a year, and it is a single-host tick. This means that the entire lifecycle of the tick (larvae, nymphs, and adults) progresses on a single host animal.
First, in late summer, larvae hatch from eggs. After lying dormant for some time, they start to ascend vegetation and to group in clusters on plants up to 1.25 m in height. This allows them to latch onto animals that pass by and begin to feed on their hosts. While on a host, the larvae go through the nymphal stage and then finally transform into adults.
Larvae became nymphs about 10 days after being applied to the moose. Nymphs then undergo a long
diapause
In animal dormancy, diapause is the delay in development in response to regular and recurring periods of adverse environmental conditions.Tauber, M.J., Tauber, C.A., Masaki, S. (1986) ''Seasonal Adaptations of Insects''. Oxford University Press I ...
before becoming adults in roughly mid-February. One moose, which had been infected with larvae 37 days after the others, still showed a similar timing of adult ticks appearing. The diapause may serve to delay maturity until the onset of warmer weather, as has been seen in other species of ticks.
During late winter, the ticks mate, and blood-filled females drop off the host to lay their eggs and die.
For captive moose observed in Ontario in 1988, tick detachment occurred in late March to early April.
Effect on ecosystems
Tick populations and their effects on moose have been observed to vary from year to year.
Winters that are shorter and warmer have been shown to correlate with increased numbers of ticks in moose populations.
[ ]
The tick not only affects moose, but also other wildlife that can be connected with the moose. In 2001, the moose abundance on
Isle Royale
Isle Royale National Park is an American national park consisting of Isle Royale – known as Minong to the native Ojibwe – along with more than 400 small adjacent islands and the surrounding waters of Lake Superior, in the state of Michigan. ...
was around 1200, but due to the ticks, the moose population fell to around 400 in 2007. With the decreased moose population, the main food source of the moose--various shrubs species and
balsam fir
''Abies balsamea'' or balsam fir is a North American fir, native to most of eastern and central Canada (Newfoundland west to central Alberta) and the northeastern United States (Minnesota east to Maine, and south in the Appalachian Mountains to ...
--has had an increase in abundance.
References
{{Taxonbar, from=Q10469436
Arachnids of North America
Ticks
Ixodidae
Animals described in 1869