{{Short description|Species of tick}} {{Speciesbox | image = Dermacentor albipictus larva.png | image_caption = Larva of winter tick | genus = Dermacentor | species = albipictus | authority = ([[Alpheus Spring Packard|Packard]], 1869) }}
'''''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]] (''Odocoileus virginianus''), [[mule deer]] (''O. hemionus'') and [[caribou]] (''Rangifer tarandus'') but is primarily known as a serious pest of [[moose]] (''Alces alces'').<ref name="Howell">{{Cite web |url=https://www.cabdirect.org/cabdirect/abstract/19431000310 |title=The Ecology of ''Dermacentor albipictus''}}</ref><ref>{{Cite book |last=Lindquist |first=Evert |title=A Handbook to the Ticks of Canada (Ixodida, Argasidae) |last2=Galloway |first2=Terry |last3=Artsob |first3=Harvey |last4=Lindsay |first4=L. Robbin |last5=Drebot |first5=Michael |last6=Wood |first6=Heidi |last7=Robbins |first7=Richard |publisher=Biological Survey of Canada |year=2016 |isbn=978-0-9689321-8-6}}</ref> As early as 1909, [[Ernest Thompson Seton]] described the winter tick as a greater enemy of the moose than were "wolves, bears, and cougars." <ref name="WAAG_review">{{cite journal |last=Addison |first=Edward M |date=January 1, 2007 |title=White as a Ghost, Winter Ticks and Moose |journal=Journal of Wildlife Diseases |volume=43 |issue=1 |pages=150–151 |doi=10.7589/0090-3558-43.1.150 |quote=Our understanding of winter ticks (''Dermacentor albipictus'') and moose (''Alces alces'') is largely a 20th century story beginning when Seton (1909) described winter ticks as a greater "enemy" of moose than were wolves, bears, and cougars. Until 1980, field observations comprised the literature on winter ticks and moose. In the last two decades of the century, Bill Samuel, along with colleagues in Alberta and others, examined the relationship between winter ticks and moose using thorough experimental and field studies. |doi-access=free }}</ref> Feral swine, another common host, is also home to many other tick species, which can help increase the population of winter tick and increase the distribution of the population in some areas, harming moose and ecosystems further.<ref name=":1">{{Cite journal |last=Musante |first=Anthony R. |last2=Pedersen |first2=Kerri |last3=Hall |first3=Parker |date=Jan 2014 |title=First reports of pseudorabies and winter ticks (Dermacentor albipictus) associated with an emerging feral swine (Sus scrofa) population in New Hampshire |url=https://pubmed.ncbi.nlm.nih.gov/24171577 |journal=Journal of Wildlife Diseases |volume=50 |issue=1 |pages=121–124 |doi=10.7589/2013-05-119 |issn=1943-3700 |pmid=24171577}}</ref> The ticks do not have a preference of host but moose are the most affected because of the areas they traverse through and their struggle to get them off. White-tailed deer are significantly better at getting rid of the pests.<ref name=":0">{{Cite web |last=Eaton |first=Dr. Alan T. |last2=Bergeron |first2=Daniel |date=June 2017 |title=Winter Tick (Dermacentor albipictus) |url=https://extension.unh.edu/sites/default/files/migrated_unmanaged_files/Resource001955_Rep2885.pdf |website=UNH Extension}}</ref>
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.<ref name="Maine">{{Cite web |title=Tick Species of Maine - Winter Tick or Moose Tick |url=https://extension.umaine.edu/ticks/maine-ticks/winter-tick-or-moose-tick/}}</ref> The tick prefers vegetation up to 1.25 m in height, for ease of finding a host.<ref name="Quebec" />
Some evidence indicates that increasing populations of the winter tick may be responsible for a steep decline in the [[eastern moose]] population throughout the southern half of their range.<ref>{{Cite episode |credits=[[Hari Sreenivasan]] |title=What’s devastating the wild moose population in New England? |series=PBS Newshour |access-date=2014-04-08 |date=2014-04-07 |url=https://www.pbs.org/newshour/show/researchers-track-new-hampshire-moose-hopes-pinpointing-cause-population-decline}}</ref> In recent years, heavy infestations up to 150,000 ticks<ref name=":0" /> have been seen on single moose, and can lead to the death of the animal.<ref>{{cite book |last=Samuel |first=Bill |title=White as a Ghost: Winter Ticks & Moose |url=https://books.google.com/books?id=h1T2zh3K-sMC |publisher=Federation of Alberta Naturalists |isbn=978-0969613466 |year=2004}}</ref>
== Description == The winter tick is [[Sexual dimorphism|sexually dimorphic]], 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.<ref name="Maine"/>
Female ticks become unusually large toward the end of winter, measuring up to {{cvt|15|mm|1}}.<ref name="Quebec">{{Cite web |url=https://mffp.gouv.qc.ca/english/wildlife/wildlife-habitats/winter-tick.jsp |title=Moose winter tick}}</ref>
== Lifecycle == The lifecycle of ''D. albipictus'' lasts for about a year, and it is a single-host tick. This means that most of their life cycle is spent on a single host. Reproduction is done at the end of the lifecycle when the female tick is fully engorged, it falls off the host in late winter to early spring into the leaf litter and lays its eggs in mass of up to 3,000. The eggs hatch in late summer or early spring.<ref name=":0" /> After lying dormant for some time, they start to ascend vegetation to group in clusters of about 1,000 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 metamorphose into adults.<ref name="Quebec" /> The male ticks live their entire nymph to adult lives on the single host, never falling off to reproduce like the female; they die on the host.
Larvae became nymphs about 10 days after being applied to the moose. Nymphs then undergo a long [[diapause]] 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.<ref name="Parasitol1988">{{cite journal |last1=Addison |first1=Edward M |last2=McLaughlin |first2=Robert F |year=1988 |title=Growth and Development of Winter Tick, ''Dermacentor albipictus'', on Moose, ''Alces alces'' |journal=The Journal of Parasitology |volume=74 |issue=4 |pages=670–678 |doi=10.2307/3282188 |quote=Engorged females first started to detach by 24 March, and many had engorged and detached by early April (190-192 days after infestation). |jstor=3282188 |pmid=3397828}}</ref>
During late winter, the ticks mate, and blood-filled females drop off the host to lay their eggs and die.<ref name="Quebec" /> For captive moose observed in Ontario in 1988, tick detachment occurred in late March to early April.<ref name="Parasitol1988"/>
== Effect on ecosystems == Tick populations and their effects on moose have been observed to vary from year to year.<ref name="WellsGray">{{cite journal |last1=Ritcey |first1=RW |last2=Edwards |first2=RY |date=1958 |title=Parasites and Diseases of the Wells Gray Moose Herd |journal=Journal of Mammalogy |volume=39 |issue=1 |pages=139–145 |doi=10.2307/1376619 |quote=There is annual variation in the abundance of ticks on these moose…In years of heavy loads some extreme conditions have been recorded. Through late March and early April in 1952, most moose beds were bloodstained and contained ticks. Thirty-one ticks were found in one bed. In that year, a weak calf, reported by Patrolman C. E. Gaglardi, was captured and examined. It had ticks over most of [its] body with the exception of the back and shoulders…There was little space for more ticks on the ears, inside or out. The body was dotted with clusters averaging three or four ticks each. |jstor=1376619}}</ref> Winters that are shorter and warmer have been shown to correlate with increased numbers of ticks in moose populations.<ref name="Minn"> {{Cite web |url=http://d.umn.edu/biology/documents/TerryPaper1.pdf |title=FACTORS AFFECTING EPIZOOTICS OF WINTER TICKS AND MORTALITY OF MOOSE |last=Samuel |first=WM |work=Alces |quote=Die-offs of moose (''Alces alces'') associated with, or attributed to, winter ticks (''Dermacentor albipictus'') are widespread and have been reported since the early part of the last century...The proposal that warmer and shorter winters result in increased survival of adult female ticks dropping off moose in March and April, and increased tick populations on moose the following winter, was generally confirmed. Annual changes in hair damage and loss on moose, which are documented from the air, coincided with annual changes in numbers of ticks on moose, providing managers with a survey tool to monitor and estimate changing numbers of ticks. |date=2007 |access-date=March 8, 2019}}</ref> In a study conducted by Vermont Fish and Wildlife Department between 2017 and 2019, they captured 36 adult cows and 90 calves and concluded that 74% of all mortalities were in relation to winter tick infestation, with 91% of those deaths being calves. <ref>{{Cite web |title=Moose Research {{!}} Vermont Fish & Wildlife Department |url=https://www.vtfishandwildlife.com/conserve/conservation-planning/animal-inventory/mammals/moose-research |access-date=2026-03-05 |website=www.vtfishandwildlife.com}}</ref>
The tick not only directly affects mammals, but also has adverse indirect effects on ecosystems, and other wildlife that can be connected with the moose. In 2001, the moose abundance on [[Isle Royale]] was around 1200, but due to the ticks, the moose population fell to around 400 in 2007. The long-term average of years of data show that moose on Isle Royale show about 51% hair loss from excessive grooming in reaction to the infestation of the winter tick. With the decreased moose population, the main food source of the moose--various shrubs species and [[balsam fir]]--has had an increase in abundance.<ref>{{Cite web |url=http://www.isleroyalewolf.org/node/44 |title=Small Creature, Big Influence}}</ref>
Winter tick also affects most other ungulates, including elk, caribou, and white-tailed deer, also causing anaemia, hair loss, and reduced fitness. Winter ticks do not have a preference for a specific mammalian host; they grab onto any animal that passes by in the larval stage. They affect moose the most aggressively because the moose struggle to detach them the most; therefore, the ticks have a higher chance of survival on the host and can cluster in larger masses. Luckily, winter ticks do not transmit diseases to moose, humans, or pets.<ref name=":1" />
==References== {{Reflist}}
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[[Category:Arachnids of North America]] [[Category:Ticks]] [[Category:Ixodidae]] [[Category:Animals described in 1869]]