What makes elk tick: winter tick (Dermacentor albipictus) grooming behavior in wild elk (Cervus canadensis)

Abstract

Ungulates groom to remove ectoparasites but grooming may interfere with foraging, vigilance, and rumination, and it is possible that these effects differ among migratory tactics due to differences in parasite infestations. We compared the effects of grooming for winter ticks (Dermacentor albipictus) on winter foraging behavior by migrating and resident elk (Cervus canadensis) in the partially migratory population at the Ya Ha Tinda, adjacent to Banff National Park, Canada. We used hair loss on the dorsal shoulder area (“withers”) measured from photographic images as an index of tick infestation of individual elk. We conducted 594 focal observations on 48 radio-collared and 18 uncollared individuals that were uniquely identifiable from ear-tags (N = 66) in 2019 to assess whether grooming for ticks in winter reduced time spent foraging, ruminating, or being vigilant. Because rubbing or hair loss from radio-collars may influence tick infestations and behavior, we controlled for whether elk were collared or uncollared in our analyses. Neck hair loss was 3−5% greater in collared elk than uncollared elk, but neither withers hair loss nor time spent grooming differed. Grooming occurred during 42% of the observations but grooming comprised only ~1% of observation time. Nevertheless, 40% of all grooming was observed during resting, and grooming interrupted vigilance behavior ~8 times more than foraging. We found no differences among elk following different migratory tactics in time spent grooming or in other behaviors, but one of the two groups of migrant elk had higher withers hair loss. Our results suggest winter ticks may have slight effects on elk relative to other ungulates, particularly moose (Alces alces), in North America.

Revealing large‐scale parasite ranges: An integrated spatiotemporal database and multisource analysis of the winter tick

“…This relative ease of collection, due in large part to modern technology, may account for the high proportion of hair‐loss related‐observations in our dataset and their recency in the past few decades. We do not have records in our database for nonmoose hosts on the basis of hair loss alone, but it should be noted that most cervids do exhibit some degree of winter tick‐induced alopecia (Calvente et al, 2020; Normandeau et al, 2022; Welch et al, 1991), even if this is usually less severe than in moose. Extremely high host burdens of winter tick have been found on woodland caribou ( Rangifer tarandus caribou ) and white‐tailed deer when hair loss has been absent (Machtinger et al, 2021; Welch et al, 1990), so the reliability of this indicator on nonmoose species may be limited, particularly when compared with conventional necropsy techniques.…”

“…This relative ease of collection, due in large part to modern technology, may account for the high proportion of hair-loss related-observations in our dataset and their recency in the past few decades. We do not have records in our database for nonmoose hosts on the basis of hair loss alone, but it should be noted that most cervids do exhibit some degree of winter tick-induced alopecia (Calvente et al, 2020;Normandeau et al, 2022;Welch et al, 1991), even if this is usually less severe than in moose.…”