title: Patterns of ectoparasitism in North American red squirrels (Tamiasciurus hudsonicus): Sex-biases, seasonality, age, and effects on male body condition.
abstract: Within many species, males are often more heavily parasitised than females. Several hypotheses have been proposed to explain this phenomenon, including immunocompetence handicaps, sexual size dimorphism and behavioural differences. Here we set out to test the latter two hypotheses and make inferences about the former by assessing patterns of ectoparasitism across various life-history stages in a population of North American red squirrels (Tamiasciurus hudsonicus). We also conducted an ectoparasite removal experiment to investigate the effects of ectoparasites on male body condition. We found that males were more intensely parasitized than females, but only during the mating period. There was no difference in ectoparasite intensity between male and female juveniles at birth or at emergence, suggesting that ectoparasites do not exploit male red squirrels for longer-range natal dispersal. Male red squirrels in our population were slightly heavier than females, however we did not find any evidence that this dimorphism drives male-biased ectoparasitism. Finally, we could not detect an effect of ectoparasite removal on male body mass. Our results lend support to the hypothesis that ectoparasites exploit their male hosts for transmission and that male red squirrels are important for the transmission dynamics of ectoparasites in this population; however, the mechanisms (i.e., immunocompetence, testosterone) are not known.
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T6E6V6, Canada.
authors.forename: Jesse E H
authors.initials: JE
authors.lastname: Patterson
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T6E6V6, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Neuhaus
authors.affiliation: Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta T2N4N1, Canada.
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Kutz
authors.affiliation: Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T6E6V6, Canada.
authors.forename: Kathreen E
authors.initials: KE
authors.lastname: Ruckstuhl
keywords: Body mass; Ectoparasite; Parasite removal; Red squirrel; Sex-biased parasitism; Tamiasciurus hudsonicus; Transmission dynamics