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.

The relationship between fleas and small mammals in households of the Western Yunnan Province, China

“…Thus, it can be seen that more flea prefers to stay in male hosts than in females. Consequently, a greater infestation of a male host than a female host in terms of abundance, prevalence and species richness of parasites, this has been reported for a wide variety of parasite and host taxa 42 , although higher levels of parasite infection have been reported in some mammalian female 43 .…”

The Relationship between Parasitic Fleas and Small Mammals in Household of Western Yunnan Province, China

“…Thus, it can be seen that more flea prefers to stay in male hosts than in females. Consequently, a greater infestation of a male host than a female host in terms of abundance, prevalence and species richness of parasites, this has been reported for a wide variety of parasite and host taxa [46], although higher levels of parasite infection have been reported in some mammalian female [47].…”

Personality predicts ectoparasite abundance in an asocial sciurid

“…Juvenile and adult males hosted higher ectoparasite prevalence than females, which is well established in rodents (e.g., Hillegasse, Waterman, & Roth, ; Perez‐Orella & Schulte‐Hostedde, ). While the effect of age and/or sex on ectoparasitism may be seasonal (Patterson et al., ), males presumably host higher prevalence than females due to sex‐specific variation in natural history, with male‐biased dispersal and/or larger home ranges in males.…”

“…Similarly, social allogrooming in meerkats ( Suricata suricatta ) increased the likelihood of acquiring Myobacterium bovis , the causative agent of tuberculosis (Drewe, ). For species that do not maintain stable social groups, transmission dynamics are mediated by other factors such as allometry (Han, Park, Jolles, & Altizer, ), space use (Han et al., ), and reproductive energetics (Patterson, Neuhaus, Kutz, & Ruckstuhl, ). For example, in red squirrels ( Tamiasciurus hudsonicus ), males tend to host more fleas than females during the mating season and females host more fleas during lactation, presumably because squirrels cannot allocate energy to grooming or immune function during these energetically costly times of year (Patterson et al., ).…”

“…For species that do not maintain stable social groups, transmission dynamics are mediated by other factors such as allometry (Han, Park, Jolles, & Altizer, 2015), space use (Han et al, 2015), and reproductive energetics (Patterson, Neuhaus, Kutz, & Ruckstuhl, 2015). For example, in red squirrels (Tamiasciurus hudsonicus), males tend to host more fleas than females during the mating season and females host more fleas during lactation, presumably because squirrels cannot allocate energy to grooming or immune function during these energetically costly times of year (Patterson et al, 2015). The reproductive season represents a period when males occupy larger home ranges as they search for potential mates.…”