From trees to fleas: masting indirectly affects flea abundance on a rodent host

Abstract

Mast seeding causes strong fluctuations in populations of forest animals. Thus, this phenomenon can be used as a natural experiment to examine how variation in host abundance affects parasite loads. We investigated fleas infesting yellow‐necked mice in beech forest after 2 mast and 2 non‐mast years. We tested 2 mutually exclusive scenarios: (1) as predicted by classical models of density‐dependent transmission, an increase in host density will cause an increase in ectoparasite abundance (defined as the number of parasites per host), versus (2) an increase in host density will cause a decline in flea abundance (“dilution,” which is thought to occur when parasite population growth is slower than that of the host). In addition, we assessed whether masting alters the relationship between host traits (sex and body mass) and flea abundance. We found a hump‐shaped relationship between host and flea abundance. Thus, the most basic predictions are too simple to describe ectoparasite dynamics in this system. In addition, masting modified seasonal dynamics of flea abundance, but did not affect the relationship between host traits and flea abundance (individuals with the highest body mass hosted the most fleas; after controlling for body mass, parasite abundance did not vary between sexes). Our results demonstrate that pulses of tree reproduction can indirectly, through changes in host densities, drive patterns of ectoparasite infestation.

Host sweet host: Rodent communities support similar ectoparasite diversity regardless of anthropogenic disturbance

“…For rodent relative abundance, a weak negative trend was observed regarding ectoparasite presence. Although previous studies have reported a positive relationship between the relative abundances of rodents and ectoparasites (Alkathiry et al., 2022; Baláž et al., 2022), this does not always translate into increased ectoparasite presence, particularly for fleas and ticks (Hawlena et al., 2005; Krasnov et al., 2007).…”

“…Ground‐dwelling rodent species had a higher probability of having ectoparasites. The ectoparasites we obtained from the rodents tended to be ground‐dwelling too, with several of them (e.g., fleas and mites) living in the underground nests of the rodent hosts (Baláž et al., 2022; Dowling, 2006; Krasnov et al., 2021). Similarly, ticks spend their intermediate moulting stages on the ground after they have detached from their hosts (Durden, 2006; Leal et al., 2020).…”

“…Ground-dwelling rodent species had a higher probability of having ectoparasites. The ectoparasites we obtained from the rodents tended to be ground-dwelling too, with several of them (e.g., fleas and mites) living in the underground nests of the rodent hosts (Baláž et al, 2022;Dowling, 2006;Krasnov et al, 2021).…”

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“…Ectoparasite (mites and ticks) prevalence decreases during the dry season, which might be due to unfavorable environmental conditions (high ambient temperatures and low humidity). Baláž et al (2022) tested how flea burden changes when their rodent hosts increase in response to massive seed production during the so-called "mast years." They found a hump-shaped relationship.…”

“…Baláž et al. (2022) tested how flea burden changes when their rodent hosts increase in response to massive seed production during the so‐called “mast years.” They found a hump‐shaped relationship. In agreement with basic models of density‐dependent transmission, when host densities were low to intermediate, the abundance of fleas had a positive relationship with rodent abundance.…”