Digging for answers: contributions of density- and frequency-dependent factors on ectoparasite burden in a social mammal

Abstract

Due to the density-dependent nature of parasite transmission parasites are generally assumed to constrain the evolution of sociality. However, evidence for a correlation between group size and parasite burden is equivocal, particularly for mammals. Host contact rates may be modified by mobility of the host and parasite as well as social barriers. In the current study, we used the common mole-rat (Cryptomys hottentotus hottentotus), a social subterranean rodent, as a model system to investigate the effect of host density and frequency of contact rates on ectoparasite burdens. To address these factors we used a study species that naturally varies in population densities and intergroup contact rates across its geographic range. We found that ectoparasite prevalence, abundance and species richness decreased with increasing host density at a regional scale. At the same time, measures of parasite burden increased with intergroup contact rates. Ectoparasite burdens decreased with colony size at the group level possibly as a result of increased grooming rates. Equating group size with population density might be too simplistic an approach when assessing parasite distributions in social mammals. Our data suggest that frequencydependent mechanisms may play a much greater role at a population level than density-dependent mechanisms in determining parasite distributions in social species. We suggest that future studies should explicitly consider behavioural mechanisms that may affect parasite distribution.

Ectoparasitic community of the Mahali mole-rat, Cryptomys hottentotus mahali: potential host for vectors of medical importance in South Africa

“…The parasite assemblage found in the present study was limited to two arthropod taxa (fleas and mites) with a low species diversity. Similar low parasite species diversity has been recorded for several other subterranean rodents [ 2 , 7 , 20 , 36 ]. The reported low parasite burden may be a result of the subterranean lifestyle of the study species, which could limit exposure to parasites [ 31 , 37 – 40 ].…”

“…Xenopsylla philoxera has not previously been reported from any South African mole-rats, although another flea species ( Cryptopsylla ingrami ) has been reported from C. h. hottentotus [ 37 ]. The two mites A. scapularis and A. capensis have been reported in previous studies from Cryptomys hottentotus hottentotus , C. h. pretoriae and Fukomys damarensis [ 31 , 36 , 37 , 39 ]. On the Mahali mole-rat, as well as on closely related species ( C. h. hottentotus and C. h. pretoriae ), mites were the dominant taxa [ 31 , 37 ].…”

Ectoparasite burden influences the denning behavior of a small desert carnivore

“…The majority of studies demonstrating impacts of ectoparasites have focused on rodents (Hawlena et al 2006, Hillegass et al 2010, Zwolak et al 2013, Archer et al 2016, Sponchiado et al 2017) and ungulates (Mooring and Samuel 1999, Vor et al 2010, Paakkonen et al 2014, Mysterud et al 2016. To our knowledge, only two other species of denning carnivores, the European badger (Meles meles; Butler and Roper 1996) and black-footed ferret (Mustela nigripes; Matchett et al 2010), have been investigated using an experimental manipulation of ectoparasites.…”

“…, Archer et al. ). Denning behavior is commonly exhibited in desert‐adapted species to reduce the energetic costs associated with thermoregulation and thermal conductance, and to mitigate predation risk (Kinlaw ).…”

“…A suite of factors can influence presence and severity of ectoparasites on hosts (Wall andShearer 2001, Hatcher and. In mammals, denning behavior, and the accompanying semi-fossorial lifestyle, is a modality often leading to increased ectoparasite presence and burden (Butler and Roper 1996, Kinlaw 1999, Roper et al 2002, Archer et al 2016. Denning behavior is commonly exhibited in desert-adapted species to reduce the energetic costs associated with thermoregulation and thermal conductance, and to mitigate predation risk (Kinlaw 1999).…”