Energetic costs of parasitism in the Cape ground squirrelXerus inauris

Abstract

Parasites have been suggested to influence many aspects of host behaviour. Some of these effects may be mediated via their impact on host energy budgets. This impact may include effects on both energy intake and absorption as well as components of expenditure, including resting metabolic rate (RMR) and activity (e.g. grooming). Despite their potential importance, the energy costs of parasitism have seldom been directly quantified in a field setting. Here we pharmacologically treated female Cape ground squirrels (Xerus inauris) with anti-parasite drugs and measured the change in body composition, the daily energy expenditure (DEE) using doubly labelled water, the RMR by respirometry and the proportions of time spent looking for food, feeding, moving and grooming. Post-treatment animals gained an average 19g of fat or approximately 25kJd-1. DEE averaged 382kJd-1 prior to and 375kJd-1 post treatment (p>0.05). RMR averaged 174kJd-1 prior to and 217kJd-1 post treatment (p<0.009). Post-treatment animals spent less time looking for food and grooming, but more time on feeding. A primary impact of infection by parasites could be suppression of feeding behaviour and, hence, total available energy resources. The significant elevation of RMR after treatment was unexpected. One explanation might be that parasites produce metabolic by-products that suppress RMR. Overall, these findings suggest that impacts of parasites on host energy budgets are complex and are not easily explained by simple effects such as stimulation of a costly immune response. There is currently no broadly generalizable framework available for predicting the energetic consequences of parasitic infection.

Reduced ectoparasite loads of deer mice in burned forest: From fleas to trees?

“…v www.esajournals.org There is growing evidence that ectoparasites can have significant negative impacts on the physiology of individual hosts, and the vital rates of host populations (Hawlena et al 2006a, Hawlena et al 2006b, Devevey et al 2008, Devevey and Christe 2009, Pfäffle et al 2009, Kam et al 2010. Therefore, it is conceivable that lowered ectoparasite loads in burned forest contribute to high post-fire deer mouse abundance, e.g., through effects on body condition (Hawlena et al 2006a, Devevey et al 2008, Devevey and Christe 2009 or feeding behavior (Scantlebury et al 2007, Raveh et al 2011), which in turn influences reproductive output of deer mice. Intriguingly, Raveh et al (2011) showed that flea-infested rodents were less vigilant and v www.esajournals.org had higher giving-up densities (i.e., tended to quit foraging at higher densities of food remaining in the patch).…”

“…In laboratory studies, fleas were found to affect body condition, growth rate, life span, and energy expenditure of their hosts (e.g., Hawlena et al 2006a, Devevey et al 2008, Devevey and Christe 2009. In free-living animals, ectoparasites influenced host energy budgets (Giorgi et al 2001, Nilsson 2003, Kam et al 2010, litter size (Neuhaus 2003), foraging and vigilance patterns (Scantlebury et al 2007, Raveh et al 2011, and juvenile survival (Hawlena et al 2006b). Such effects could translate into effects on host population abundance, but evidence for such impacts is lacking.…”

MHC influences infection with parasites and winter survival in the root vole Microtus oeconomus

“…In November 2008, animals from the experimental group were injected subcutaneously with Ivomec (Merck, 0.2 lg/g body mass), an anti-nematode drug widely used in rodent studies (e.g., Scantlebury et al 2007), and the control group was injected with propylene glycol, an Ivomec medium. The injections were administered within 24-72 h after trapping.…”

Ectoparasites and fitness of female Columbian ground squirrels

“…[22,[65][66][67][68]), there is increasing evidence from studies that show few or no effects (rodents: [55][56]69], bats: [24,70], birds: [71,72]). In female Columbian ground squirrels, contradictory results for adult females and their offspring were obtained for populations in the same geographical area, though during different times (this study versus [27]).…”