Fear of Parasites: Lone Star Ticks Increase Giving-up Densities in White-Tailed Deer

Abstract

Nonconsumptive effects of predators on their prey are extensive and diverse, with significant consequences for community structure and ecosystem function. However, despite many theoretical similarities between predator-prey and host-parasite interactions, nonconsumptive effects of parasites on their hosts remain poorly understood. Further, such effects may be of consequence to human and wildlife health, when host-parasite interactions involve hematophagous arthropods that vector infectious diseases. We used giving-up density estimation techniques to measure the response of white-tailed deer(Odocoileus virginianus)to the risk of parasitism by lone star ticks(Amblyomma americanum), an important vector of several infectious diseases in the southeastern United States. We also deployed carnivore scent stations to estimate activity levels of potential deer predators, conducted deer dung count surveys to control for effects of deer abundance, and controlled for topographic aspect, a primary determinant of vegetative biomass and community composition. We found a significant, positive correlation between giving-up densities in deer and the densities ofA. americanum, but no effect of canid predators, deer abundance, or topographic aspect. Our results are consistent with the few other empirical examples that demonstrate nonconsumptive effects of parasites on their hosts. Considering that host-parasite interactions have enormous potential to influence the prevalence of vector-borne diseases that affect human health, incorporating indirect effects of parasites on their hosts into infectious disease ecology may be necessary to effectively mitigate disease risk.

Advances in population ecology and species interactions in mammals

“…Predation risk shapes the foraging of many mammals (e.g., Brown and Kotler 2004;Caro 2005;Verdolin 2006;Steele et al 2014). Foraging mammals also are cognizant of the risk of parasitism; white-tailed deer (Odocoileus virginianus) and domestic sheep (Ovis aries) alter foraging to reduce the likelihood of encountering parasites (Hutchings et al 2001;Allan et al 2010b).…”

“…Although much early optimal foraging theory focused on selecting optimal diet components (Stephens and Krebs 1986), recent advances (Stephens et al 2007) have broadened the focus to incorporate variation in information transfer (Bednekoff 2007), temporal variation in predation risk and prey state (Lima and Bednekoff 1999;Bednekoff 2007), the role of anthropogenic factors in affecting mammalian foraging (Gaynor et al 2018), and the interplay of the metabolic costs of foraging, predation risk, and missed-opportunity costs (Brown 1988). Indeed, the giving-up density (GUD) framework (Brown 1988) has proven incredibly useful for evaluating foraging because it can be expanded to include additional factors (reviewed in Brown and Kotler 2004;Bedoya-Perez et al 2013), such as variation in food quality under risk of predation (Schmidt 2000) or parasitism (Allan et al 2010b). This framework is amenable to experimental approaches, making it possible to evaluate different costs of foraging in an integrated manner.…”

Lesser of Two Evils? Foraging Choices in Response to Threats of Predation and Parasitism

“…Strong anti-parasite behaviours should be favoured if they decrease the costs of immunological defences and direct damage from parasites [ 15 ] but could have significant pre-encounter effects analogous to those incurred by predators. Despite this possibility, there have been few studies of this nature to date [ 18 , 19 , 20 , 21 ].…”

Predation Fear, Prey Behavior, and Community Structure: A Brief Review of Their Relationship

“…Slower and less perfect responses by the prey to the predator may have the tendency to stabilise the interaction by introducing a positive slope to the predator's isoclines. Adaptive fear responses by the prey induce positive slope to the isoclines of the predators (Allan, Varns, & Chase, 2010).The positive slope of isoclines of the predators has reflected the negative impact of the predators on themselves via their non-lethal effects on prey behaviors (Brown, Kotler, & Bouskila, 2001).The behavioral games between the predators and prey have strongly impacted the stability of predator-prey interaction. It can be also analysed that the landscape of fear is to act as a useful framework to develop the mechanistic, community-level understanding of predator and prey interactions.…”