DOI: 10.5061/dryad.jsxksn0fw
title: A meta-analysis of how parasites affect host consumption rates

description: Parasites are known to mediate trophic interactions and can, for example,
 modify how consumers acquire resources. These modifications of host
 feeding behaviour can be imposed through three interconnected mechanisms
 affecting: (1) host food acquisition, (2) host food digestion or (3) host
 energy budgets. As a result, infected hosts may consume more, less or the
 same amount of food compared to their uninfected conspecifics. It is
 commonly assumed that infected hosts have lower consumption rates than
 uninfected hosts, but a comprehensive quantitative synthesis investigating
 the effects of parasites on host consumption rate has been lacking thus
 far. To fill this knowledge gap, we systematically searched for
 experimental studies that evaluated changes in consumption rate of
 infected vs uninfected hosts. In total, we extracted 158 effect sizes from
 68 studies. We then performed meta-analyses of mean differences in host
 consumption rates and their variation. The analyses were carried out for
 all taxonomic groups as well as separately for vertebrate and invertebrate
 hosts. The main-effects meta-analyses confirmed a generally negative
 effect of parasites on host consumption rates; infected hosts consumed on
 average 25% less food than their uninfected conspecifics. In addition,
 there was a significant increase in the variability in host consumption
 rate, on average by 25%, indicating that parasites can have variable
 effects on the foraging behaviour of their hosts. The meta-regression
 models revealed that several moderator variables related to host and
 parasite characteristics influence host consumption rate. Experimental
 infection had a stronger influence on variance effects than natural
 infection. Parasitic infections reduced consumption rate of vertebrate
 hosts by 28% and thus more strongly than those of invertebrates, which
 were reduced by 22%. We conclude with recommendations to facilitate future
 ecological research syntheses on host-parasite interactions and beyond.
description: We systematically searched for experimental studies that
 evaluated changes in consumption rate of infected versus uninfected hosts.
 The literature search was performed on the Web of Science Core Collection
 (WoS) following the guidelines of the PRISMA statement (Moher et al.,
 (2010) <em>Int J Surg</em> 8, 336–341). The detailed description of
 the search strategy can be found in the associated publication.
 Articles were included in the meta-analysis based on pre-defined
 eligibility criteria. The final dataset consists of 68 studies published
 between 1973 and 2019, from which we extracted 158 effect size estimates.
 From each study, we also recorded year of publication, parasite taxonomy
 (phylum and species), type of parasite (micro- or macroparasite), parasite
 life cycle (complex or direct), host taxonomy (group [vertebrate or
 invertebrate], class and species), details about the host (i.e., sex,
 age), infection type (natural or experimental), infected organ (body
 cavity, circulatory, digestive, muscular, sensory, whole body), prey
 mobility (immobile, mobile, unknown), study environment (freshwater,
 marine or terrestrial) and the geographic place where the experiment was
 performed (continent and country). We performed
 meta-analyses of mean differences in host consumption rates and their
 variance. Two types of models were applied: (1) main-effects models to
 test for the general effect of parasites on host consumption rates and (2)
 multilevel meta-regression models to assess the contribution of the
 moderator variables to the magnitude and direction of the effect
 sizes.
description: All analyses were performed in R ver. 4.0.3.