Females facilitate male food patch discovery in a wild fish population

Abstract

1. Responding to the information provided by others is an important foraging strategy in many species. Through social foraging, individuals can more efficiently find unpredictable resources and thereby increase their foraging success.2. When individuals are more socially responsive to particular phenotypes than others, however, the advantage they obtain from foraging socially is likely to depend on the phenotype composition of the social environment. We tested this hypothesis by performing experimental manipulations of guppy, Poecilia reticulata, sex compositions in the wild.3. Males found fewer novel food patches in the absence of females than in mixedsex compositions, while female patch discovery did not differ regardless of the presence or absence of males. 4. We argue that these results were driven by sex-dependent mechanisms of social association: Markov chain-based fission-fusion modelling revealed that less social individuals found fewer patches and that males reduced sociality when females were absent. In contrast, females were similarly social with or without males. Our findings highlight the relevance of considering how individual-and popula-tion-level traits interact in shaping the advantages of social foraging in the wild. K E Y W O R D Sfission-fusion, foraging ecology, guppy, Markov chain analysis, Poecilia reticulata, sex ratio, social facilitation, social learning | INTRODUC TI ON

Causal evidence for the adaptive benefits of social foraging in the wild

“…In our earlier work with wild Trinidadian guppies living upstream in resource-poor environments, we revealed that more social individuals located more novel food patches [21,41], suggesting that sociality plays a relevant role in resource detection in this population. Due to the lack of predators [42] and the infrequent use of aggression [21] in our population, we did not expect a strong increase or decrease in resource acquisition with conspecific number. Previous work showed that male guppies are generally less social [21,[43][44][45][46][47] and more risk-taking than females [43,[48][49][50].…”

“…Experimental fish were caught from a nearby stretch of the same river and were, upon capture, sexed (194 females, 143 males), sized (females: Mean ± SD = 24.6 ± 3.7 mm, males: Mean ± SD = 21.6 ± 1.6 mm) and individually marked using Visible Implant Elastomer (VIE) tags (©Northwest Marine Technology Inc.) [21,46,53].…”

“…Due to the lack of predators [42] and the infrequent use of aggression [21] in our population, we did not expect a strong increase or decrease in resource acquisition with conspecific number. Previous work showed that male guppies are generally less social [21,[43][44][45][46][47] and more risk-taking than females [43,[48][49][50]. We therefore predicted a shallower increase in foraging performance, in terms of both resource detection and acquisition, with increasing number of conspecifics for males than for females.…”

“…To evaluate whether any observed sex difference in social foraging performance may have been driven by males having male foraging companions [21], rather than by males generally being poor or proficient social foragers, we compared the foraging performance of males in the company of other males to that of 'control' males in the company of females. We again used the statistical procedures described above, but excluding the interaction effects, female-only treatments and treatments with originally fewer than eight fish.…”

“…food abundance [17]), the presence of conspecifics is generally thought to increase the mean (or reduce the variance in) individual foraging performance [14,18]. Due to the challenges of setting up, and subsequently replicating, different social compositions in the field, few studies have been able to experimentally manipulate the social environment in vertebrate species and study its effects on foraging performance in the wild [19][20][21].…”