Abstract
Two key factors that influence the foraging behaviour of group-living herbivores are food availability and individual dominance status. Yet, how the combination of these factors influences the patch-joining decisions of individuals foraging within groups has scarcely been explored. To address this, we focused on the patch-joining decisions of group-living domestic goats (Capra hircus). When individuals were tested against the top four ranked goats of the herd, we found that at patches with low food availability they avoided these dominant patch-holders and only joined subordinates (i.e. costs outweighed benefits). However, as the amount of food increased, the avoidance of the top ranked individuals declined. Specifically, goats shifted and joined the patch of an individual one dominance rank higher than the previous dominant patch holder when the initial quantity of food in the new patch was twice that of the lower ranking individual’s patch (i.e. benefits outweighed costs). In contrast, when individuals chose between patches held by dominant goats, other than the top four ranked goats, and subordinate individuals, we found that they equally joined the dominant and subordinate patch-holders. This joining was irrespective of the dominance gap, absolute rank of the dominant patch-holder, sex or food availability (i.e. benefits outweighed costs). Ultimately, our results highlight that herbivores weigh up the costs and benefits of both food availability and patch-holder dominance status when making patch-joining decisions. Furthermore, as the initial quantity of food increases, food availability becomes more important than dominance with regard to influencing patch-joining decisions.
Highlights
Living in groups has two broad benefits: reduced predation risk and increased foraging efficiency [1,2]
Experiment 1: Patch-joining against top ranked goats When we tested patch choice of goats against the top four ranked individuals, we found significant effects of rank (GEE: x2 = 28.118, P,0.001), food availability (GEE: x2 = 15.419, P = 0.004) and their interaction (GEE: x2 = 21.019, P = 0.05)
By fitting a logarithmic trendline to these data (y = 2 1.1611Ln(x) +8.3519), where y is the top ranked goat that is avoided and x is food availability, we were able to predict that at,563 g, the amount of food in a patch becomes more important than patch-holder dominance status with regard to the patchjoining decisions of our goats (Figure 5)
Summary
Living in groups has two broad benefits: reduced predation risk and increased foraging efficiency [1,2]. By watching conspecifics, individuals can increase their ability to find and assess the quality of food patches [8,9]. This may lead to individuals joining patch-holders at their patches, resulting in costs such as increased competition and greater social conflicts between group members [10,11,12]. Patch quality influences joining decisions, as foragers prefer to feed from high quality patches [19]. To obtain food in poor quality patches, patch-holders tend to defend these patches more aggressively [21]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
