Abstract: ABSTRACT For many ecosystems, feral horses are increasingly becoming an important if not dominant component of ungulate biomass and hence influence on community dynamics. Yet we still know little of how horses contribute to key ecological interactions including predator-prey and indirect competitive relationships at a community level. Notably, feral species like horses can exhibit life-history traits that differ from that of native (mainly artiodactyl) herbivore competitors. Artificial selection for traits like increased, early, or extended reproduction that have yet to be reversed by natural selection, coupled with naturally selected differences in anatomy and behavior, in addition to unique management objectives for horses compared to other species, means that the dynamics of feral horse populations are not likely to align with what might be expected of other large herbivores. Unexpected population dynamics and inherent biological asymmetries between native ungulates and feral horses may therefore influence the former via direct competition for shared resources and through enemy-mediated interactions like apparent competition. In several localities feral horses now co-exist with multiple native prey species, some of which are in decline or are species at risk. Compounding risks to native species from direct or indirect competitive exclusion by horses is the unique nature and socio-political context of feral horse management, which tends towards allowing horse populations to be limited largely by natural, density-dependent factors. We summarize the inherent asymmetries between feral horse biology and that of other ungulate prey species with consequences for conservation, focusing on predator-prey and emerging indirect interactions in multi-prey systems, and highlight future directions to address key knowledge gaps in our understanding of how feral horses may now be contributing to the (re)structuring of food webs. Observations of patterns of rapid growth and decline, and associated skews in sex ratios of feral horse populations, indicate a heightened potential for indirect interactions among large ungulate prey species, where there is a prevalence of feral horses as preferred prey, particularly where native prey are declining. In places like western North America, we expect predator-prey interactions involving feral horses to become an increasingly important factor in the conservation of wildlife. This applies not only to economically or culturally important game species but also at-risk species, both predators (e.g., wolves [Canis lupus], grizzly bears [Ursus arctos]) and prey (e.g., woodland caribou [Rangifer tarandus caribou]), necessitating an ecological understanding of the role of horses in natural environments that goes beyond that of population control. ? 2021 The Wildlife Society.

Abstract: In polygynous species with high reproductive skew in males, mothers often show differential investment between sons and daughters; however consistent sex differential investment has not been found by previous studies in horses. We investigated sex differences in mother-offspring relationships in nutritionally independent sub-adult semi-feral Carneddau Welsh mountain ponies Equus ferus caballus. Mothers and their sub-adult sons had consistently closer relationships than mothers and daughters. Stronger affiliative bonds between mothers and sons were quantified by their maintenance of closer proximity, higher rates of affiliative interactions and more frequent suckling bouts. These measures of affiliation were temporally associated with higher aggression levels directed towards sub-adults by other band members, particularly stallions. We suggest that aggression may serve as the proximate mechanism driving male dispersal in feral horses and that the stronger mother-son bond signals an attempt to delay their dispersal, highlighting conflict within the band concerning dispersal timing. Since males become increasingly central within the band over time, with mature stallions requiring excellent social skills in order to both acquire and keep a band of mares, we propose that delaying colts' dispersal allows for further development of these skills in a relatively safe environment. This additional investment is expected to maximise their reproductive success. This study illustrates how social network theory can be used to quantify individuals' social experiences, contributing to a greater understanding of the evolution of group living. It also gives us further insight into the mechanisms underlying dispersal in wild and semi-wild horse populations and how conflict often arises when individual needs differ.