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Spasskaya, N. N. (2012). Results of investigations of an island population of the feral horse (Rostov Region, Russia). In K. Krueger (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: A feral horse population inhabiting the Vodnyi Isl, Manych-Ghudilo Lake, on the territory of Rostov Region, S Russia, has been established in 1950s according to questionnaire data (Paklina, Klimov, 1990). It is a sole permanent grouping of feral horse known to exist in European Russia (Spasskaya, Spasskyi, 2007; Spasskaya, 2008). Range of this group is part of Federal Reserve “Rostovsky” established in 1995, and its monitoring has being been conducted since 2006. The principal aim of monitoring includes gathering data on demographic, spatial, and ethological structure of the island horse population, along with investigation of its phenotypic and ethological patterns. Analysis of previously published (Paklina, Klimov, 1990) and recently obtained data on the color patterns of the island horse indicate that they have become isolated supposedly about 18–20 years ago. Some trends in variation of several phenotypic traits indicate slight rising of inbreeding level in this population, including decrease in the horse withers height, changes in body proportions, increase of heterogeneity in body color patterns (size and number of head and leg spots), and increase of frequency of dental malformations, especially of false polydonty of P1 (Spasskaya et al., 2010). Principal demographic parameters of this population are similar in general to those known for other feral horse studied by now. However, several peculiar features of this population were revealed: its age structure appeared to be of steadily fading type judging by high proportion of mature individuals (64–72 %); high mortality rate of individuals of the first year of life (16–25 %); predominance of males among newborns with increase of population size. Ethological structure of the population included standard harem bands and bachelor groups, with few solitary animals (usually old or sick stallion). The most of individuals (58.2–84.3 %) were the part of harem bands, which appeared to be the most stable groupings. The harems were small in their numbers with predominatingly 3–8 individuals. The bachelor groups were inconstant in composition, their portion in population being not high (7.7–15.4 % of the total number). A lot of “mixed” groupings of various composition were recorded in the population during its high number phase: harem bands with several mature stallions; associations consisting of several harem bands; youth groupings consisting of approximately coeval stallions and mares. These “mixed” groupings appeared to be rather stable, with their total number reaching up to 25.8 % of the population. They however used to disappear with population number decrease. The Rostov population is characterized by absence of conspicuous home range of social groupings (Spasskaya, Shcherbakova, 2007; Spasskaya, 2009), so the latter form a united herd with minimal intergroup distances. This phenomenon is probably not related to population density or to the island size, but is rather caused by some other factors to be revealed.
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Ermilina, J. A. (2012). Dominance hierarchy in feral horses in Rostov Region. In K. Krueger, & (Ed.), Proceedings of the 2. International Equine Science Meeting (Vol. in press). Wald: Xenophon Publishing.
Abstract: Horses maintain the social structure through the establishment of dominant-subordinate hierarchical relationships, both within and between groups. The object of study was the feral horse population, living on the Vodnyi Isl, Manych-Ghudilo Lake, on the territory of Rostov Region, S Russia the State Nature Biosphere Reserve “Rostov”. The social structure of this population is represented by the harem and bachelor groups, and their variety – the “mixed”groups, the presence and composition of which is atypical for the populations of feral horses. The main objectives of this work were to identify the hierarchical structure of different types of social groups and the role of the stallions in them, defining the dominance rank of animals. The method of continuous logging occurred aggressive reaction, ritualized interaction between stallions, take into account the direction of interactions between individuals. We observed 5 harem, 3 bachelor and 3 mixed groups. Each group was studied for a total of 60 h (8 h per group per days).Behavioral observations were carried out in summer 2009-2011. Based on the number and direction of aggressive interactions the hierarchical coefficient was calculated for individual horses (Ivanov et al, 2007). Harem group consists of an adult stallion (<5 years old) and a few mares with their offspring. Our observations of harem groups confirm the previously known information about this type of social groups (Berger, 1986; Carson, Wood-Gush, 1983, Keiper, 1983). Hierarchical system between mares is close to linear with reversal. The stallion is not included in the hierarchy of the mares; he is the leader and serves to maintain the integrity of the group and inter-group hierarchy, and has reproductive function. Bachelor groups consist of stallions 2-3 years and older who do not have their own harem. It is known that dominance hierarchy in these groups is linear, young males or males who recently had joined the group have low ranks (Berger, 1977; Houpt, Keiper, 1982; Kirillov Paklina, 1990). In observed bachelor groups dominant stallion have a significantly higher rank in the hierarchy. However, among other stallions is not always observed strict linear hierarchy – some individuals have very similar ranks. Function of managing the group and maintaining the intergroup hierarchy can be distributed among the all stallions in the group. Mixed groups are composed of several mature stallions, one or more mares (sometimes with the offspring). In the study population in this type of social groups animals may be mature (age 5 and older) and semi-mature (2-5 years). The hierarchy of these atypical groups has not been studied. In the studied 3 mixed groups stallions have very similar hierarchical rank, dominant and subordinate stallions share a function of managing the group, participation in ritualized interactions. Our studies have revealed the plasticity of the hierarchical structure of groups of horses and the need to further investigate the distribution of social roles among stallions.
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Boyce, P. N., & McLoughlin, P. D. (2021). Ecological Interactions Involving Feral Horses and Predators: Review with Implications for Biodiversity Conservation. Jour. Wild. Mgmt., n/a(n/a).
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.
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