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Abstract: Relationships between males defending the same harem are described as cooperative or competitive and explained by mutualism, reciprocal altruism, and reproductive concessions or limited control between unequal contestants. These alternate hypotheses can be tested by removing males from harems. Some feral horse (Equus caballus) harems are defended by more than one and up to five stallions. We temporarily removed the subordinate stallion from two of six multi-stallion bands (a harem and its stallions) for three weeks during the breeding season. We monitored harems for changes in composition, and measured and compared rates of (i) intra- and inter-band stallion aggression, (ii) stallion aggression towards mares, and (iii) stallion-mare proximity before subordinate stallion removal and after his return with rates during his absence. Harems were successfully defended during the subordinate''s absence and stallion-mare aggression was substantially reduced. Dominant stallions did not require assistance in harem defence, and heightened harassment of mares is directly attributable to subordinate stallion''s residence, not characteristics of the dominant stallion or mares. Cooperative hypotheses do not appear to explain multi-stallion bands but the experiments in this study should be replicated further. The limited control hypothesis (e.g., mate-parasitism) appears better supported but we outline its limitations too. [Copyright &y& Elsevier]

In many mammals, females form close social bonds with members of their group, usually between kin. Studies of social bonds and their fitness benefits have not been investigated outside primates. and are confounded by the relatedness between individuals in primate groups. Bonds may arise from kin selection and inclusive fitness rather than through direct benefits of association. However, female equids live in long-term social groups with unrelated members. We present 4 years of behavioral data, which demonstrate that social integration between unrelated females increases both foal birth rates and survival, independent of maternal habitat quality, social group type, dominance status, and age. Also, we show that such social integration reduces harassment by males. Consequently, social integration has strong direct fitness consequences between nonrelatives, suggesting that social bonds can evolve based on these direct benefits alone. Our results support recent studies highlighting the importance of direct benefits in maintaining cooperative behavior, while controlling for the confounding influence of kinship. [ABSTRACT FROM AUTHOR]

Play behaviour is widespread in mammals, but benefits to play have been difficult to demonstrate. Physical training is one of the many proposed hypotheses, suggesting that males and females should play differently, that increased maternal investment should lead to increases in play, and that increases in play should result in physical advantages. In a population of feral horses, Equus caballus, males and females did not differ in their play behaviour except that males initiated more of their play bouts than females. Maternal condition influenced play behaviour only in males, with sons of mothers in good condition playing more. However, when we controlled for maternal effects by comparing a son and a daughter of the same mother, daughters played more when their mother was in poor condition and sons played more when their mother was in good condition. Mothers of foals that played more lost more condition. Therefore, the difference in play behaviour could not be explained by offspring sex or maternal condition alone, but play behaviour mirrored variation in maternal investment. In addition, those individuals that played more survived better and had better body condition as yearlings despite weaning earlier. Since increased activity has been linked to enhanced musculoskeletal development in domestic horses, we suggest that play provides a link between increased maternal investment, increased body condition and future reproductive success in feral horses, and probably in other species. [Copyright &y& Elsevier]

The risk of infant injury or mortality influences maternal behaviour, particularly protectiveness. Mares are found in bands with a single stallion or bands with more than one stallion in which paternity is less certain. We investigated maternal behaviour in relation to band type. Mares in bands with more than one stallion were more protective of their foals, particularly when stallions and foals approached one another. The rate of aggression between the stallion and foal was a significant predictor of maternal protectiveness, and mare protectiveness was significantly correlated with reduced reproductive success in the subsequent year. Mares that changed band types with a foal at foot, or had their band type experimentally altered, were more protective of their foal in multi-stallion bands than they were in single-stallion bands. Equids are unusual amongst ungulates in that infanticide and feticide have been reported. Both occur where paternity has been uncertain, and equid social structure is similar to other species in which infanticide has been reported. Stallions benefit from infanticide as the mare has greater reproductive success in the subsequent year. Stallion aggression is a significant modifier of mare behaviour and maternal effort, probably due to the risk of infanticide. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined the political issues related to funding for biological research on feral horse population and behavior. Information on an independent research contracted by the New Zealand Department of Conservation for Kaimanawa feral horse management; Importance of biological research in pragmatic feral horse management; Conclusions.

Compares the behavior and ecology of Kaimanawa, New Zealand feral horses in single and multistallion breeding groups with those described elsewhere. Band composition and structure; Hierarchical relationship of stallions in multistallion bands; Reproductive success of stallions in multistallion versus single-stallion bands; Group defense effort between subordinate and dominant stallions.

Presents a study on the sex-biased maternal investment in feral horses, Equus caballus, conforming to the assumptions of Trivers-Willard hypothesis. Postulate of the hypothesis; Concept of maternal investment; Significance of mare conditions to maternal behavior; Details on the ability to invest and costs.

Contraception is increasingly used as a management technique to reduce fertility in wildlife populations; however, the feasibility of contraceptive formulations has been limited until recently because they have required multiple treatments to achieve prolonged infertility. We tested the efficacy and evaluated potential side effects of two contraceptive formulations, a porcine zona pellucida (PZP) formulation, SpayVac® and a gonadotrophin-releasing hormone (GnRH) formulation GonaCon-B™, in a population of free-roaming feral horses (Equus caballus). Both formulations were developed to provide several years of infertility with one injection. Females were treated in June 2005 with either GonaCon-B (n = 24), SpayVac (n = 20), adjuvant only (n = 22), or received no injection (n = 18). Females were monitored for fertility status year round for 3 years after treatment. Both contraceptive treatments significantly reduced fertility for 3 years. Fertility rates for GonaCon-B mares were 39%, 42% and 31%, respectively, and 37%, 50% and 44% for SpayVac mares. During the same seasons, 61%, 67% and 76% of control females were fertile. We found no significant effects from contraceptive treatment on the sex ratio of foals, birthing season or foal survival. These results demonstrated that both vaccines are capable of significantly reducing fertility for several years without boosters. Contraceptive vaccines examined in the present study represent a useful tool for the management of feral horses, because of their being efficacious for 3 years in the absence of booster immunisations. [ABSTRACT FROM AUTHOR]

In most mammalian species, mothers must protect offspring from multiple sources of risk. In Australia, feral horses, Equus ferus caballus , have naturalized in many ecosystems, and foals are at risk from both predation by dingoes and sexually selected infanticide by nonpaternal stallions. This study tested maternal responses to these two forms of risk: risk of predation through dingo call playbacks and infanticide risk through a comparison of maternal protectiveness of foals in single- and multistallion bands. Mares were more vigilant and spent more time close to foals in bands with multiple resident stallions, where there is a higher risk of infanticide, relative to bands with a single stallion. Dominant stallions spent more time close to foals following the dingo call playbacks, indicating that stallions may play an important role in detecting and protecting foals from interspecific sources of risk. There was no significant increase in maternal protectiveness in response to dingo call playbacks, indicating that mares did not perceive dingo calls to be an immediate threat to foals. While predators were present, infanticide risk appeared to be the most significant modifier of maternal behaviour in this study. • Mothers need to respond to different types of risks to protect offspring. • Mothers increase vigilance and protective behaviour when infanticide risk is higher. • Dingo calls did not modify maternal behaviour. • Mothers perceived nonpaternal stallions to be riskier than dingoes. • Dominant stallions spent more time close to foals following dingo call playbacks. [ABSTRACT FROM AUTHOR]