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Interferências sexuais nos cavalos de Sorraia da Coudelaria de Alter
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Embora existam referências a interferências sexuais (interrupção da cópula por outra fêmea) em equídeos, nenhum trabalho em cavalos sobre este tema foi publicado e anteriores resultados não foram conclusivos. Por isso, este estudo pretendia averiguar quais as causas, funções e o impacto deste comportamento numa raça autóctone portuguesa, considerada em risco crítico de extinção. Para tal foram realizadas observações de uma subpopulação de cavalos de Sorraia presente na Coudelaria de Alter, constituída por 16 éguas e 1 macho. A anteceder a análise das interferências sexuais, foi determinada a posição de dominância de cada indivíduo e as preferências sexuais do macho. Como esperado a hierarquia era aproximadamente linear e o macho, por representar um novo membro no grupo, apresentou uma posição de dominância inferior. Embora o grau hierárquico estivesse correlacionado com a idade, os resultados sugerem que o tempo de residência é o principal factor da posição individual de dominância. As tentativas de acasalamento foram dirigidas preferencialmente a éguas com quem o vínculo ao garanhão era mais forte. No entanto, o nível de selecção sexual do macho era baixo e a idade e grau hierárquico das éguas não influenciaram as investidas sexuais, possivelmente devido à inexperiência do garanhão. As interferências sexuais ocorreram em 30% das tentativas de acasalamento observadas e apresentaram uma elevada taxa de sucesso na sua interrupção. Em geral a égua interferente era dominante, com elevado parentesco à fêmea do casal e a interferência consistia, predominantemente, em comportamentos agonísticos. Quando a interferente se encontrava sexualmente receptiva raramente ameaçava o macho e viceversa. A maioria das interacções dirigidas à égua do casal era realizada por uma fêmea em estro. Das hipóteses analisadas as que melhor se enquadram nos resultados são: dominância em relação ao macho e competição sexual entre éguas aparentadas
Although there are references to sexual interferences (copulation interruption by other female) in equines, no work in horses about this issue as been published and the previous results have not been conclusive. For that reason, this study aimed to investigate what were the causes, functions and impact of this behaviour on an autochthonous Portuguese breed, considered to be at critical risk of extinction. Therefore, observations where made to a sub-population of Sorraia horses present in Coudelaria de Alter, composed of 16 mares and 1 stallion. Anticipating the analysis of the sexual interferences, both the position of dominance of each individual and the male sexual preferences were determined. As expected, the hierarchy was approximately linear and the male, once it constituted a new member on the group, presented a lower dominance position. Although the hierarchical degree was correlated with age, the results suggest that residence time is the main factor for the individual dominance position. Mating attempts were mainly directed to mares with which the stallion had a greater bond. However, the level of ale sexual selection was low and the mare's age and hierarchical degree didn't influence sexual attempt, possibly due to the stallion's inexperience. The sexual interferences occurred in 30% of the observed mating attempts and presented a high level of success in its interruption. In general, the interferer mare was dominant, with a high kinship to the female of the couple and the interference itself consisted, predominantly, in agonistic behaviours. When the interferer was sexually receptive, it rarely threatened the male and vice-versa. The majority of interactions directed to the mare of the couple were done by an oestrus female. The investigated hypotheses that better fit in the results are: dominance in relation to the male and sexual competition between related mares
Although there are references to sexual interferences (copulation interruption by other female) in equines, no work in horses about this issue as been published and the previous results have not been conclusive. For that reason, this study aimed to investigate what were the causes, functions and impact of this behaviour on an autochthonous Portuguese breed, considered to be at critical risk of extinction. Therefore, observations where made to a sub-population of Sorraia horses present in Coudelaria de Alter, composed of 16 mares and 1 stallion. Anticipating the analysis of the sexual interferences, both the position of dominance of each individual and the male sexual preferences were determined. As expected, the hierarchy was approximately linear and the male, once it constituted a new member on the group, presented a lower dominance position. Although the hierarchical degree was correlated with age, the results suggest that residence time is the main factor for the individual dominance position. Mating attempts were mainly directed to mares with which the stallion had a greater bond. However, the level of ale sexual selection was low and the mare's age and hierarchical degree didn't influence sexual attempt, possibly due to the stallion's inexperience. The sexual interferences occurred in 30% of the observed mating attempts and presented a high level of success in its interruption. In general, the interferer mare was dominant, with a high kinship to the female of the couple and the interference itself consisted, predominantly, in agonistic behaviours. When the interferer was sexually receptive, it rarely threatened the male and vice-versa. The majority of interactions directed to the mare of the couple were done by an oestrus female. The investigated hypotheses that better fit in the results are: dominance in relation to the male and sexual competition between related mares
Descrição
Tese de mestrado em Ecologia e Gestão Ambiental, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2007
Palavras-chave
Equinos Mamíferos Cavalo do Sorraia Teses de mestrado