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Séminaire présenté par le Dr Shirley RAVEH, Université de Neuchâtel

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Mating behaviour and the effects of parasites on reproductive success in male Columbian ground squirrels (Urocitellus columbianus)

Par : Dr Shirley RAVEH, Laboratoire d’Eco-éthologie, Université de Neuchâtel (Suisse). Invitée de V. Viblanc

Date : jeudi 1er juillet 2010 à 13h30
Lieu : IPHC, Salle de réunion du DEPE, bât.60

Résumé :

Multiple mating by females is common in many mammalian species, often resulting in mixed paternity litters. In such mating systems, mating order frequently plays an important role in determining male reproductive success. To evaluate whether mating order has an influence on male reproductive success in free-living Columbian ground squirrels (Urocitellus columbianus), we studied five colonies over four breeding season from 2005 to 2008 in the Sheep River Provincial Park, Alberta, Canada. The observational data were combined with paternity analyses to assess detailed information concerning male reproductive success. We tested whether mating order affects mating success in males and whether order effects are influenced by the number of mating partners a female had (i.e. due to increased sperm competition). Furthermore, we examined the mechanisms involved in shaping mating order effects e.g. the duration of copulations, the occurrence of mate guarding, the age of the individuals. Finally, we evaluated whether experimental parasite removal influenced mating success in Columbian ground squirrels.

We found that (1) the majority of all litters were multiply sired, while singly sired litters did occur as well and were mainly produced by the first mating partner. The first position within a mating sequence was the most successful position in terms of reproductive success. Nevertheless, subsequent males up to the fifth position did fertilise offspring. The first male advantage diminished with increasing number of male mating partners, indicating that sperm competition plays an important role. Males of intermediate age were more successful than younger and older males, and corrected for age effects, heavier males were more likely to mate first. (2) The time a male spent with a female in a burrow and mate guarding durations were positively correlated. Both durations positively correlated with male reproductive success, but only for the first and the second male to mate. Mate guarding by the first male significantly reduced, but did not exclude, the number of additional males a female mated with. (3) Contrary to our expectations, our findings showed that the parasite removal treatment did not significantly affect male reproductive success.

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