Faculté des sciences

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

Raveh, Shirley ; Bshary, Redouan (Dir.)

Thèse de doctorat : Université de Neuchâtel, 2009 ; Th. 2106.

I examined the influence of mating order and male mating behaviour using Columbian ground squirrels (Spermophilus columbianus) as study species. The data were collected in the Sheep River Provincial Park, Canada including field seasons 2005 - 2008. Field work provided trapping and observational data of free-living ground squirrels. The observational data were combined with paternity... Plus

Ajouter à la liste personnelle
    Summary
    I examined the influence of mating order and male mating behaviour using Columbian ground squirrels (Spermophilus columbianus) as study species. The data were collected in the Sheep River Provincial Park, Canada including field seasons 2005 - 2008. Field work provided trapping and observational data of free-living ground squirrels. The observational data were combined with paternity analyses to assess detailed information concerning male reproductive success.
    (1) I tested whether mating order affects mating success in males and whether order effects are influenced by the number of mating partners a female had.
    (2) I examined the mechanisms involved in shaping mating order effects.
    Finally (3) I evaluated whether experimental parasite removal influenced mating success in S. columbianus.
    I found (1) that 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.
    (2) The time a male spent mating with a female 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 not excluded, the number of additional males a female mated with. Finally, male investment in reproductive behaviours increased with male and female age, but was also increased when partners mated age-assortatively.
    (3) Contrary to our expectations, our findings showed that the parasite removal treatment did not significantly affect male reproductive behaviour and hence did not change male reproductive success. Furthermore, parasite-free males did not gain more body mass than control animals. Taken together, the results support the idea that male-male competition and/or mate choice are of primary importance for shaping reproductive strategies in S. columbianus. The role of parasites for variation in male reproductive success, however, remains elusive.