Correlate of reproductive success within alternative mating tactic of the common shrew
Stockley P., Searle JB., Macdonald DW., Jones CS.
Male common shrews (Sorex araneus) adopt two discrete mating tactics. The most successful males, in terms of number of offspring fathered, are those that establish large overlapping home range in areas of high female density early in the breeding season. An alternative, less successful mating tactic is to travel long distances in search of mating opportunities. This study is an investigation of correlates of reproductive success for male adopting thee different mating tactics. Reproductive success under natural conditions was assessed using DNA fingerprinting, and survival of offspring was monitored in the field. The number of offspring fathered by male with overlapping home and was positively correlated with the number of female ranges overlapped during the breeding season and with testes mass. The number of offspring lathered by male that made long-distance movement was positively correlated with their sperm counts. It is argued competitively (overlapping) males achieve reproductive success by competing to maximize the number of females inseminated, whereas those adopting an alternative mating tactic instead compete largely via sperm competition aiming to maximize insemination success with any particular female. There was no significant difference in the fluctuating asymmetry (FA) of males adopting different mating tactics (FA) was measured as the difference in length of the paired lateral scent glands). Fluctuating asymmetry was not related to the number of offspring lathered to males adopting either mating tactic, but was significantly correlated with the population of male offspring lathered that survived sexual maturity tactic, but was significantly correlated with mating success in this species FA may reflect some aspect of genetic quality that effect offspring survival.