Variation of life history traits and mating patterns in female langur monkeys ( Semnopithecus entellus )

Loss of oestrus, concealed ovulation and paternity confusion in free-ranging Hanuman langurs

“…As predicted, and in line with the paternity-confusion hypothesis, these periods were markedly variable in length (range 4^15 days) and, with an average duration of 9^10 days (cf. Borries et al 2001), were also signi¢cantly longer than in females living in one-male groups at Jodphur (4 days; Sommer et al 1992) in which paternity confusion is less of an option. Furthermore, females in our study group showed a substantial overlap in receptive phases, with as many as six females being receptive at the same time.…”

“…In the Ramnagar population, infanticide accounts for 31%^63% of infant mortality (Borries 1997), and has been shown to represent an evolved strategy to optimize male reproductive success (Borries 1997;Borries et al 1999a). Since a male's decision to commit infanticide appears to be highly dependent on his past mating history with the mother (Borries et al 1999a), a female strategy to mate polyandrously with all available males (including those from adjacent groups: this study; Launhardt et al 2001), and thereby maximize the number of possible sires through paternity confusion, should be highly adaptive in preventing male infanticidal behaviour. Moreover, since putative fathers in langurs are highly engaged in infant protection against attacking (potentially infanticidal) males (Borries et al 1999b), by confusing paternity females would also ultimately bene¢t from a reduction in the infanticidal risk posed by males who were not present during the female's mating (conception) period (cf.…”

“…A receptive period was classi¢ed as such if the sexual behaviours mentioned above were shown for a minimum of 3 consecutive days and, if lasting longer, were without interruptions of more than 2 days. Observations of displacement interactions were used to establish the dominance relationships between the three group males, according to the procedure described by Borries et al (1991).…”

“…The species shows a high £exibility in social organization, forming multi-female groups that can contain both single and multiple males (Sommer et al 1992;Borries 1997). In multi-male groups females usually mate with all males during an extended period of receptivity (Borries et al 1999a(Borries et al ,b, 2001. Moreover, there is also extensive documentation of infanticide by male Hanuman langurs (Sommer 1994;Borries 1997), as well as recent genetic evidence that this behaviour is adaptive, forming part of a strategy to increase male reproductive success (Borries 1997;Borries et al 1999b).…”

Genital swellings in silvered langurs: what do they indicate?

“…Following Beach [1976], the data were analyzed three times (detailed behavioral definitions in Sommer et al [1992] and Borries et al [2001]): 1) We assessed proceptivity by summarizing three female soliciting behaviors: head shaking (horizontally), presenting, or simultaneously head shaking and presenting (also called inviting). 2) Receptivity included copulatory attempt (male mounts without intromission) and copulation (male mounts with intromission and pelvic thrusting).…”