Reproductive Behaviors Of The Sichuan Snub-nosed Monkeys, Rhinopithecus Roxellana

A year-round observation on reproductive behaviors of the Sichuan snub-nosed monkeys (Rhinopithecus roxellanae) was conducted in Shanghai Wild Animal Park from May 2000 to May 2001. Four facets about this monkey species were involved as follows: 1) Take-over of dominant male and its impact on the social organization, 2) Male copulatory patterns, 3) Reproductive behavior, and 4) Relationship between testosterone secretion and social behavior of the adultmale monkeys. The reproductive unit is one-male-multi-female with maturing males'migration to join bands of all-male troop around the bisexual troop and female philopatry. The social hierarchy between the adult males threatens harem tenure of the resident male, and resident male changes occur due to illness, aging, fight ability of the males and human manipulation. When the new adult male gains residency and defends its harem for a longer period of time, the social situation will stabilize. The observations suggest that the presence of alpha male strongly inhibits behaviors of subordinate males outside the breeding unit, and determines the period of the social stabilization. In my study, it was failed to find that infanticide by a new resident during his gaining residency, which is prevalent in other colobines. The main anti-infanticide reason is the existence of the all-male band outside the breeding group at the population level of this species. The concealed ovulation, sexual skin deficiency and long-time sexual receptivity of the adult females not only obfuscate paternity but also reduce infanticide on the female's side. Infanticide under captivity suggested that artificial group organization should be imitative of the ones in the wild of this monkey. Sexual selection influenced how long the new resident male was accepted by the females during the dominant male change. This study quantitatively confirmed this monkey species is a rigorous seasonal breeder and employs a single birth season between late-March and early-June of the year. Lactation will continue until the baby monkey reaches about 1.5 years old or if the infant doesn't survive. Thus, the interbirth interval of this animal is approximately 24-25 months. If the newborn died, the interbirth interval would be reduced about to 11.6 months. Rhinopithecus roxellana indeed exhibits a gradient in the timing of reproduction corresponding to latitudinal differences in day length between Beijing and Shanghai. A southward shift of about 10°makes the group in Shanghai resulted in the delayed onset of female impregnation about 1 month from Beijing, but the receptive duration maintains the same as 5 months in the both study sites. The dominance index between adult females didn't impact their reproductive...