INFANTICIDE IN SEASONALLY BREEDING MULTIMALE GROUPS OF HANUMAN LANGURS (PRESBYTIS-ENTELLUS) IN RAMNAGAR (SOUTH NEPAL)

In the seasonally breeding langur (Presbytis entellus) population of R amnagar, South Nepal, where multimale groups prevail, 25 attacks on 11 infants (including one actual killing) by seven adult males were witn essed in five groups by six observers between 1990 and 1996. Circumsta ntial evidence also indicates three additional attempts at infanticide and in seven additional cases infanticide was presumed or likely. Inf anticide presumably accounted for 30.8-62.5% of infant mortality in th e first 2 years of life. Most attackers (91.4%) were residents of the infants' group and had immigrated after the infants had been born (75. 0%) or conceived (25.0%). Thus, they were not related to the victims. The interbirth interval was shortened if an infant died either prior t o September of its 1st year of life (mean = 1.2 years), or its 2nd yea r (mean = 2.0) and even its 3rd year (mean = 2.4). All attackers remai ned in the group at least until the next mating season; high-ranking m ales maintained their dominance rank and lower-ranking males rose in r ank. Since rank and mating success were correlated and rank and reprod uctive success might be correlated, all attackers had a good chance of siring the next infant of the victims' mothers and could thus have be nefited by their action. Infanticide seems to be a male reproductive s trategy at Ramnagar. Infanticide has never before been reported among seasonally breeding langurs living at such low densities. This is also the first detailed report of infanticide as a male reproductive strat egy in a seasonally breeding primate population.