Territoriality and monogamous pairs in a solitary ungulate, the Japanese serow, Capricornis crispus

Abstract

The social organization of Japanese serows was studied in a 320-ha forest for 7 years. Serows were usually solitary (79% of sightings), but temporally formed groups of two to four animals (mostly mother–kid units, or male–female pairs with or without a kid). Home ranges of adult males and adult females (10–15 ha) were stable, and most parts of the ranges were defended as territories against other individuals of the same sex throughout the year. Several adult males were non-territorial residents. The main mating unit consisted of a monogamous pair of which the male's range almost completely overlapped the female's. About 20% of territorial males were polygynous each year, their ranges overlapping the ranges of two females; they could produce nearly twice as many offspring as monogamous males. Mating units were usually maintained for several years, although polygynous groups were not as stable as monogamous pairs. Female territories, which function to defend food resources, were dispersed and seemed to restrict the number of mates available to territorial males. This is why the serow formed predominantly monogamous pairs, although the male's strategy is polygyny.