Can the mating system of the size-monomorphic Indian muntjac (Muntiacus muntjak) be inferred from its social structure, spacing behaviour and habitat? A case study from lowland Nepal

Abstract

The mating system of small ungulates inhabiting dense habitats is poorly known. In a ca 12-km2 area in lowland Nepal, we captured most individuals (18 of 23) of the elusive, size-monomorphic Indian muntjac (< 20 kg) and monitored their spacing behaviour with radio telemetry, and their use of latrines by remote cameras. The sex ratio favoured females (61%). Measured by the 90% Minimum Convex Polygon (MCP) method, male home ranges averaged 77 ha and those of females averaged 40 ha (P < 0.05); by the 90% Kernel method, range sizes were not different (P > 0.3). Although total home ranges and core areas overlapped both inter- and intrasexually, individuals were solitary. Temporally, males tended to avoid each other, whereas females were randomly distributed with respect to each other. A spatial attraction was detected between individuals of opposite sexes. Daily movement was longer among males than females (P < 0.01). Different individuals of both sexes – both adults and subadults – visited the same latrines, which were located in discrete and randomly distributed latrine areas, and the frequency of visiting latrines was similar among the two sexes. Animal spacing behaviour and distribution pattern suggested neither monogamy, nor strict resource or female defence polygyny. From the results, we hypothesize that muntjacs have evolved a form of polygynous mating system based on what might be termed an ‘inspection strategy’: males regularly inspecting the breeding status of adjacent females through extensive mutual scent and latrine markings, with dominating individuals presumably achieving most matings. This might be an optimal mating strategy for small, cryptically coloured ungulates living in rather stable and uniform environments, which breed asynchronously nearly twice a year.