The occupation of space and interindividual relations of a nocturnal Madagascan prosimian (Microcebus murinus)

Abstract

Five male and four female grey lesser mouse lemurs, Microcebus murinus, were trapped with Sherman traps in the Forestry Reserve of Ampijoroa, near Majunga, N.W.-Madagascar and equipped with individual radio-transmitters with a range of 220-300 m. These 9 individuals were then followed and observed (alternatively or simultaneously) for a total of 30 nights spread over a period of 6 weeks (26 September to 11 November 1985). In this dry deciduous forest zone, the subpopulation of 9 M. murinus observed occupied a total area of 7 ha. The home ranges of 4 males were significantly larger than those of 4 females (means: 3.2 +/- 0.2 and 1.8 +/- 0.1 ha, respectively). Nevertheless, because of the larger degree of overlap between home ranges of males, the available mean area per individual did not differ greatly between the sexes (a total of 5.5 ha for 4 males, with 65% overlap, versus a total of 4.2 ha for 4 females, with only 44% overlap). Overlapping of all nine home ranges produced a 'common zone' in the centre of the study area, where meetings between animals of either sex took place. This pattern can be interpreted as representing a pregregarious form of social structure. During nocturnal activity, the animals foraged individually, though an average of 11% of time was spent less than 10 m away from a conspecific. The tendency for dispersion of individuals was most pronounced during foraging for insects, when travel speeds were also relatively high. The most obvious social interactions occurred when females were on their way back to a common nest, calling and following each other. Such behaviour was not exhibited by males, even by those that shared a nest. Away from the nest, physical contacts were rare and brief. During the few days preceding oestrus, females were approached by several males, without agonistic interactions between males being observed at this period. Most observed agonistic interactions were initiated by females and directed against males.