Hapalemur griseus griseus (Link, 1795)
The nominate subspecies, Hapalemur griseus griseus, is the most widespread. It is found throughout the eastern forests from Tsaratanana Massif in the north to Taolanaro (Fort Dauphin) in the south (Tattersall, 1982). Tattersall (1982) reports that it is rare in the north-western part of its range, but Petter and Petter-Rousseaux (1979) show it occurring further north and west than does Tattersall.
Population numbers are unknown. Pollock (1979) estimates a density of 47-62 individuals per sq. km in the eastern rain forest around Analamazaotra (Perinet). Richard (1982) gives densities of 1.1-1.2 per ha (i.e. 110-120 individuals per sq. km). Pollock (1986) suggests that the total population size must be substantial, though Tattersall (1982) considers that H. g. griseus is rarely found at great density and Richard and Sussman (1975, 1987) consider it to be declining. However, it has been suggested that H. g. griseus will not suffer from forest destruction as it apparently occurs at higher densities in areas where bamboo has replaced the original forest (Petter and Peyrieras, 1970, 1975 Jolly et al, 1984). Pollock (in litt.), however, considers it unlikely that the Grey Gentie Lemur will benefit from the destruction of the forests.
H. g. griseus is confined to forests characterised by bamboo or bamboo vines (Petter and Peyrieras, 1970; Tattersall, 1982). A two month study of this subspecies at Analamazaotra in "winter" found that 90% of feeding time was spent eating the new shoots, leaf bases and stem pith of the bamboo Bambusa (Wright, 1986). The Grey Gentle Lemur browsed continuously on the bamboo, at a rate of 10-12 leaf stems per minute and spent 48% of the day feeding. Other foods included fig leaves, leaf stems of terrestrial grasses, young leaves from trees and small berries (Wright, 1986). It was suggested that fruit eating might increase when more was available (Wright, 1986). The Gentle Lemurs ranged in all habitats that contained bamboo, including stream edges and ridge tops, feeding at all heights from the ground to tree canopies (Wright, 1986).
Group size ranged from between four and six individuals at Analamazaotra, eight groups were counted (Wright, 1986). Petter and Peyrieras (1970) found the most usual group size to be between three and five individuals and Pollock (1986) gives a mean group size of 2.6 individuals with sightings of between one and five individuals together. In Wright's study (1986), each group contained at least one adult pair, one juvenile and an infant (Wright, 1986). Petter and Peyrieras (1970) and Pollock (1986) found that it was not uncommon to have a second adult female in a group. Wright (1986) reported that home range sizes of between 6 and 10 ha; one group had a mean daily path length of 425 m (range 375495m). At Ranomafana, a group of H. g. griseus, composed of an adult pair with two offspring, defended a 15 ha territory (Wright, 1989). Gentle Lemurs were active throughout the day except for an hour or so around midday when they rested, they were not active at night at Analamazaotra (Wright, 1986). Petter and Peyrieras (1970, 1975) found them to continue to be active for a couple of hours after sunset at Maroansetra. They are often considered to be crepuscular (Pollock, 1979; Jolly et al, 1984). In the wet season at Analamazaotra, Grey Gentle Lemurs can be active by 04.30 hr (Pollock, in litt.). During Wright's (1986) study, they left the emergent trees that they used as sleeping sites between 06.00 and 06.30 hours and returned between 15.45 and 17.25. The group members slept in contact in trees located throughout their home range (Wright, 1986).
In the area around Maroantsetra, the females give birth to single infants (Petter and Peyrieras, 1970), this is also the rule in captivity, (Pollock, 1979). Gestation period is reported to be 140 days and infants at Maroantsetra are bom in December and January (Petter and Peyrieras, 1970). Pollock (1986) suggests a birth season from late October to January at Analamazaotra. The infants ride on their mothers back from when they are first born (Petter and Peyrieras, 1970), rather than initially in a ventral position as appears to be more common in most other lemurs. In captivity, both the male and the female carry the infant (Petter and Peyrieras, 1970, 1975).
The main threat to this subspecies is the destruction of the rain forest. FAO/UNEP (1981) estimated that in each year between 1976 and 1980, 40,000 ha of previously undisturbed forest was cleared and it is likely that most of this was in the eastern forests. It is, however, reported that in areas burned and abandoned long ago, where bamboo had entirely replaced the original forest, the density of H. g. griseus appeared to be higher than in undisturbed habitat (Petter and Peyrieras, 1975).
This subspecies is reported in Tsaratanana, Marojejy Zahamena, Betampona and Andohahela Nature Reserves and in Anjanaharibe-Sud Analalmazaotra and Manombo Special Reserves (Pollock, 1984, Nicoll and Langrand 1989; O'Connor et al, 1986; Safford et al, 1989). It is also found in Ranomafana, Masoala and Mananara, all of which have been proposed as protected areas (Nicoll and Langrand, 1989).
No conservation measures have been suggested for this subspecies other than a range wide survey (St Catherine's Workshop, 1986). It would be useful to ascertain if it does reach higher densities in disturbed areas where bamboo has replaced the original forest. Its conservation status cannot be assessed unless some estimates of its numbers are made.
There are around 35 H. g. griseus held in captivity. This subspecies has been bred in captivity at Duke Primate Center. However, apparently only certain females breed there, so only one or two infants are born in a year (E. Simons, in litt.). ISIS lists 17 individuals in Duke Primate Center in June 1989. Paris Zoo is recorded as having one pair in December 1988 (ISIS) and two pairs in June 1989 (ISIS). None has bred there (J.-J. Petter, in litt.). Cologne Zoo has one female (ISIS, June, 1989). Wilde et al (1988) report five individuals at Mulhouse Zoo, but these were not listed as being held there by J.-M. Lernould (in litt.) in March 1989. In Madagascar, there is a pair of this subspecies at Ivoloina and eight individuals at Parc Tsimbazaza, some of which were born there (A. Katz, M. Pidgeon, G. Rakotoarisoa, in litt.).
H. griseus griseus is overall a brown-grey colour and it weighs around 700-1000g. (Tattersall, 1982). One individual trapped at Ranomafana weighed 770 g, whereas the average weight of five captive H. griseus at Duke Primate Center was 936 g (range 941-1226g) (Grander et al, in press). Its Malagasy names are bokombolo and kotrika.