As the common name suggests, bamboo lemurs specialise in feeding almost exclusively on bamboo (2) (6) (9), and are the only primates known to do so (5) (8). Bamboo constitutes at least 75 percent of the diet of the eastern lesser bamboo lemur, with the rest made up of fig leaves, grass stems, other young leaves, small fruits, flowers and fungi (3) (5) (9). Each species of bamboo lemur appears to specialise on different parts of the bamboo plant (2) (10), with the eastern lesser bamboo lemur preferring the new shoots, leaf bases and stem pith (2) (3) (5) (9). However, some bamboos contain toxic cyanide compounds that would poison most other mammals. How bamboo lemurs deal with these toxins is not exactly known, but the eastern lesser bamboo lemur may limit its intake by selecting young growth, which contains lower cyanide levels (8) (9). It also appears to have a more flexible diet than other bamboo lemurs, using different bamboo species or different food sources depending on the season (9) (11), which may help explain its wider geographic distribution (9). Although often considered cathemeral, with regular bouts of activity both day and night (3) (5), others report the eastern lesser bamboo lemur to be mainly diurnal (11). Group size ranges from around two to nine, with each group typically containing an adult male, one or two breeding females, and offspring (3) (5) (8) (9). The adults are highly territorial, defending the group's territory with scent-marking, vocal displays and chases. Breeding occurs between October and January, the female usually giving birth to a single offspring each year, after a gestation period of 137 to 140 days. The infant may be carried in the female's mouth for the first few weeks, after which it may ride on the female's back, or be “parked” for short periods while the female is foraging (3) (5) (8). The young eastern lesser bamboo lemur is weaned after about four months, and young of both sexes are thought to disperse from the group on reaching maturity (5) (8). In captivity, the eastern lesser bamboo lemur may live up to 17 years (6).

One of the smallest of the bamboo lemurs (5), the eastern lesser bamboo lemur has a dense, woolly coat that is grey to olive-grey on the upperparts, with chestnut-brown tinges on the head, shoulders, and sometimes the back. The face and underparts are a paler grey, becoming creamy-grey on the belly, and the long tail is generally dark (2) (3) (5). Like other bamboo lemurs, the head is rounded, and bears a characteristically short muzzle and small, furred ears (2) (3) (6). Relatively long back legs allow bamboo lemurs to leap easily between vertical bamboo stems (3) (5). Bamboo lemurs are reported to use a variety of different calls (6) (7), including distinct calls in response to different types of predators (7).

This species is endemic to Madagascar. In the wake of the study of Rabarivola et al. (2007), this species has a more restricted distribution in the eastern rainforests than previously believed, being found from about Lake Aloatra south to about Ranomofana (where it is then gradually replaced by H. meridionalis). Further, based on the findings of Rabarivola et al. (2007), animals in western Madagascar from the Tsingy de Bemaraha, Tsiombikibo, Baie de Baly, Tsingy de Namoroka and Bongolava regions between the Mahavavy du Sud and the Tsiribihina Rivers also are H. griseus (they were formerly considered to be H. occidentalis). Upper elevation limit unclear as animals from 1,600 m on the Andringitra Massif are now either H. meridionalis or hybrids between H. griseus and H. meridionalis).

Hapalemur griseus is the endemic to Madagascar. It is the most widespread of all bamboo lemurs. Each of the 4 subspecies occupies a slightly different zone with Hapalemur griseus griseus being the most widely distributed subspecies. Hapalemur griseus griseus is found throughout the eastern rainforest zone except for the far southern portion. Hapalemur griseus alaotrensis is only found around Lac Alaotra, living in reedbeds and floating reed islands. Hapalemur griseus occidentalis is found in small rainforest region in northwestern Madagascar. Hapalemur griseus meridionalis is only found near the Fort Dauphin area of extreme southeast Madagascar.

Biogeographic Regions: ethiopian (Native )

Other Geographic Terms: island endemic

Endemic to Madagascar, the eastern lesser bamboo lemur is the most widespread of the bamboo lemurs (3) (5). It is found throughout much of the forests of eastern Madagascar, although the exact limits of its distribution are unclear, and populations may also exist in western Madagascar (1) (5).

Hapalemur griseus is a small to medium-sized lemur, with an average length of 66 cm and an average weight of 0.935 kg. Males tend to be slightly larger than females. In general, H. griseus has grey fur; however, four different subspecies have been documented, all of which exhibit subtle variations in physical appearance. It has a non-prehensile tail, its forearms are shorter than its hindlimbs, it has sweat glands on its forearms and near its armpits, and it has a dental formula of 2:1:3:3. Hapalemur griseus griseus is mostly gray with olive tones, a dark gray tail and lighter gray fur along the venter. It has large ears, which are mostly hidden in the fur, and its tail is longer than the head and body combined. Hapalemur griseus alaotrensis is darker than H. g. griseus, is slightly larger, and its large ears are also relatively hidden by its fur. Its tail is generally the same length as the head and body combined. Hapalemur griseus occidentalis is lighter than that of Hapalemur griseus griseus and its large ears are relatively less hidden. Its tail is longer than its head and body combined. Hapalemur griseus meridionalis is dark gray or beige. Its ears extend out noticeably from its fur, but to a lesser extent than that of Hapalemur griseus occidentalis and its tail is equal to or slightly longer than the head and body combined.

Average mass: 0.935 kg.

Average length: 66 cm.

Sexual Dimorphism: male larger

Average mass: 1347.5 g.

Habitat and Ecology

Systems

• Terrestrial

Hapalemur griseus is endemic to Madagascar. Average air temperature of this area is 21°C, but varies from 4°C to 30°C. The environment is typically very humid. It is commonly found in areas containing bamboo, marshlands, lowlands, and forests and primarily inhabits primary and secondary forests. Four different sub-species of Hapalemur griseus have been documented (H. g. griseus, H. g. alaotrensis, H. g. occidentalis, and H. g. meridonalis), all of which occupy slightly unique habitats at different elevations throughout the species' geographic range. The overall range for the species occur from sea level to 2050 meters.

Range elevation: 0 to 2050 m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; rainforest

Wetlands: marsh

The eastern lesser bamboo lemur occurs in tropical moist lowland forest and montane forest, in areas where bamboo and bamboo vines are present, and may inhabit both disturbed and undisturbed forest (1) (3) (5) (8).

The primary forage of Hapalemur griseus is bamboo. There are over 40 species of bamboo, but the main species consumed by H. griseus is giant bamboo. Although bamboo is considered toxic due to high concentrations of cyanide found throughout the plant, bamboo lemurs do not experience cyanide poinsoning. The mechanism of how this is accomplished is still unknown. A typical diet for this species is 72% bamboo, 16% grasses, 5% fruits, 4% leaves (usually from various lianas), and 3% from other sources. Hapalemur griseus eats the bases and the inner walls of young bamboo shoots. It feeds through one side of its mouth and chews the bamboo on the other side. Around 70% of its time is spent feeding on bamboo. Food preferences are contingent on time of year and resource availability. Females tend to eat more than the males because of the physiological stress induced by gestation and lactation.

Plant Foods: leaves; wood, bark, or stems; fruit

Primary Diet: herbivore (Folivore , Frugivore , Lignivore)

Other than their role as prey for a number of Malagasy predators, little is known of the potential impact of Hapalemur griseus on their local environment. Major predators of H. griseus include Malagasy tree boas as well as other boas, ring-tailed mongooses, humans, fossas, owls, and Madagascar serpent eagles. There is no information available regarding parasites of this species.

Known predators include Malagasy tree boas as well as other boas, ring-tailed mongooses, humans, fossas, owls, and Madagascar serpent eagles. Other potential predators include other raptors, lemurs, dogs, and cats. Visual monitoring and vocal communication are the primary means of evading predation by H. griseus. In addition, their arboreal nature likely reduces risk of predation as well.

Known Predators:

• Malagasy tree boas, (Sanzinia madagascariensis)
• boas, (Boidae)
• ring-tailed mongoose, (Galidia elegans)
• humans, (Homo sapiens)
• fossas, (Cryptoprocta ferox)
• owls, (Strigiformes)
• Madagascar serpent eagles, (Eutriorchis astur)

Hapalemur griseus has scent glands that assist in olfactory communication with group members and rivals. Many forms of communication occur on or with papyrus plants, including substrate marking. When substrate marking, individuals scratch papyrus leaves with their teeth and either rub the piece of papyrus on its scent glands or urinate on it. Hapalemur griseus also performs scent marking with its tail by rubbing the forearm scent glands along the length of the tail while watching staring at a rival. Other forms of communication include running around a patch of vegetation in circles to identify ones location, by confronting individuals, by chasing away individuals, and by staring. Tactile communication is largely restricted to social grooming. Vocal communication of H. griseus is accomplished through a variety of grunts, clicks, screeches, trembles, teeth grinding, and purrs. Infants often purr when licked by their mother and perform a high-pitched distress call when separated from its mother. When reunited with their young, mothers create a grunt-like sound. Hapalemur griseus also performs mating calls, low-intensity alarm calls, high-intensity alarm calls, intimidation calls, and calls that are used to identify the location of conspecifics.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: scent marks

Perception Channels: visual ; acoustic

There is no information available regarding the lifespan of Hapalemur griseus in the wild. In captivity, records indicate a maximum age of 23 years. The primary cause of death in the wild is predation.

Range lifespan

Status: captivity: 23 (high) years.

Average lifespan

Sex: female

Status: captivity: 17.1 years.

Average lifespan

Sex: male

Status: captivity: 12.8 years.

Maximum longevity: 23.3 years (captivity)

Hapalemur griseus primarily lives in groups. Studies have shown that 42% of groups have one adult male and one adult female. Around 27% of groups have multiple adults of each gender, 19% have two adult females and 1 adult male, and 12% have two adult males and one adult female. Most groups have more reproducing males than females. Although most breeding relationships are monogamous, they can also be polygynous. Polygynous groups tend to have more offspring. Many groups also include sub-adults. Mating season runs from June to July, with births occurring in October and November. Females have on average one baby per year and they usually once annually. Intragroup females are often related; however, males tend to be unrelated. Mating occurs almost exclusively within group. One study found that only 8.5% of births had extra-group paternity. The sub-species H. g. alaotrensis has a longer breeding season than other sub-species of H. griseus.

Mating System: monogamous ; polygynous

H. griseus comes into estrus once a year. It typically gives birth to only one offspring, and rarely has twins. Breeding season occurs during the dry season (i.e., summer or fall) and birthing typically occurs during the rainy season, during which time bamboo, their primary forge, is abundant. Gestation lasts roughly 140 days and most young are completely weaned by 20 weeks of age. Most females are reproductively mature by 2 years old, and most males are reproductively mature by 3 years old.

Breeding interval: Hapalemur griseus breeds once yearly.

Breeding season: Breeding season in Hapalemur griseus occurs during the dry season, from June-August.

Average number of offspring: 1.

Average gestation period: 140 days.

Average birth mass: 45 g.

Average weaning age: 20 weeks.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 3 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Average birth mass: 45.2 g.

Average gestation period: 140 days.

Average number of offspring: 1.2.

Average age at sexual or reproductive maturity (female)

Sex: female: 880 days.

Average birth weight for Hapalemur griseus is 45.2 g. The mother carries the infant in her mouth for about two weeks until young are strong enough to hold on. Infants then cling to the mother until they are a little larger. Sometimes the father or a sibling carries the infant, but most often it is the mother’s responsibility. Young are carried for approximately 3 months; however, once young become a little bigger, they remain in a tree while the mother searches for food. Once the infant is about three weeks old they are able to jump around, hop, and walk. Young can eat bamboo by 6 weeks of age, but still depend on their mother to provide them with food. Females reach reproductive maturity by 2 years of age, and males reach reproductive maturity by 3 years of age.

Parental Investment: female parental care ; pre-weaning/fledging (Provisioning: Female)

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Lower Risk/least concern
• 1988
  Insufficiently Known
  (IUCN Conservation Monitoring Centre 1988)
• 1986
  Insufficiently Known
  (IUCN Conservation Monitoring Centre 1986)

Hapalemur griseus is classified as vulnerable on the IUCN's Red List of Threatened Species. Although it is currently recognized as common, populations are decreasing due to hunting and the pet trade. In addition, habitat loss due the clearing of bamboo stands and slash-and-burn agriculture have had a negative impact on the range and abundance of this species. CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) lists H. griseus under Appendix I and it occurs in a number of national parks and habitat reserves.

CITES: appendix i

IUCN Red List of Threatened Species: vulnerable

Classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix I of CITES (4). Subspecies: the eastern lesser bamboo lemur (Hapalemur griseus griseus) is classified as Vulnerable (VU) and Gilbert's lesser bamboo lemur (Hapalemur griseus gilberti) is classified as Data Deficient (DD) on the IUCN Red List (1).

Population

Population Trend

Major Threats

The eastern lesser bamboo lemur, like many other lemurs, is threatened by ongoing habitat loss (1) (3) (8), although paradoxically the species may actually have benefitted from forest clearance in some areas, as older cleared areas often contain more bamboo than the original forest (3) (6). However, the eastern lesser bamboo lemur is also one of the most heavily hunted lemurs, often being kept as a pet, and these combined threats have led to an ongoing population decline (1) (3) (5).

Conservation Actions

As well as strict control on international trade in the species under its listing on Appendix I of the Convention on International Trade in Endangered Species (CITES) (4), the eastern lesser bamboo lemur also occurs in a number of protected areas within Madagascar, including Ranomafana National Park, Baie de Baly National Park, Mantadia National Park, and Tsingy de Bemaraha Strict Nature Reserve (1) (5) (8) (12). However, there is ongoing debate about the species' exact distribution and, in particular, further research is needed on the recently described subspecies H. g. gilberti before its distribution and conservation status are fully known (1).

There are no known adverse effects of Hapalemur griseus on humans. Questions have been raised about the potential transmission of zoonotic diseases from lemurs to humans and domestic animals.

Hapalemur griseus is hunted by humans throughout their geographic range and is also collected for the local pet trade.

Positive Impacts: pet trade ; food