LAC ALAOTRA GENTLE LEMUR
Geographic Distribution and Habitat
The Lac Alaotra gentle lemur (Hapalemur alaotrensis), also known as the Alaotra reed lemur, Alaotran gentle lemur, Lac Alaotra bamboo lemur, or locally as the bandro, is, like all lemurs, endemic to the island of Madagascar. Lac Alaotra gentle lemurs have a very limited range of about 49,000 acres (20,000 ha), found only in the papyrus and reed beds around Lac Alaotra, Madagascar’s largest lake. Lac Alaotra gentle lemurs are the only primate species in the world to live exclusively in a wetland environment. There are two known subpopulations: a small one in the northern area of the lake and a larger group along the southwestern shores.
TAXONOMY IN QUESTION
The genus Hapalemur is populated by gentle lemurs, also known as bamboo lemurs. There is some disagreement in the taxonomy of the genus. Some consider there to be five distinct species, while others believe there to be only a single species, the bamboo lemur (H. griseus) with four subspecies, including Lac Alaotra gentle lemurs, which are given the scientific name H. griseus alaotrensis. Some consider Lac Alaotra gentle lemurs to be synonymous with another recognized subspecies, the eastern lesser bamboo lemur (H. griseus griseus).
Size, Weight, and Lifespan
Lac Alaotra gentle lemurs have an average head and body length of about 16 inches (40 cm) and an average weight of about 2.7 pounds (1.24 kg). Males are slightly larger than females. In captivity, the maximum lifespan of a bamboo lemur has been recorded at 23 years.
Upon first glance, you might mistake a Lac Alaotra gentle lemur in the wild for a wayward teddy bear. Their long, fluffy tail may be your first clue that you’re mistaken. They are covered in dense, woolly hair that partially obscures their large ears. They have charismatic faces with large, reddish eyes and a short snout. Their thick fur is reddish brown on their backs and transitions to a muted gray on their faces and underbellies.
What Does It Mean?
Social grooming within a species.
Native or restricted to a certain area or country.
Having a diet that consists of leaves.
Refers to mothers leaving their young alone in the nest at night.
Having only one sexual partner.
The group into which an animal is born.
A mating system in which one male mates and lives with multiple females.
A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.
Visit the Glossary for more definitions
Although Lac Alaotra gentle lemurs are also known as “Lac Alaotra bamboo lemurs,” they do not eat bamboo like their cousins. While they are also fully folivious, Lac Alaotra gentle lemurs feed almost exclusively on papyrus and reed.
Behavior and Lifestyle
Lac Alaotra gentle lemurs have an irregular pattern of daily activity. They are neither fully diurnal or nocturnal, nor are they regularly active during twilight, like crepuscular species. This irregular activity pattern is known as “cathemerality.” They tend to cling onto reeds vertically and leap short distances to move about, only moving quadrupedally on the ground. Because of their locomotion style and tendency to stick to areas of dense vegetation, they are likely significantly impacted by habitat fragmentation as they are disinclined to cross large areas of open space. They practice latrine behavior, all members of a group defecating in the same spot. While they can swim, they rarely do and tend to avoid open water.
Daily Life and Group Dynamics
Lac Alaotra gentle lemurs live in small groups often composed of a mated pair and their offspring. However, groups can also be composed of multiple adults of either gender. Females in a group are usually related to one another, while males, except for a father and his sons, are usually unrelated. Typical group sizes range from two to nine individuals. They are very territorial, maintaining territories of about 2.5 to 5 acres (1–2 ha), the boundaries of which are often man-made channels that are cut for fishing access. As for many lemur species, females are dominant. Males are responsible for defending their territory from rival groups. However, these altercations are rarely violent. Upon reaching adulthood, females may remain in their natal group or disperse, while males always disperse.
Lac Alaotra gentle lemurs are the only primate species in the world to live exclusively in a wetland environment.
Allogrooming is a very important form of social bonding. Territorial behaviors include chasing, vocalizing, body language displays, and staring. Olfactory communication is particularly important. Individuals scratch papyrus leaves with their teeth and urinate on them or rub them onto their scent glands to leave their scent. Vocalizations include grunts, clicks, screeches, trembles, teeth grinding, and purring. Infants purr when being groomed and screech when separated from their mother. Mothers emit a low-pitched grunt sound when reunited with their young.
Reproduction and Family
Most breeding relations are monogamous, although polygynous relationships are not uncommon and tend to result in more offspring. Almost all mating occurs within the group, with one study showing that 8.5% of babies are born to a father that is not a member of the group. Mating occurs during the dry season and babies are born during the wet season, from September through February. Females usually have one offspring every year after a gestation period of about 140 days. Twins are uncommon but not unheard of. When babies are first born, they are carried by their mother in her mouth until they are strong enough to cling to her. Sometimes they are carried by their father or an older sibling. They are carried for about three months, after which the mother practices infant parking while she forages. They can begin to eat solid food at about six weeks of age, although they aren’t fully weaned until about 20 weeks. Females are sexually mature at about age two, and males at age three.
Lac Alaotra gentle lemurs are likely preyed upon by snakes, fossas, owls, and eagles. One researcher even observed a newly discovered Durrell’s vontsira, a carnivorous mammal, attempt to predate a Lac Alaotra gentle lemur! These two species are both so incredibly rare, it was a once-in-a-lifetime observation. In that instance, the Lac Alaotra gentle lemur got away.
Conservation Status and Threats
Lac Alaotra gentle lemurs are currently considered Critically Endangered by the IUCN, based on their most recent assessment in 2018 (IUCN, 2018). This status is based on their population loss of more than 80% over the last 27 years. This loss is largely due to habitat area and quality decline, compounded by hunting pressure. In 1994, there were an estimated 7,500 individuals alive. That number dwindled to about 3,000 in 2001. In 2008, the total population was estimated at 2,500 and falling.
While hunting for human consumption and collection for the pet trade pose threats to Lac Alaotra gentle lemurs, habitat loss, as for many imperiled species, is the main threat to their conservation. The tropical forest surrounding Lac Alaotra was once responsible for feeding a large part of the island’s human population by supporting rice fields, earning it the moniker “Madagascar’s rice bowl.” Sadly, much of that habitat has been destroyed for farmland. The removal of the forest caused massive erosion as the now-unprotected soil bled into the lake. The lake is becoming increasingly shallow and is no longer able to support the agriculture or fishing it once had. Invasive species such as water hyacinth now clog the lake. The situation is a vicious cycle, as locals burn back the reedbeds around the lake to create more rice fields and fishing access, further speeding erosion. About 6% of the marsh habitat is destroyed annually. This is a devastating loss for the plants and animals that rely on the lake as well as the humans that depend on it for their livelihoods. This is especially pertinent considering that more than 80% of Malagasies live on less than $1.25 (USD) per day.
Unfortunately, Lac Alaotra gentle lemurs are in good company as imperiled species that rely on the lake. In fact, other species from the area have already been declared extinct: the Alaotra Grebe, a water bird, was declared extinct in 2010. That same year, Durrell’s vontsira was discovered in the forests surrounding the lake, becoming the first new species of carnivorous mammal to be discovered in 24 years. Clearly, the lake has ecological significance beyond what humans could ever hope to fully understand. Sadly, it is being destroyed before its secrets can be uncovered.
Lac Alaotra gentle lemurs are listed on Appendix I of the Convention on International Trade in Endangered Species (CITES). Lac Alaotra has been considered a Ramsar site since 2003. These are sites designated to be of international importance under the Ramsar Convention, also called “The Convention on Wetlands.” The Durrell Wildlife Conservation Trust of Madagascar and other conservation groups formed a 162 square mile (42,000 ha) protected area at the lake, which includes both areas of strict conservation and areas where sustainable uses, such as fishing, are permitted. The area is managed by the local community, which is critical as they can then secure livelihoods while sustainably managing the land.
Outreach and education has had successes for Lac Alaotra gentle lemur conservation. The Durrell Trust has led public engagement initiatives to discuss the importance of the marshes surrounding Lac Alaotra and the uniqueness of the Lac Alaotra gentle lemur to the area. Hunting of the species, which was previously its most significant threat, fell drastically. A 2017 study surveyed locals from the Lac Alaotra region and found that the group of people most knowledgeable about the local resources and most concerned with the Lac Alaotra gentle lemur’s decline are fishers. This makes sense, as the more often people encounter these animals in the wild, the more they know about them, and the more likely they are to be concerned with their conservation. This demonstrates a willingness of the local community to protect the species and habitats that make it so unique.
- Guillera-Arroita, G., J. J. Lahoz-Monfort, E. J. Milner-Gulland, R.P. Young, E. Nicholson. 2010. Monitoring and conservation of the Critically Endangered Alaotran gentle lemur Hapalemur alaotrensis. Madagascar Conservation & Development 5(2).
- Ralainasolo, F. B., P. O. Waeber, J. Ratsimbazafy, J. Durbin, R. Lewis. 2006. The Alaotra gentle lemur: Population estimation and subsequent implications. Madagascar Conservation & Development 1(1):9-10.
- Reibelt, L. M., L. Woolaver, G. Moser, I. H. Randriamalala, L. M. Raveloarimalala, F. B. Ralainasolo, J. Ratsimbazafy, P. O. Waeber. 2016. Contact Matters: Local People’s Perceptions of Hapalemur alaotrensis and Implications for Conservation. International Journal of Primatology 38(4).
- Rendigs, A., L. M. Reibelt, F. B. Ralainasolo, J. H. Ratsimbazafy, P. O. Waeber. 2015. Ten years into the marshes– Hapalemur alaotrensis conservation, one step forward and two steps back?. Madagascar Conservation & Development 10(1):13-20.
Written by K. Clare Quinlan, February 2022