The golden bamboo lemur was first discovered in 1985, and was described two years later (Meier et al., 1987). With an adult weight of approximately 1.3–1.7 kg, it is the largest member of the genus Hapalemur, since the greater bamboo lemur (formerly H. simus) has now been placed in its own genus, Prolemur (see Groves, 2001). Head-body length is about 34 cm and tail length about 41 cm, for an overall length of 70–80 cm. The dorsal coat is reddish-brown; darker on the shoulders, back, top of the head and tail. The tail also darkens toward the tip. The ventral coat, including the inner limbs, is a paler golden-brown. A pink nose contrasts with the dark muzzle, which is surrounded by a ring of gold-colored hair on the cheeks and around the eyes. The ears are tipped with golden-brown hairs, but are not tufted. Hapalemur aureus is sympatric with H. griseus ranomafanensis in Ranomafana National Park, with H. meridionalis in Andringitra National Park, and with Prolemur simus in both of these protected areas. However, it can be readily distinguished from all of these taxa by its golden coloration, especially on the face. It is larger than the other two Hapalemur and smaller than Prolemur, and the lack of ear tufts also differentiates it from the latter. Molecular data support its inclusion in the genus Hapalemur (Pastorini et al., 2002a, 2002b).
The golden bamboo lemur is active during the day but has a distinct midday rest period. It lives in small groups of 3–4 individuals that maintain home ranges of up to 30 ha (Tan, 1999). At times, it can be quite vocal. Females give birth to a single young in November or December after a gestation of about 138 days. The young are born in an altricial state, and are kept safe in dense vegetation for the first two weeks of life (Mutschler and Tan, 2003). Based on studies at Ranomafana National Park, as much as 90% of this lemur’s diet consists of bamboo, principally giant bamboo (Cathariostachys madagascariensis), and the number of plant species it eats is quite low (Meier and Rumpler, 1987; Meier et al., 1987; Mutschler and Tan, 2003). Young leaves and shoots are the plant parts most readily eaten. Glander et al. (1989) found astonishingly high levels of cyanide in the shoots of giant bamboo as well as in the blood and feces of the golden bamboo lemur, and suggest that similar levels in the diets of other mammals would be lethal. Presumably, this tolerance to dietary toxins allows H. aureus to live in sympatry with three other bamboo-eating lemurs, H. meridionalis, H. g. ranomafanensis and Prolemur simus, all of which appear to avoid either plant species or plant parts with such high cyanide levels (Wright, 1989).
Hapalemur aureus is known from tropical moist lowland and montane forests of southeastern Madagascar, at altitudes of 600–1,400 m (Arrigo-Nelson and Wright, 2004). It occurs in and around Ranomafana National Park, where it has been observed as far to the north as Miaranony, and also occurs at least as far south as Andringitra National Park and in the forest corridor that connects Ranomafana with Andringitra (Sterling and Ramaroson, 1996; Lehman and Wright, 2000; Goodman et al., 2001; Arrigo-Nelson and Wright, 2004; Rakotondravony and Razafindramahatra, 2004; Irwin et al., 2005). However, there has recently been an unconfirmed sighting of this species as far south as the Vevembe Forest (west of Vondrozo) (P. Rabeson, pers. comm.).
The IUCN Red List assessment of 2008 classified H. aureus as Endangered (EN). The principal threat to its survival is habitat loss due to slash-and-burn agriculture and the harvesting of bamboo for local use (e.g., building houses, carrying water, making baskets). Hunting for food can also be a threat in some areas. Known to occur in only two national parks (Andringitra and Ranomafana) and probably numbering less than 2,500 individuals, its distribution is patchy and it typically occurs at low population densities (Nicoll and Langrand, 1989; Sterling and Ramaroson, 1996). The Ranomafana / Andringitra forest corridor has been proposed as a conservation unit in conjunction with efforts to propagate and re-establish stands of bamboo species that serve as food for this species. As of 2010, this species was not being kept in captivity (ISIS, 2009; E. E. Louis Jr., pers. comm.).
The golden bamboo lemur can be seen in Ranomafana National Park around the research station at Talatakely, but a visit of at least two or three days is recommended. The use of local guides to find this animal is essential. This genus contains a single species, Prolemur simus. Tattersall (1982) and other earlier authors had placed this animal in the genus Hapalemur as Hapalemur simus, but a recent taxonomic revision of the primates by Groves (2001) placed it in its own genus and resurrected the name Prolemur (Gray, 1871). It is still referred to as a bamboo lemur along with all members of the genus Hapalemur, and like other bamboo-eating lemurs has a broadened and shortened muzzle. However, it is much larger than any of the other species (Albrecht et al., 1990), and has at least nine cranio-dental features that are distinctive (Vuillaume-Randriamanantena et al., 1985). Genetic studies further support its separation from the other bamboo lemurs and suggest that the genus Hapalemur may, in fact, be more closely related to Lemur (Rumpler et al., 1989; Macedonia and Stanger, 1994; Stanger- Hall, 1997).