Introduction

Although we first saw John Cleese's woolly lemur in 1990 (Mutschler and Thalmann 1990) and, as a result of our revision of the western woolly lemurs (Thalmann and Geissmann 2000), we had realized then that we had found a new taxon, we officially described and named the species only recently (Avahi cleesei Thalmann and Geissmann, 2005). In this article we summarize all available conservation-relevant information (published or unpublished), including information and recommendations that will facilitate future surveys for the species.

Species Description

The single individual of Avahi cleesei captured so far, an adult male (Fig. 1), had a body mass of 830 g. The facial fur is only slightly paler than that of the upper forehead and crown. The facial area above the nose extends upward toward the forehead. This upward extension contrasts with the virtually opposite pattern created by the triangle of forehead pelage that invades the facial area in other western Avahi (for example, A. occidentalis and A. unicolor). The forehead fur immediately bordering the facial area is blackish and forms a dark chevron pattern above the facial area. The eyes are maroon, and the eyelids are black and hairless. The snout is also black and hairless. The fur surrounding the corners of mouth is whitish. The fur on the head and body has a brown-gray coloration and a woolly (slightly curled) flecked appearance. The tail is beige or brown-gray, and is slightly reddish only on the dorsal side of the root. The inner dorsal surface of the lower limbs is white. The fur of the chest, belly, and inner surface of the upper limbs is relatively thin, downy, and very light gray. Avahi cleesei is distinguished from A. occidentalis by its lack of a white facial mask and broad dark eye-rings, and from both A. occidentalis and A. unicolor by the presence of a dark chevron pattern on the forehead.

Figure 1.

Photograph of adult male Avahi cleesei (type) after capture on 3 October 1991.

Geographic Range

So far, Avahi cleesei is known to occur in only a single location, the Tsingy de Bemaraha National Park in central western Madagascar (Fig. 2), a UNESCO World Heritage Site. Within the reserve it has been sighted in two localities, in the forest of Ankindrodro (19°08′S, 44°49′E; n = 5 weaned individuals in two groups) and the type locality (18°59′S, 44°45′E), a forest 3–4 km east-northeast of the village of Ambalarano at the base of the western Tsingy precipice (n = 4 weaned individuals in two groups). The species was outside the reserve's boundaries in 1994, in the heavily disturbed forest in the surroundings of the village of Ankinajao (19°03′S, 44°47′E; n =10 weaned animals in five groups: Thalmann and Geissmann 2000). The forest was completely destroyed since we made the sightings at Ankinajao, and no woolly lemurs have been found there since 2003 (U. Thalmann pers. obs.). It appears that the species was last detected on 1 October, 2003 by one of us (UT), approximately 2 km to the south of the type locality. Surveys in the vicinity and wider surroundings of the Bemaraha region (different forests and forest types including the southern bank of the Manambolo River to the south and reaching as far north as the National Park of Namoroka, the Mahavavy du Sud River, and the Betsibioka River) did not reveal any evidence for the presence of the species (Rakotoarison et al. 1993; Thalmann and Rakotoarison 1994; Curtis 1997; Ausilio and Raveloanrinoro 1998; Hawkins et al. 1998; Sterling 1998; Thalmann et al. 1999; U. Thalmann unpubl. data). Based on these findings, it has to be concluded at present that the species occurs only in the Reserve Tsingy de Bemaraha to the north of the River Manambolo, and in certain forest types within the closer surroundings of the Tsingy de Bemaraha region (see ‘Habitat’). The northern distribution beyond the type locality is completely unknown, but is evident, under any circumstances, that the species has an extremely restricted geographic range. Moreover, its ecological range may also be very narrow (see below).

Figure 2.

Distribution map of western taxa of woolly lemurs, Avahi.

Habitat

Avahi cleesei definitely occurs in subhumid, dry deciduous forests close to the western Tsingy precipices (Ankindrodro, type locality close to Ambalarano, Figs. 3, 4), in the larger Tsingy crevasses or gorges, and forests along small seasonal rivulets and seasonal swamps close to the Bemaraha massif (forest 2 km south of type locality, Ankinajao). To date, A. cleesei has not been detected in any of the region's typical dry deciduous forests of western-type, similar to the Kirindy (Ganzhorn and Sorg 1996) or Marosalaza forests (Hladik 1980). Based on a comparison of a 400 m² forest sample (Fig. 4) from the type locality of A. cleesei with the forest of Marosalaza (Hladik 1980), the subhumid dry deciduous forest has more green-leafed trees during the dry season, a higher floristic diversity, and the trees are larger in diameter at breast height and in canopy height (Thalmann et al. 1994; Thalmann unpubl.).

Figure 3.

Subhumid, dry deciduous forest at the base of the tsingy precipice (type locality).

Figure 4.

Schematic drawing of the subhumid dry deciduous forest (10 × 40 m). Note that most trees have mature leaves even toward the end of the dry season (October).

Behavior and Ecology

A short-term field study of A. cleesei using telemetry was conducted 4–14 October 1991 (Figs. 5 and 6). During this time, the group (which included the type specimen) was only active at night; used a home range of approximately 2 ha and five different sleeping sites; and fed on buds, sprouting buds, and young leaves. According to the signals of the activity transmitter, Cleese's woolly lemur shows three distinct nocturnal activity peaks: the first between 18:00 and 20:00, a second more variable between 22:00 and 24:00, and the third between 03:00 and 05:00. Although detailed observations on feeding behavior have not been made, it is probable that Cleese's woolly lemur exhibits a comparable feeding behavior as its northerly congener A. occidentalis. The latter is a specialized folivore, feeding on selected relatively rare tree species that, in addition, are relatively large in size (Thalmann 2001, in press). Such a narrow niche may explain why members of the genus Avahi may occur locally in high densities but may be absent in other localities due to the lack of preferred tree species.

Figure 5.

Nocturnal activity (18:00–06:00) of the study group in the nights from 5/6 to 13/14 October 1991 (total observation time 92 hours and 40 minutes). Error bars indicate standard error.

Figure 6.

Map of the study site (type locality) near Ambalarano, Bemaraha.

Vocalizations

We recorded three different classes of vocalizations for Cleese's woolly lemur in Bemaraha: ‘vou-hy’ calls (Fig. 7), whistles, and growls. Only the ‘vou-hy’ call is loud and conspicuous, whereas the other vocalizations are difficult to hear and locate. The ‘vou-hy’ calls did not occur every night and did not appear to be uttered at any regular times during the active period. They seem, however, to be linked with the activity peaks. During 85 hours and 10 minutes of indirect observations we noted 105 such calls. ‘Vou-hy’ or whistle calls by one indiviual were often answered by a corresponding call by another individual. Examples of typical ‘vou-hy’ and whistle calls can be heard on the Internet as soundfiles (WAV-format) at  http://www.gibbons.de/main/non-gibbon/2006avahi_cleesei.html.

Figure 7.

Sonagrams of typical Avahi cleesei ‘vou-hy’ calls (a) and whistle calls (b) at Ambalarano, Bemaraha, 9 October 1991, 19:40–20:14. Calls can be heard at  http://www.gibbons.de/main/non-gibbon/2006avahi_cleesei.html.

Survey Recommendations

Given the extremely small known range of Cleese's woolly lemur, surveys are obviously urgently needed to find additional populations. Interviews with local inhabitants may be one source of information, it became evident to us that Cleese's woolly lemur is one of the least known species, along with the aye-aye (Daubentonia madagscarensis), and is considered very rare. The local name is Dadintsifaky. Some people call it Bekola be — the big Bekola — Bekola being the local name for Hapalemur occidentalis (Rakotoarison et al. 1993; Thalmann unpubl. data). Field surveys in potential habitat are necessary as a second source of information. During daytime surveys, the immobile and cryptically colored Cleese's woolly lemurs are virtually impossible to find. Therefore, surveys at night with head lamps are necessary, using the reflecting eye shine to find them. Given the comparable size and eye shine of the sportive lemurs (Lepilemur ruficaudatus) and A. cleesei, four main characteristics besides knowledge of their general appearance (such as body proportions) may be used to distinguish between Lepilemur and Avahi at night: (1) Avahi are often encountered in groups, thus several animals may be spotted sitting or feeding closely together, although this may also sometimes apply for Lepilemur. (2) In Lepilemur, the ears are clearly protruding, whereas A. cleesei has much smaller ears. (3) When resting, woolly lemurs usually hide their tail between their body and the substrate, whereas in sportive lemurs the tail hangs down. (4) Sportive lemurs often move their heads sideways, probably to have a better look at the observer. Woolly lemurs seem to be less curious, and look at the observer without moving the head in the same way as do the sportive lemurs.

Conservation Assessment

According to the IUCN Red List categories and criteria, A. cleesei clearly falls into the category Endangered under the criteria B1ac(i, ii, iii, v) (IUCN 2001): The extent of occurrence is estimated to be less than 5,000 km² (B1), the species is known from just one location (B1a), and the known population is declining (B1c) in extent of occurrence (i); area of occupancy (ii); area, extent and/or quality of habitat (iii); and in number of mature individuals (v).

More detailed analyses and surveys may reveal, however, that this avahi should even be moved to the Critically Endangered category. For example, the disturbed forest close to the village of Ankinajao, which supported a substantial number of individuals in 1994 (Thalmann and Geissmann 2000) had been cut completely by 2003 (Thalmann unpubl. data). The subhumid forest occurring at the base of the escarpment of the Tsingy de Bemaraha is under continuous pressure from annual bushfires. In some places, the forest has been reduced to only a few meters in width (Fig. 6). Such subhumid forests are the only habitat where A. cleesei is known to occur. In addition, migrating individuals are forced to travel through stretched ranges (Fig. 6) that are possibly much easier to control and defend by the range holders because part of the borders are made up of savanna and the rocky tsingy precipice (Fig. 6). This may make it extremely difficult for migrating animals (for example, young animals leaving the family group) to cross established territories in order to find a mate and its own range.