a Exc: a food species eaten exclusively by one of the two lemur species. Dif: both lemurs ate the species, and either lemur ate the species one-third more than did the other lemur. Sim: both lemurs ate the same species, and neither lemur ate the food species at least one-third more than did the other lemur.
Do Polyspecific Associations Exist outside of Mt. d'Ambre?
Prior to 2004, few researchers had identified populations of Sanford's lemurs outside of the continuous canopy forests of Mt. d'Ambre, Ankarana, and Analamerana. Wilson et al. (1989) suspected that the two species associated in Ankarana. Freed (1996) found no populations outside of these three reserved forests. One might have inferred that the two species associated, given an overabundance of resources.
In 2004, populations of Sanford's lemurs were found west of Mt. d'Ambre in at least four forests that stretch west and north of Mt. d'Ambre to the Mozambique Channel (Figure 1). In most previously studied regions Sanford's lemurs are known locally as ankombabe, or "big lemurs." West of Mt. d'Ambre in traditional Sakalava/Antankarana language, they are known as barivaokao, or "bearded ones." By surveying at early morning, dusk, and by listening for nocturnal vocalizations, populations of both crowned lemurs (ankomba fieky) and Sanford's lemurs were found within 100 m of one another in isolated forests near Bobakilandy (Figure 1, #1: 12°37' 0.3'' S lat., 49°2' 44.1'' E long., elevation 304 m), Bemanevikakely (Figure 1, #2: 12°32' 27'' S lat., 49°3' 43'' E long., elevation 455 m), Befotaka (Figure 1, #3: 12°29' 14.3'' S lat., 48°56' 42.8'' E long., elevation 3 m), Ambatomitangolo (Figure 1, #4: 12°29' 41.2'' S lat., 48°56' 54.3'' E long., elevation 16 m), and Baie d'Antalaha (Figure 1, #5: 12°18' 2.0'' S lat., 49°2' 50'' E long., elevation 0 m). All but one other site had crowned lemurs living in them. In Bemanevikakely one group of each species was observed for 45 minutes foraging, feeding, and traveling with one another in Lantana camara and Bombax sp. on successive days, on the edge of a rice field. The observed groups exchanged calls at dusk with neighboring groups of both species. Local people reported populations of both species that live together. Neighboring groups were also found traveling beside a rice field near Bobakilandy.
Associations of crowned lemurs and Sanford's lemurs may also occur in the Cap d'Ambre peninsula. The east coast of Cap d'Ambre (e.g., Anjiabe, Figure 1, #6) has crowned lemurs throughout its forests. These forests are almost identical to those of Mt. des Français, a limestone-based set of forests that contain only crowned lemurs, found east and southeast of the city of Antsiranana. I found no evidence of Sanford's lemurs along these forests. In contrast, forest structure along the Cap d'Ambre center and west coast is not unlike that of the northernmost forests of Mt. d'Ambre. This region includes primary deciduous forests connected by small forests (less than 25 m wide) that line seasonal riverbeds. Beside the Antsahabe River (Figure 1, #7: 12°05' 43.2'' S lat., 49°13' 25.5'' E long., elevation 27 m) I found five groups of crowned lemurs and one group of Sanford's lemurs traveling together and exchanging vocalizations. The groups did not appear to be afraid of humans. Local guides also report populations of both species nearby (Figure 1, #8: 12°14' 10'' S lat., 49°10' 2'' E long., elevation 191 m), but this could not be verified.
Far from being limited to forests that have continuous canopy, Sanford's lemurs are now known from a number of forests that are structurally much different from the protected areas of Mt. d'Ambre, Ankarana, and Analamerana. These forests are extremely different from those that have been investigated, but polyspecific associations most likely occur throughout this region.
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