Sheth's dwarf lemur, Cheirogaleus shethi, is a small, recently discovered nocturnal primate endemic to northern Madagascar. Unlike many other nocturnal lemurs, C. shethi lives sympatrically with morphologically similar species of its cryptic genus, making it difficult for biologists to determine its population density and distribution. Here, we present new data and observations of this species. During a series of rapid biodiversity assessments in the SAVA region of north-eastern Madagascar, we observed C. shethi in 10 different sites, 9 of which were not previously known to harbour C. shethi populations. More significantly, 2 of these sites, in Analamanara, were situated approximately 20 km south of the previously known southern extremity of this species' distribution. This represents a large increase in the previously limited geographic range of this species. Moreover, our relatively high encounter rates at these sites suggest that C. shethi population densities may be high. We also observed C. shethi in human-altered (e.g., vanilla plantations) and non-forest, savannah environments, suggesting that this species can tolerate disturbed habitats. Our findings therefore provide important additional information on the distribution of C. shethi populations and highlight the necessity of further study for the conservation of this species.
Primate encounter rates often vary throughout the year due to seasonal differences in activity, ecology, and behaviour. One notably extreme behaviour is continuous hibernation. Although a rare adaptation in primates, the dwarf lemurs of Madagascar (genus Cheirogaleus) enter obligate hibernation each year during the dry season, after spending the wet season consuming high-energy foods. Whilst seasonal changes in activity in some Cheirogaleus populations are well-known, many species remain little-studied, and there is no specific information on their encounter rates, nor when they enter and emerge from hibernation. This uncertainty critically affects reliable calculation of population density estimates for these highly threatened lemurs. In this study, we assessed how encounter rates of the fat-tailed dwarf lemur (C. medius) vary seasonally in the transitional forests of the Sahamalaza-Iles Radama National Park, northwest Madagascar, during a 4-year period. We established a system of line transects (N = 60) throughout our study area, on which we conducted distance sampling of C. medius. We then used our distance sampling data to calculate encounter rate and population density data. We found encounter rates of C. medius to be significantly higher during the wet season compared with the dry season. Furthermore, encounter rates of C. medius were particularly low from May–August. These results provide some evidence to suggest the time period that C. medius hibernate in Sahamalaza-Iles Radama National Park. These findings underpin the importance of careful study design when surveying threatened species with seasonal differences in activity, such as those that hibernate. This study also demonstrates the importance of species-specific behavioural data for accurate population density assessment, which is required to inform conservation action.
It has been proposed that primates use advertisement calls exclusively to negotiate spacing, but the function of female calls has rarely been studied. Here, we investigated the function of male and female advertisement calls in the northern giant mouse lemur (Mirza zaza), a non-gregarious nocturnal primate from north-western Madagascar. We recorded advertisement calls and associated behaviours of 35 M. zaza individuals at the Duke University Lemur Center. We found that females of M. zaza exclusively use their advertisement calls to advertise oestrus. In contrast, male advertisement calls appeared to be used in a spacing context. These findings show that primates can use their advertisement calls for both spacing and mate attraction, and that the sexes may differ in how they use these calls. The novel find of females of M. zaza attracting mates with loud advertisement calls contrasts with many non-primate taxa, where acoustic mate attraction is usually a function of male advertisement calls, and with other primates, where females use visual and olfactory cues to attract males. The loud female advertisement calls of M. zaza likely ensure mating success during the short receptive phase in this non-gregariously foraging, nocturnal primate.
We provide an anecdote of daytime activity within the northern giant mouse lemur (Mirza zaza), a small threatened primate that has always been considered strictly nocturnal, in the Anabohazo forest of northwestern Madagascar. During the dry season, we witnessed two individual M. zaza travelling separately in the afternoon period of three different days. Our observations indicate that M. zaza may undertake activity that is essential for their survival within both the light and dark periods of a day-cycle, and our findings suggest that the activity cycle of this species may be highly flexible. These observations have important implications to understand the evolution of activity patterns in M. zaza, and these findings warrant future, long term studies to establish the annual activity patterns of M. zaza and to determine whether this species is potentially cathemeral and why.
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