New density estimates of a threatened sifaka species (Propithecus coquereli) in Ankarafantsika National Park.

Propithecus coquereli is one of the last sifaka species for which no reliable and extensive density estimates are yet available. Despite its endangered conservation status [IUCN, 2012] and recognition as a flagship species of the northwestern dry forests of Madagascar, its population in its last main refugium, the Ankarafantsika National Park (ANP), is still poorly known. Using line transect distance sampling surveys we estimated population density and abundance in the ANP. Furthermore, we investigated the effects of road, forest edge, river proximity and group size on sighting frequencies, and density estimates. We provide here the first population density estimates throughout the ANP. We found that density varied greatly among surveyed sites (from 5 to ∼100 ind/km2) which could result from significant (negative) effects of road, and forest edge, and/or a (positive) effect of river proximity. Our results also suggest that the population size may be ∼47,000 individuals in the ANP, hinting that the population likely underwent a strong decline in some parts of the Park in recent decades, possibly caused by habitat loss from fires and charcoal production and by poaching. We suggest community-based conservation actions for the largest remaining population of Coquerel's sifaka which will (i) maintain forest connectivity; (ii) implement alternatives to deforestation through charcoal production, logging, and grass fires; (iii) reduce poaching; and (iv) enable long-term monitoring of the population in collaboration with local authorities and researchers.

Density estimates of two endangered nocturnal lemur species from northern Madagascar: new results and a comparison of commonly used methods.

Very little information is known of the recently described Microcebus tavaratra and Lepilemur milanoii in the Daraina region, a restricted area in far northern Madagascar. Since their forest habitat is highly fragmented and expected to undergo significant changes in the future, rapid surveys are essential to determine conservation priorities. Using both distance sampling and capture-recapture methods, we estimated population densities in two forest fragments. Our results are the first known density and population size estimates for both nocturnal species. In parallel, we compare density results from four different approaches, which are widely used to estimate lemur densities and population sizes throughout Madagascar. Four approaches (King, Kelker, Muller and Buckland) are based on transect surveys and distance sampling, and they differ from each other by the way the effective strip width is estimated. The fifth method relies on a capture-mark-recapture (CMR) approach. Overall, we found that the King method produced density estimates that were significantly higher than other methods, suggesting that it generates overestimates and hence overly optimistic estimates of population sizes in endangered species. The other three distance sampling methods provided similar estimates. These estimates were similar to those obtained with the CMR approach when enough recapture data were available. Given that Microcebus species are often trapped for genetic or behavioral studies, our results suggest that existing data can be used to provide estimates of population density for that species across Madagascar.

Spatial variation in density and total size estimates in fragmented primate populations: the golden-crowned sifaka (Propithecus tattersalli).

The golden-crowned sifaka (Propithecus tattersalli) is an endangered lemur species found only in the Daraina region, a very restricted area in north-eastern Madagascar. Its forest habitat is highly fragmented and expected to suffer from significant changes in the near future. The species is poorly known and only one census study, carried out in 2000, has ever been published. It is thus crucial to update the conservation status of the golden-crowned sifaka before major anthropogenic environmental changes take place. Using the line-transect approach, we estimated the species density in the main forest fragments located in both the peripheral and central parts of the distribution range, including both protected and unprotected areas. In parallel, we tried to determine whether an edge effect could be detected by comparing densities at different distances from the forest edges. We found important variation of sifaka densities among forest fragments. The total species abundance is thus difficult to determine, but we estimated that it is likely to be over 18,000, two to three times higher than previously thought. However, our data also suggested that most P. tattersalli live in forests located in the central part of the distribution range and that the estimated densities in the central part were high (>80 individuals/km(2)). Two forest fragments, found to host a large part of the total population, are currently outside the managed area and their incorporation to the managed area is strongly recommended. Lastly, as expected for a folivorous and not heavily hunted species, our results are consistent with the hypothesis that this species does not experience a clear edge effect, at least during the first half of the dry season. This could be due to a high resiliency to habitat fragmentation or to the fact that fragmentation has been going on for some time.