Lemur population density in Sahamalaza-Iles Radama National Park, Madagascar
Cite this dataset
Hending, Daniel (2024). Lemur population density in Sahamalaza-Iles Radama National Park, Madagascar [Dataset]. Dryad. https://doi.org/10.5061/dryad.rr4xgxdg1
Abstract
The clearing and fragmentation of tropical forest is the single biggest threat to primate populations who depend on this habitat for survival. In contrast to primates that live in continuous, undisturbed forests, primate communities of fragmented forests need to adapt to decreased food availability and increased inter- and intraspecific competition typical of these degraded and anthropogenically disturbed habitats. Some primate species are highly sensitive to habitat fragmentation, whilst other species can adapt and even thrive in fragmented and degraded forests. Here, we assessed how forest fragmentation and associated edge-effects impact the population density of four species of nocturnal lemur in the Sahamalaza-Iles Radama National Park, North West Madagascar. We conducted 118 transect walks over a three-year period covering a total distance of 107 km to collect encounter rate (N/km) and population density (N/Ha) data for each species, which we then compared between the edge and core areas of a continuous forest and a fragmented forest. Our results were highly species-specific, with the population densities of two species (Lepilemur sahamalaza and Microcebus sambiranensis) increasing in edge and fragmented habitat, whilst we observed the opposite for Cheirogaleus medius. Mirza zaza density appeared consistent between the continuous and fragmented forest and in both edge and core areas. We also found evidence of species-specific population density relationships with fragment size, core area, and fragment shape; however, further work is needed to support these findings. This study demonstrates that some nocturnal lemurs can adapt to degraded habitats and thrive within fragmented forests, whilst other species are less capable of doing so.
README
This dataset contains two data sheets. The first, Transects, contains the raw transect distance sampling data. The "Individuals" sheet contains individual lemur observations, where each row represents a single lemur individual. For each individual (Observation_Number), information on the time of observation (Date, Time), location of observation (Forest, Fragment, Edge_or_Core, Transect, Transect_ID, Latitude, Longitude), the species and individual (Species, Lemur_ID) and their perpendicular distance from the transect in metres (Distance) is provided. The length of the transect in metres is provided in the Transect_Length field. The "Transects" sheet contains summary information on each transect walk , where each row represents a single transect walk. For each walk (Transect_Number), information on the transect location (Forest, Fragment, Edge_or_Core, Transect, Tranect_ID), its length in metres (Length), the date (Date) and the number of each species observed (Mirza_zaza, Lepilemur_sahamalaza, Cheirogaleus_medius, Microcebus_sambiranensis) is provided.
The second sheet, Transect_Properties, contains information on transect and forest fragment properties. Both raw data sheets enable the calculation of the population density values that have been analysed in the associated publication. The "Ankarafa Properties" sheet contains location (Centre Latitude, Centre Longitude) and size (Total Area (Ha), Area of Forest Core (Ha), Forest Core (%)) information on each of the 10 forest fragments of Ankarafa. Size information is in hectares. This sheet also contains information on transect properties fir the Ankarafa fragments (Transect Length (m), Transect Core Length (m), Transect Core (%)), where lengths are given in metres. The "Anabohazo Properties" sheet provides the same transect information for the transects location in the Anabohazo Forest.
Funding
National Geographic Society
La Vallée des Singes
Global Wildlife Conservation
Primate Conservation
Primate Society of Great Britain
Lemur Conservation Association (AEECL)
Idea Wild
University of Bristol
Bristol Zoological Society