Population size and habitat preference of the Omo River guereza (Colobus guereza guereza) in a multi-habitat matrix in the central highlands of Ethiopia

Djaffa Mountains guereza (Colobus guereza gallarum) abundance in forests of the Ahmar Mountains, Ethiopia

The size and density of a population are essential parameters in primate ecology and conservation. Such information, however, is still scarce for many forest primate species. The Djaffa Mountains guereza (Colobus guereza gallarum) is an endemic Ethiopian taxon for which data about its distribution and population size are missing. Therefore, we aimed to estimate the abundance and population size of the Djaffa Mountains guereza in four forests in the Ahmar Mountains southeast of the Ethiopian Rift Valley. We conducted line-transect surveys in the forests. Within an area of 183 km2 , we sampled 19 transects covering a distance of 75.9 km. We encountered 73 guereza clusters which most likely represent social groups. Since the detection distances and cluster sizes did not differ among the four forests, we applied a conventional distance sampling (CDS) model and estimated a population density of 20.6 clusters per square kilometer, i.e., 109.6 individuals per square kilometer or 20 061 individuals within the complete study area. This abundance is relatively high compared to other C. guereza taxa. However, given that the habitat and population of C . g . gallarum are already highly fragmented, further monitoring of the population and exploration of the possibilities of reconnecting its habitat should be priorities for the conservation of this taxon.

Plant community and native primate as drivers of habitat use by an exotic primate (Saimiri spp. Linnaeus, 1758) in an Atlantic Forest fragment

Understanding how and why exotic species use their habitats is crucial for defining effective conservation strategies. We aimed to investigate habitat use by an exotic population of squirrel monkeys living in an Atlantic Forest fragment and identify factors associated with their habitat preferences. Over 6 months of scan sampling observations, we collected data on native and exotic plants consumed by the squirrel monkeys, food availability, and interactions between the squirrel monkeys and the native common marmosets. We also georeferenced the estimated centroid point of the study group during each scan. Squirrel monkeys used Secondary Old Forest habitats more often than the other habitats available. The consumption of native and exotic plants and the association with common marmoset appear to have influenced the habitat use of the exotic squirrel monkeys; however, the choice habitat did not demonstrate to be associated with food availability. The exotic squirrel monkeys preferred to use less disturbed habitats to consume a high amount of food (often associated with the common marmoset), potentially optimizing their food intake. Our findings demonstrated the adaptive success of an exotic primate in its non-natural habitat and the key role of the plant community in maintaining this population.