Population Density and Abundance of Ebony Leaf Monkeys (Trachypithecus auratus) in West Bali National Park, Indonesia

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.

Habitat suitability analysis reveals high ecological flexibility in a "strict" forest primate

Background

Research of many mammal species tends to focus on single habitats, reducing knowledge of ecological flexibility. The Javan lutung (Trachypithecus auratus) is considered a strict forest primate, and little is known about populations living in savannah. In 2017-2018, we investigated the density and distribution of Javan lutung in Baluran National Park, Indonesia. We conducted ad libitum follows and line transect distance sampling with habitat suitability analysis of Javan lutung.

Results

Estimated density was 14.91 individuals km^- 2 (95% CI 7.91-28.08), and estimated population size was 3727 individuals (95% CI 1979 - 7019). Long-tailed macaque (Macaca fascicularis) habitat suitability was the main driver of lutung habitat suitability as the probability of lutung occurrence increased greatly with macaque habitat suitability. Distance to roads, and distance to secondary forest had a negative relationship with lutung occurrence. Lutung habitat suitability decreased with increasing elevation, however, Mt Baluran and the primary forest on Mt Baluran was under-sampled due to treacherous conditions. Follows of six focus groups revealed considerable use of savannah, with terrestrial travel. The follows also revealed polyspecific associations with long-tailed macaques through shared sleeping sites and inter-specific vocalisations.

Conclusions

Our study provides new knowledge on the general ecology of Javan lutung, such as use of savannah habitats, underlining our need to branch out in our study sites to understand the flexibility and adaptability of our study species. Another undocumented behaviour is the polyspecific association with long-tailed macaques. We encourage more research on this subject.

Nonvolant mammalian populations in primary and secondary Central American rainforests as revealed by transect surveys

Secondary forests are now prominent features in Neotropical landscapes, yet little is known about their conservation value for nonvolant mammalian communities. We performed a 20-month study using transect walks to survey the nonvolant mammal fauna in primary and secondary forests at La Selva Biological Station in the Caribbean lowlands of northeastern Costa Rica. We found that secondary forests can hold complex mammalian communities and no species exhibited habitat preferences between primary and secondary forests. With few exceptions, behavioral and group dynamic characteristics of mammal species were similar between forest types. Our research allows us to address methodological questions and assess the effectiveness of transect sampling. Monthly detection rates vary widely by species and likely reflect short-term changes in behavior rather than population fluctuations. Air temperature and rainfall are the factors most associated with monthly detection rates for various species. Small-scale areas of higher and lower use are evident for several species. Neither time of morning for surveys nor number of observers per trail affects detection rate. We report current abundances for the most commonly observed species and note generally lower densities in the Caribbean lowlands than elsewhere in the Neotropics. This research highlights that in less seasonal, evergreen forests climatic factors can still affect mammalian behavior. Overall, we find that secondary forests are of high conservation value and that transect walks are an effective methodology to sample many nonvolant mammal species, and we present recommendations on how to sample properly to conduct rigorous and long-term studies.

Los bosques secundarios son mucho más comunes en el neotrópico, pero poco se sabe sobre su importancia en la conservación de comunidades de mamíferos no voladores. Durante 20 meses llevamos a cabo un estudio usando líneas de transectos para investigar la fauna de mamíferos no voladores en bosques primarios y secundarios en la Estación Biológica La Selva en las tierras bajas caribeñas al noreste de Costa Rica. Pudimos constatar que los bosques secundarios pueden albergarcomplejas comunidades de mamíferos y ninguna especie exhibe preferencias de hábitat entre bosque primario y secundario. Con pocas excepciones, las características dinámicas de grupo y comportamiento de especies de mamíferos fueron similares entre los dos tipos de bosque. Nuestra investigación nos permite abordar cuestiones metodológicas y evaluar la eficacia del muestreo con transectos. Las tasas mensuales de detección varían de acuerdo a la especie y probablemente reflejan cambios a corto plazo en las fluctuaciones del comportamiento en vez de la población. La temperatura del aire y la precipitación son los factores más asociados con las tasas mensuales de detección de distintas especies. Encontramos que varias especies muestran diferentes incidencias de uso en zonas pequeñas. Ni la hora de la mañana, ni el número de observadores en las encuestas por transecto afectan la tasa de detección. Presentamos la abundancia actual de las especies más comúnmente observadas y notamos en general bajas densidades en las tierras bajas del Caribe más que en otras partes del neotrópico. Esta investigación resalta que en los bosques menos estacionales, factores climáticos aún pueden afectar el comportamiento de mamíferos. En general, encontramos que los bosques secundarios son de alto valor para la conservación y que los muestreos en transectos son una metodología eficaz para estudiar muchas especies de mamíferos no voladores y presentamos recomendaciones sobre cómo llevar a cabo muestreos adecuados para realizar estudios rigurosos a largo plazo.

The role of anthropic, ecological, and social factors in sleeping site choice by long-tailed macaques (Macaca fascicularis)

When choosing their sleeping sites, primates make adaptive trade-offs between various biotic and abiotic constraints. In human-modified environments, anthropic factors may play a role. We assessed the influence of ecological (predation), social (intergroup competition), and anthropic (proximity to human settlements) factors in sleeping site choice by long-tailed macaques (Macaca fascicularis) occupying a habitat at the interface of natural forests and human-modified zones in Bali Barat National Park, Indonesia. Over the course of 56 nights, we collected data relating to physical features of sleeping trees, patterns of the use of sleeping sites within the home range, pre-sleep behavior, diurnal ranging patterns and availability of natural and human food. Overall, the macaques used 17 sleeping sites with 37 sleeping trees. When the monkeys slept in forest zones, they selected sleeping trees that had larger trunks but were not significantly taller than surrounding trees. Though the macaques rarely re-used sleeping sites on consecutive nights, they frequently re-used four sites over the study period. The group favored sleeping within the core area of its home range, despite the occurrence of frequent agonistic intergroup encounters there. Macaques preferentially selected sleeping trees located within or near human-modified zones, especially when human food was abundant and natural food was scarce. These results partially support the hypothesis that long-tailed macaques choose their sleeping sites to avoid predation; proximity to human settlements appears to be the primary factor influencing sleeping site choice in this primate species. Our results reflect the strong influence that anthropic factors have on primates, which subsist in increasingly human-dominated landscapes.