Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP’s boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land-use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP’s boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged-over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
Tag: habitat conservation
Occupancy winners in tropical protected forests: a pantropical analysis
The structure of forest mammal communities appears surprisingly consistent across the continental tropics, presumably due to convergent evolution in similar environments. Whether such consistency extends to mammal occupancy, despite variation in species characteristics and context, remains unclear. Here we ask whether we can predict occupancy patterns and, if so, whether these relationships are consistent across biogeographic regions. Specifically, we assessed how mammal feeding guild, body mass and ecological specialization relate to occupancy in protected forests across the tropics. We used standardized camera-trap data (1002 camera-trap locations and 2–10 years of data) and a hierarchical Bayesian occupancy model. We found that occupancy varied by regions, and certain species characteristics explained much of this variation. Herbivores consistently had the highest occupancy. However, only in the Neotropics did we detect a significant effect of body mass on occupancy: large mammals had lowest occupancy. Importantly, habitat specialists generally had higher occupancy than generalists, though this was reversed in the Indo-Malayan sites. We conclude that habitat specialization is key for understanding variation in mammal occupancy across regions, and that habitat specialists often benefit more from protected areas, than do generalists. The contrasting examples seen in the Indo-Malayan region probably reflect distinct anthropogenic pressures.
Generalist, selective or ‘mixed’ foragers? Feeding strategies of two tropical toads across suburban habitats
Suitable habitats for anurans can be found in the ever-growing tropical urban environments but anurans’ adaptations to urban conditions, including their trophic ecology remain largely unknown. We studied the food habits of two generalist, widespread West African Sclerophrys adult toads: African common (Sclerophrys regularis) and Hallowell’s toad (Sclerophrys maculata). The first was studied in Lomé (Togo), Cotonou (Benin) and Ikeja (Nigeria), and the second in Port Harcourt and Ikeja (both Nigeria); the latter city represents the only studied sympatric occurrence. Mean dietary overlap between population pairs was relatively high, and diet composition of the two species when sympatric did not differ significantly. Food niche width was significantly positively correlated with local rainfall in both species, and diet composition changed significantly between the dry and wet seasons. Diversity metrics revealed that females had a more diversified diet, with higher evenness and lower dominance index values than males. The diet of both species was not correlated to prey type availability, in both the wet and dry season. Both toad species targeted specific food items rather than opportunistically consume prey as observed in most anurans which may be a response to high anuran diversity typically found in the tropics or an adjustment to urban habitats.
Testing hypotheses of habitat use and temporal activity in relation to body plan in a Mediterranean lizard community
A body plan (= bauplan) is a suite of morphological characters shared by phylogenetically related animals at some point during their development. Despite its value, the bauplan concept is still rarely employed to characterize functional groups in community ecology. Here, we examine habitat use and spatio-temporal activity correlates of an entire seven-species community of lizards with different bauplans. The study was carried out in three locations in central Italy, encompassing a complex landscape with a patchy mosaic of a wide variety of habitats and microclimates. We tested four hypotheses regarding niche breadth, habitat use and activity patterns. The first hypothesis, niche complementarity, in which species with similar body shapes should non-randomly partition available habitats, was not supported. By contrast, the hypotheses that larger-bodied species should have a wider niche breadth, that slower species should inhabit habitat types of higher cover, and species inhabiting open sunny habitats should exhibit more seasonally variable activity patterns, were all supported by the data. Sympatric lizard communities in our study area were clearly organized by autecological constraints and eco-physiological attributes.
Community Characteristics of Sympatric Freshwater Turtles from Savannah Waterbodies in Ghana
Despite increasing pressures on freshwater resources worldwide, and the threatened status of most freshwater turtles, there is still limited knowledge of habitat use and niche partitioning in Afrotropical freshwater turtle communities. In this study, we describe habitat associations, community diversity, and temporal patterns of occurrence of freshwater turtle species in the Dahomey Gap ecoregion of Ghana (West Africa). We gathered data from 13 sites in central Ghana and along the Sene Arm of Lake Volta in the Digya National Park (Bono East Region). We employed opportunistic short-term surveys (at seven sites) together with longer-term (six-months duration) standardized evaluations of turtle presence and numbers in different habitats (at six sites). Overall, a total of 210 turtle individuals of four species (Trionyx triunguis, Cyclanorbis senegalensis, Pelomedusa sp. and Pelusios castaneus) were recorded; precise capture sites and habitat type were recorded for 139 individuals, but the 71 individuals observed in marketplaces were not considered in our analyses. At a local scale, we observed three sympatric species in various study sites. In each of these sites, the dominant species was either C. senegalensis or Pelomedusa sp., with the latter species being more abundant in temporary waterbodies and C. senegalensis more numerous in permanent ones. A Multiple Correspondence Analysis suggested that, in permanent waterbodies all species were associated with similar physical habitat variables. In a Canonical Correspondence Analysis, we showed that the density of herbaceous emergent vegetation was more important for P. castaneus than for C. senegalensis. Comparisons of diversity metrics between our study sites and previous studies revealed that turtle community composition was similar across savannah sites.
Evolutionary history and environmental variability structure contemporary tropical vertebrate communities
Tropical regions harbour over half of the world’s mammals and birds, but how their communities have assembled over evolutionary timescales remains unclear. To compare eco-evolutionary assembly processes between tropical mammals and birds, we tested how hypotheses concerning niche conservatism, environmental stability, environmental heterogeneity and time-for-speciation relate to tropical vertebrate community phylogenetic and functional structure. We used in situ observations of species identified from systematic camera trap sampling as realized communities from 15 protected tropical rainforests in four tropical regions worldwide. We quantified standardized phylogenetic and functional structure for each community and estimated the multi-trait phylogenetic signal (PS) in ecological strategies for the four regional species pools of mammals and birds. Using linear regression models, we test three non-mutually exclusive hypotheses by comparing the relative importance of colonization time, palaeo-environmental changes in temperature and land cover since 3.3 Mya, contemporary seasonality in temperature and productivity and environmental heterogeneity for predicting community phylogenetic and functional structure.
Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP’s boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land-use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP’s boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged-over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP’s boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land-use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP’s boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged-over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP’s boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land-use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP’s boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged-over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP’s boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land-use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP’s boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged-over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.