Small-scale dung survey reveals high forest elephant density and preference for mixed species forest in an intact protected area

Understanding the ecological factors influencing African forest elephant (Loxodonta cyclotis) abundance and distribution is crucial for their conservation management in Central Africa. Dung surveys have been conducted at the landscape scale and confirmed the overwhelming impact of anthropogenic activities on forest elephants. We present results from a small-scale survey in a pristine protected area without anthropogenic activities to elucidate the ecological factors influencing forest elephant density. We conducted a line transect dung survey in a small study area (110 km²) around Mbeli Bai, a natural forest clearing in the Nouabalé-Ndoki National Park, Republic of Congo, and compare results with a landscape survey conducted during the same period. We used habitat specific dung decay data collected on site to estimate elephant density using distance sampling. We fitted Generalized Additive Models to elephant dung encounter rate using explanatory variables collected during the transect survey and from geospatial data. The small-scale survey revealed a precise estimate of forest elephant density that was twice as high as the result from a landscape survey with higher density in mixed species forest for the small-scale survey. We could not find an impact of the proximity of forest clearings and proximity to rivers at the small scale. Fine-scale habitat features, e.g. degree of canopy and understorey closure, had little explanatory power for elephant dung encounter rate. Small-scale dung surveys are a useful method to reveal spatio-temporal variation in forest elephant density and distribution which can inform conservation practitioners in a timely manner. Combining monitoring methods at various spatial scales improves our knowledge and conservation efforts of forest elephants. Nouabalé-Ndoki National Park is a stronghold for forest elephants and of global importance for their conservation.

     

Estimating Abundance of an Unmarked,Low-Density Species using Cameras

Estimating abundance of wildlife populations can be challenging and costly, especially for species that are difficult to detect and that live at low densities, such as cougars (Puma concolor). Remote, motion-sensitive cameras are a relatively efficient monitoring tool, but most abundance estimation techniques using remote cameras rely on some or all of the population being uniquely identifiable. Recently developed methods estimate abundance from encounter rates with remote cameras and do not require identifiable individuals. We used 2 methods, the time-to-event and space-to-event models, to estimate the density of 2 cougar populations in Idaho, USA, over 3 winters from 2016–2019. We concurrently estimated cougar density using the random encounter model (REM), an existing camera-based method for unmarked populations, and genetic spatial capture recapture (SCR), an established method for monitoring cougar populations. In surveys for which we successfully estimated density using the SCR model, the time-to-event estimates were more precise and showed comparable variation between survey years. The space-to-event estimates were less precise than the SCR estimates and were more variable between survey years. Compared to REM, time-to-event was more precise and consistent, and space-to-event was less precise and consistent. Low sample sizes made the space-to-event and SCR models inconsistent from survey to survey, and non-random camera placement may have biased both of the camera-based estimators high. We show that camera-based estimators can perform comparably to existing methods for estimating abundance in unmarked species that live at low densities. With the time- and space-to-event models, managers could use remote cameras to monitor populations of multiple species at broader spatial and temporal scales than existing methods allow. © 2020 The Wildlife Society.     

Group size, density and biomass of large mammals in the Réserve de Faune du Petit Loango, Gabon

Group size, density and biomass of large‐bodied diurnal mammal species in the Réserve de Faune du Petit Loango, Gabon (now Parc National de Loango) was determined over a 12‐month period using standard line‐transect methods. Petit Loango encompasses a range of distinct habitat types, including coastal scrub, savanna, swamps and disturbed and mature forest. Such intact coastal habitats are increasingly rare on the Central‐West African coastline. Faecal censusing indicated highest forest elephant (Loxodonta africana cyclotis) and buffalo (Syncerus caffer nanus) ecological densities at the extreme coast (2.48 and 1.29 km⁻² respectively), probably reflecting high intensity of use of this habitat. Ape density was comparable with that at other Central African study sites at 1.01 individuals km⁻². Mean total biomass of diurnal primates, elephants and other ungulates over the 20 km² site was 3290 kg km⁻². Forest elephants and red river hogs (Potamochoerus porcus) constituted the bulk of the biomass, at 67% and 14% respectively. Primates made up 5% of the biomass. This is the first estimation of mammal density and biomass over an annual cycle at a Central African coastal site, and provides baseline data for long‐term studies in such habitats and to aid habitat and wildlife management decisions.     

Hyper‐abundance of Native Wild Pigs (Sus scrofa) in a Lowland Dipterocarp Rain Forest of Peninsular Malaysia1

This study reports extraordinarily high density estimates for the wild pig (Sus scrofa) from an aseasonal tropical forest site within the species'native range. At Pasoh Forest Reserve, a 2500 ha area of lowland dipterocarp rain forest in Peninsular Malaysia, line transects were used to estimate pig density from May to October in 1996 and 1998. In 1996, 44 sightings of S. scrofa consisting of 166 individuals were recorded along 81 km of transects. In 1998, 39 sightings documented 129 individuals along 79.9 km of transects. Estimated population density was 47.0 pigs/km² in 1996 and 27.0 pigs/km²‐ in 1998. Sus scrofa biomass in this forest was estimated at 1837 kg/km² and 1346 kg/ km² in 1996 and 1998, respectively. Differences between years were attributed to changes in the density of young pigs, coincident with a mast‐seeding year of dipterocarp trees in 1996. Pig densities at Pasoh Forest Reserve were much higher than at other forest locations within the species' native range in Europe and Asia. Because Pasoh Forest Reserve is a forest fragment, two factors likely account for the extremely high pig densities: (1) local extinction of natural predators (mainly tigers and leopards) and (2) an abundant year‐round food supply of African oil palm fruits from extensive plantations bordering the reserve.     

Estimating Deer Populations Using Camera Traps and Natural Marks

Despite the ubiquity of camera traps in wildlife monitoring projects, the data gathered are rarely used to estimate wildlife population demographics, a critical step in detecting declines, managing populations, and understanding ecosystem health. In contrast to abundant white-tailed deer (Odocoileus virginianus) in the eastern United States, black-tailed deer (Odocoileus hemionus columbianus) in the western United States have declined over the past several decades. We tested whether passively operating camera traps can be used to quantify population characteristics for black-tailed deer. We used images of naturally occurring physical characteristics of deer to develop movement and activity data and inform a Bayesian spatial mark-resight model that estimates deer abundance, density, sex ratio, ratio of fawns to adult females, and home range size. We developed the model to account for the effect of attractants (bait) on encounter rate. We placed 13 cameras on all known water sources of a private ranch in California and provided bait once a month in front of each camera. Over 9,000 visits occurred between 24 May 2012 and 21 January 2013, and we identified 50 individual deer from ear notches or antler characteristics. We estimated density at 7.7 deer/km² in summer and 8.6 deer/km² in fall. In the summer, home ranges were 2.3 km² for females and fawns and 16.8 km² for males. Home ranges constricted slightly in fall. We estimated a sex ratio of 12.5 males/100 females, and a ratio of 47.0 fawns/100 adult females. Bait increased baseline encounter rates (visits/week) by 3.7 times in summer and 4.95 times in fall. We found slightly higher densities of deer in our study area compared to other recent studies in more mountainous areas of California, and lower male:female sex ratios. This approach shows that commonly deployed camera traps can be used to quantify population characteristics, monitor populations, and inform harvest or habitat management decisions. © 2019 The Wildlife Society.     

Primate diversity,habitat preferences,and population density estimates in Noel Kempff Mercado National Park,Santa Cruz Department,Bolivia

This report documents primate communities at two sites within Noel Kempff Mercado National Park in northeastern Santa Cruz Department, Bolivia. Diurnal line transects and incidental observations were employed to survey two field sites, Lago Caiman and Las Gamas, providing information on primate diversity, habitat preferences, relative abundance, and population density. Primate diversity at both sites was not particularly high, with six observed species: Callithrix argentata melanura, Aotus azarae, Cebus apella, Alouatta caraya, A. Seniculus, and Ateles paniscus chamek. Cebus showed no significant habitat preferences at Lago Caiman and was also more generalist in use of forest strata, whereas Ateles clearly preferred the upper levels of structurally tall forest. Callithrix argentata melanura was rarely encountered during surveys at Lago Caiman, where it preferred low vine forest. Both species of Alouatta showed restricted habitat use and were sympatric in Igapo forest in the Lago Caiman area. The most abundant primate at both field sites was Ateles, with density estimates reaching 32.1 individuals/km² in the lowland forest at Lago Caiman, compared to 14.1 individuals/km² for Cebus. Both Ateles and Cebus were absent from smaller patches of gallery forest at Las Gamas. These densities are compared with estimates from other Neotropical sites. The diversity of habitats and their different floristic composition may account for the numerical dominance of Ateles within the primate communities at both sites. Am. J. Primatol. 46:197–211, 1998. © 1998 Wiley-Liss, Inc.     

Focusing Conservation Efforts for the Critically Endangered Brown-headed Spider Monkey (<Emphasis Type="Italic">Ateles fusciceps</Emphasis>) Using Remote Sensing,Modeling, and Playback Survey Methods

Brown-headed spider monkeys (Ateles fusciceps), endemic to the Choco-Darien forests and lower Andean forests of NW Ecuador, are considered critically endangered. Unfortunately, scientific data regarding the actual status of populations is lacking. We combined satellite image analysis, species-specific habitat assessment, and a field survey technique using playback to focus conservation efforts for this species. First, we identified remaining forest via a LANDSAT mosaic and then applied species-specific criteria to delineate remaining forest with potential to hold populations. By combining this with the historical distribution from ecological niche modeling and predicted hunting intensity we generated a species-specific landscape map. Within our study area, forest capable of sustaining Ateles fusciceps covers 5872 km², of which 2172 km² (40%) is protected. Unprotected forest considered suitable for Ateles fusciceps extends to 3700 km² but within this only 989 km² (23%) is under low hunting pressure and likely to maintain healthy populations of Ateles fusciceps. To overcome problems of sampling at low primate density and in difficult mountain terrain we developed a field survey technique to determine presence and estimate abundance using acoustic sampling. For sites under low hunting pressure density of primates varied with altitude. Densities decreased from 7.49 individuals/km² at 332 masl to 0.9 individuals/km² at 1570 masl. Based on combining data sets in a gap analysis, we recommend conservation action focus on unprotected lowland forest to the south and west of the Cotacachi-Cayapas Ecological Reserve where hunting pressure is low and population densities of Ateles fusciceps are greatest.     

Methodology matters when estimating deer abundance: a global systematic review and recommendations for improvements

Deer (Cervidae) are key components of many ecosystems and estimating deer abundance or density is important to understanding these roles. Many field methods have been used to estimate deer abundance and density, but the factors determining where, when, and why a method was used, and its usefulness, have not been investigated. We systematically reviewed journal articles published during 2004–2018 to evaluate spatio-temporal trends in study objectives, methodologies, and deer abundance and density estimates, and determine how they varied with biophysical and anthropogenic attributes. We also reviewed the precision and bias of deer abundance estimation methods. We found 3,870 deer abundance and density estimates. Most estimates (58%) were for white-tailed deer (Odocoileus virginianus), red deer (Cervus elaphus), and roe deer (Capreolus capreolus). The 6 key methods used to estimate abundance and density were pedestrian sign (track or fecal) counts, pedestrian direct counts, vehicular direct counts, aerial direct counts, motion-sensitive cameras, and harvest data. There were regional differences in the use of these methods, but a general pattern was a temporal shift from using harvest data, pedestrian direct counts, and aerial direct counts to using pedestrian sign counts and motion-sensitive cameras. Only 32% of estimates were accompanied by a measure of precision. The most precise estimates were from vehicular spotlight counts and from capture–recapture analysis of images from motion-sensitive cameras. For aerial direct counts, capture–recapture methods provided the most precise estimates. Bias was robustly assessed in only 16 studies. Most abundance estimates were negatively biased, but capture–recapture methods were the least biased. The usefulness of deer abundance and density estimates would be substantially improved by 1) reporting key methodological details, 2) robustly assessing bias, 3) reporting the precision of estimates, 4) using methods that increase and estimate detection probability, and 5) staying up to date on new methods. The automation of image analysis using machine learning should increase the accuracy and precision of abundance estimates from direct aerial counts (visible and thermal infrared, including from unmanned aerial vehicles [drones]) and motion-sensitive cameras, and substantially reduce the time and cost burdens of manual image analysis.     

Historical range and movements of the Elephants in Babile Elephant Sanctuary,Ethiopia

A study on historical range and movement patterns of the African savannah elephants (Loxodonta africana africana) in Ethiopia was made from December 2004 to November 2008. Babile Elephant Sanctuary is one of the strongholds of elephants in the country, where it now supports approximately 27% of the elephant population in Ethiopia. Elephant movement routes and ranges were identified based on interviews of local people and by tracking the animals in the field. Elephants of the Sanctuary were categorized into two distinctive groups or clans based on their movement patterns and their associations to each other. Three major valleys, namely Gobele, Erer and Dakata, were crossed by elephants. Elephants in the population had an estimated annual range of 3014 km². Of this, 85.7% (2583 km²) was inside the Sanctuary and 14.3% (430 km²) outside but adjacent to the Sanctuary. Elephant use outside of the Sanctuary included three different areas: Upper Erer Valley (8 km²), Upper Gobele Valley (48 km²) and west of Gobele Valley (374 km²). The extent of range varied seasonally. During the wet season, elephant range was restricted to Erer Valley and its tributaries (1266 km² and a density of approximately 0.25 animal km^?2), or 42% smaller than the dry season range (1417 km², 0.23 elephant km^?2). Range use was smallest (332 km²) in October to November and from April to May. During the dry season, elephants were found in two distinctive groups, one using Gobele Valley and the other Erer Valley.     

Ape Abundance and Habitat Use in the Goualougo Triangle, Republic of Congo

Chimpanzee (Pan troglodytes troglodytes) and western gorilla (Gorilla gorilla gorilla) populations in central Africa are rapidly declining as a result of disease epidemics, commercial bushmeat hunting, and habitat destruction. Our main objective was to estimate the absolute abundance and habitat utilization of chimpanzees and gorillas in the intact forests of the Goualougo Triangle in the Republic of Congo, and in an adjacent area in which selective logging will take place in the near future. The estimates provide a unique baseline for apes inhabiting an undisturbed environment. A second objective was to compare estimates of abundance and patterns of habitat utilization generated by different techniques: 1) distance sampling of individual ape nests and nest sites along line transects, 2) direct observations of apes during reconnaissance surveys, and 3) observations of ape traces during reconnaissance surveys. We completed a total of 222 km of line transect surveys in 4 sampling areas, resulting in overall density estimates of 1.53 chimpanzees/km² and 2.34 gorillas/km² from nest sites. We generated a density estimate of 2.23 chimpanzees/km² from direct observations during reconnaissance surveys of a semihabituated community in 1 of the 4 sampling areas. Habitat use profiles that nest surveys depicted on transects differed from those of direct observations and traces we encountered on reconnaissance surveys. We found the highest overall abundance of chimpanzee nests in monodominant Gilbertiodendron forest, whereas our direct observations showed that chimpanzees preferred mixed species forest. Transects that traversed the core area of the community range had the highest encounter rates of chimpanzee nests and nest sites. Gorilla nests on transects showed a preference only for mixed species forest with an open canopy, but direct observations and traces on reconnaissance surveys clearly indicated that gorillas use several habitat types. We conclude by evaluating the precision of these nest surveys and our ability to detect future trends in ape densities in the Goualougo Triangle.

A population survey of forest elephants (Loxodonta africana cyclotis) in northern Congo

From February to April of 1989 transects were run in four forested areas of northern Congo (Brazzaville) to census elephant populations using dung counts. A total of 401.0 km of line transects was completed during the survey. An overall extrapolated density of 0.7 elephants/km² was obtained with a variation from 0.3 to 0.9 elephants/km². This study shows for the first time that elephants occur in high densities in a number of sites in northern Congo. When elephant dung density is plotted against distance from the nearest village for each transect a significant positive linear correlation results. Based on this correlation we hypothesize that the population of elephants in much of northern Congo is high. Local reports and our own observations indicate that elephant poaching is heavy in northern Congo and that the CITES ban on trade in African elephant ivory has had a limited effect on the level of poaching.     

The Influence of Habitat,Season, and Detectability on Abundance Estimates across an Amazonian Parrot Assemblage

The Amazon basin holds very high parrot species richness but almost nothing is known of parrot population densities in the region or how these vary between species, habitats, sites, and seasons. Such data are becoming important as humans impact on increasing areas of the region. Seventeen parrot species were surveyed using a line transect distance sampling method over 3 yr in floodplain and terra firme forests at two sites in the Tambopata region of southeast Peru. Density estimates for most species were in the range of 3.3–7.8/km², with Brotogeris cyanoptera and Amazona farinosa reaching densities of 22 and 23/km² in floodplain forest during the dry season. Parrot densities were higher in floodplain forest than in terra firme forest at both sites. The parrot communities of terra firme forests were similar across sites and seasons, but those in floodplain forests differed widely across sites and across seasons. Upper canopy birds are notoriously difficult to survey. We introduce a procedure to correct for the likely violation of the assumption that all birds on the transect line are detected (distance sampling assumption g(0) = 1). We correct g(0) based on calling rates of birds using a cue‐counting technique. Multipliers for g(0) differ across species and site, but not season. This method yielded density estimates on average 22 percent higher (6–40% higher in individual species) than those from the standard method.     

Trio under threat: can we secure the future of rhinos,elephants and tigers in Malaysia?

Three of Malaysia’s endangered large mammal species are experiencing contrasting futures. Populations of the Sumatran rhino (Dicerorhinus sumatrensis) have dwindled to critically low numbers in Peninsular Malaysia (current estimates need to be revised) and the state of Sabah (less than 40 individuals estimated). In the latter region, a bold intervention involving the translocation of isolated rhinos is being developed to concentrate them into a protected area to improve reproduction success rates. For the Asian elephant (Elephas maximus), recently established baselines for Peninsular Malaysia (0.09 elephants/km² estimated from one site) and Sabah (between 0.56 and 2.15 elephants/km² estimated from four sites) seem to indicate globally significant populations based on dung count surveys. Similar surveys are required to monitor elephant population trends at these sites and to determine baselines elsewhere. The population status of the Malayan tiger (Panthera tigris jacksoni) in Peninsular Malaysia, however, remains uncertain as only a couple of scientifically defensible camera-trapping surveys (1.66 and 2.59 tigers/100 km² estimated from two sites) have been conducted to date. As conservation resources are limited, it may be prudent to focus tiger monitoring and protection efforts in priority areas identified by the National Tiger Action Plan for Malaysia. Apart from reviewing the conservation status of rhinos, elephants and tigers and threats facing them, we highlight existing and novel conservation initiatives, policies and frameworks that can help secure the long-term future of these iconic species in Malaysia.     

Estimating forest elephant density in Sapo National Park (Liberia) with a rainfall model

The number of elephant dung‐piles lying on the forest floor is a function of the number of elephants present and the rainfall in the 2 preceding months. We present the results of a stochastic model that describes this relationship and we show how it can be used to estimate elephant numbers. The data from a survey in Sapo NP (Liberia) in 1989 are used as an example. The dung‐pile density was estimated at 152 km^?2 with confidence interval from 72 to 322, and the number of elephants was estimated to be 313 with confidence interval from 172 to 617.     

Long‐Term Population Survey of the Sulawesi Black Macaques (Macaca nigra) at Tangkoko Nature Reserve,North Sulawesi,Indonesia

The Sulawesi black macaque (Macaca nigra) population at Tangkoko Nature Reserve in North Sulawesi, Indonesia has been the focus of periodic study for over 30 years. The population has shown considerable decline during much of that time. Here we present the results of a long‐term population survey of the Tangkoko M. nigra, conducted over the past decade, to provide updated information and on‐going assessment of the population. Line‐transect sampling was conducted annually from 1999 to 2002 and 2005 to 2011 along the same transect during a 2‐ to 3‐week survey period. Although further decline in the population was observed at the outset of the survey, over the subsequent 12‐year period we have seen stability in the population parameters with evidence of modest increases in both group and population density. During the 1999–2002 survey periods, there was a mean group density of 3.6 groups/km² and a mean population density of 39.8 individuals/km². During 2005–2011, mean group density increased to 3.8 groups/km² and mean population density was 51.4 individuals/km². The 2011 survey data indicated an estimated group density of 4.3 groups/km² and a population density of 61.5 individuals/km². Given that our transect was located in the core of the Tangkoko reserve, our density estimates should be limited to that area of the reserve. One explanation for the apparent stabilization of the population may be tied to the increasing and sustained number of training and research programs being conducted at the reserve. This collective effort by local and international groups may be helping to reduce illegal activity in the reserve (i.e., hunting and habitat destruction) and generate greater awareness of this critically endangered species. Without the continued vigilance afforded by the existing research and training programs and the support and involvement of the local people, the M. nigra at the Tangkoko Nature Reserve will likely face further decline. Am. J. Primatol. 75:88‐94, 2013. © 2012 Wiley Periodicals, Inc.     

Effects of Forest Type and Human Presence on Bonobo (Pan paniscus) Density in the Salonga National Park1

Our study elucidates how forest type characteristics and human presence influence bonobo (Pan paniscus) densities and assesses whether the Salonga National Park harbors a substantial bonobo population. We searched 11 locations in the Salonga for the presence of bonobos and sampled 9 study sites using line transects to estimate relative bonobo nest density, the proportion of forest types, and the intensity of human activity. We classified forests into broad types by overstory and understory composition, canopy cover, and hydrology, and calculated encounter rates for bonobo, human, and large mammal signs. Bonobo signs occurred in 8 of 11 locations but varied widely in frequency. Mean density was 0.72 nest-builders/km², but density was not uniform across sites (range=0–2.8 nest-builders/km²). Of 11 forest types encountered, the most common were mixed mature forest with an herbaceous (Marantaceae) understory (36.8%), with a woody understory (23.6%), and old secondary forest with a Marantaceae understory (10.5%). Nest sites occurred only in these forest types, called nest-forest types. Bonobo density was highest in locations comprising >80% nest-forest types. Nests occurred more frequently in the mixed mature/Marantaceae forest. Nest-site density correlates positively with the nest-forest patch length we encountered on transects, implying that forest patch size and consistency may influence bonobo density. Mean nest group size correlates positively with proportion of nest-forest types found at a site, suggesting that increased resource availability—nesting sites and food—allows larger group size. A significant inverse association existed between bonobo density and human presence. An erratum to this article can be found at     

西双版纳国家级自然保护区勐腊子保护区亚洲象种群和栖息地评价

通过社区村寨访问、监测网络、痕迹追踪和生态位因子分析(ENFA)等方法对西双版纳国家级自然保护区勐腊子保护区内亚洲象的种群和栖息地状况进行研究。结果显示:2007年勐腊子保护区的亚洲象种群数量约为25—32头,2009年其数量增至35—42头;2006—2007年期间,亚洲象的分布区包含保护区东南部和东部的两片区域,面积共221 km2,占保护区总面积的19.2%;象群在分布区内开辟了固定的活动路线,总长约65 km,它们利用这些路线巡回取食天然植物和农作物并导致严重的人象冲突;栖息地评价研究表明亚洲象对栖息地具有一定的选择偏好性,保护区内亚洲象喜好的栖息地面积为328.5 km2,仅占保护区总面积的28.5%,且主要被分为两大斑块1和2,分别位于保护区的东南部和西北部。     

Density and habitat use of lions and spotted hyenas in northern Botswana and the influence of survey and ecological variables on call-in survey estimation

Top predators significantly impact ecosystem dynamics and act as important indicator species for ecosystem health. However, reliable density estimates for top predators, considered necessary for the development of management plans and ecosystem monitoring, are challenging to obtain. This study aims to establish baseline density estimates for two top predators, spotted hyena and lion, in the Okavango Delta in northern Botswana. Using calling stations, we surveyed free-ranging populations of the two species and investigated methodological variables that might influence results about distributions and densities, including habitat type, seasonality, and different types of playback sounds. Calling stations were distributed over a survey area of approximately 1,800 km² characterized by three major habitat types: mopane woodland, floodplain and mixed acacia sandveld. Results indicate spotted hyenas were evenly distributed independent of habitat type and season throughout the survey area with an overall density estimate of 14.4 adults/100 km². In contrast, lion distribution and density varied significantly with habitat and season. Lion density in the prey-poor mopane woodland was near zero, while in the comparatively prey-rich floodplains it was estimated at 23.1 individuals/100 km² resulting in a weighted average density of 5.8 individuals/100 km² across the entire study area. In testing the effect of varying playback sounds we found that both species were significantly more likely to respond to calls of conspecifics. Our results show how several methodological variables may influence density estimates and emphasize the importance of standardized calling-station survey methods to allow consistent replication of surveys and comparison of results that can be used for landscape-scale monitoring of large predator species.     

北京地区同域分布的普通和黑头种群密度比较

2007年4月至7月,2007年12月至2008年1月,分别在北京市门头沟区小龙门森林公园、百花山自然保护区以及延庆县松山自然保护区,对同域分布的普通(Sitta europaea)和黑头(Sitta villosa)两种同域分布的类种群密度进行了调查。普通在小龙门森林公园、百花山自然保护区和松山自然保护区的种群密度分别是40.92、96.67只/km2和16.67只/km2。而黑头在上述3个调查区域的种群密度分别是2.03、16.67只/km2和23.33只/km2。普通的总体平均密度(51.4只/km2)高于黑头(20.68只/km2)。两种类分布的海拔和林型存在着差异。普通在海拔高度1070—1350 m的分布比较多。在海拔段1070—1250 m区间,普通的数量随海拔高度的增加呈递增的趋势。而黑头在海拔600—800 m分布较多,随着海拔高度的增加,种群数量呈递减趋势。普通主要分布在阔叶林和针阔混交林中,而黑头主要分布在针叶林中。     

Environmental determinants and use of space by six Neotropical primates in the northern Brazilian Amazon

The Guiana Shield has large pristine tracts of tropical forest with high biological diversity and is an area of endemism within the Amazon Basin. However, the conservation status of primates in eastern Amazonian Brazil is still poorly known. Here, we report information on relative abundance, group size, density estimates, plus the effects of environmental variables and seasonality of primates in a sustainable-use reserve in the eastern Brazilian Amazon. From a 603 km transect-based census conducted in October–December 2013 and March–June 2014 we obtained 122 sighting records of six primate species. The most common were Ateles paniscus (45 detections) and Saguinus midas (40 detections). The high calculated density estimates for Sg. midas (2.01 groups/km² or 12.05 individuals/km²) and for At. paniscus (3.44 groups/km² or 10.31 individuals/km²) underscore the conservation importance of the study area for the vulnerable At. paniscus. We found no effect of environmental variables on the number of detections of primates, except for At. paniscus and Cebus olivaceus, with the former showing a higher number of detections in more open canopy forest during the rainy season, and the later having a higher number of detections in areas with higher density of palms in the dry season.