An evaluation of camera traps for inventorying large- and medium-sized terrestrial rainforest mammals

Mammal inventories in tropical forests are often difficult to carry out, and many elusive species are missed or only reported from interviews with local people. Camera traps offer a new tool for conducting inventories of large- and medium-sized terrestrial mammals. We evaluated the efficiency of camera traps based on data from two surveys carried out at a single site during 2 consecutive years. The survey efforts were 1440 and 2340 camera days, and 75 and 86% of the 28 large- and medium-sized terrestrial mammal species known to occur at the site were recorded. Capture frequencies for different species were highly correlated between the surveys, and the capture probability for animals that passed in front of the cameras decreased with decreasing size of the species. Camera spacing and total survey area had little influence on the number of species recorded, with survey effort being the main factor determining the number of recorded species. Using a model we demonstrated the exponential increase in survey effort required to record the most elusive species. We evaluated the performance of different species richness estimators on this dataset and found the Jackknife estimators generally to perform best. We give recommendations on how to increase efficiency of camera trap surveys exclusively targeted at species inventories.     

Comparing methods for sampling large- and medium-sized mammals: camera traps and track plots

Activities involving fauna monitoring are usually limited by the lack of resources; therefore, the choice of a proper and efficient methodology is fundamental to maximize the cost–benefit ratio. Both direct and indirect methods can be used to survey mammals, but the latter are preferred due to the difficulty to come in sight of and/or to capture the individuals, besides being cheaper. We compared the performance of two methods to survey medium and large-sized mammal: track plot recording and camera trapping, and their costs were assessed. At Jataí Ecological Station (S21°31'15"–W47°34'42"-Brazil) we installed ten camera traps along a dirt road directly in front of ten track plots, and monitored them for 10 days. We cleaned the plots, adjusted the cameras, and noted down the recorded species daily. Records taken by both methods showed they sample the local richness in different ways (Wilcoxon, T = 231; p ;; 0.01). The track plot method performed better on registering individuals whereas camera trapping provided records which permitted more accurate species identification. The type of infra-red sensor camera used showed a strong bias towards individual body mass (R ² = 0.70; p = 0.017), and the variable expenses of this method in a 10-day survey were estimated about 2.04 times higher compared to track plot method; however, in a long run camera trapping becomes cheaper than track plot recording. Concluding, track plot recording is good enough for quick surveys under a limited budget, and camera trapping is best for precise species identification and the investigation of species details, performing better for large animals. When used together, these methods can be complementary.     

Interactions between aroids and arboreal mammals in the Brazilian Atlantic rainforest

The Brazilian Atlantic rainforest harbours at least 129 non-volant mammal species. There is also a diverse and numerous epiphytic flora associated with this Neotropical rainforest, including several species of Araceae. Nevertheless, knowledge of the ecology of this group of plants and its interaction with animals is poor. In this study we investigated the interactions between epiphytic aroids and arboreal mammals in the Atlantic forest. We carried out the field work between November 1995 and June 1997 in the Parque Estadual Intervales, southeastern Brazil, a still well preserved forest area of approximately 490 km². We analysed faecal samples from primates (Cebus apella and Brachyteles arachnoides), collected during observations in the field, and marsupials (Didelphis aurita, Micoureus demerarae, Gracilinanus microtarsus), collected from animals captured monthly or bi-monthly in live-traps. We recorded 17 species of Araceae in the study area. The seeds of eight species occurred in the faecal samples: Anthurium harrissi, Monstera adansonii, Philodendron corcovadense, P. appendiculatum, P. exymium, P. crassinervium, P. obliquifolium, and Heteropsis oblongifolia. Aroids were present in faecal samples of the primates during most of the year, with a mean monthly percentage of occurrence of about 56.2%. For marsupials, aroids also were a seasonally important food source, as between November and June the mean monthly percentage of occurrence in faecal samples was about 26.5%. Our data indicate that aroids are an important food source for arboreal and semi-arboreal mammals and that these animals may play an important role as seed dispersers of this group. Aroids and arboreal mammals appear to interact more strongly in Atlantic forest than in other Neotropical forests.     

Preservation of biodiversity in small rainforest patches: rapid evaluations using butterfly trapping

Determining the capacity of small forest remnants to support biodiversity is of critical importance, especially in the tropics where high rates of land conversion coincide with extraordinarily high species richness and endemism. Using fruit-baited traps, we conducted rapid evaluations in 1993 and 1994 of the forest butterfly diversity of seven small patches (3–30 ha) and a single remaining large patch (227 ha) of Costa Rican mid-elevation moist forest. Our results suggest that even recently isolated 20–30 ha fragments of primary forest retain surprisingly depauperate butterfly faunas relative to that supported by the 227 ha patch only 0.5–1.0 km away. If forest butterflies are an index of the diversity of small-bodied organisms in general, preservation of the latter may require unexpectedly large patches. In 1994 we also surveyed a 16 ha botanical garden, situated between and contiguous to both the 227 ha patch and an exceptionally species-rich 25 ha patch. In the garden, we discovered adults of many butterfly species associated with forest interior, suggesting that even heavily managed systems of largely exotic plants (such as agricultural systems) could be designed to serve as corridors for butterflies and perhaps some other groups of organisms. We discuss some implications for a planned restoration of biotic connections between lowland and montane forests in southern Costa Rica.     

Estimation of abundance and distribution of Japanese macaques using track counts in snow

We introduced a technique based on ground-based track counts in snow for simultaneously estimating the abundance and distribution of Japanese macaques Macaca fuscata (Blyth, 1875) and evaluated its efficiency by conducting a field trial in northern Japan. Within the 50-km² area, we selected five transects with consideration of the spatial distribution of vegetation, local climate, and geographical conditions contained in the entire area. Five trained researchers recorded the track counts three times in those geolocations that intersected with each transect. We estimated the macaque abundance by the line-intercept sampling (LIS) technique using the number of tracks and predicted its distribution by ecological-niche factor analysis (ENFA) using the tracks as a proof of macaques’ presence. We confirmed that the LIS-based technique could yield reasonably accurate estimates of the number of individuals and troops, compared with the population estimates of macaques based on the home-range method. We successfully used ENFA in constructing a macaque distribution model that had a high predictive performance; this was verified by comparing the predicted macaque distribution with the actual use of habitat obtained by tracking radio-tagged troops in the study area.     

Population dynamics of large and small mammals

We offer an evaluation of the Caughley and Krebs hypothesis that small mammals are more likely than large mammals to possess intrinsic population regulating mechanisms. Based on the assumption that intrinsic regulation will be manifest via direct density-dependent feedbacks, and extrinsic regulation via delayed density-dependent feedbacks, we fit autoregressive models to 30 time series of abundance for large and small mammals to characterize their dynamics. Delayed feedbacks characterizing extrinsic mechanisms, such as trophic-level interactions, were detected in most time series, including both small and large mammals. Spectral analyses indicated that the effect of such delayed feedbacks on the variability in population growth rates differed with body size, with large mammals exhibiting predominantly reddened and whitened spectra in contrast with predominantly blue spectra for small mammals. Large mammals showed less variance and more stable dynamics than small mammals, consistent with, among other factors, differences in their potential population growth rates. Patterns of population dynamics in small versus large mammals contradicted those predicted by the Caughley and Krebs hypothesis.     

The distribution and status of large mammals in Benin

Records of the occurrence of larger mammals in Benin for the period 1974—79 are summarized. Quarter degree square distribution maps are given for the more conspicuous species. Abundant populations of savanna mammals exist in the Pendjari and ‘W’ National Parks and adjoining hunting reserves in the north. Programmes to eradicate trypanosomiasis and onchocerciasis will lead to increased agricultural development and a consequent loss of savanna wildlife outside these parks and reserves. There are no effectively protected areas in the forested south and uncontrolled logging followed by agricultural development threatens all forest mammals.     

Feeding ecology of a large social antelope in the rainforest

We studied the feeding ecology of the bongo (Tragelaphus eurycerus) in the Dzanga National Park in the rainforest of the Central African Republic to understand better the trade-off between food selectivity, ranging behaviour and social organization of a large, forest-dwelling, social antelope. Food plants and vegetation types were registered along a 311-km route travelled by bongos. Food availability was determined by identifying and counting the plants in 19 randomly chosen forest plots. Bongos showed pronounced selectivity for 26 out of 100 woody forest species. They predominantly consumed younger leaves, which suggests that high protein and low fibre content influence plant choice. In addition to leaves, bongos also ate fruits of two and flowers of one species. Furthermore, the diet was supplemented by grasses and herbs consumed on large natural licks. Such licks were regularly visited by the bongos. According to Jarman's ecological classification of antelopes, selective browsers are relatively small and live alone or in pairs to avoid competition over food. The bongo's large size and gregariousness should not allow it to survive in the rainforest as a pure selective browser. Our data suggest that the bongo relies on the opportunity to graze in bulk which it finds on the natural licks. We hypothesize that such licks either limit the distribution of bongos in other rainforest areas or allow larger group sizes than in areas without licks. Received: 8 June 1998 / Accepted: 30 November 1998     

Role of African protected areas in maintaining connectivity for large mammals

The African protected area (PA) network has the potential to act as a set of functionally interconnected patches that conserve meta-populations of mammal species, but individual PAs are vulnerable to habitat change which may disrupt connectivity and increase extinction risk. Individual PAs have different roles in maintaining connectivity, depending on their size and location. We measured their contribution to network connectivity (irreplaceability) for carnivores and ungulates and combined it with a measure of vulnerability based on a 30-year trend in remotely sensed vegetation cover (Normalized Difference Vegetation Index). Highly irreplaceable PAs occurred mainly in southern and eastern Africa. Vegetation cover change was generally faster outside than inside PAs and particularly so in southern Africa. The extent of change increased with the distance from PAs. About 5% of highly irreplaceable PAs experienced a faster vegetation cover loss than their surroundings, thus requiring particular conservation attention. Our analysis identified PAs at risk whose isolation would disrupt the connectivity of the PA network for large mammals. This is an example of how ecological spatial modelling can be combined with large-scale remote sensing data to investigate how land cover change may affect ecological processes and species conservation.     

The use of camera trapping for estimating Iberian lynx (Lynx pardinus) home ranges

The use of non-invasive long-term monitoring data to estimate home ranges of the critically endangered Iberian lynx has been evaluated. This programme began in 2002 and consisting of both annual latrine and camera-trap surveys, with the aims of detecting and individually identifying the maximum number of individuals and delineating female home range boundaries. Radio-tracking data were used to evaluate the accuracy of home range estimates constructed with camera-trapping data. There was little overlap of camera-trapping home ranges (7.0%?±?1.47), which suggests the existence of real territories consistent with the land tenure system expected for the species. Camera trapping home range estimates were half the size of radio-tracking data (54.1%?±?6.0 of overlapping). When comparing core areas, only the radio-tracking data did not yield improved results (36.7?±?5.4 of overlapping). Estimation of territories, which escaped detection each year, ranged from 0.0% to 5.7%. The results produced by camera-trapping data in this non-intrusive monitoring programme could be considered precise, and are therefore well suited to provide the knowledge required for appropriate conservation of this endangered species.