Factors influencing ocelot occupancy in Brazilian Atlantic Forest reserves

Over 80% of Atlantic Forest remnants are <50 ha and protected areas are embedded in a matrix dominated by human activities, undermining the long‐term persistence of carnivores. The ocelot (Leopardus pardalis) is an opportunistic species, but little is known about its tolerance to habitat alterations and the influence of other species on its occupancy in Atlantic Forest remnants. We used camera traps to assess ocelot occupancy in protected areas of Atlantic Forest in southeastern Brazil. We found a positive correlation between the occupancy of ocelots and top predators (jaguars, Panthera onca, and pumas, Puma concolor), and a weaker negative effect between the number of domestic dogs (Canis familiaris) detected and ocelot occupancy. Ocelot detection was higher at sites with more eucalyptus, suggesting that ocelots frequently use these areas. Better‐protected areas surrounded by permeable matrices may be critical to the persistence of ocelots in the fragmented Atlantic Forest.     

Factors influencing the habitat use by ocelots in one of the last large Atlantic Forest remnants in southeastern Brazil

Ocelots (Leopardus pardalis) are widely distributed throughout the Americas, being dependent on forested areas to survive. Although ocelot ecology is broadly studied throughout the species range distribution, studies concerning factors that may affect ocelot occupancy in the Atlantic Forest are still scarce. We used camera traps to evaluate factors influencing the probabilities of detection and occupancy of ocelots in a protected area of the Atlantic Forest, the Rio Doce State Park (RDSP), southeastern Brazil. To assess ocelot occupancy and detection probabilities, we measured the distances between sampling stations and rivers, lakes, cities, pasture, and Eucalyptus plantations. In addition, we recorded the mean rainfall levels for each sampling occasion, and native grassland areas within a 500 m‐buffer around each sampling station. We found a strong and positive association between ocelot detection and the dry season, which might be due to a higher number of individuals moving through the Park during this season. Moreover, we found a strong and positive association of ocelot detection with native grassland areas around lakes, which may be related to the ocelot behavior of searching for prey in these areas. Conversely, the ocelot occupancy probability was intermediate (Ψ^ = 0.53, 95% CI = 0.36–0.69) and was not strongly associated with the evaluated covariates, which may be explained by the high‐quality of forest habitats and water resources that are homogeneously distributed within the Park. Our study indicates that the RDSP still provides a structurally suitable forest habitat for ocelots, but because of the current worrying scenario of over fragmentation, reduction of forest cover, and weakness of the protective legislation of this biome, the long‐term persistence of the species in RDSP is uncertain.     

Ocelot Population Status in Protected Brazilian Atlantic Forest

Forest fragmentation and habitat loss are detrimental to top carnivores, such as jaguars (Panthera onca) and pumas (Puma concolor), but effects on mesocarnivores, such as ocelots (Leopardus pardalis), are less clear. Ocelots need native forests, but also might benefit from the local extirpation of larger cats such as pumas and jaguars through mesopredator release. We used a standardized camera trap protocol to assess ocelot populations in six protected areas of the Atlantic forest in southeastern Brazil where over 80% of forest remnants are < 50 ha. We tested whether variation in ocelot abundance could be explained by reserve size, forest cover, number of free-ranging domestic dogs and presence of top predators. Ocelot abundance was positively correlated with reserve size and the presence of top predators (jaguar and pumas) and negatively correlated with the number of dogs. We also found higher detection probabilities in less forested areas as compared to larger, intact forests. We suspect that smaller home ranges and higher movement rates in smaller, more degraded areas increased detection. Our data do not support the hypothesis of mesopredator release. Rather, our findings indicate that ocelots respond negatively to habitat loss, and thrive in large protected areas inhabited by top predators.     

First ocelot (Leopardus pardalis) monitored with GPS telemetry

We report the first study to monitor ocelot (Leopardus pardalis) spatial patterns with Global Positioning System (GPS) telemetry. The study area was in southern Texas in areas of dense thornshrub (closed habitat) and open grasslands interspersed with small patches of dense thornshrub cover (open habitat). We used a 200-g GPS-Posrec collar (Televilt, TVP Positioning AB, Lindesberg, Sweden). We obtained 61% of GPS fixes from the ocelot GPS collar. The ocelot preferred closed habitat, even with GPS bias against closed habitat, and used small patches and corridors of dense thornshrub. Due to the success of this pilot study, we recommend that GPS telemetry be used to monitor ocelots.     

Habitat use of the ocelot (Leopardus pardalis) in Brazilian Amazon

Amazonia forest plays a major role in providing ecosystem services for human and sanctuaries for wildlife. However, ongoing deforestation and habitat fragmentation in the Brazilian Amazon has threatened both. The ocelot is an ecologically important mesopredator and a potential conservation ambassador species, yet there are no previous studies on its habitat preference and spatial patterns in this biome. From 2010 to 2017, twelve sites were surveyed, totaling 899 camera trap stations, the largest known dataset for this species. Using occupancy modeling incorporating spatial autocorrelation, we assessed habitat use for ocelot populations across the Brazilian Amazon. Our results revealed a positive sigmoidal correlation between remote‐sensing derived metrics of forest cover, disjunct core area density, elevation, distance to roads, distance to settlements and habitat use, and that habitat use by ocelots was negatively associated with slope and distance to river/lake. These findings shed light on the regional scale habitat use of ocelots and indicate important species–habitat relationships, thus providing valuable information for conservation management and land‐use planning.     

Co‐occurrence of bobcats,coyotes, and ocelots in Texas

Interspecific competition among carnivores has been linked to differences in behavior, morphology, and resource use. Insights into these interactions can enhance understanding of local ecological processes that can have impacts on the recovery of endangered species, such as the ocelot (Leopardus pardalis). Ocelots, bobcats (Lynx rufus), and coyotes (Canis latrans) share a small geographic range overlap from South Texas to south‐central Mexico but relationships among the three are poorly understood. From May 2011 to March 2018, we conducted a camera trap study to examine co‐occurrence patterns among ocelots, bobcats, and coyotes on the East Foundation's El Sauz Ranch in South Texas. We used a novel multiseason extension to multispecies occupancy models with ≥2 interacting species to conduct an exploratory analysis to examine interspecific interactions and examine the potential effects of patch‐level and landscape‐level metrics relative to the occurrence of these carnivores. We found strong evidence of seasonal mutual coexistence among all three species and observed a species‐specific seasonal trend in detection. Seasonal coexistence patterns were also explained by increasing distance from a high‐speed roadway. However, these results have important ecological implications for planning ocelot recovery in the rangelands of South Texas. This study suggests a coexistence among ocelots, bobcats, and coyotes under the environmental conditions on the El Sauz Ranch. Further research would provide a better understanding of the ecological mechanisms that facilitate coexistence within this community. As road networks in the region expand over the next few decades, large private working ranches will be needed to provide important habitat for ocelots and other carnivore species.     

Helminths of the ocelot from southern Texas

In the USA, the ocelot (Leopardus pardalis) is a highly endangered felid found only in a few remaining vestiges of native thornshrub brushland in the Lower Rio Grande Valley (LRGV) of extreme southern Texas. From 1987-1998, carcasses of 15 adult ocelots that died of vehicular accidents or natural causes were examined for helminths. All cats had 1-8 (mean = 3) helminth species. All were infected with 1-101 (mean +/- SE = 32 +/- 7) Toxascaris leonina. Other helminths from these ocelots were Alaria marcianae, Brachylaima sp., Mesocestoides lineatus, Taenia rileyi, Oncicola canis, Dirofilaria immitis, Physaloptera rara, Ancylostoma tubaeformae, Cylicospirura chevreuxi, Vogeloides felis, and Metathelazia californica. Additionally, two cats had scarring of the aorta with lesions typical of those caused by Spriocerca lupi, although larval nematodes were not seen. A clinal variation in size of nearly three orders of magnitude was noted in the diplostomatid trematodes in the small intestine of one adult male ocelot. Despite the differences in size, all specimens appeared morphologically identical and were regarded as A. marcianae. Helminth prevalences and abundances, including those of potentially pathogenic species like D. immitis, were low. Although a single heartworm infection may have contributed to the death of one ocelot, helminth infections in general seemed to be of no great consequence to this endangered ocelot population. The helminth fauna of ocelots in the LRGV is reflective of that from wild felids in general; all have been reported previously from the bobcat (Lynx rufus) and mountain lion (Puma concolor) elsewhere in Texas.     

Food habits of three carnivores in a mosaic landscape of São Paulo state,Brazil

São Paulo is the most developed state in Brazil, but despite intense land use changes, some mammal species still inhabit remnant fragments of native vegetation of the state. We used fecal analyses to investigate prey diversity, trophic niche breadth, and trophic niche overlap of pumas, ocelots, and maned wolves in protected and non-protected areas in São Paulo state. During 18 months, we inspected more than 10,000 km of roads and trails and collected 233 fecal samples. Maned wolves showed generalist food habit, ocelots were predominantly carnivores, and pumas were strict carnivores. The European hare, an exotic species which had not yet been reported in the study area, was identified in the feces of a puma. Trophic niche breadth was the lowest for maned wolves (BA?=?0.339) and the highest for pumas (BA?=?0.723). Trophic niche overlap was high between maned wolves and ocelots (O_jk?=?0.765) and between pumas and ocelots (O_jk?=?0.639). Significantly different diets of maned wolves and ocelots were observed between dry and rainy seasons. Our findings indicate that these three species may adapt their diets to the disturbed landscapes. This is the second study characterizing food habits of ocelots in Cerrado areas but the first considering a large number of samples.     

SURVIVAL AND SOURCES OF MORTALITY IN OCELOTS

Abstract: Survival and cause-specific mortality estimates are needed to develop effective conservation strategies for the endangered ocelot (Leopardus pardalis) in the United States. We radiomonitored 80 ocelots (36 F, 44 M) from 1983 to 2002 and analyzed survival and cause-specific mortality rates. Pooled estimates of annual survival rates differed between resident (Ŝ = 0.87) and transient (Ŝ = 0.57) ocelots (P = 0.02); therefore, survival and cause-specific mortality analyses were partitioned for resident and transient ocelots. Sex-specific annual survival was similar between resident ocelots (M = 0.92, F = 0.83, P = 0.16) and transient ocelots (M = 0.53, F = 0.63, P = 0.75). Most mortalities were from human (e.g., ocelot-vehicle collisions; M = 45%) and natural (e.g., animal attack, disease; M = 35%) sources. Transient ocelots had higher natural mortality rates (disease, intraspecific mortality; M = 0.26) than resident ocelots (M = 0.04, P = 0.03). Other sources of mortality did not differ (P ≥ 0.10) between resident or transient ocelots or male and female resident or transient ocelots (P ≥ 0.08). Human population expansion within the Lower Rio Grande Valley of southern Texas, USA, will increase transportation-related problems and decrease the quantity of ocelot habitat, leading to increased ocelot-vehicle collisions and possibly cause more transient behavior, thus significantly lowering ocelot survival. Research and development of ocelot road underpasses should be conducted to mitigate ocelot-vehicle collisions.     

Influence of land use on the taxonomic and functional diversity of dung beetles (Coleoptera: Scarabaeinae) in the southern Atlantic forest of Argentina

The degradation and replacement of native ecosystems affects both their taxonomic and functional biodiversity. However, native species may find a gradient of habitat suitability in different land uses within a region. The aim of this study was to evaluate the effect of land use on the taxonomic and functional diversity of dung beetle assemblages in the southern Atlantic forest of Argentina. Dung beetles were sampled in both the native forest (control) and different land uses (Pine and Yerba mate plantations and cattle pastures) during the 2014 summer, using pitfall traps baited with human feces and rotten meat. Samplings were taken from 20 different sites, with five replicates of each land use and the native forest (100 pitfall traps in total). A total of 1699 beetles of 27 species were captured. Canthon quinquemaculatus, Canthon conformis and Dichotomius sericeus were the most abundant species. Cattle pastures were the land use most negatively affected in their taxonomic and functional diversity, particularly large paracoprid dung beetles. Pine plantations maintained their taxonomic and functional diversity in relation to the native forest and Yerba mate plantations showed, in general, an intermediate situation. Microclimatic conditions (average temperature and humidity and maximum temperature) were correlated with functional diversity (the proportion of large paracoprid dung beetles decreased with increasing temperature) and are probably good predictors to explain the observed patterns of functional diversity of dung beetles. The development of sustainable production systems that preserve the native biodiversity requires the conservation of key components from the ecological niche of native species, especially microclimatic conditions.     

How Small is too Small? Camera Trap Survey Areas and Density Estimates for Ocelots in the Bolivian Chaco

Studies on carnivores, which are generally difficult to observe directly because they are elusive and nocturnal, are carried out through indirect methods, e.g. , camera trapping and radiotracking. The first method has been used to estimate population densities of species that can be differentiated as individuals using unique pelage patterns. However, the use of capture–recapture methodology has raised doubts regarding the estimation of the sampling area around the camera traps, which is obtained using maximum distances traveled by individuals photographed at two or more different locations. In this paper, the results from camera traps are compared with a radiotracking study carried out simultaneously with ocelots ( Leopardus pardalis ) to confirm whether maximum distances observed in camera traps coincide with ranging patterns determined from radio telemetry, and in turn whether the sampling areas estimated from camera traps are appropriate for estimating density. Mean maximum distance moved was 2880 m according to camera trap records during a 60-d survey period while, with radiotracking, the maximum distance moved was 3176 m during the same period. The difference is not significant, and the sampling areas estimated with camera traps to assess ocelot density are reliable. However, if the area covered by cameras is reduced to less than three to four times average home range for the target species, then density estimates from camera trapping are exaggerated because of the reduced observed distances and the fact that multiple individuals can overlap in relatively small areas.     

Fruit‐feeding Butterfly Communities are Influenced by Restoration Age in Tropical Forests

Currently, a large‐scale restoration project aims to restore around 15 million hectares of Atlantic Forest in Brazil. This will increase forest cover and connectivity among remnant sites as well as restore environmental services. Currently, studies on recovery of fauna in restored areas of the Atlantic Forest are practically nonexistent. To address this knowledge vacuum, our study compares diversity patterns of fruit‐feeding butterflies in three forest areas with different restoration ages (11, 22, and 54 years), and uses a native forest area as reference. Results showed butterfly communities in maturing restored areas becoming more similar to the ones found in the native forest, with an increase in the proportional abundance of forest species, and a decrease of edge and grassland species. Moreover, we found a higher diversity among sites at the intermediate restoration age, with a community composed of both grassland and forest species. Butterfly species composition differed significantly among sites, showing interesting patterns of potential species replacement over time. Our results indicate that, although restored sites were located in a fragmented landscape, they provide suitable habitats for recolonization by fruit‐feeding butterfly assemblages. Hence, restored areas can be considered important habitat for forest animal species, increasing local biodiversity and, possibly, restoring some of the ecosystem services provided by them.     

Scaling relationships within the maxillary tooth row of the Felidae, and the absence of the second upper premolar in Lynx

Suggestions that short-faced members of the Felidae tend to lack the second upper premolar (P2) imply a possible shift in scaling associated with the palate and maxillary tooth row in Lynx , which lacks P2, as compared to felids that retain it. This hypothesis is tested using a scaling model that relates the lengths of the palate, and the upper tooth row and its components, to post-palatal skull length in the small to moderately large felids Felis catus (domestic cat), L. canadensis (Canada lynx), F. pardalis (ocelot), and F. concolor (cougar). Scaling relationships of both palate and tooth row length to post-palatal skull length do not differ significantly from isometry in all four species. However, ocelots have a significantly shorter palate and tooth row than lynxes over their overlapping ranges of post-palatal skull length, suggesting that the absence of P2 is not correlated with the length of the face in these species. CI, P3 and P4 tend to be relatively longer in larger felids; none the less, ocelots have a relatively small P3 and lynxes have a proportionately large P4. Because both lynxes and ocelots have a relatively small gap between CI and P3, the absence of P2 is not correlated with available space within the tooth row in adults. However, lynxes also appear to have a relatively long dP3 that almost obliterates the diastema within the deciduous tooth row. The absence of P2 in Lynx may be an engineering artefact that is associated with a shift in proportions within the deciduous toothrow, resulting in inhibition of the development of P2 and dP2 early in ontogeny. Despite the variable occurrence and polymorphism associated with P2 in the Felidae, this character has systematic value within this clade and is a synapomorphy for Lynx.     

Conservation and historical distribution of two bumblebee species from the Atlantic Forest

In this study, we analysed the processes resulting in the origin of two endemic sister species of bumblebees in the Brazilian Atlantic Forest. We studied the historical distribution pattern of Bombus bahiensis, which is restricted to small fragments in eastern Brazil and the phylogeographic pattern and historical demography of B. brasiliensis, which is widely distributed in southern and south-eastern Brazil and neighbouring regions of Uruguay, Paraguay, and Argentina. We used ecological niche models, niche analyses, and genetic and distribution data (i) to test the role of niche differentiation on the divergence between the two species, (ii) to find potential distribution areas for the most restricted B. bahiensis, and (iii) to evaluate the conservation status of both species. Our results showed that B. brasiliensis populations are able to disperse across mosaics of anthropogenic and preserved areas and exhibit low levels of spatial genetic structure. Otherwise, B. bahiensis presented a restricted distribution range and likely a lower diversity, where it is suffering with an increasing habitat loss. The climatic oscillations of the Pleistocene influenced the population structure of both species in different ways, probably due to differences in their effective population sizes, physiology and past demographic fluctuations. Specifically, while B. brasiliensis expanded its distribution range in the last 500,?000?years throughout most of the Atlantic Forest, B. bahiensis remained restricted to a small rainforest area between southern Bahia and northern Espírito Santo states in Brazil. In its southern distribution, in the state of Espírito Santo, B. bahiensis is currently very rare or extinct. Currently, the adjacent ranges of Bombus brasiliensis and B. bahiensis do not overlap and our results indicate that these species may have further diversified through a reinforcement process associated to niche specialization and differentiation.     

Phylogeographic Patterns and Evolution of the Mitochondrial DNA Control Region in Two Neotropical Cats (Mammalia, Felidae)

The ocelot (Leopardus pardalis) and margay (L. wiedii) are sister-species of Neotropical cats which evolved from a lineage that migrated into South America during the formation of the Panamanian land bridge 3–5 million years ago. Patterns of population genetic divergence of each species were studied by phylogenetic analyses of mitochondrial DNA (mtDNA) control region sequences in individuals sampled across the distribution of these taxa. Abundant genetic diversity and remarkably concordant phylogeographic partitions for both species were observed, identifying parallel geographic regions which likely reflect historical faunal barriers. Inferred aspects of phylogeography, population genetic structure, and demographic history were used to formulate conservation recommendations for these species. In addition, observed patterns of sequence variation provided insight into the molecular evolution of the mtDNA control region in closely related felids. Received: 26 January 1998 / Accepted: 14 May 1998     

Bird Assemblages in Anthropogenic Habitats: Identifying a Suitability Gradient for Native Species in the Atlantic Forest

Traditional approaches to the study of species persistence in fragmented landscapes generally consider a binary classification of habitat being suitable or unsuitable; however, the range of human‐modified habitats within a region may offer a gradient of habitat suitability (or conservation value) for species. We identified such a gradient by comparing bird assemblages among contrasting land uses (pine plantations of different age, annual crops, clear cuts and cattle pastures) in the Upper Parana Atlantic forest. Bird assemblages and vegetation structure were characterized in an extensive area of 4400 km² in Argentina and Paraguay during the breeding seasons of 2005–2010. Similarity of bird assemblages between anthropogenic habitats and the native forest and the proportion of forest species increased with vegetation vertical structure, while the proportion of open‐area species decreased. As a consequence, mature tree plantations were the most suitable habitats for forest species and were mainly used by frugivores and bark insectivores. In contrast, open habitats were the least suitable habitat for forest species and were used primarily by insectivores. Human‐created habitats that are structurally complex can be used by a subset of forest species, and may improve functional connectivity and mitigate edge effects. The conservation of large tracks of native forests, however, is critical for the long‐term persistence of the entire bird assemblage, especially for native forest dependent species.     

Small mammal community structure in West Africa: a meta‐analysis using null models

Peer‐reviewed studies on the community structure of small mammals (Rodentia and Soricomorpha) from the Gulf of Guinea region of West Africa were reviewed. To detect nonrandom patterns in the various assemblages under study, the original datasets were re‐analysed using null models [two independent randomization algorithms (RA) for niche overlap] and Monte Carlo simulations. The total species richness in the countries considered in this review was 45 species for soricomorphs and 101 for rodents, and the studies reviewed here reported data for 53.3% of these soricomorph species and for 76.2% of these rodent species. Nonrandom habitat niche partitioning was rarely observed in both rodents and soricomorphs. Instead, aggregated use of habitat resources was frequently detected in both groups. Forest habitat was generally selected as aggregating resource type by small mammal assemblages. Thus, contrary to expectations, our review revealed little evidence for interspecific competition along the habitat niche axis in West African small mammals. However, it is possible that the aggregated use of the forest resource by small mammal species may be apparent, but that the various species partitioned space at a lower scale, for instance selecting different microhabitats. Interspecific competition appeared to be stronger in altered habitats, as predicted by previous studies on other forest organisms in West Africa.     

Relationship between land uses and diversity of dung beetles (Coleoptera: Scarabaeinae) in the southern Atlantic forest of Argentina: which are the key factors?

The loss of natural habitats is one of the main drivers of biodiversity decline. Anthropogenic land uses preserving biotic and abiotic conditions of the native ecosystem are more suitable to preserve the native biodiversity. In this study, we explored changes in species richness and composition in different land uses of the southern Atlantic forest, considering three independent factors: (1) canopy (presence–absence), (2) type of vegetation (native–exotic) and (3) livestock (presence–absence). We expected a gradient of response in the richness and composition of the native forest dung beetle community, from land uses preserving canopy and native vegetation to open land uses with exotic vegetation. Dung beetles were sampled in protected native forests and four land uses, using two potential food resources: human dung and carrion. The species richness and composition of each habitat, as well as differences in composition and the influence of factors over diversity, were then analyzed. As expected, our results showed that land uses preserving canopy and native vegetation maintain the dung beetle diversity of the native forest. Moreover, while the three factors analyzed influenced dung beetle diversity, canopy cover was the main driver of dung beetle diversity loss. The main conclusion of this study is that the conservation of canopy (either native or exotic) is determinant to preserve highly diverse dung beetle communities and subsequently, the ecological functions performed by this taxon. However, the ecophysiological mechanism behind the response of dung beetles to habitat disturbance is poorly understood.     

A forest habitat network for the Atlantic Oakwoods in Highland region,Scotland

Summary

The need to conserve biological diversity and ensure the future viability and integrity of Atlantic oakwoods in a fragmented landscape has led to strategies that facilitate a more holistic view of biodiversity conservation across extensive areas. The Scottish Forestry Strategy contains a major aspiration to develop forest habitat networks through the restoration and improvement of existing woodland and the expansion of new woodland. The Forest Research landscape ecology model BEETLE (Biological and Environmental Evaluation Tools for Landscape Ecology) uses a focal species approach to assess the functional connectivity of habitat within the wider landscape matrix. This model has been used to predict the current habitat network for Atlantic oakwood specialists in the Highland region of Scotland. The analysis outputs are presented with an approach to help practitioners and planners visualise the opportunities to target expansion, conversion or restoration of Atlantic oakwoods and their intrinsic biodiversity.     

Ranging Patterns of Two Syntopic Howler Monkey Species (Alouatta guariba and A. caraya) in Northeastern Argentina

To avoid competition, ecologically similar and closely related species tend to differ in their patterns of habitat use when they live in sympatry. We compared ranging patterns of brown howler (Alouatta guariba) and black and gold howler (A. caraya) monkeys living syntopically, i.e., co-occurring and overlapping their ranges in the same habitat within the zone of sympatry, in the Atlantic Forest of northeastern Argentina with the objective of evaluating whether their use of space contributes to the avoidance of interspecific competition for food resources. During 12 mo we collected data on the ranging behavior of 2 groups of each howler species. We analyzed annual and seasonal daily path lengths and movement rates, home range size, use and overlap, habitat and vertical strata use, and intergroup encounters. Black and gold howlers traveled farther and faster during the time of relative food abundance (abundant season) than during the time of relative food shortage (lean season), and their movement rates were affected by group identity and increased with the proportion of fruits in the diet. Brown howlers’ traveling patterns were not affected by any of these factors. Home ranges for both species (95% fixed kernel; brown howlers: 31–70 ha, black-and-gold howlers: 17–112 ha) were among the largest recorded for Alouatta. For both species, core areas (50% fixed kernel) were larger for larger versus smaller groups, and decreased in the lean season compared to the abundant season. Both species showed similar patterns of habitat use, except for a slight vertical stratification. Groups of different species overlapped their ranging areas consistently more and responded to one another less aggressively during encounters than groups of the same species, suggesting that interspecific spatial niche separation for these two syntopic species is not occurring. The vertical stratification, as well as a day-to-day avoidance strategy, may be the only responses of species to one another that could reduce the potentially high levels of competition for food suggested by their elevated trophic niche overlap. A high degree of niche overlap may explain the parapatric distribution of howlers and other closely related and ecologically similar species of primates.