Macrohabitat Use Research Articles

Dietary Specialization and Habitat Shifts in a Clade of Afro-Asian Colubrid Snakes (Colubridae: Colubrinae)

Speciation through niche divergence often occurs as lineages of organisms colonize and adapt to new environments with novel ecological opportunities that facilitate the evolution of ecologically different phenotypes. In snakes, adaptive diversification may be driven by the evolution of traits relating to changes in their diets. Accordingly, habitat-mediated differences in prey available to ancestral snakes as they colonized and occupied novel dynamic landscapes are likely to have been a strong selective agent behind the divergence and radiation of snakes across the globe. Using an ancestral reconstruction approach that considers the multivariate nature of ecological phenotypes while accounting for sampling variation between taxa, we explored how diet and macro-habitat use coevolved across a phylogeny of 67 species of Afro-Asian colubrine snakes. Our results show that the most recent common ancestor of this clade was likely a dietary generalist that occupied tropical forests in Asia. Deviations from this generalist diet to a variety of specialist diets each dominated by the utilization of single prey types repeatedly occurred as ancestral colubrines shifted from tropical forests to savanna and grassland habitats across Africa. We additionally found that dietary specialist species were on average smaller in maximum length than dietary generalists, congruent with established predator-size, prey-diversity dynamics in snakes. We speculate that adaptive divergence in ancestral colubrines arose as a result of a selective regime that favored diets comprised of terrestrial prey, and that partitioning of different prey types led to the various forms of dietary specialization evident in these lineages today. Our findings provide new insights into the ecological correlates associated with the evolution of diet in snakes, thereby furthering our understanding of the driving forces behind patterns of snake diversification.

Role of microhabitat and temporal activity in facilitating coexistence of endemic carnivores on the California Channel Islands

AbstractMost extinctions worldwide have occurred on islands, primarily due to interactions with exotic species, but rarely due to interactions among endemic species. This potential exists on two of the California Channel Islands, Santa Cruz and Santa Rosa, as endemic island spotted skunks (Spilogale gracilis amphiala) appear to have rapidly declined to rarity, possibly due to interference competition with endemic island foxes (Urocyon littoralis). Niche partitioning is expected in response to interference competition; hence, it is surprising that skunks and foxes show extensive overlap in macrohabitat use and circadian activity. However, the role of microhabitat associations and fine-scale temporal activity in facilitating coexistence of the two species has not been explored. We evaluated microhabitat associations of island spotted skunks and island foxes across both islands using data from live traps and wildlife cameras collected during 2015–2017, and we analyzed fine-scale temporal activity using camera data from 2016 and 2017. On both islands, skunks had a positive response to ground-level cover provided by rugged topography or woody vegetation such as shrubs or trees, whereas foxes had a weak or negative response, suggesting partitioning of these microhabitat characteristics. Additionally, on both islands the peak in timing of skunk activity offset the peak for foxes, which implies that skunks use fine-scale adjustments in activity to avoid foxes. Past grazing by exotic herbivores likely reduced habitat refuges for skunks; however, as vegetation on both islands recovers, regrowth of shrubs and trees may provide cover that will improve prospects for coexistence of island spotted skunks and island foxes.

Movements and Macrohabitat Use of Alligator Gar in Relation to a Low Head Lock and Dam System

AbstractLoss of habitat, targeted removals, and overharvest has contributed to the decline of Alligator Gar Atractosteus spatula. There is agreement among commercial fishers, some recreational anglers, conservationists, and natural resource managers that this species warrants conservation. Appropriate management actions require research to further understand the life history and ecology of Alligator Gar populations. We conducted a movement study of 16 Alligator Gar in the lower Ouachita River, Arkansas–Louisiana, for 1 year using acoustic telemetry. The Alligator Gar were stationary at least 28% of the year. We documented 1,552 movement events during the study. The mean (SD) movement rate during the movement events was 1.13 (0.18) km/h, but it varied among individuals. Only 2 of the 16 Alligator Gar were detected upstream of Felsenthal Dam. The tailwater habitat just below Felsenthal Dam was used heavily by the Alligator Gar. The linear home range was 11.9 (7.1) river kilometers. Due to the hydrology of the system, access to the floodplain is not a hindrance to the lateral movement of Alligator Gar in the Ouachita River. The Felsenthal Dam did seem to hinder longitudinal movement, even though high water allowed the fish to move over and around the dam during spring and early summer. Management plans to rebuild Alligator Gar populations in regulated river systems should consider the negative consequences of barriers to lateral or longitudinal movement.

Habitat use and age structure of the Fer-de-Lance (Bothrops asper, Viperidae) in Braulio Carrillo National Park, Costa Rica

The Fer-de-lance or terciopelo (Bothrops asper) inhabits a wide range of environmental conditions and habitats across Central America. While much information on the species is based on anecdotal observations and useum specimens, data collected under natural conditions are more limited. To better document its natural history, this study sought to determine the habitat use and age structure of B. asper in the Quebrada Gonzalez sector of Braulio Carrillo National Park, Costa Rica. Snake surveys were conducted from January 2015 to August 2017 and used to evaluate the population age-class distribution and sex ratio. To evaluate macrohabitat use, surveys were conducted in four habitat types (mature forest, late succession, early succession, and human infrastructure). Microhabitat use was determined by recording several structural variables at each snake location and at random sites. Amphibians were sampled in each habitat type to evaluate the available prey base. Fifty-five individuals were captured, mostly females and juveniles, with five recaptures. Snakes were encountered in all habitat types but most often in early succession forests, which have dense vegetation cover and high prey availability. Snakes selected areas with heavy understory cover when resting, and more exposed sites, often closer to bodies of water, when ambushing prey or moving. Human-disturbed sites were used least. Although snake encounters did tend to correlate with higher amphibian abundance, other factors such as mammalian prey abundance could also influence snake distribution.

Hierarchy in adaptive radiation: A case study using the Carnivora (Mammalia).

Simpson's "early burst" model of adaptive radiation was intended to explain the early proliferation of morphological and functional variation in diversifying clades. Yet, despite much empirical testing, questions remain regarding its frequency across the tree of life. Here, we evaluate the support for an early burst model of adaptive radiation in 14 ecomorphological traits plus body mass for the extant mammalian order Carnivora and its constituent families. We find strong support for early bursts of dental evolution, suggesting a classic Simpsonian adaptive radiation along dietary resource axes. However, the signal of this early burst is not consistently recovered in analyses at the family level, where support for a variety of different models emerges. Furthermore, we find no evidence for early burst-like dynamics in size-related traits, and Bayesian analyses of evolutionary correlations corroborate a decoupling of size and dental evolution, driven in part by dietary specialization. Our results are consistent with the perspective that trait diversification unfolds hierarchically, with early bursts restricted to traits associated with higher level niches, such as macrohabitat use or dietary strategy, and thus with the origins of higher taxa. The lack of support for early burst adaptive radiation in previous phylogenetic studies may be a consequence of focusing on low-level niche traits (i.e., those associated with microhabitat use) in clades at shallow phylogenetic levels. A richer understanding of early burst adaptive radiation will require a renewed focus on functional traits and their evolution over higher levelclades.

Population density and annual and seasonal space use by feral cats in an exurban area

Feral cats (Felis catus) exhibit contrasting behavior in urban and rural areas. Urban cats form dense social groups with small home range sizes while feral cats occupying rural areas are typically solitary and inhabit larger home ranges. Because feral cat behavior is influenced by their surroundings and exurban areas possess components of both urban and rural areas, it is expected that feral cats in exurban areas will demonstrate an intermediate behavior pattern. Given that feral cat ecology is understudied in exurban areas, our objectives were to estimate feral cat density, quantify annual and seasonal home range areas, and characterize macrohabitat use among annual and seasonal home ranges of feral cats within the exurban city of Russellville, Arkansas during October 2012–December 2013. In our study, home ranges of male feral cats (29.17 ± 7.70 ha) were larger than female home ranges (12.26 ± 2.90 ha), but the size of core areas did not differ by sex. Feral cats in Russellville disproportionately used developed areas and pasture and hay fields more than other habitats within the exurban matrix. Feral cat density in Russellville was found to be relatively low (0.10 cats/ha) and although home ranges (19.76 ± 4.28 ha) were similar to rural feral cat populations, areas of core use (3.73 ± 0.95 ha) were similar to urban and suburban living cats. Therefore, this exurban feral cat population appears to share characteristics with both rural and urban feral cat populations.

Spatial ecology and multi-scale habitat selection of the Copperhead (Agkistrodon contortrix) in a managed forest landscape

We evaluated the spatial ecology and habitat use of the Copperhead (Agkistrodon contortrix) in managed, pine-hardwood forests in the William B. Bankhead National Forest, Alabama. We used radiotelemetry to monitor 31 snakes (23 males, 8 females [5 gravid and 3 non-gravid females]) over a period of 3years (2006–2008). Snakes were tracked for one or more seasons in a series of 18 forest stands composed of 6 treatments (Control, Burn, Light Thin, Heavy Thin, Light Thin with Burn, and Heavy Thin with Burn) replicated three times. Home-range estimates for male snakes averaged 17.8±2.3 (based on Utilization Distributions [UD]) and 12.0±1.9ha (based on 100% Minimum Convex Polygons [MCP]), whereas home-range estimates for gravid female snakes averaged 7.1±1.8ha (based on UD) and 4.1±1.1ha (based on MCP) and were significantly different between both sexes for all home-range analyses. We did not detect an effect of forest management on home-range size of male snakes. Macrohabitat use differed among male and gravid female snakes, where male snakes used edge (field and secondary road edges) and Southern Pine Beetle macrohabitats in significantly greater proportion than what was available. Gravid female snakes did not use macrohabitats differently than what was available, but tended to use thinned stands and forest stand canopy gaps for parturition sites. Microhabitat use patterns were similar between male and gravid female snakes, where both sexes tended to use microhabitat sites with relatively greater litter depth and coarse woody debris percent cover compared to random microhabitat sites. Microhabitat use patterns for male snakes tended to differ based on forest management treatment (Thin and Thin with Burn versus Control and Burn stands), where selected microhabitat sites had lower ambient and soil temperatures compared to random sites in thinned stands. Collectively, we illustrated that male A. contortrix displayed hierarchical habitat use, whereas female A. contortrix displayed preference for habitat features at the microhabitat scale only. Overall, our short-term study provides evidence that recently-thinned pine-hardwood stands are not initially used at a frequency greater than their availability, which suggests that microhabitat and microclimate conditions likely limit use immediately following management.

Winter Macro- and Microhabitat Use of Winter Roost Sites in Central Missouri

Northern bobwhite (Colinus virginianus) managers and biologists have expressed concern regarding the apparent decline of northern bobwhite populations throughout the Unites States. The decline has been attributed to habitat loss; however, the decline may be the result of multiple factors. Several studies concluded that reproduction was not a limiting factor, and recommended that investigations of winter habitat use at the microhabitat level are needed. In our study, we used data from 166 roost sites obtained from 194 radiomarked bobwhites to analyze winter macrohabitat use and microhabitat characteristics of roosts selected by bobwhites in central Missouri. At the macrohabitat level, bobwhites showed a preference for early successional vegetation (ESV), native warm-season grass (NWSG), and old (idle) fields. Most roost locations (5l.2%) were in old fields, in ESV (23%), and NWSG (l7%). For all 3 habitat types (old fields, ESV, NWSG), litter at the roost site was higher (P < 0.05) than the surrounding vegetation. In the 2 most preferred habitat types, visual obstruction reading (VOR) and maximum vegetation height were higher (P < 0.05) than the surrounding vegetation. In NWSG and old fields, litter depth was significantly higher (P < 0.05) than the surrounding vegetation. Habitat management of winter cover in central Missouri will benefit from the maintenance of dense ground litter (> 65%), tall vegetation (91 cm), VOR (29 cm), and litter depth about 1.5 cm in ESV, NWSG, and old fields.

Effects of Micro-Habitat, Macro-Habitat, and Predator Space-Use on Success of Northern Bobwhite Nests (Poster Abstract)

Northern bobwhite (Colinus virginianus) exhibit high reproductive potential allowing populations to rapidly respond to newly created habitat and recover from high annual mortality. However, they experience low individual nest success, ranging from 16–50%. Survival of nests, particularly first nests, is an important demographic parameter that influences overall population performance and participation in alternative reproductive strategies such as renesting, double-clutching, and male-incubation. As bobwhite populations continue to decline, old paradigms regarding the relationships among habitat characteristics, predator abundance, and bobwhite productivity are being reexamined. A new emerging paradigm hypothesizes that habitat structure, landscape context, and predator context interact in a complex manner to influence fate of individual nests. Vegetation characteristics at nest sites, and components of bobwhite nesting habitat have been described, but few studies have shown relationships between vegetation characteristics and nest success. In contrast, several studies have demonstrated relationships between landscape structure and nest success, and ongoing research in the southeastern United States is demonstrating relationships between predator context and productivity. Although numerous studies have estimated nest success, no study has simultaneously examined effects of vegetation structure, landscape structure, and predator context on survival of bobwhite nests. We use incubated nests (n = 104) of radiomarked bobwhite on a managed area in east-central Mississippi from 1996–00 to examine effects of micro-habitat, macro-habitat, and predator space-use on nest survival. At each nest we characterized microhabitat by measuring vegetation height, density (Robel Visual Obstruction Reading), grass canopy coverage, forb canopy coverage, litter coverage, litter depth, and % bare ground. Within 50-, 200-, and 400-m concentric circles around nest sites we characterized landscape context using measures of patch richness, patch diversity, and interspersion/juxtaposition indices, and habitat specific measures of patch density, patch shape index, edge density, and % of landscape. We used year-specific harmonic mean utilization distributions of radiomarked raccoons to construct cumulative raccoon utilization distributions to measure intensity of space use by an important bobwhite nest predator. We used logistic regression on nest fate (hatched/failed) to develop predictive models of nest success as a function of micro-habitat, macro-habitat, and predator space-use. We constructed a set of candidate models that hypothesized nest fate as a function of micro-habitat, macro-habitat, predator space-use, micro and macro habitat, microhabitat and predator space use, macrohabitat and predator space use, and a global model that included all 3 groups of predictor variables. We used information theoretic approaches for model selection and inference.

Habitat Use by Five Turtle Species in the Middle Mississippi River

Abstract Turtles face unique conservation challenges in modern modified river systems. Despite their ecological importance, gaps in knowledge still exist that may hinder their conservation. Turtle by-catch data from the US Army Corps of Engineers' Long-Term Resource Monitoring Program were analyzed for 5 turtle species (false map turtle, Graptemys pseudogeographica; red-eared slider, Trachemys scripta; common snapping turtle, Chelydra serpentina; smooth softshell turtle, Apalone mutica; and spiny softshell turtle, Apalone spinifera) to better understand macrohabitat and mesohabitat use. These species demonstrated differences in habitat use between various macrohabitats, substrata, velocity classes, and depth classes. Common snapping turtles and spiny softshell turtles were captured most often in tributaries, whereas red-eared sliders were captured most often in tributaries and closed side channels. Smooth softshell turtles used open side channels and unstructured main-channel borders most often. False map...

Age- and sex-specific variations in microhabitat and macrohabitat use in a territorial lizard

Animals should select microhabitats with features that enhance fitness. However, the fitness benefits of different habitats may vary across ages and between sexes. By quantifying microhabitat choice in relation to age or sex, as well as the specific fitness consequences of habitat selection, we can better understand the factors that shape the way organisms distribute themselves across landscapes. Studies of Anolis lizards have provided critical insights into population and community structure, but most studies have focused on interspecific variation in habitat use, rather than intraspecific patterns. We quantified habitat use of Anolis sagrei at two scales (microhabitat and macrohabitat) for males and females of two distinct age classes (juvenile vs adult). We show that age, sex, size, and macrohabitat have significant effects on how A. sagrei utilize available microhabitat and that age, sex, size, and season influence macrohabitat use. In addition, large individuals of both age classes had increased survival during the breeding season. However, body size did not influence overwinter survival, but lizards that used relatively low perches had increased overwinter survival. Overall, this study demonstrates that the complex variation in habitat use by A. sagrei is explained by interactions among age, sex, size, season, and habitat scale. Habitat choice behaviors can have important effects on fitness, yet optimal habitat may vary across ages and between sexes. In this paper, we quantified microhabitat and macrohabitat use of the brown anole lizard (Anolis sagrei) and subsequently estimated selection on these behaviors via mark recapture. We show that the complex variation in habitat use by A. sagrei is explained by interactions among age, sex, size, season, and habitat scale. In addition, body size influenced survival of both age classes during the breeding season but not over winter. However, lizards that used relatively low perches had increased overwinter survival. These findings provide new insights into the factors that shape the way these organisms distribute themselves across landscapes and provide a rare assessment of selection on behavioral traits.

Analysis of movement patterns and macrohabitat use in Hermann’s tortoises (Testudo hermanni hermanni, Gmelin 1789) reintroduced in a coastal area dominated by pinewood in eastern Spain

The Hermann’s tortoise is a strictly European species found mostly in areas with Mediterranean and sub-Mediterranean climes and, especially the subspecies T. hermanni hermanni, has to deal with various threats which reduced its geographic distribution to only a few isolated populations. Thus, with the objective of recovering natural populations of the species, numerous reintroduction projects are being carried out throughout its historical and prehistorical geographic distribution. The aim of our study is to evaluate the success of the T. hermanni reintroduction project carried out in the Albufera de Valencia Natural Park since 2011, through the analysis of movements, home range sizes and habitat use in a new environment. The recorded activity pattern presents two peaks, one in spring and another in August, and the hibernation period (from December to February) is the same as observed in other populations. We did not find significant differences in home range sizes between sexes, but a tight relation between home range sizes and body sizes with larger individuals having larger home ranges. This relation was not observed for core areas (Kernel at 50%). Considering the habitat use, we did not find differences between the groups of individuals we defined, but different types of habitats were used differently. “Scrub” was the most frequented (∼50%), followed by “dunes” (∼20%), “mallaes” (∼20%) and “forest” (&lt;20%). Our results can be used to improve the success of future reintroduction projects by directing ideal habitat, timing and carapace size of released Hermann’s tortoises.

Behaviour-Related Scalar Habitat Use by Cape Buffalo (Syncerus caffer caffer).

Studies of habitat use by animals must consider behavioural resource requirements at different scales, which could influence the functional value of different sites. Using Cape buffalo (Syncerus caffer caffer) in the Okavango Delta, Botswana, we tested the hypotheses that behaviour affected use between and within habitats, hereafter referred to as macro- and microhabitats, respectively. We fitted GPS-enabled collars to fifteen buffalo and used the distances and turning angles between consecutive fixes to cluster the resulting data into resting, grazing, walking and relocating behaviours. Distance to water and six vegetation characteristic variables were recorded in sites used for each behaviour, except for relocating, which occurred too infrequently. We used multilevel binomial and multinomial logistic regressions to identify variables that characterised seasonally-preferred macrohabitats and microhabitats used for different behaviours. Our results showed that macrohabitat use was linked to behaviour, although this was least apparent during the rainy season, when resources were most abundant. Behaviour-related microhabitat use was less significant, but variation in forage characteristics could predict some behaviour within all macrohabitats. The variables predicting behaviour were not consistent, but resting and grazing sites were more readily identifiable than walking sites. These results highlight the significance of resting, as well as foraging, site availability in buffalo spatial processes. Our results emphasise the importance of considering several behaviours and scales in studies of habitat use to understand the links between environmental resources and animal behavioural and spatial ecology.

Seasonal dynamics of macrohabitat use by small mammals in the Okavango Delta, Botswana: implications for landscape‐level disturbance resilience

AbstractIn a changing climate, it is imperative to understand potential ecosystem resilience at all taxonomic levels. I compare seasonal small mammal utilization of woodlands (tree islands) and grasslands in the Okavango Delta, Botswana, to elucidate macrohabitat relationships and to test whether the two macrohabitats are similar in their ability to serve as a source of colonizers for the other after disturbance. Capture–mark–recapture data revealed that abundances for Dendromus mesomelas and Gerbilliscus leucogaster were higher in grasslands than tree islands, while Mus indutus abundance appeared higher in the grasslands in the dry season but roughly equal in the rainy season. Mastomys spp. and Steatomys pratensis maintained low levels in the grassland habitat throughout the year and experienced a population peak in the tree island habitat during the rainy season. There were no significant differences in sex ratio, mean mass or breeding condition. Dominance and total biomass were higher in the grasslands with the trend more pronounced in the rainy season. Terrestrial small mammals in the Okavango Delta employ differing strategies in macrohabitat selection and some exploit tree islands when herbaceous cover is present. Metacommunity dynamics exist for some species, and both habitats can serve as a source of colonizers under certain conditions.

Habitat selection by the viscacha rat (Octomys mimax, Rodentia: Octodontidae) in a spatially heterogeneous landscape

AbstractThe viscacha rat

Alligator Gar Movement and Macrohabitat Use in the Lower Trinity River, Texas

AbstractUsing acoustic telemetry, we characterized movements and macrohabitat use of 46 Alligator Gars Atractosteus spatula in the lower 180 km of the Trinity River, Texas. Although several Alligator Gars used over 100 km of the river, 83% of the tagged fish had linear home ranges less than 60 km during the 22 months of study. As a result, home ranges of fish that were tagged in different parts of the study area rarely overlapped. Home range size varied by season, with the smallest home ranges occurring in winter. Greatest movements occurred during the spawn (May–June) and postspawn (July–October) seasons, and movements were correlated with increasing water temperatures based on detections of tagged fish at fixed receiver stations. Tagged Alligator Gars were most often associated with main‐channel habitats when river stage was at base level and during small flood pulses (&lt;3‐m rise). When in the main channel, tagged Alligator Gars selected water that was deeper than the average within their home ranges. In contrast, during large flood pulses (≥3‐m rise), tagged fish were found in tributaries and inundated floodplains, regardless of season. Use of tailwater and estuarine macrohabitats was seasonal and limited to fish that had been tagged near those areas. Limited home ranges and observed spatial segregation of fish tagged near the upper and lower boundaries of the 180‐km study area suggest that the fish have access to critical habitats needed for reproduction, feeding, and migration within relatively small spatial scales. As such, Alligator Gars in the lower Trinity River do not appear to represent a single panmictic population, indicating that localized rather than regional management efforts would be appropriate.

Rodent diversity and habitat use in a protected area of Buenos Aires province, Argentina

Habitat use of rodents is associated to environmental variables, species requirements and biological interactions. The aim of this study was to analyse the macro and microhabitat use and spatial variation in the abundance of small sylvan rodents that inhabit Otamendi Natural Reserve, Argentina. We studied rodent communities in six habitats: riparian forest, Celtis tala forest, lowland grassland, salt marsh and two highland grasslands. We captured a total of 153 individual of Scapteromys aquaticus Thomas 1920, Akodon azarae Fischer 1829, Oxymycterus rufus Fischer 1814, Oligoryzomys flavescens Waterhouse 1837, Deltamys kempi Thomas 1917 and O. nigripes Olfers 1818 with a trapping effort of 3636 trap-nights. The species richness is maintained by the presence of different habitats that satisfy specific requirements from specialist species to more generalist species using differentially the reserve and forming communities of different specific composition in each habitat. A differential macrohabitat use by all species and a certain level of selectivity at microhabitat scale in individuals of two species were observed. This study shown that the diversity of environments of a Natural Reserves allows the maintenance of many sylvan species of small rodents; confirming the high ecological and conservational value of the reserves inside an urban region.

Spatial Dynamics of the Red-Tailed Hawk in the Luquillo Mountains of Puerto Rico

Abstract The Red-tailed Hawk (Buteo jamaicensis) is a top predator of upland ecosystems in the Greater Antilles. Little information exists on the ecology of the insular forms of this widely distributed species. We studied movements and resource use of the Red-tailed Hawk from 2000 to 2002 in the montane forests of northeastern Puerto Rico. We captured 32 and used 21 radio-marked Red-tailed Hawks to delineate home range, core area shifts, and macrohabitat use in the Luquillo Mountains. Red-tailed Hawks in the Luquillo Mountains frequently perched near the top of canopy emergent trees and were characterized by wide-ranging capabilities and extensive spatial overlap. Home range size averaged 5,022.6 ± 832.1 ha (305–11,288 ha) and core areas averaged 564.8 ± 90.7 ha (150–1,230 ha). This species had large mean weekly movements (3,286.2 ± 348.5 m) and a preference for roadside habitats. Our findings suggest fragmentation of contiguous forest outside protected areas in Puerto Rico may benefit the Red-tailed Hawk.

Summer food resource partitioning between four sympatric fish species in Central Spain (River Tormes)

Knowledge of food resource partitioning between sympatric fish species is critical for understanding the fish communities functioning. Four sympatric fish species (Salmo trutta, Pseudochondrostoma duriense, Squalius carolitertii and Barbus bocagei) were captured in August 2010 in the River Tormes (Ávila, Central Spain) in order to study food resource partitioning between fish species such us as a possible mechanism enabling their coexistence, using a fuzzy principal component analysis (FPCA). Diet comparison among species shows that detritus are present in P. duriense, B. bocagei and S. carolitertii, although in different occurrence, showing that these species present typically omnivorous feeding habits. Regarding prevalent food, in all species, benthic prey constituted the most important prey in abundance terms, and terrestrial invertebrates were only consumed by S. trutta, S. carolitertii and P. duriense. High overlap values (Schoener's index from 0.8 up to 1) were found, but it may not indicate competition, since species can adopt different strategies to overcome competence. Thus, prey traits analyses suggest that differences in macrohabitat use, drift behaviour of prey and prey size are important adaptive features that may reduce the inter-specific competition in the fish community and permit the food partitioning that allows coexistence.

Niche partitioning between sympatric rhesus macaques and Yunnan snub-nosed monkeys at Baimaxueshan Nature Reserve, China.

Here we provide a preliminary assessment of dietary and habitat requirements of two sympatric primate taxa, a "simple-stomached" and "complex-stomached" species (Rhinopithecus bieti Colobinae vs. Macaca mulatta Cercopithecinae), as a basis for illuminating how the two coexist. Of ca. 22 plant food species consumed by the macaques, at least 16 were also eaten by the snub-nosed monkeys. Both species showed a preference for fruits. While the snub-nosed monkeys did not utilize any resources associated with human communities, rhesus macaques did occasionally raid agricultural crops. The mean elevation of the snub-nosed monkey group was 3,218 m, while the mean elevation of the macaque group was 2,995 m. Macaques were also spotted on meadows whereas snub-nosed monkeys evidently avoided these. For both species, mixed deciduous broadleaf/conifer forest was the most frequently used ecotype, but whereas evergreen broadleaf forest (Cyclobalanopsis community) accounted for only 3% of the location records of the snub-nosed monkeys, it accounted for 36% of the location records of the macaques. Groups of the two species usually kept a considerable spatial distance from one another (mean 2.4 km). One close encounter and confrontation between groups of the two species resulted in the macaque group moving away. Our findings suggest that the coexistence of the two taxa is facilitated via differential macrohabitat use and spatial avoidance. Although divergent habitat-use strategies may reflect interspecific competition, they may also merely reflect different physiological or ecological requirements.