Niche separation between the maned wolf (Chrysocyon brachyurus), the crab-eating fox (Dusicyon thous) and the hoary fox (Dusicyon vetulus) in central Brazil

JÁCOMO, A.T.A.; SILVEIRA, L.; DINIZ-FILHO, J.A.F. 2004. Niche separation between the maned wolf (Chrysocyon brachyurus), the crab-eating fox (Dusicyon thous) and the hoary fox (Dusicyon vetulus) in central Brazil. Journal of Zoology, London 262:99-106. DOI:10.1017/S0952836903004473

Abstract. Four species of canids occur in the Cerrado of central Brazil. Three of them, the maned wolf Chrysocyon brachyurus, the crab-eating fox Dusicyon thous and the hoary fox Dusicyon vetulus, were studied in Emas National Park between 1996 and 1999 to investigate niche separation. The diet of the three species was studied to understand niche breadth and degree of overlap. Habitat and activity patterns were used as second and third ecological parameters to define niche dimensions, and were estimated using camera-trap data. The maned wolf is the largest species, weighing c. 21 kg, and is about three times larger than the crab-eating fox and six times larger than the hoary fox. The major ecological differences between the three species were found in their food niche and habitat use, where crab-eating fox presented higher differences from the hoary fox (Pianka’s index of niche overlap (O) = 0.405). Despite differences in niche breadth, habitat use between the hoary fox and the maned wolf were more similar, explaining their larger overlap, in comparison with habitat use by the crab-eating fox. Activity patterns among the species showed less divergence. The three species presented two activity peaks, one in the dusk–night period and another in the morning period. These data permit a better understanding of the ecological separation of the three Cerrado canids that enables their coexistence.

Niche partitioning among white-lipped peccaries (Tayassu pecari), collared peccaries (Pecari tajacu), and feral pigs (Sus scrofa)

DESBIEZ, A.L.J.; SANTOS, S.A.; KEUROGHLIAN, A.; BODMER, R.E. 2009. Niche partitioning among white-lipped peccaries (Tayassu pecari), collared peccaries (Pecari tajacu), and feral pigs (Sus scrofa). Journal of Mammlogy 90(1):119-128.

Abstract. The introduction of a species into an ecosystem with species already occupying a similar trophic level is predicted to lead to a high degree of niche overlap. The feral pig (Sus scrofa), one of the world’s worst invasive species, was introduced to the Pantanal about 200 years ago and is thought to compete with the native whitelipped peccary (Tayassu pecari) and collared peccary (Pecari tajacu). Resource partitioning between the 3 species was examined, including analysis of fruit items and plants in fecal samples as well as encounter rates in different habitats, to help generate hypotheses about competitive interactions among the species. Overlaps in food resources and habitat use between feral pigs and peccaries were found to be lower than expected. In fact, niche overlap as highest between the native species. Results indicate that currently, feral pigs are not a direct threat to the native peccaries in the study area. Differences in morphology and behavior indicate possible mechanisms of niche partitioning between the species. Feral pigs may, nevertheless, impact the wildlife community in other ways as predators of eggs, by destruction of vegetation through rooting, or by functioning as disease reservoirs. Cattle-ranching activities may favor feral pigs and the current anthropogenic changes in the landscape could lead to changes in competitive dynamics between feral pigs and native species.

Use of arboreal and terrestrial space by a small mammal community in a tropical rain forest in Borneo, Malaysia

WELLS, K. PFEIFFER, M.; LAKIM, M.B.; LINSENMAIR, K.E. 2004. Use of arboreal and terrestrial space by a small mammal community in a tropical rain forest in Borneo, Malaysia. Journal of Biogeography 31:641-652.

Abstract:
Aim: Small mammals were live-trapped in a primary rain forest to evaluate the relative distribution of species to each other and to microhabitat properties on the ground and in the canopy.
Location: Kinabalu National Park in Borneo, Sabah, Malaysia.
Methods: Seven trapping sessions were conducted along two grids with 31 trap points at distances of 20 m on the ground and in the lower canopy at an average height of 13.5 m.
Results: Species diversity and abundance of small mammals proved to be high: 20 species of the families Muridae, Sciuridae, Tupaiidae, Hystricidae, Viverridae and Lorisidae were trapped, with murids being dominant in both habitat layers. The terrestrial community was significantly more diverse with 16 captured species (Shannon–Wiener’s diversity index H'terr = 2.47), while 11 species were trapped in the canopy (H'arb = 1.59). The Whitehead’s rat, Maxomys whiteheadi, and the red spiny rat, Maxomys surifer, dominated the terrestrial community whereas the large pencil-tailed tree mouse, Chiropodomys major, was by far the most abundant species in the canopy. Other abundant species of the canopy community, the dark-tailed tree rat, Niviventer cremoriventer, and the lesser treeshrew, Tupaia minor, were also abundant on the ground, and there was no clear boundary between arboreal and terrestrial species occurrences.
Main Conclusions: As most species were not confined to specific microhabitats or habitat layers, species seemed to rely on resources not necessarily restricted to certain microhabitats or habitat layers, and separation of species probably resulted mainly from a species’ concentrated activity in a preferred microhabitat rather than from principal adaptations to certain habitats. Ecological segregation was stronger in the more diverse terrestrial community, though microhabitat selection was generally not sufficient to explain the co-occurrences of species and the variability between local species assemblages. Constraints on small mammal foraging efficiency in the three-dimensional more complex canopy may be responsible for the similarity of microhabitat use of all common arboreal species. Community composition was characterized by mobile species with low persistence rates, resulting in a high degree of variability in local species assemblages with similar turnover rates in both habitats.

Activity, habitat use, density, and reproductive biology of the crab-eating fox (Cerdocyon thous) and comparison with the pampas fox (Lycalopex gymnocercus) in a Restinga area in the southern Brazilian Atlantic Forest

FARIA-CORRÊA, M.; BALBUENO, R.A.; VIEIRA, E.M.; FREITAS, T.R.O. 2009. Activity, habitat use, density, and reproductive biology of the crab-eating fox (Cerdocyon thous) and comparison with the pampas fox (Lycalopex gymnocercus) in a Restinga area in the southern Brazilian Atlantic Forest. Mammalian Biology 74:220-229.

Abstract. The ecology and reproductive biology of the crab-eating fox (Cerdocyon thous) and the pampas fox (Lycalopex gymnocercus) were studied in Itapuã State Park, an Atlantic Forest fragment. In this study we describe their activity patterns (diel, lunar, and seasonal), reproductive period, density, spatial distribution, and habitat overlap. The crab-eating fox was more abundant than the pampas fox, occurring in all types of habitats and overlapping with the pampas fox only in the southern portion of the study area, covered by open vegetation. Both canid species presented nocturnal habits and C. thous showed no significant differences in activity among lunar phases or else year season. The density of C. thous was estimated to be 0.78 ind/km². The crab-eating fox reproduced once a year, generating pups during spring (October to December). In comparison with C. thous populations from lower-latitude regions the relatively low density and one reproductive event per year that we observed are probably related to a colder climate, shorter photoperiod, and shortage of food resources in the winter, characteristic of southern Brazil.

Effects of intraguild predation: evaluating resource competition between two canid species with apparent niche separation

KOZLOWSKI, A.J.; GESE, E.M.; ARJO, W.M. 2012. Effects of intraguild predation: evaluating resource competition between two canid species with apparent niche separation. International Journal of Ecology, v. 2012, Article ID 629246, 12 pages. doi: 10.1155/2012/629246.

Abstract. Many studies determine which habitat components are important to animals and the extent their use may overlap with competitive species. However, such studies are often undertaken after populations are in decline or under interspecific stress. Since habitat selection is not independent of interspecific stress, quantifying an animal’s current landscape use could be misleading if the species distribution is suboptimal. We present an alternative approach by modeling the predicted distributions of two sympatric species on the landscape using dietary preferences and prey distribution.We compared the observed habitat use of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) against their predicted distribution. Data included locations of kit foxes and coyotes, carnivore scat transects, and seasonal prey surveys. Although habitats demonstrated heterogeneity with respect to prey resources, only coyotes showed habitat use designed to maximize access to prey. In contrast, kit foxes used habitats which did not align closely with prey resources. Instead, habitat use by kit foxes represented spatial and behavioral strategies designed to minimize spatial overlap with coyotes while maximizing access to resources. Data on the distribution of prey, their dietary importance, and the species-specific disparities between predicted and observed habitat distributions supports a mechanism by which kit fox distribution is derived from intense competitive interactions with coyotes.

Microhabitats in a forest-floor small mammal fauna

DUESER, R.D.; SHUGART JR., H.H. 1978. Microhabitats in a forest-floor small mammal fauna. Ecology 59(1):89-98.

Abstract. This study examines microhabitat  configurations for 3 small mammal species occupying second-growth mesic forest on Walker Branch Watershed in eastern Tennessee. Small mammal populations were sampled in oak-hickory, chestnut oak and pine forest types, with three 0.36-ha live-trapping grids per forest type. There were 255 total captures for 4 forest-floor species during 9,696 trap-nights between 1 May and 16 August 1973. These captures included 2% Blarina brevicauda, 66% Peromyscus  leucopus,  5% Ochrotomys  nuttalli  and 27% Tamias striatus.  Blarina was  captured most frequently in the pine forest type, Peromyscus and Tamias most frequently in the oak-hickory, and Ochrotomys exclusively in the pine. Twenty-nine variables describing proximate habitat structure were measured at each small mammal capture site. There were significant overall species differences on  18 of these  variables. A subset of variables was identified for each of the 3 most frequently observed species, consisting of only the variables of particular significance for distinguishing the capture sites of that species from those of the other species collectively. Discriminant analysis of these few variables both described the average microhabitat configuration for a species and indicated the relative importance of each variable for characterizing or describing that configuration, subject to the assumptions of the analysis. The observed differences between species in microhabitat  configuration are consistent with both the composition by  forest type of  each  species  sample and the  literature information for  each species. Microhabitat segregation among these species is discussed with reference to recent theories of habitat selection, ecological specialization and resource partitioning in equilibrium faunas.

A new study method of microhabitat structure of small mammals

CERQUEIRA, R.; FREITAS, S.R. 1999. A new study method of microhabitat structure of small mammals. Revista Brasileira de Biologia 59(2):219-223.

Abstract. The variables in habitat studies are usually transformed in such a way that they become abstractions and intuition is lost. We tested a new method for the analysis of habitat using data collected in a grid laid at the “restinga de Maricá”, in Rio de Janeiro State, Brazil. Thirty-seven microhabitat variables were measured at each trap station. We assume that these variables characterize the microhabitat structure at the moment when measurements were taken. The data are transformed in 3 ways: (1) the averages of the measured variables were calculated, as usual in habitat studies; (2) the data are transformed in densities per area in square meters without reduction in the number of variables; and (3) we calculated the natural logarithms of the data thus transformed. The 3 sets were analised through discriminant analysis. The logarithms of densities were the most efficient kind of transformation. This transformation resulted in a significance of p = 0.0001 with 39.72% of variance in the 1st discriminant function and of p = 0.0426 with 31.45% of variance in the 2nd function, and 84.62% of groups correctly classified. We obtained better classification results than previous similar works and we kept the intuition through the data analysis.

Arboreal walking performance in seven didelphid marsupials as an aspect of their fundamental niche

DELCIELLOS, A.C.; VIEIRA, M.V. 2006. Arboreal walking performance in seven didelphid marsupials as an aspect of their fundamental niche. Austral Ecology 31:449-457.

Abstract. Species of didelphid marsupials (Didelphimorphia, Didelphidae) differ in their use of the forest strata, but it is not clear whether these differences are in fundamental or realized niches. The fundamental niche of seven species of didelphids (Caluromys philander, Didelphis aurita, Gracilinanus microtarsus, Marmosops incanus, Metachirus nudicaudatus, Micoureus demerarae, and Philander frenatus) was compared using their performance in arboreal walking. The association between performance and vertical use of the forest also was tested accounting for phylogenetic and allometric effects. Tests consisted of making the animal cross five 3 m long horizontal supports of different diameters, 1 m from the ground. The cycle of maximum speed was chosen to measure stride length, frequency and velocity. Arboreal species performed better than the terrestrial ones, but a major part of the variation in stride length (70.95%) and stride frequency (88.10%) was associated with body size. Part of the variation in stride length independent of body size (14.05%) was associated with the degree of vertical use of the forest, after phylogenetic effects were accounted for. Fundamental niches of six of the seven species were discriminated with the performance tests used. Discrepancies between the realized and fundamental niches can be inferred for two of these species, D. aurita and P. frenatus.

Niche overlap and resource partitioning between two sympatric fox species in southern Brazil

VIEIRA, E.M.; PORT, D. 2007. Niche overlap and resource partitioning between two sympatric fox species in southern Brazil. Journal of Zoology, London 272:57-63.

Abstract. Mechanisms that favour the co-occurrence of morphologically and ecologically similar species in South America are potentially relevant, because two or more species often occur in sympatry. In the present study, we investigated possible mechanisms of resource partitioning between two sympatric species of foxes, the crab-eating fox Cerdocyon thous and the pampas fox Pseudalopex gymnocercus, in the National Park of Aparados da Serra in southern Brazil (29º10'S, 50º05'W). We considered three main niche dimensions – habitat, diet and time – and evaluated the overlap between the two species in these dimensions. We conducted the study from June 2000 to October 2001 in an area composed of open grasslands and Araucaria forests. We studied the foxes by using a combination of scat analysis and direct observation. A comparison of their diet indicated that it was very similar for both species in all seasons (Pianka’s indexes ranging from 0.920 to 0.957). The most common food item for both species of foxes was rodents, followed by coleopterans, birds and plant remains (seeds and fruits). As expected by the nichecomplementarity hypothesis, we detected differences along other niche axes. Pseudalopex gymnocercus seemed to occur only in open areas, including grasslands and dirt roads, whereas C. thous was more generalist in habitat use, occurring both inside and at the edge of forests. However, both fox species were common in grassland habitats, where they might compete for resources. The differences were more marked for activity time, with the crab-eating fox being significantly more nocturnal (circular mean of time of sighting=23:39 h, SE=56 min) than the pampas fox (circular mean=19:56 h, SE=64 min; Watson’s F=6.06, P=0.02). We suggest that the larger C. thous could be limiting the activity of P. gymnocercus by interference competition.

Padrão de atividade de Akodon montensis e Oryzomys russatus na Reserva Volta Velha, Santa Catarina, sul do Brasil

GRAIPEL, M.E.; MILLER, P.R.M.; GLOCK, L. 2003. Padrão de atividade de Akodon montensis e Oryzomys russatus na Reserva Volta Velha, Santa Catarina, sul do Brasil. Mastozoología Neotropical 10(2):255-260.

Resumo. São apresentadas informações preliminares sobre o padrão de atividade de duas espécies de roedores em uma área de Floresta Atlântica do sul do Brasil. Sistemas com relógios analógicos foram usados para determinar o horário de captura de pequenos mamíferos e um modelo exponencial foi usado para transformar o número de capturas no padrão de atividade de cada espécie. Foram capturadas três espécies de roedores e três de marsupiais em armadilhas com estes sistemas, porém, analisou-se apenas o padrão de atividade das duas espécies mais abundantes, A. montensis e O. russatus. Os padrões de atividade destas duas espécies foram significativamente diferentes (p < 0,05). A primeira espécie foi caracterizada como possuindo padrão de atividade bicrepuscular enquanto a segunda como nortuna. Os padrões de atividade registrados para estas espécies simpátricas podem ter um importante papel na partição de recursos.

Consumo de pequenos mamíferos por canídeos simpátricos do sul do Brasil: sobreposição de nichos e seleção de presas

ABREU, M.S.L.; WIELICZKO, A.R.; MESQUITA, A.; VIEIRA, E.M. 2010. Consumo de pequenos mamíferos por canídeos simpátricos do sul do Brasil: sobreposição de nichos e seleção de presas. Neotropical Biology and Conservation 5(1):16-23.


Resumo. O graxaim-do-mato (Cerdocyon thous) e o graxaim-do-campo (Lycalopex gymnocercus) são dois canídeos endêmicos da região Neotropical que ocorrem em simpatria no estado do Rio Grande do Sul, sul do Brasil. Estudos anteriores indicaram que ambas as espécies se alimentam principalmente de pequenos mamíferos, sem diferenças detectáveis em suas dietas, ao menos quando não há a determinação dos gêneros de mamíferos consumidos. No presente estudo, o objetivo foi avaliar a real similaridade na composição da dieta desses animais, procurando identifi car os gêneros de pequenos mamíferos consumidos. Além disso, investigaram-se possíveis padrões de seleção de presas pelos canídeos. Para isso, foram analisadas 222 amostras fecais coletadas no Parque Nacional dos Aparados da Serra (RS) entre os anos de 2000 e 2005, identificando a espécie de canídeo por meio de análise de pelos. Também foi realizado, entre 2000 e 2002, um levantamento de pequenos mamíferos ocorrentes na área, mediante a utilização de técnicas de captura, marcação e recaptura. Os resultados indicaram que as duas espécies de canídeos não diferem signifi cativamente em relação aos gêneros de pequenos mamíferos consumidos. Além disso, verifi cou-se que as duas espécies parecem preferir se alimentar de roedores do gênero Akodon. Por outro lado, esses canídeos predaram as espécies do gênero Oligoryzomys em grau menor do que o esperado. Os resultados obtidos sugerem que a similaridade de dieta entre os canídeos estudados é muito alta, mesmo sob uma análise mais refinada dos itens consumidos por esses animais. Tais resultados fundamentam a hipótese de que a separação de nicho entre C. thous e L. gymnocercus deve ocorrer por meio de fatores diferentes da dieta, como hábitat ou horário de atividade.