Water absorption of the fur and swimming behaviour of semiaquatic and terrestrial oryzomine rodents

SANTORI, R.T.; VIEIRA, M.V.; ROCHA-BARBOSA, O.; MAGNAN-NETO, J.A.; GOBBI, N. 2008. Water absorption of the fur and swimming behaviour of semiaquatic and terrestrial oryzomine rodents. Journal of Mammalogy 89(5):1152-1161.

Abstract. Locomotion in land and water requires different adaptations, hence semiaquatic mammals must deal with conflicting demands of the 2 environments. Semiaquatic rodents of the tribe Oryzomyini are considered semiaquatic mostly based on habitat use and morphology, but locomotory specializations were not yet determined for most species of the group. We compared water absorption of the fur and swimming behavior between 2 species of oryzomyine water rats (Nectomys) and 2 terrestrial species of Cerradomys. We used adult rodents captured in the wild but acclimated to laboratory conditions. Water absorption rate was determined by the relative increase in body mass after a 5-min swimming session. Animals were videotaped swimming in an aquarium to determine gaits, body posture, maneuverability, and speed. Water absorption rate was significantly lower in semiaquatic species, with no significant difference between sexes. Bipedal paddling was the more frequently used gait by all 4 species, but semiaquatic species were faster and maintained a more hydrodynamic body posture, with a short gliding phase during the gait cycle. Only semiaquatic species were capable of floating effortlessly, and used the swimming bound, a gait similar to the half bound of terrestrial locomotion. Submerged swimming was the fastest swimming gait, used by 1 terrestrial and 1 semiaquatic species. The better performance during bipedal swimming of semiaquatic water rats was related to the improved buoyancy provided by reduced water absorption of the fur, which seemed to represent an important adaptation to move in the water without compromising locomotion on land.

Fotos: Armadilha Fotográfica

Esta é uma das armadilhas fotográficas que tenho, da Tigrinus®, modelo Convencional 6.0C. As armadilhas fotográficas consistem em aparelhos fotográficos (digitais ou analógicos) acoplados a um sensor de movimento. Toda vez que algum animal passa em frente à armadilha, o sensor ativa e a armadilha obtêm o registro fotográfico.  Geralmente são presas em árvores, com a lente e o sensor voltados para uma trilha. Pode-se usar isca para atrair os animais ou não. Maiores informações no site da Trigrinus (http://www.tigrinus.com.br/).
Fotógrafo: Maury S.L. Abreu
Contato: maury.abreu@gmail.com

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.

Fotos: Myotis cf. nigricans

Não sou muito bom com morcegos, mas este parece um Myotis nigricans. Foi capturado em rede de neblina, perto das 19:00 (foi a hora em que fomos revisar a rede).
Espécie: Myotis cf. nigricans.
Fotógrafo: Paulo T. Sarti.
Contato: paulo.tomasi@gmail.com

Distribution extension and sympatric occurrence of Gracilinanus agilis and G. microtarsus (Didelphimorphia, Didelphidae), with cytogenetic notes

GEISE, L.; ASTÚA, D. 2009. Distribution extension and sympatric occurrence of Gracilinanus agilis and G. microtarsus (Didelphimorphia, Didelphidae), with cytogenetic notes. Biota Neotropica 9(4):269-276.

Abstract. Gracilinanus microtarsus, from the Atlantic Forest and G. agilis, widespread in central Brazil in the Cerrado and in the northeastern Caatinga are two small Neotropical arboreal opossum species not frequently recorded in simpatry. Here we report eight G. agilis specimens from three localities and 17 G. microtarsus, from 10 localities, all in Minas Gerais, Rio de Janeiro and Bahia states. Species proper identification followed diagnostic characters as appearance of dorsum pelage, ocular-mark, ears and tail lengths and size proportion of the posteromedial vacuities in cranium. Chromosomes in metaphases of five specimens were obtained for both species. Our records extend the previous known geographical distribution of G. microtarsus to Chapada Diamantina, in Bahia State and report the occurrence of both species in simpatry. G. microtarsus, in coastal area, was captured in dense ombrophilous and in semideciduous forests, in deciduous seasonal forest and Cerradão in Chapada Diamantina. G. agilis was recorded in gallery forests of Cerrado and very green and dense bush formation of Caatinga. Autosomal complement showed the same diploid and autosomal number already described for both species (2n = 14, NA = 24). Measurements are according to those given in literature and pelage characteristics were useful for the correct species identification. Here we report both G. agilis, described to be endemic to the Cerrado/Caatinga, in opposite to G. microtarsus, considered to be endemic to Atlantic Forest occurring in simpatry in two localities of the Cerrado. Such results indicates that long term trapping effort are necessary to a better definition of species taxonomy, distribution patterns along time and comprehensive understanding how anthropic environmental changes can be interfering in their evolutionary history.

VI Congresso Brasileiro de Mastozoologia - Quarta Circular

Já está no ar o site do VI Congresso Brasileiro de Mastozoologia: http://www.eventus.com.br/sbmz2012/index.html.

Para quem ainda não sabe o VICBMz ocorrerá em Corumbá, MS, entre 25 e 29 de junho de 2012, no Centro de Convenções do Pantanal (mapa no site). A programação já está disponível no site, mas ainda não há confirmação das mesas redondas e mini-cursos.

The question of scale in threat analysis: a case study with Brazilian mammals

GRELLE, C.E.V.; FONSECA, G.A.B.; FONSECA, M.T.; COSTA, L.P. 1999. The question of scale in threat analysis: a case study with Brazilian mammals. Animal Conservation 2:149-152.

Abstract. Rates of biodiversity loss are clearly associated with a reduction in the extent of original habitat. The most frequently used method to derive such estimates comes from the well-known species–area relationship. We explored the relationship between habitat loss and area for the Brazilian mammal fauna on a biome level (Atlantic Forest, Cerrado and the Brazilian portion of the Amazon basin), as well as on a smaller regional scale (the Rio Doce Valley of the Atlantic Forest). Habitat loss overestimates the number of threatened species when the entire species pool is considered (endemics and wideranging species). Restricting the analyses to the endemic species, the predicted extinction as a function of habitat loss in the Atlantic Forest and in the Cerrado is found to be greater than the number of taxa actually listed as threatened. This relation is reversed in the Amazon. When considering only the localized species pool for the Rio Doce Valley region of the Atlantic Forest, the function accurately predicts the number of extinctions resulting from habitat loss. We suggest that there is both theoretical and empirical evidence to suggest that threat analysis will generate more accurate estimates of species loss when conducted on a more local scale, particularly for the fauna of non-insular, continental regions. Furthermore, other phenomena affecting the likelihood of extinction of certain groups of species, such as hunting, need to be taken into account in order to better understand the dynamics of biodiversity loss.

Spatial scale, species diversity, and habitat structure: small mammals in Australian Tropical Rain Forest

WILLIAMS, S.E.; MARSH, H.; WINTER, J. 2002. Spatial scale, species diversity, and habitat structure: small mammals in Australian Tropical Rain Forest. Ecology 83(5):1317-1329.

Abstract. We investigated patterns of mammal assemblage structure on the Atherton Tableland in the Wet Tropics biogeographic region of northeastern Australia. We used live trapping and quantitative estimates of stratified vegetation density to examine the relationships between the structure of the mammal assemblage and habitat structure over three nested spatial scales across a natural vegetation gradient from rain forest to dry, open forest. The narrow transition zone enabled us to examine the relationships between mammal assemblage structure and habitat structure while minimizing the confounding effects of distance, climate, and biogeographic history. The structure of the mammal assemblages was closely related to vegetation structure across and within habitats, and over all spatial scales examined. Vegetation complexity and heterogeneity both influenced assemblage structure, but the relationships varied with spatial scale. Species richness was highest in the open forest and decreased across the gradient into the rain forest. Point diversity was only weakly explained by vegetation structure, whereas .80% of the variation in species richness at the local scale could be explained by vegetation structure. Local-scale species richness of ground-dwelling mammals was mostly a product of the spatial variability in assemblage structure (b diversity), which was associated with the spatial variability in vegetation structure. Local-scale habitat heterogeneity thus promoted local-scale species richness via the close ecological interaction between mammals and habitat structure. The multiscale approach used here, and the nesting of spatial variability in within-habitat vegetation structure, enabled us to demonstrate the scale-dependent effects of spatial habitat heterogeneity and complexity on the structure and diversity of the small-mammal assemblage.