Diogo Loretto

THE EFFECTS OF REPRODUCTIVE AND CLIMATIC SEASONS ON MOVEMENTS IN THE BLACK-EARED OPOSSUM (DIDELPHIS AURITA WIED-NEUWIED, 1826)

Abstract Resource availability and reproductive activity can exert contrasting demands on movements of promiscuous or polygynous mammals. Movements of the black-eared opossum (Didelphis aurita) vary seasonally in the Atlantic Rainforest of Brazil, so our objectives were to test the relative importance of reproductive activity and resource abundance on movement areas and intensity of use by opossums. We used a spool-and-line device to map the path of individuals, to estimate daily movement areas, and to measure intensity of habitat use. Two models were compared by generalized linear models, by grouping movements by reproductive or climatic season. Males used larger areas less intensively in the breeding season, whereas the movement of females did not differ between breeding and nonbreeding season. Differences between movements of females were significant only when grouped by climatic seasons, with females using larger areas less intensively in the dry season. Movements of females were determined by resource availability, whereas movements of males were determined by reproductive season.

Comparing the effectiveness of tracking methods for medium to large-sized mammals of Pantanal

Most Neotropical mammals are not easily observed in their habitats, and few studies have been conducted to compare the performance of methods designed to register their tracks. We compared the effectiveness of track registry between sand plots and two tracking methods that use artificial materials to record tracks: the sooted paper, and the plastic board methods. The latter is described here for the first time. From 2002 to 2005, we conducted two experiments in three study sites in the Pantanal region of Brazil. We compared the artificial methods with the sand plot by registering track presence/absence, the number of identifiable tracks, and the total number of tracks (identifiable and unrecognizable) in each tracking plot. Individuals avoided artificial tracking plots either by not stepping on them or by doing it fewer times than on the sand plots. The use of artificial materials to register mammal tracks resulted in underestimates that are especially relevant to short-term ecological studies. We recommend the use of the traditional sand plot method whenever possible and the development of detailed studies on the efficiency of artificial methods under a variety of environmental conditions and time lengths. Despite their relatively lower efficiency, we believe that artificial methods are useful under specific conditions and may be more efficient if used in more comprehensive sampling efforts.

Edentates of the Saracá-Taquera National Forest, Pará, Brazil

Introduction The order Xenarthra contains 31 living species distributed in 13 genera, all but one of which are restricted to the Neotropics (Wetzel, 1982; Fonseca and Aguiar, 2004). Nineteen of these species, distributed in ten genera and four families, can be found in Brazil (Fonseca et al., 1996). This order embodies a substantial amount of the evolutionary history of mammals (Fonseca, 2001) and is potentially a basal offshoot of the earliest placental mammals (Murphy et al., 2001). Despite their ecological importance and the need to highlight them in conservation programs, xenarthrans are virtually unstudied when compared with other, better-known mammals (Fonseca, 2001).

Artificial nests as an alternative to studies of arboreal small mammal populations: a five-year study in the Atlantic Forest, Brazil

Despite the great diversity of Brazilian Atlantic forest small mammals, natural history of most species is unknown due to their cryptic and nocturnal habits, but also due to the inadequacy of methods to capture some species, especially those of arboreal habits. A new technique, based on the use of artificial nests (AN) to record arboreal marsupials, is presented. Artificial nests were combined with traditional live traps to study the population ecology of four didelphid marsupial species. After 62 months of monitoring, 119 individuals were recorded 243 times (total success = 5.2%). Only 26 individuals (22%) were recorded by both AN and live trap methods, and two of the four species were never captured by live traps, only by AN. Live traps alone would have provided biased data of the structure of small mammal assemblages, creating artificial tendencies in population dynamics of many species. Detectability estimates based on mark-recapture data could correct bias resulting from the use only live traps, but these estimates require that at least some individuals of each age class or stage are captured. Only the combination of AN and live traps can produce more accurate data on population dynamics and assemblage structure. This study demonstrates that artificial nests represent a new method that should be combined with live traps in studies of small mammal assemblages and populations.

Defense behavior and nest architecture of Metachirus nudicaudatus Desmarest, 1817 (Marsupialia, Didelphidae)

The behavior repertory of didelphid marsupials remains mostly unknown, not surprisingly considering their nocturnal habits. Most observations come from individuals in captivity of Monodelphis domestica, and of species of Didelphis (review in Kimble 1997). Based on these species, nest architecture has been briefly described in the context of protection from environmental extremes, and safety against predators (Kimble 1997). However, didelphids differ in their usage of the forest strata (Charles-Dominique et al. 1981; Cunha & Vieira 2002), in microhabitat preference (Freitas et al. 1997), and even in food habits (Santori et al. 1995a, b). Different forest strata, habitats and microhabitats likely differ in appropriate sites and building material for nest construction. Hence, didelphid species might differ in nest architecture, and possess unknown associated behaviors and activities within the nest. The brown-eyed opossum, Metachirus nudicaudatus, is the most morphologically cursorial didelphid (sensu Szalay 1990). It rarely leaves the forest floor (Miles et al. 1981; Julien-Laferrière 1991; Fleck and Harder 1995; Cunha & Vieira 2002) where it builds its nests (Miles et al. 1981). It is more insectivorous compared to other didelphids (Santori et al. 1995b; Freitas et al. 1997) and has large exploratory movements or home ranges (Gentile & Cerqueira 1995). Individuals of M. nudicaudatus have been tracked as part of another study on population ecology of small mammals. Their nest has been found occasionally, when we could observe a unique defense behavior by the occupants. Here, we describe the nest architecture and the defense behavior of M. nudicaudatus in a disturbed site of the Atlantic rainforest of Brazil. The study area was located on the edge of the Serra dos Órgãos National Park, State of Rio de Janeiro, Brazil, in the municipality of Guapimirim, locally known as Garrafão (22°28’28”S, 49°59’86”W). Animals were captured from April 1997 to June 2002 in three 0,64 ha trapping grids located at different altitudes as part of a Diogo LORETTO Emiliano RAMALHO Marcus Vinicius VIEIRA Laboratorio de Vertebrados, Departamento de Ecologia Unversidade Federal do Rio de Janeiro CP 68020 Rio de Janeiro, RJ–21941 590 (Brazil) diogoloretto@bol.com.br mvvieira@biologia.ufrj.br