First evidence of gregarious denning in opossums (Didelphimorphia,Didelphidae), with notes on their social behaviour

The Didelphidae are considered solitary opossums with few social interactions, usually limited to mating-related or mother–pouch young interactions. Anecdotal reports suggest that additional interactions occur, including den sharing by a few individuals, usually siblings. Here, we report novel observations that indicate opossums are more social than previously thought. These include nest sharing by males and females of Marmosa paraguayana, Gracilinanus microtarsus and Marmosops incanus prior to the onset of the breeding season and without signs of sexual activity; this is taken to indicate early pair-bonding matching and cooperative nest building. We also recorded den sharing among recently weaned siblings of Didelphis aurita and Caluromys philander. In addition, we observed 13 individuals of Didelphis albiventris representing three age classes resting without agonistic interactions in a communal den. These are the first reports of gregarious behaviour involving so many individuals, which are either unrelated or represent siblings from at least two litters, already weaned, sharing the same den with three adults. Sociality in opossums is probably more complex than previously established, and field experimental designs combining the use of artificial nests with camera traps or telemetry may help to gauge the frequency and extent of these phenomena.     

Distribution of histoplasma capsulatum in Amazonian wildlife

In a survey of 296 sylvatic animals captured from virgin forests in the north-eastern and south-western Amazon of Brazil, Histoplasma capsulatum was isolated, via the indirect hamster inoculation method, from the liver and spleen of four common opossums Didelphis marsupialis and two pacas Agouti paca. The infected animals did not show any clinical symptoms or histopathology. The known Amazonian mammalian species with natural histoplasmosis now total five, the previously reported species being the spiny rat Proechimys guyannensis, the two-toed sloth Choloepus didactylus and the nine-banded armadillo Dasypus novemcinctus.     

Coccidial dispersion across New World marsupials: Klossiella tejerai Scorza,Torrealba & Dagert, 1957 (Apicomplexa: Adeleorina) from the Brazilian common opossum Didelphis aurita (Wied-Neuwied) (Mammalia: Didelphimorphia)

Klossiella tejerai Scorza, Torrealba & Dagert, 1957 is a primitive coccidian parasite reported from the New World marsupials Didelphis marsupialis (Linnaeus) and Marmosa demerarae (Thomas). The current work describes K. tejerai from the Brazilian common opossum Didelphis aurita (Wied-Neuwied) in Southeastern Brazil, evidencing the coccidial dispersion across opossums of the same family. The sporocysts recovered from urine samples were ellipsoidal, 20.4 × 12.7 µm, with sporocyst residuum composed of scattered spherules and c.13 sporozoites per sporocyst, with refractile bodies and nucleus. Macrogametes, microgametes, sporonts, sporoblasts/sporocysts were identified within parasitophorous vacuoles of epithelial cells located near the renal corticomedullary junction. Didelphis marsupialis should not have transmitted K. tejerai to D. aurita because they are not sympatric; however M. demerarae is sympatric with D. marsupialis and D. aurita. Therefore, D. aurita becomes the third host species for K. tejerai in South America.     

Host-parasite association between <Emphasis Type="Italic">Didelphis albiventris</Emphasis> (Didelphimorphia: Didelphidae) and <Emphasis Type="Italic">Ixodes loricatus</Emphasis> (Acari: Ixodidae) in their southern ranges

The parasitism of Ixodes loricatus Neumann on white-eared opposum, Didelphis albiventris Lund, was analysed in the southern ranges of both. In central Argentina, 118 wild opossums were captured from 2005 to 2012. Adults of I. loricatus were collected (prevalence?=?66.1%, mean?=?7.03, median?=?4), but no immature stage. Tick infestation was not affected by sex (p?=?0.27) or age (p?=?0.37) of hosts. In line with previous studies about seasonality of larvae and nymphs of I. loricatus, adult tick infestation showed no seasonal trend. This lack of seasonal pattern of infestation for all parasitic stages of I. loricatus may indicate a life cycle governed by nidicolous behaviour, in such a way that this habit would contribute to minimize the influence of external environmental variables. The tick sex ratio was female biased, with two females per one male (p?=?0.002). The absence of I. loricatus immatures on D. albiventris suggests that in the study region there is clear segregation of immatures in rodents and adults in marsupials.     

Microhabitat use by Rhipidomys mastacalis and Marmosops incanus (Mammalia) in a restinga areas in north‐eastern Brazil

Differences in the patterns of microhabitat use by small mammals have been largely related to the coexistence process of the species. The present study analyses how the marsupial Marmosops incanus and the rodent Rhipidomys mastacalis use the microhabitat in a areas of arboreal restinga in the Brazilian north‐east. Through capture‐marking‐recapture, sampling was performed monthly from September 2017 to August 2018 using Sherman traps and pitfall. Six microhabitat variables were measured at all capture stations. The use of vertical strata (ground and understory) was compared using a chi‐square test, and associations of species abundances with microhabitat characteristics were explored using redundancy analysis. The results indicate that the species use the vertical strata at different frequencies, with R. mastacalis found exclusively in the understory and M. incanus found more in the understory than in the ground. The variation in the abundance of the species was associated with the density of the understory, with an increase in M. incanus abundance and a decrease in R. mastacalis. Differences in the patterns found for these species in other environments indicate plasticity in relation to the use of vertical strata and the approaches used suggest that the differential use of the arboreal stratum can be a facilitator in the process of coexistence in areas of restinga. Abstract in Portuguese is available with online material.     

A methodological approach to assess the small mammal community diversity in the temperate rainforest of Patagonia

Assessing small mammal diversity is a common procedure, which usually employs widespread standard techniques, for gathering information for a wide range of studies. Traditional methods, however, may be biased against capturing arboreal marsupials, such as Dromiciops gliroides, an endemic marsupial currently considered a rare species in the Patagonian temperate rainforest due to the low abundances reported previously. I tested a new capturing methodology to assess the small mammal diversity of an old-growth forest in Patagonia, based on a randomized and balanced design, which incorporated a combination of different trap types, bait types, and placement heights. The proposed methodology included four trap types (two for live-capturing: wire-mesh and Sherman traps, and two sign-recording traps for tracks and hair), two types of bait (banana and rolled oats), and two trap placements (ground level and 1.5–2.5 m above the ground). Trap type, bait type, and height of placement all had significantly different effects on capturing and detecting rodents or marsupials; environmental variables at the trap location also affected the ability to detect rodents and marsupials. Traditional methods used for sampling small mammals performed well for rodents but are not effective for capturing marsupials and vice versa, showing species-specific sampling protocols. There is no single combination of trap-bait-height capable to assess the entire small mammal community, but the combination of the most effective protocol for rodents and the most effective protocol for marsupials guarantee better results.     

Parasitological aspects of Schistosoma haematobium (Iran) infection in the American opossum (Didelphis marsupialis L.)

Parasitological studies on 25 American opossums (Didelphis marsupialis) exposed to 1000 cercariae each of S. haematobium (Iran) have indicated a host-parasite situation and general parasitological conditions which show this marsupial to be a satisfactory host for experimental schistosomiasis. The return of schistosomes in relation to cercarial exposure was not excessively high, but there were egg deposits in the major visceral organs. Varied macroscopic pathology due to egg deposits in different organs was demonstrated as well as a potential for urinary bladder involvement, including tumor formation. Even though the precise nature of tumor pathology is not yet known, availability of the host, a good host-parasite compatability, and a low death rate in infected hosts favor this mammal as a model for experimental schistosomiasis haematobia.     

Sandflies (Diptera: Psychodidae) associated with opossum nests at urban sites in southeastern Brazil: a risk factor for urban and periurban zoonotic Leishmania transmission?

Sandflies associated with opossum nests are reported for the first time in the yards of residences located in the urban area of the municipality of Monte Mor, situated in the metropolitan region of Campinas, state of São Paulo, Brazil. Eleven specimens of Evandromyia cortelezzii and one of Evandromyia lenti were captured in two Didelphis albiventris nests. Ev. cortelezzii is considered a secondary vector species for the transmission of Leishmania (Viannia) braziliensis and Leishmania (Leishmania) infantum in the Neotropics. This association may contribute to the introduction, establishment and maintenance of urban and periurban zoonotic transmission outbreaks of Leishmania and should therefore be investigated further.     

Mammalian community structure in lowland, tropical Peru, as determined by removal trapping

Amazonian lowland rain forests are complex three-dimensional formations consisting of a variety of arboreal and terrestrial habitats. The small mammal faunas, particularly of arboreal habitats, are poorly studied, and field research generally has been limited to a few faunal inventories. We sampled the terrestrial and arboreal small mammal fauna in two floodplain forest study zones at Reserva Cuzco Amazonico, southeastern Peru, by removal trapping for 12 consecutive days in dry (June-July 1989) and rainy seasons (January-February 1990). Nineteen taxa of marsupials and rodents were captured. Small mammals were more abundant in the rainy season than in the dry season, but the relative proportions of the 11 most abundant species remained stable between seasons and study zones. Most species showed no decline in capture rates through the 12-day period, indicating that either population densities were high or animals were quite mobile. The small mammal fauna exhibited strong vertical stratification; among the 11 most abundant species, four exhibited strong biases toward terrestrial and five toward above-ground captures. The distinct arboreal small mammal community is grossly underrepresented if traps are placed only at ground level.     

Relationship between moonlight and nightly activity patterns of the ocelot (Leopardus pardalis) and some of its prey species in Formosa,Northern Argentina

The moon can profoundly influence the activity patterns of animals. If predators are more successful under bright moonlight, prey species are likely to respond by shifting their own activity patterns (predator-avoidance hypothesis). However, the assumption that prey will necessarily avoid full-moon nights does not take into account that moonlight also allows prey to more easily detect predators, and to forage more efficiently. Thus, nightly activity patterns could depend on night vision capabilities (visual-acuity hypothesis). To consider the possible influences of moonlight and to distinguish between these hypotheses, we used camera-trapping records of a predator, the ocelot (Leopardus pardalis), and several of its night-active prey to compare activity patterns under different moonlight conditions. The ocelots' activity patterns were not strongly related to moonlight, but showed a slight tendency for higher activity during brighter nights. Tapeti rabbits (Sylvilagus brasiliensis) and brocket deer (Mazama americana) showed a clear preference for brighter nights. White-eared opossums (Didelphis albiventris) also showed a trend to be less active in new moon light. In contrast, smaller grey four-eyed opossums (Philander opossum) and the poor eye-sight nine-banded armadillo (Dasypus novemcinctus) showed similar activity patterns across all moon phases. Since activity patterns of most prey species were not shifted away from the activity of the ocelot, the differences between species are probably linked to their night vision capabilities, and emphasise the need for more information on the visual system of these taxa. Their activity patterns seem to be less strongly linked to avoidance of predation than previously thought, suggesting that foraging and predator detection benefits may play a more important role than usually acknowledged.     

Two multigene families for marsupial neurohypophysial hormones? Identification of oxytocin,mesotocin, lysipressin and arginine vasopressin in the North American opossum (Didelphis virginiana)

Oxytocin, mesotocin ([Ile⁸]-oxytocin), lysipressin ([Lys⁸]-vasopressin) and arginine vasopressin have been identified in the North American opossum ($\text{Didelphis virginiana}$) by amino acid composition and high pressure liquid chromatography. The same peptides with the exception of mesotocin have previously been found in two South American opossums ($\text{Didelphis marsupialis}$ and $\text{Philander opossum}$). Although a dual heterozygocity could also explain the simultaneous presence of oxytocin/mesotocin on one hand, lysipressin/arginine vasopressin on the other, it is assumed, from the results obtained with individual glands of Australian and South American marsupials, that distinct genes encode for the four peptides.     

Reasons for arboreality in wood mice Apodemus sylvaticus and Bank voles Myodes glareolus

Although it is broadly accepted that small mammals often climb trees, only few studies explore arboreality in woodland rodents systematically. Here, we investigate the three-dimensional habitat use of wood mice Apodemus sylvaticus and bank voles Myodes glareolus at three different sites in Wytham Woods, Oxfordshire, under varying environmental conditions. A total of 12 trapping sessions was carried out between March and September 2003 and 2004. During each session, 100 Longworth live-traps with shrew escape holes were set in a 25-point-grid for 3 succeeding nights. Each time, 50 traps were placed on the ground, and 50 in surrounding trees at heights of 30–250 cm. Wood mice were significantly more arboreal than bank voles, and male wood mice spent significantly more time in trees than did females. Arboreality in bank voles occurred only under high population densities and food shortage, and both species were significantly more arboreal in woodland with dense understorey. Thus we conclude that while arboreality is predominantly a result of inter- and intra-specific competition, of the two species we studied, only wood mice, being more agile, can afford to utilize trees without getting caught by predators, and that sex differences are due to male territoriality. Estimates of population sizes and distribution, as well as studies of inter-specific interactions and socio-spatial behaviour are presumed to be affected by these results, and are currently likely to underestimate rodent numbers considerably.     

Reproduction ofDidelphis marsupialis (Didelphimorphia: Didelphidae) in the Venezuelan Andes

The reproductive cycle of the common opossumDidelphis marsupialis Linnaeus, 1758, inhabiting an agricultural area in the Venezuelan Andes was studied by live-trapping for 18 months (from July 1998 to December 1999). Trap success was slightly higher in the less humid months. Most females captured breed during the least rainy period, with two different birth peaks: January-March and April-June, a minor reproductive event occurs from August to October. Reproductive activity ofD. marsupialis appears closely associated with precipitation.     

DNA/DNA hybridization studies of carnivorous marsupials. III. Relationships among species ofDidelphis (Didelphidae)

We report three sets of DNA hybridization experiments conducted to determine relationships among species ofDidelphis (D. albiventris, D. marsupialis, D. virginiana). The 1989 and 1991 sets had fewer replicates per cell than the 1990 series (3.4 and 5.4 vs 9), but in 1991 we distinguished two populations ofD. marsupialis and utilized several individuals for each heterologous comparison. BothPhilander opossum andLutreolina crassicaudata were used as outgroups in 1989, but onlyLutreolina was included in subsequent sets. For each set, we calculated all four standard indices of thermal stability (T _mode,T _m,T ₅₀ H, and NPH) and constructed trees by least-squares (FITCH) and neighbor-joining methods, both before and after correction for asymmetric reciprocal cell values. Subsets of the 1989 data lacking eitherPhilander orLutreolina were analyzed similarly. To explore measurement imprecision, the corrected and uncorrected matrices for each of the four indices were bootstrapped 100 times for the 1989 set and subsets and 1000 times for the 1990 and 1991 sets. Again, for the 1990 and 1991 data, an additional 100 bootstrapped distances were fitted to user trees representing the three possible pairings ofDidelphis spp. to determine the significance of the FITCH branch lengths. The successive experimental sets generated increasingly consistent evidence for pairingD. marsupialis withD. albiventris. The 1989 experiments involved just 85 comparisons, and only T _mode's pairedD. marsupialis withD. albiventris (at bootstrap percentages of 70% or above), but did so whetherPhilander orLutreolina or both were included as the outgroup(s). FITCH and neighbor-joining trees had identical topologies for T _mode's but sometimes differed for the other measures. In contrast, all but one of the corresponding FITCH and neighborjoining trees matched for the 1990 and 1991 data, and three of the four distance measures (T _mode, T _m, and T ₅₀ H) unitedD. marsupialis withD. albiventris at bootstrap percentages averaging 81%; NPH gave a different result for 1990, associatingD. marsupialis withD. virginiana. Further, all but 2 of the 16 matrices for 1990 and 1991 gave mean bootstrapped branch lengths for a consensus pairing that were positive and at least one standard deviation from zero, despite the very short internodes recovered. These results illustrate that the potential of DNA hybridization for resolving very close relationships depends on both the index and the experimental design employed. We conclude that of the three species,D. albiventris andD. marsupialis shared a more recent common ancestor and estimate thatDidelphis spp. have diverged at about 0.39% in nucleotide sequence per myr.Deceased.     

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

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 = 2.47), while 11 species were trapped in the canopy ( = 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.     

Is footprint shape a good predictor of arboreality in sigmondontine rodents from a neotropical savanna?

We investigated the relation between the footprint shape of the fore and hind feet of sigmodontine rodents and their levels of arboreal activity. Footprint shape was obtained by analyzing the impressions left by identified animals captured in the field after being forced to pass through ink-tracking tunnels or by pressing their previously inked feet on a paper sheet. We used geometric morphometric techniques that use superimposition of landmarks (centers of the pads) to obtain footprint shape variables, which were reduced using multivariate analysis (principal component analysis). Arboreal activity was inferred on the basis of the proportions of individuals captured in arboreal traps (1.5–2.5 m height). Regression analysis of body size and the variable that best represented the footprint shapes (first principal component—PC1) did not indicate significant allometric effects on such shapes. We did not detect any significant phylogenetic effects on the arboreal activity of the rodents, either. The results indicated that the PC1 concerning footprint shapes of ten sigmodontine rodents efficiently reflects the degree of use of arboreal strata by these animals. The species studied showed different levels of arboreal activity and their hind footprints (r ² = 0.94) were better indicators of arboreality than the fore footprints (r ² = 0.53). These findings suggest a likely trade off for the fore feet functions. Such functions are probably not strictly related to locomotion. Other biomechanical functions (e.g., shock absorption) and/or manipulation (e.g., food manipulation and grooming) may exert relatively greater influence on the shape of fore feet.     

Microhabitat preferences and spatial distribution of the vesper rat (Nyctomys sumichrasti) in Colima,Mexico

The vesper rat (Nyctomys sumichrasti), a little-known arboreal rodent, was encountered during mark-recapture studies in Colima, Mexico, in January 2003-2007. We trapped on the Pacific coast at Playa de Oro (2003-2005) and in northern Colima (2006-2007). Each year five trap grids were established in heavily vegetated areas and typically run for 8 nights (100 trap stations per grid, each station with a ground trap and an arboreal trap elevated 1-2 m, 10×10 configuration with adjacent stations 10 m apart; 1,600 trap-nights per grid; 40,000 trap-nights total). Nyctomys sumichrasti occurs throughout most of Colima. On grids we captured 29 individuals a total of 41 times, with 90.2% of captures in arboreal traps and 69.0% of animals being adults. The sex ratio of adults was 1.22:1 (males:females), not statistically different from 1:1. Most adult females (77.8%) were pregnant or lactating. Mean mass was 41.3 and 38.6 g for males and females, respectively (P>0.05). Mean greatest distances traveled were longer for males (60.6 m) than females (20.2 m), with an overall mean of 40.4 m. One to six individuals were captured on 9 of 25 grids, with density estimates of 0.87-4.09/ha. We contrasted 14 environmental measures (most involving vegetation structure) for stations where N. sumichrasti was caught and not caught using logistic regression and nonparametric multiplicative regression, finding the species frequented sites flat to moderate in slope with considerable ground litter and relatively sparse high vegetation. In northern Colima, N. sumichrasti used areas with close trees, an open understory, and little grass. Other studies indicate the species sometimes occupies similar areas but with a relatively dense understory.     

Blood meal sources of mosquitoes captured in municipal parks in São Paulo,Brazil

The aim of this study was to investigate blood meal sources of mosquitoes captured in municipal parks in the city of São Paulo, Brazil, and to identify possible associations between mosquito species and their food preferences. Fourteen species of blood hosts of 510 engorged adult female mosquitoes were identified using PCR assays with a vertebrate‐specific primer set based on cytochrome b mitochondrial DNA of the following vertebrates: birds, dogs, cats, rodents, humans, and other primates. Mosquitoes were captured using a manual aspirator, CDC traps in the canopy, CDC traps at ground level, and Shannon traps. With the exception of cats, all other vertebrates were used as hosts by mosquitoes in the parks. Statistical analysis failed to show any trend toward association between most culicid species captured and the sources of blood meals. Instead, they revealed random patterns, indicating that the mosquitoes fed on the most abundant or convenient blood meal sources. Although feeding preferences were observed in two species (birds in the case of Cx. nigripalpus and dogs in the case of Cx. quinquefasciatus), our results highlight the opportunistic feeding habits of the female mosquitoes in this study.     

Microhabitat use by rodent species in a central Brazilian cerrado

We analysed microhabitat use by the rodents Calomys tener, Necromys lasiurus and Thalpomys lasiotis and the factors that may influence their abundances in “murundu” grasslands (open fields with termite mounds) at Aguas Emendadas Ecological Station, Planaltina, Federal District, Brazil. Two grids with 100 sampling points were established and traps were placed at each intersection of the grid, where five microhabitat variables were also measured. Rodents were trapped from June through October 2008. Microhabitat explained 21% of the variation in community structure, with grass density and the number of termite mounds explaining most of the variation. Necromys lasiurus was most often captured in areas with dense grasses, whereas T. lasiotis and C. tener were most often in areas less dense with grasses.     

Shell colour diversification induced by ecological release: A shift in natural selection after a migration event

Ecological release is often attributed to the rapid adaptive diversification of phenotypic traits. However, it is not well understood how natural selection changes its strength and direction through the process of ecological release. Herein, we demonstrated how shell colour of the Japanese land snail Euhadra peliomphala simodae has diversified via a shift in natural selection due to ecological release after migration from the mainland to an island. This snail''s shell colour diversified on the island due to disruptive selection after migration from the mainland. We used trail camera traps to identify the cause of natural selection on both the mainland and the island. We then conducted a mark–recapture experiment while collecting microhabitat use data. In total, we captured and marked around 1,700 snails on the mainland, some of which were preyed upon by an unknown predator. The trail camera traps showed that the predator is the large Japanese field mouse Apodemus speciosus, and the predatory frequency was higher on the mainland than on the island. However, this predation did not correlate with shell colour. Microhabitat use on the island was more extensive than on the mainland, with snails on the island using both ground and arboreal microhabitats. A Bayesian estimation showed that the stabilizing selection on shell colour came from factors other than predation. Our results suggest that the course of natural selection was modified due to ecological release after migration from the mainland, explaining one cause of the phenotypic diversification.