Lack of adequate taxonomic knowledge may hinder endemic mammal conservation in the Brazilian Atlantic Forest

The Atlantic Forest is one of the most diverse and threatened ecosystems of the world, being thus classified as one of the most important biodiversity hotspots. However, habitat loss, overexploitation, alien species, disease and pollution are not the only threats faced by native fauna and flora. The lack of adequate taxonomic knowledge hinders conservation and management efforts of endemic species. This is true even for mammals, which is the most charismatic group of animals and traditionally receive a good deal of attention from scientists and the public in general. A few examples show how this gap in local fauna information can be demise for species conservation, even misguiding management strategies: molecular data reveal a hidden marsupial diversity; the lack of taxonomic studies at the species level seriously threatens rodent conservation; and the taxonomic rearrangement of the genusBrachyteles revealed a new species and had a great impact on management strategies. New species are discovered, described and taxonomically rearranged at an astounding rate. We can only be successful in biodiversity conservation if we have at least a minimum level of knowledge about what we are trying to preserve. That is true both for researchers and for the general public. Recent taxonomic revisions may represent the turning point in Neotropical fauna knowledge, which, coupled with a greater awareness of local people about the rich biodiversity that dot their backyards, can represent a better conservation prospect for the endemics of the Atlantic Forest.     

Effects of fragmentation on parasite burden (nematodes) of generalist and specialist small mammal species in secondary forest fragments of the coastal Atlantic Forest,Brazil

Parasites are considered to play an important role in the regulation of wild animal populations. We investigated parasite burden of gastrointestinal nematodes and body condition in specialist and generalist small mammal species in secondary forest fragments in the highly endangered coastal Atlantic Forest. We hypothesized that body condition decreases with increasing parasite load and that parasite burden increases with increasing fragmentation in specialist species but not in generalist species as a consequence of differing responses to fragmentation effects. Investigated species were Akodon montensis, Oligoryzomys nigripes, and Delomys sublineatus (rodents) and the marsupials Marmosops incanus and Gracilinanus microtarsus. Prevalence of parasites was high in all species except for the arboreal G. microtarsus, presumably because of decreased infection probability. No correlation was found between body condition and parasite load in any of the species. Contrary to our expectations, body condition of the specialists D. sublineatus and M. incanus increased in both species with increasing fragmentation. In D. sublineatus, parasite burden increased and body condition decreased in fragments with relatively high density probably due to increased contact rates and facilitation of infection with nematodes. In all generalist species, low or no correlation between parasite burden and fragmentation was detected, suggesting little effect of fragmentation on population health.     

Post-fire succession of small mammals in the Cerrado of central Brazil

In the Cerrado savannas from Brazil fire events are common and strongly influence the vegetation structure and, consequently, the associated small mammals. In this paper, we investigate changes in the structure of small mammal communities related to sites of different post-fire ages. Mammals were captured in similar Cerrado sites that differed in time since the last burn (1 to 26 yr). We sampled six sites in the wet season of 1997 (phase 1) and, three years later, six sites in the wet and dry seasons (phase 2). Six rodent species and four marsupials were captured. Community composition changed drastically as a function of time since fire. The diversity and abundance of small mammals reached maximum values in the early successional stages. The rodent Calomys tener was present only in early seral stages. The rodent Bolomys lasiurus was more frequent in mid-successional stages and decreased in later seral stages, and the rodent Oryzomys subflavus occupied all successional stages. The marsupial Gracilinanus agilis was dominant in the area that did not burn for at least 23 yr. Changes in composition of the community of small mammals were more accelerated in early successional stages, when there are more drastic vegetational changes. The ability of small mammals to cope with Cerrado fires and the great dissimilarity among post-burning seral stages suggest that a mosaic of areas representing different post-fire seral stages could increase the regional diversity of this group.     

Linking changes in small mammal communities to ecosystem functions in an agricultural landscape

Global increases in agricultural production have significant implications for biodiversity and ecosystem processes. In southern Africa, sugarcane production has converted native vegetation into agricultural monocultures. We examined functional group abundance along a conservation-agriculture gradient in the Lowveld of Swaziland. We captured small mammals representing 4 functional groups: omnivores, insectivores, granivores, and herbivores and found evidence of distinct changes in small mammal functional groups across the conservation-agriculture boundary. Granivores declined with increasing distance into the sugarcane and were completely absent at 375 m from the boundary while omnivores increased in the sugarcane. Insectivores and herbivores showed no differences between the two land uses; however, during the dry season, there were significantly more insectivores at the conservation-agriculture interface than in the conservation lands. Shifts in small mammal communities have clear implications for ecosystem processes as the removal of granivores from savannah systems can drastically alter vegetative structure and potentially lead to shrub encroachment via reduced levels of seed predation, while abundant omnivorous small mammals can cause significant crop damage and increase the prevalence of vector borne diseases in the environment.     

A mathematical analysis of small mammal populations

Populations of Microtus montanus, the montane vole, have been extensively studied. It is known that their reproductive activity is closely linked to the availability of the chemicals in growing plants. We use a mathematical model here to study how the length of the vegetative season and the natural reproduction rhythm of voles are involved in the long term dynamics of the population numbers. In particular, we use data obtained from Timpie Springs, Utah, and from Jackson Hole, Wyoming, to formulate a model. The novelty of this model is its use of littering curves that highlight the temporally discrete nature of vole reproduction. The model shows how the timing of the vegetative season can influence vole population sizes.This work was supported in part by NSF Grant No. MCS-82-08986 and DMS85-14000 (FCH) and by the University of Utah where Dr. Murphy was a visitor     

Benefits of habitat restoration to small mammal diversity and abundance in a pastoral agricultural landscape in mid-Wales

Changes in agricultural practice are predicted across the UK following agricultural reform driven by government policy. The suitability of agri-environment schemes for many species is currently debated because limited quantitative data are collected. In order to understand the changes to biodiversity due to agri-environment schemes, there is a need for studies to not just compare biodiversity and species composition in and out of agri-environment areas, but to factor in the influence of temporal habitat changes. In this study, we investigate the suitability of an agri-environment initiative to support and enhance a small mammal fauna among pastoral hill farms in mid-Wales. Grazed and ungrazed woodlands, riparian habitats, and broadleaf plantations, were compared for small mammal abundance and diversity following a trapping study. Mammal diversity was similar across habitats, though abundance varied significantly. A principle component analysis identified that mammal abundance clustered into three main habitat groups separated by seral stage (early, mid, late). No relationship between mammal abundance and stock grazing was found. A canonical correspondence analysis confirmed that vegetation structure was important in explaining the distribution of captures of mammal species across the landscape. The results for habitat type, and habitat context, suggest that a mix of vegetation seral stages, reflecting a varied vegetation structure, is important to maintain small mammal diversity and abundance across the study area. Heterogeneity in structural diversity at the landscape scale is important to maintain a variety of ground-dwelling mammal species, and particularly because trends in countryside surveys show that woodlands are skewed towards late seral stages. Habitat heterogeneity can be maintained because the hill farms neighbour each other, and the farmers co-operate as a group to manage the landscape. Habitat diversity is therefore possible. These results help us to advocate, and anticipate, the benefits of groups of farms within a landscape.     

Untangling the roles of fire,grazing and rainfall on small mammal communities in grassland ecosystems

In grassland systems across the globe, ecologists have been attempting to understand the complex role of fire, grazing and rainfall in creating habitat heterogeneity and the consequences of anthropogenic control of these factors on ecosystem integrity and functioning. Using a South African grassland ecosystem as a model, we investigated the impact of fire and grazing pressure on small mammal communities during three differing periods of a rainfall cycle. Over 2 years, 15,203 trap nights revealed 1598 captures of 11 species (nine rodents, one macroscelid and one insectivore). Results highlighted the importance of the interplay between factors and showed that the role of fire, grazing and rainfall in determining small mammal abundance was species-dependant. While no two species were affected by the same environmental variables, grass cover or height was important to 56% of species. Considered independently, high rainfall had a positive influence on small mammal abundance and diversity, although the lag period in population response was species-specific. High grazing negatively affected overall abundance, but specifically in Mastomys coucha; fire alone had little immediate impact on small mammal diversity. Six months after the fire, vegetation cover had recovered to similar levels as unburned areas, although small mammal diversity and richness were higher in burned areas than unburned areas. Grazing levels influenced the rate of vegetation recovery. In conclusion, low-level grazing and burning can help to maintain small mammal biodiversity, if conducted under appropriate rainfall levels. A too high grazing pressure, combined with fire, and/or fire conducted under drought conditions can have a negative impact on small mammal biodiversity. To maintain small mammal diversity in grassland ecosystems, the combined effects of the previous year’s rainfall and existing population level as well as the inhibition of vegetation recovery via grazing pressure need to be taken into consideration before fire management is applied. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Identification of vertebrate scavengers of small mammal carcasses in a forested landscape

We identified vertebrate scavengers of small mammal carcasses at the 780-km² Savannah River Site during the winter of 2000–2001. Rodent carcasses, differing in size and visual conspicuousness, were placed in upland pine forests and bottomland hardwood forests during six 2-week periods. Sixty-two of the 96 carcasses (65%) were removed by vertebrates. With the aid of remote photography, we identified 11 species of scavengers removing carcasses. RaccoonsProcyon lotor, gray foxesUrocyon cinereoargenteus, and feral pigsSus scrofa scavenged most frequently. The mean elapsed time for carcass removal was 5.6 days. The number of carcasses removed by vertebrates did not differ significantly with respect to carcass size, visual conspicuousness, or habitat type; however, air temperature was strongly correlated (positively) with carcass removal. Our study demonstrates that many mammal species are capable of utilizing small carrion items as a food resource, and suggests that scavenging may account for a higher proportion of the diet of some facultative scavengers than is now widely assumed.     

Assessment of habitat quality for four small mammal species of the Monte Desert, Argentina

In the temperate desert of Argentina, the combined action of climatic and anthropogenic factors has contributed to the formation of a highly heterogeneous landscape. In the central region of the Monte desert, four small mammal species (Eligmodontia typus, Calomys musculinus, Akodon molinae and Graomys griseoflavus) coexist and show different habitat uses in response to spatial variability. Three main habitat types are present in the region: mesquite forest, the creosotebush community and sand dunes. These habitat types are present also in the surrounding grazing area.The objective of this study was to determine habitat quality for these species in a protected area (Reserve MaB Ñacuñán) and in the adjacent grazed area. For each species we estimated demographic parameters that are highly correlated to fitness in each habitat, and for both treatments (protected and grazed).We found that the protected area offered a higher quality habitat than the grazed area for all species, but principally A. molinae and G. griseoflavus. At a local scale, we found that A. molinae and C. musculinus clearly showed higher fitness in the more complex habitats as the creosotebush community and the mesquite forest. In contrast, for E. typus, open and simplest patches, such as sand dunes, were optimal for its survival and reproduction.     

Degree of landscape fragmentation influences genetic isolation among populations of a gliding mammal

Forests and woodlands are under continuing pressure from urban and agricultural development. Tree-dependent mammals that rarely venture to the ground are likely to be highly sensitive to forest fragmentation. The Australian squirrel glider (Petaurus norfolcensis) provides an excellent case study to examine genetic (functional) connectivity among populations. It has an extensive range that occurs in a wide band along the east coast. However, its forest and woodland habitat has become greatly reduced in area and is severely fragmented within the southern inland part of the species' range, where it is recognised as threatened. Within central and northern coastal regions, habitat is much more intact and we thus hypothesise that genetic connectivity will be greater in this region than in the south. To test this we employed microsatellite analysis in a molecular population biology approach. Most sampling locations in the highly modified south showed signatures of genetic isolation. In contrast, a high level of genetic connectivity was inferred among most sampled populations in the more intact habitat of the coastal region, with samples collected 1400 km apart having similar genetic cluster membership. Nonetheless, some coastal populations associated with urbanisation and agriculture are genetically isolated, suggesting the historic pattern observed in the south is emerging on the coast. Our study demonstrates that massive landscape changes following European settlement have had substantial impacts on levels of connectivity among squirrel glider populations, as predicted on the basis of the species' ecology. This suggests that landscape planning and management in the south should be focused on restoring habitat connectivity where feasible, while along the coast, existing habitat connectivity must be maintained and recent losses restored. Molecular population biology approaches provide a ready means for identifying fragmentation effects on a species at multiple scales. Such studies are required to examine the generality of our findings for other tree-dependent species.     

The ecological connections of dispersal in small mammal populations]

The dispersal of 27 Holarctic species of rodents was quantitatively described on the base of long-term catch method. The relative proportion of non-territorial individuals is an important parameter that reflects the intensity of dispersal. This parameter is statistically related to population (abundance and population type) and species characters (the size of species range and the level of intraspecific differentiation). The contribution of species characters to the variance of migrant portion is lower than contribution of population ones. Isolation and population specialisation are accompanied by the decrease in the portion of disperser, while in pessimal environment the increase in population fluidity is observed. Intensity of dispersal is positively correlated with the size of species range and negatively--with the level of intraspecific differentiation. Thus the dispersal in populations of small mammals serves for colonisation and reparation, providing the stable existence of given group in variable environment.     

On the problem of trap-response types of small mammal populations

1. So far as the population data thus far amassed go, commensal rats in residential habitats are of type II; house mice may be of type I or III in fields but might show type II in residences, and fieral species or subspecies may range from type I to III. Altogether alloresponsive populations seem to be much commoner than the isoresponsive.
2. It is as yet little disclosed to what degree the differentiation of the type is correlated with speciation or subspeciation, even if only a proof that a subspecific population would hold type III as its fixed feature is given. The response types are supposed to be associated with the levels of population shyness. Hence some characters reflected in those may possibly be connected with sexual isolation provoking speciation.
3. Some awkward respects due to the heterogeneous trappability, depending upon the trap-response type, among a mixed population of marked and unmarked animals have been confirmed regarding the methodology for estimating parameters.

     

Habitat structure and disturbance affect small mammal populations in Mediterranean forests

Habitat structure, the physical arrangement of objects in space, affects animal populations, ecological interactions, species diversity, and ecosystem functioning. Conventional forest management practices that reduce habitat structural complexity are thus under reappraisal, and there are increasing efforts to understand how habitat structure affects functionally important species. We investigate here the effect of habitat structures on small mammal dens and their interactions with widespread antagonistic species (wild boars). Among habitat structures we considered tree dimension (diameter), shrub cover, rock cover, dead wood volume, and stump area. Ground cover with rooting signs measured wild boar disturbance. The number of small mammal dens was related positively to rock cover and tree diameter, and negatively to wild boar disturbance. Additionally, a positive interaction between wild boar disturbance and tree diameter emerged, showing that the effect of big trees on small mammal nesting was more evident with higher levels of disturbance. This study suggests that habitat structures that can be affected by forest management provide effective refuges for functionally important species. The effect of habitat structure on species survival and interactions thus needs to be addressed to understand ecosystem management and functioning.     

Synchrony in small mammal populations of montane forest patches in southern India

1. Small mammal populations were studied in montane evergreen forests in the Nilgiris, southern India, using live-trapping from January 1994 to September 1996. Two sites were selected, one with a single large forest patch and adjoining plantations, and the other with several small forest patches separated by grassland.
2. Nine species were recorded, of which eight were trapped in the forest patches, two in the grasslands and five in plantations. Rattus rattus was the most abundant species (2–36 individuals ha⁻¹) followed by Suncus montanus (0–11 individuals ha⁻¹). Densities of seven other species recorded were very low.
3. Synchrony in various population variables – density, biomass, mean weight, density of adults and adult females, and proportion of adults, adult females and sub-adults – was examined for Rattus rattus populations in the forest patches and plantations. Density and biomass were studied in seven other species recorded at these sites. Spearman's rank order correlation was used as a measure of synchrony between the population variables.
4. Within-site synchrony was higher than between-site synchrony in population characters. Synchrony was also higher between plots within the unfragmented site than they were between plots in the fragmented site. Relatively high synchrony in proportions of adults, adult females and juveniles in the forest patches implied that breeding is probably influenced by climate and food availability, which are seasonal in this habitat.
5. Given the small patch sizes (≈1–10 ha) and low population sizes, asynchrony is likely to be an outcome of demographic and environmental stochasticity, and low dispersal rates may impede establishment of synchrony.     

A small mammal community in a forest fragment, vegetation corridor and coffee matrix system in the Brazilian Atlantic forest

The objective of our work was to verify the value of the vegetation corridor in the conservation of small mammals in fragmented tropical landscapes, using a model system in the southeastern Minas Gerais. We evaluated and compared the composition and structure of small mammals in a vegetation corridor, forest fragments and a coffee matrix. A total of 15 species were recorded, and the highest species richness was observed in the vegetation corridor (13 species), followed by the forest fragments (10) and the coffee matrix (6). The absolute abundance was similar between the vegetation corridor and fragments (F = 22.94; p = 0.064), and the greatest differences occurred between the vegetation corridor and the matrix (F = 22.94; p = 0.001) and the forest fragments and the matrix (F = 22.94; p = 0.007). Six species showed significant habitat preference possibly related to the sensitivity of the species to the forest disturbance. Marmosops incanus was the species most sensitive to disturbance; Akodon montensis, Cerradomys subflavus, Gracilinanus microtarsus and Rhipidomys sp. displayed little sensitivity to disturbance, with a high relative abundance in the vegetation corridor. Calomys sp. was the species least affected by habitat disturbance, displaying a high relative abundance in the coffee matrix. Although the vegetation corridors are narrow (4 m width), our results support the hypothesis in which they work as a forest extension, share most species with the forest fragment and support species richness and abundance closer to forest fragments than to the coffee matrix. Our work highlights the importance and cost-effectiveness of these corridors to biodiversity management in the fragmented Atlantic Forest landscapes and at the regional level.     

Epidemic cycles in agricultural populations: a cross-cultural study

A cross-cultural analysis of mortality patterns is of interest to biological anthropologists and genetic epidemiologists. In this paper, we examine four agricultural populations from Costa Rica, Hungary, and the United States in order to determine if they suffered from a cyclical distribution of epidemics. When possible, we look at the mortality time series of adults and children separately. Of the 2 series, only 2 show significant epidemic cycles. Both are in the Hungarian groups and both affect subadults. Otherwise, the Costa Rica, U.S., and adult series of the Hungarian groups do not show any periodicity of mortality peaks. Our results indicate that epidemic cycles are not as ubiquitous in small agricultural groups as the literature would suggest.     

A long term experimental study of canine visceral leishmaniasis

Previous studies on Leishmania infantum and the canine immune response are derived mainly from short-term studies. To date, there have been no longitudinal studies that perform a serial analysis of the intensity of infection in conjunction with immunological parameters and clinical signs in Leishmania-infected dogs. For this purpose, six dogs were infected experimentally by the i.v. route and were monitored for 1 year. Clinical, immunological (humoral and cellular response) and parasitological (parasitaemia) parameters were evaluated monthly. Four dogs developed clinico-pathological signs compatible with leishmaniasis, whereas two dogs showed few abnormalities during the study. Evaluation of clinical, immunological and parasitological parameters showed that the intensity of Leishmania infection in blood samples, as indicated by the amount of Leishmania DNA, was correlated significantly with IgG, IgG1, IgG2, IgA, and IgM concentrations and with clinical signs. Parasitaemia and Leishmania-specific cell-mediated immunity were inversely correlated. Moreover, higher quantities of Leishmania DNA were detected in the liver, spleen, lymph node, skin and bone marrow of dogs exhibiting clinical signs than those exhibiting few such signs. These findings suggest that progressive disease in experimental canine leishmaniasis is associated with specific T-cell unresponsiveness and unprotective humoral responses which allow the dissemination and multiplication of L. infantum in different tissues.     

The short and long term effects of docetaxel chemotherapy on rodent object recognition and spatial reference memory

Aims

Previous animal studies have examined the potential for cytostatic drugs to induce learning and memory deficits in laboratory animals but, to date, there is no pre-clinical evidence that taxanes have the potential to cause cognitive impairment. Therefore our aim was to explore the short- and long-term cognitive effects of different dosing schedules of the taxane docetaxel (DTX) on laboratory rodents.

Main methods

Healthy male hooded Wistar rats were treated with DTX (6 mg/kg, 10 mg/kg) or physiological saline (control), once a week for 3 weeks (Experiment 1) or once only (10 mg/kg; Experiment 2). Cognitive function was assessed using the novel object recognition (NOR) task and spatial water maze (WM) task 1 to 3 weeks after treatment and again 4 months after treatment.

Key findings

Shortly after DTX treatment, rats perform poorly on NOR regardless of treatment regimen. Treatment with a single injection of 10 mg/kg DTX does not appear to induce sustained deficits in object recognition or peripheral neuropathy.

Significance

Overall these findings show that treatment with the taxane DTX in the absence of cancer and other anti-cancer treatments causes cognitive impairment in healthy rodents.