Mid-sized Mammals Research Articles

Ecological function maintained despite mesomammal declines

Mid-sized mammals (i.e., mesomammals) fulfill important ecological roles, serving as essential scavengers, predators, pollinators, and seed dispersers in the ecosystems they inhabit. Consequently, declines in mesomammal populations have the potential to alter ecological processes and fundamentally change ecosystems. However, ecosystems characterized by high functional redundancy, where multiple species can fulfil similar ecological roles, may be less impacted by the loss of mesomammals and other vertebrates. The Greater Everglades Ecosystem in southern Florida is a historically biodiverse region that has recently been impacted by multiple anthropogenic threats, most notably the introduction of the Burmese python (Python molurus bivittatus). Since pythons became established, mesomammal populations have become greatly reduced. To assess whether these declines in mesomammals have affected two critical ecosystem functions—scavenging and frugivory—we conducted experiments in areas where mesomammals were present and absent. We did not observe significant differences in scavenging or frugivory efficiency in areas with and without mesomammals, but we did observe significant differences in the communities responsible for scavenging and frugivory. Despite the observed evidence of redundancy, the changes in community composition could potentially lead to indirect consequences on processes like seed dispersal and disease dynamics within this ecosystem, emphasizing the need for further study.

Millennial-scale drivers of small mammal isotopic niche dynamics in southern California

Quantifying the niche of contemporary and fossil organisms is key to identifying the primary factors driving species and community dynamics through time, in particular teasing apart abiotic and biotic drivers of change. However, niche quantification can be difficult due to short time spans (for contemporary systems), time averaging (for fossil systems), and incomplete information on different aspects of ecology and environment (for both contemporary and fossil systems). Here, we use stable isotope analyses coupled with specimen-level radiocarbon dating from the Rancho La Brea Tar Pits in Los Angeles, California to examine niche dynamics over the last >55,000 years. We sampled over 100 specimens of small and mid-sized mammals, mostly sciurids (squirrels) and leporids (rabbits), from Rancho La Brea to quantify their isotopic niche, track niche changes through time, and identify probable cause(s) of those changes. Individual specimens were radiocarbon dated and niches were quantified from stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of fossil collagen to track individual isotopic niches at precise points in time. Overall, sciurids and leporids exhibit different isotopic signals, suggesting niche variation among taxa. Comparison of animals during the Pleistocene versus the Holocene reveals overall greater δ13C values and greater δ13C and δ15N isotopic niche breadth among Holocene individuals, suggesting that small mammal resource use changed from the last glacial to current interglacial period. Evaluating the isotopic data continuously through time against a high-resolution regional paleoclimate record shows that climate contributed to small mammal niche variation over the last 55,000 years in the Los Angeles Basin. These findings reveal the complexity of long-term abiotic and biotic forcings on organismal niches and emphasize the importance of scale and data resolution when quantifying and interpreting (paleo)ecological patterns and processes.

Using biological records to infer long-term occupancy trends of mammals in the UK

Conservation action is usually triggered by detecting trends in species’ population size, geographical range, or occupancy (proportion of sites occupied). Robust estimates of these metrics are often required by policy makers and practitioners, yet many species lack dedicated monitoring schemes. An alternative source of data for trend estimation is provided by biological records, i.e., species presence information. In the UK, there are millions of such records, but biological trend assessments are often hindered by biases caused by the unstructured way in which they are collected. Recent advances in occupancy modelling that account for changes in survey effort and detectability over time mean that robust occupancy trends can now be estimated from these records. By grouping mammal species into survey assemblages — species likely to be recorded at the same time — and applying occupancy models, this study provides estimates of long-term (1970 to 2016) occupancy trends for 37 terrestrial mammal species from the UK. The inter-annual occupancy growth rates for these species ranged from -4.26% to 11.25%. This information was used to classify two species as strongly decreasing, five as decreasing, 12 as no change, 11 as increasing and seven as strongly increasing. Viewing the survey assemblages as a whole, the occupancy growth rates for small mammals were, on average, decreasing (-0.8% SD 1.57), whereas bats and deer (0.9% SD 1.30) were increasing (3.8% SD 3.25; 0.9% SD 1.30 respectively), and mid-sized mammals were stable (-0.3 SD 1.72). These results contribute much-needed information on a number of data deficient species, and provide evidence for prioritising conservation action.

A global review of the threats of mining on mid-sized and large mammals

Mineral exploitation threatens wildlife by the contamination of soil and water sources, vegetation suppression, and due to changes in landscape configuration. The large and mid-sized forest-dependent mammals need large areas to support their ecological needs, and are frequently impacted by these landscape alterations. Hitherto, there have not been comprehensive reviews of scientific papers reporting on the impacts of the legal mineral exploitation on these animals worldwide. We used the Web of Science and Scopus to select peer-reviewed research articles reporting on those impacts on the large and mid-sized mammals with terrestrial and arboreal habits. Thus, we i) classified the scientific articles according to their methodological approach, ii) examined the main methods of data collection, iii) identified the main impacts recorded, iv) associated the number of studies published by country to the measures of social welfare and economic growth of countries, and v) evaluated the density of mineral resources within the species extent of occurrence, as a proxy to the threat level of mining activities on these species. We found only 39 peer-reviewed articles describing the impacts of mining activities on these animals. These researches mostly quantify the population reduction associated to mining activities, based on line-transect surveys of wildlife. Forest suppression around mining zones is the most frequent threat assessed, and is reported as the main impact on these mammals. We found 153 mammal species to be affected by mining activities, but mining is not mentioned as a threat in the IUCN Red list for 84% (128 spp) of these. Thus, we suggest the inclusion of mining threats in the IUCN assessments of these species, and we urge researchers to intensify the studies of the direct and indirect impacts of mining on large and mid-sized mammals across all ecosystems.

A small neighborhood well-organized: seasonal and daily activity patterns of the community of large and mid-sized mammals around waterholes in the Gobi Desert, Mongolia

BackgroundAnimal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics.ResultsComplex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species.ConclusionsAltogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.

Evaluating connectivity for two mid-sized mammals across modified riparian corridors with wildlife crossing monitoring and species distribution modeling

The movement of wildlife can be constrained by river development projects owing to the presence of artificial structures. This study analyzes the spatial riparian crossing patterns of two mammal species, the leopard cat (Felis bengalensis euptilura) and water deer (Hydropotes inermis). We examine their ability to traverse from habitat on one side of the river to the other, through riparian vegetation, embankments, and the river,. We used 34 months of monitoring on 104 stream segments with varying levels of human modification on the Seom river, South Korea, to analyze their riparian crossing preferences across the river between suitable habitats on either side of the steam. Environmental variables were used for two scales of analysis: a watershed scale and a stream segment scale that examined both riparian habitat suitability and riparian crossings. At the watershed scale, habitat suitability was determined using species distribution modeling. The resulting maps were inputted with other predictor variables to logistic regression models to predict areas of high probability for the species' occurences. For the river segment analyses, we determined species’ presences and potential crossings from snow tracking, heat sensor cameras, and scat. We compared the predicted crossing locations from the watershed scale model to observed crossings. The watershed models indicate that leopard cats prefer upland forest, while water deer prefer the forest edge and riparian corridor. For both target species, the best riparian habitats were characterized by the presence of vegetation cover on the embankment and by at least one side of an embankment being adjacent to farmland or forest cover. The two species showed different riparian crossing preferences. Water deer crossed through large culverts or under bridges, whereas leopard cats utilized drainage pipes and smaller culvert boxes. Stream reaches located close to a river tributary had the highest connectivity values, and areas modeled as good habitats were linked near riparian and watershed areas with high density for both species as well as culvert boxes with a high openness ratio. Artifacts such as steep banks, concrete embankments, and adjacent roads were found to degrade the riparian connectivity of wildlife. These outcomes can be used to identify suitable riparian wildlife habitats of mammals, to evaluate lateral connectivity of riparian corridors for mammals, and to develop criteria for river conservation and restoration in urbanizing areas and developing countries.

Interannual and daily activity patterns of mid-sized mammals in Maracaibo Lake Basin, Venezuela

Despite its biogeographic importance, the mammals of Maracaibo lake basin have been poorly studied. The objectives of this study were to: 1) provide a list of the mammal species detected by combining information from camera traps and other sources, and 2) describe diurnal and annual activity patterns for some of the species detected. Camera-trapping was carried out for one year in five localities within the Burro Negro Protection Zone (Spanish acronym ZPBN). Records of terrestrial mammals (excluding Chiroptera) were compiled from: 1) direct and indirect opportunistic records during field visits, 2) informal interviews with local inhabitants, 3) three national natural history collections, and 4) scientific literature. The complementarity between sources, similarity with other localities within the region, and temporal changes in composition were evaluated with the Sorensen Similarity Index (RS), and annual differences in the number of detections per sampling effort were evaluated using a X 2 test. Sampling effort was 1,799 camera days, resulting in 569 events of mammal detection recorded and 20 species from 17 families in 9 orders identified. Four species ( Dasypus novemcinctus, Dasyprocta leporina, Cerdocyon thous and Leopardus pardalis ) were captured all year round. Camera traps detected half of the non-flying mammal species in the area , including five that had not been previously reported by other sources ( Cuniculus paca, Coendou prehensilis, Sylvilagus floridanus, Procyon cancrivorus and Puma yagouaroundi ). At least three species ( Panthera onca , Odocoileus virginianus , and Hydrochoerus hydrochaeris ) had been reported as historically abundant, but were not detected during the year of camera trapping, which could be due to recent declines in their populations. Camera trapping provides reliable records on the presence of four species with data gaps in their distribution ranges ( Myrmecophaga tetradactyla, Coendou prehensilis, Cerdocyon thous and Procyon cancrivorus ), as well as baseline data for evaluating the distribution overlap between pairs of species, such as Tamandua mexicana and T. tetradactyla , and Dasyprocta leporina and D. punctata . A higher species richness was observed between June and August, in the rainy season.

You can’t run but you can hide: the negative influence of human presence on mid-sized mammals on an Atlantic island

Here, we report the results of a camera-trapping survey of mid-sized (1–50 kg) mammals on an oceanic Atlantic forest island in Brazil. Despite 80% of the island being formally reserved for conservation, the island’s northern areas support a small, but rapidly growing human population that we expected would disturb the mammals and their foraging and movement behaviors. Hunting activities are also more frequent and severe on the north side of the island, closer to the villages. We tested the following hypothesis: the probability of occupancy, detectability, and abundance of mid-sized mammals will be higher in less-disturbed areas on southern parts of the island than in more-disturbed areas to the north. Ordination using multi-dimensional scaling (MDS) highlighted that mammal assemblages were differentiated between the northern and southern slope areas, and regression analyses showed MDS scores to be associated strongly with an index of human population density. Occupancy models for Didelphis aurita, Dasypus novemcinctus, Dasyprocta leporina, and Cuniculus paca showed no effect of habitat covariates, but there were marked effects of human activity impact on the detection probability of all species, except D. aurita. Species detections and local abundances were higher in the less disturbed southern parts of the island. Our results support the notion that mid-sized mammals will change their movement and foraging behaviors as a function of human activities, even inside reserved, protected areas.

Harmonizing methods for wildlife abundance estimation and pathogen detection in Europe-a questionnaire survey on three selected host-pathogen combinations.

BackgroundThe need for wildlife health surveillance as part of disease control in wildlife, domestic animals and humans on the global level is widely recognized. However, the objectives, methods and intensity of existing wildlife health surveillance programs vary greatly among European countries, resulting in a patchwork of data that are difficult to merge and compare. This survey aimed at evaluating the need and potential for data harmonization in wildlife health in Europe. The specific objective was to collect information on methods currently used to estimate host abundance and pathogen prevalence. Questionnaires were designed to gather detailed information for three host-pathogen combinations: (1) wild boar and Aujeszky’s disease virus, (2) red fox and Echinococcus multilocularis, and (3) common vole and Francisella tularensis.ResultsWe received a total of 70 responses from 19 European countries. Regarding host abundance, hunting bags are currently the most widely accessible data source for widely distributed mid-sized and larger mammals such as red fox and wild boar, but we observed large differences in hunting strategies among countries as well as among different regions within countries. For small rodents, trapping is the method of choice, but practical applications vary among study sites. Laboratory procedures are already largely harmonized but information on the sampled animals is not systematically collected.ConclusionsThe answers revealed that a large amount of information is available for the selected host-pathogen pairs and that in theory methods are already largely harmonized. However, the comparability of the data remains strongly compromised by local differences in the way, the methods are applied in practice. While these issues may easily be overcome for prevalence estimation, there is an urgent need to develop tools for the routine collection of host abundance data in a harmonized way. Wildlife health experts are encouraged to apply the harmonized APHAEA protocols in epidemiological studies in wildlife and to increase cooperation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0935-x) contains supplementary material, which is available to authorized users.

Patterns and Composition of Road-Killed Wildlife in Northwest Argentina.

Roads have important effects on wildlife, such as natural habitat fragmentation and degradation and direct killing of fauna, which leads to reductions in wildlife population size. We focused on a principal road in Northwest Argentina to test for the effect of seasonality and landscape features on the composition of road-killed wildlife. We conducted regularly scheduled road trips during the dry and wet seasons. We recorded the presence or absence of a vegetation curtain or hedge along the road. We measured land use by remote sensing in a 500 m bufferalong the road. We compared the abundance of animals killed between seasons (dry and wet) for different taxonomic groups (mammals, birds and reptiles) and for different origins (domestic and native). We built linear mixed models to test the effect of landscape features on the abundance of killed animals. Two hundred and ninety-three individuals were killed, belonging to 35 species; 75.8 % were native and 24.2 % domestic species. The majority of animals killed were mid-sized mammals. More animals were killed during the dry season. The most important factors to explain the wildlife road-killing were the season and the proportion of agricultural landscape. The composition of the killed animals changed with the season. The proportion of agricultural landscape incremented the number of killed birds and mammals during both seasons, without affecting reptiles. The ratio of wild to domestic animals killed was dependent on the season. This study sets a precedent as the first in road ecology in Northwest Argentina and should be taken into account for road planning and regulation.

Trait-dependent changes in assemblages of mid-sized and large mammals along an Asian urban gradient

To plan a management strategy for the urban mammal community, it is necessary to understand the mechanisms by which many mammalian species are eliminated from the urban ecosystem. We analyzed ecological traits of assemblages of mid-sized and large mammals in the Tokyo Metropolitan Area to determine the key traits necessary for inhabiting urban landscapes. Using a cluster analysis, we roughly classified camera-trapped mammals in 10 quadrats, each nearly 5 km × 5 km, into assemblage types. In terms of its species composition, the assemblages in the more urbanized landscapes were a subset of the assemblages in more forested landscapes, except for domestic cats, which were much more common in the urban landscapes. To explain the species occurrence in each quadrat, we applied a generalized linear model with four ecological traits (i.e., body weight, annual reproductive capacity, food habit, and tree-climbing ability) and an environmental force (i.e., urban area) used as covariates. We found that a high annual reproductive capacity and an omnivorous food habit were the most critical traits enabling a species to live in urbanized landscapes. Species with low reproductive capacity were found in forested landscapes and were absent from landscapes with intermediate to high levels of urbanization. Herbivorous species, however, occurred in intermediate landscapes but not in urban landscapes. These key ecological traits can thus be used to predict the species composition of a mammalian assemblage, and they can also be used to devise appropriate strategies for managing species in urban environments.

In Vitro Study and Comparison of Caecal Methanogenesis and Fermentation Pattern in the Brown Hare (Lepus europaeus) and Domestic Rabbit (Oryctolagus cuniculus)

The brown hare and the domestic rabbit are mid-sized herbivorous mammals and hindgut fermenters, though their digestive physiologies differ in some traits. The objective of this study was to estimate and compare the caecal microbial activity in hares and rabbits via an analysis of the following end-products of in vitro caecal fermentation: methane, total gas production, short chain fatty acids and ammonia concentration. Hare caecal methanogenesis occurred at a much lower level (0.25 mmol/kg for samples incubated without substrate and 0.22 mmol/kg for samples incubated with substrate) than that of the rabbit (15.49 and 11.73 mmol/kg, respectively) (P<0.001). The impact of the substrate’s presence on caecal methanogenesis was not significant, though its presence increased the total gas production during fermentation (P<0.001). Hare caecal microflora produced a lower short chain fatty acids concentration than did rabbit microorganisms (P<0.05). In unincubated hare samples, the short chain fatty acids concentration was 28.4 mmol/kg, whereas in unincubated rabbit samples, the short chain fatty acids concentration was 51.8 mmol/kg. The caecal fermentation pattern of the hare was characterised by higher propionate and isobutyrate molar proportions compared with those observed in rabbit caecum (P<0.01). No significant changes in the ammonia concentration in either rabbit or hare caecum were found. The results obtained indicate some differences in the activity of the microbial populations colonising the hare and rabbit caecum, particularly in regards to methanogenic Archaea.

The Effect of Roads on the Movement of Large and Mid-sized Mammals

Abstract Infrastructure development is one of the major threats to biodiversity in the forest. Roads are barriers which restrict the movement of animals. It is therefore urgent to explore characteristics of mammal life associated with forest road crossings. Mammals cross forest roads very rarely compared to the intensity of their movement within the forest. Data sets were created by observing footprints in the snow. The study concludes that forest roads are not an insurmountable obstacle for medium and large mammals.

Distribution of Wild Mammal Assemblages along an Urban–Rural–Forest Landscape Gradient in Warm-Temperate East Asia

Urbanization may alter mammal assemblages via habitat loss, food subsidies, and other factors related to human activities. The general distribution patterns of wild mammal assemblages along urban–rural–forest landscape gradients have not been studied, although many studies have focused on a single species or taxon, such as rodents. We quantitatively evaluated the effects of the urban–rural–forest gradient and spatial scale on the distributions of large and mid-sized mammals in the world's largest metropolitan area in warm-temperate Asia using nonspecific camera-trapping along two linear transects spanning from the urban zone in the Tokyo metropolitan area to surrounding rural and forest landscapes. Many large and mid-sized species generally decreased from forest landscapes to urban cores, although some species preferred anthropogenic landscapes. Sika deer (Cervus nippon), Reeves' muntjac (Muntiacus reevesi), Japanese macaque (Macaca fuscata), Japanese squirrel (Sciurus lis), Japanese marten (Martes melampus), Japanese badger (Meles anakuma), and wild boar (Sus scrofa) generally dominated the mammal assemblage of the forest landscape. Raccoon (Procyon lotor), raccoon dog (Nyctereutes procyonoides), and Japanese hare (Lepus brachyurus) dominated the mammal assemblage in the intermediate zone (i.e., rural and suburban landscape). Cats (feral and free-roaming housecats; Felis catus) were common in the urban assemblage. The key spatial scales for forest species were more than 4000-m radius, indicating that conservation and management plans for these mammal assemblages should be considered on large spatial scales. However, small green spaces will also be important for mammal conservation in the urban landscape, because an indigenous omnivore (raccoon dog) had a smaller key spatial scale (500-m radius) than those of forest mammals. Urbanization was generally the most important factor in the distributions of mammals, and it is necessary to consider the spatial scale of management according to the degree of urbanization.

Molting Success of Ixodes scapularis Varies Among Individual Blood Meal Hosts and Species

The blacklegged tick (Ixodes scapularis) is an important vector of emerging human pathogens. It has three blood-feeding stages, as follows: larva, nymph, and adult. Owing to inefficient transovarial transmission, at least for the Lyme disease agent (Borrelia burgdorferi), larval ticks rarely hatch infected, but they can acquire infection during their larval blood meal. Nymphal ticks are primarily responsible for transmitting pathogens to hosts, including humans. The transition from uninfected host-seeking larva to infectious host-seeking nymph is therefore a key aspect of human risk of infection. It can be divided into a series of steps, as follows: finding a host, taking a blood meal, becoming infected, molting, and overwintering. The chance of succeeding in each of these steps may depend on the species identity of the blood meal host. We used a Bayesian method to estimate the molting success of larval I. scapularis collected from four commonly parasitized species of birds and eight commonly parasitized small and mid-sized mammals found in the forests of Dutchess County, New York. We show that molting success varies substantially among host species; white-footed mice, veeries, and gray catbirds support particularly high molting success, whereas ticks feeding on short-tailed shrews, robins, and wood thrushes were less successful. We also show that larval molting success varies substantially between individual blood meal hosts, and that this intraspecific variability is much higher in some species than in others. The causes of both inter- and intraspecific variation in molting success remain to be determined.

Density of Fishers in Boreal Mixed-Wood Forests of Northeastern British Columbia

Fishers (Martes pennanti) are medium-sized carnivores of the family Mustelidae that are found in boreal and temperate coniferous and deciduous-coniferous forests across North America (Proulx and others 2004). Fishers are rare, but important members of the forest ecosystems that they occupy, and as mesocarnivores may play an essential role in regulating populations of many mid-sized mammals in these forests (Roemer and others 2009). In British Columbia, Fishers are harvested for their fur and can be legally trapped on registered traplines in the central and northern portions of the province between 1 November and 15 February. Harvest of Fishers has declined considerably in British Columbia over the past 30 y. Causes for harvest declines are unexplained, but may include both declining populations and declining trapper effort. Fishers currently have a provincial status of S2S3 in British Columbia, designating it as a species of ‘‘special concern’’ (BCCDC 2010). To ensure that Fisher harvests are sustainable, wildlife managers and trappers need basic population information. Population density is a key piece of data upon which harvest levels should be based. Because Fishers are secretive and difficult to inventory (Powell and Zielinski 1994), until recently harvest management of Fishers in British Columbia has been largely based on studies from eastern North America, where density estimates range from 50 to 385 Fishers/1000 km (Powell and Zielinski 1994; Fuller and others 2001). Recent work in northcentral British Columbia, however, has demonstrated that the density of Fishers in coniferousdominated western forests are substantially lower (for example, 8.8 Fishers/1000 km, Weir and Corbould 2006), and more conservative harvest management is required relative to eastern Fisher populations. Habitat quality is not uniform throughout British Columbia and, as a result, Fisher density is believed to vary among regions (Weir 2003; Lofroth 2004). This is reflected in the variability of Fisher harvest across the province. The boreal mixed-wood forests of northeastern British Columbia have consistently high harvests of Fishers and are believed to be among the most productive areas for this species in the province (Lofroth 2004). To improve our knowledge of Fisher density in British Columbia, we estimated the density of Fishers in a representative boreal mixed-wood forest landscape in northeastern British Columbia. This information will provide wildlife managers and trappers with better data to evaluate sustainable harvest levels and help facilitate population persistence. Our work builds upon Weir and Corbould’s (2006) estimation of Fisher density in the subboreal spruce forests of north-central British Columbia by applying their methods to Fishers in boreal mixed-wood forests. Because our data was collected, analyzed, and interpreted following methods identical to that of Weir and Corbould (2006), readers are directed to this article for comprehensive details of the capture methodology, density estimation, its biases, and resultant implications for interpretation of the results. Our study area covered 950 km of boreal mixed-wood forests (that is, the moist-warm subzone of the Boreal White and Black Spruce biogeoclimatic zone; DeLong and others 1990) in the Kiskatinaw Plateau and Peace Lowlands ecosections (Demarchi 1995) to the south and west of Dawson Creek, BC (UTM: Zone 10, 674000 E, 6182000 N, NAD83). The climate of the study area is cold and dry, which is typical of continental boreal forests. Mean annual GENERAL NOTES

野生動物におけるロードキル，バリアー効果とミティゲーション技術に関する研究の現状と課題

This study reviewed recent studies of road-kill, barrier effect and mitigation techniques on wild animals. It also surveyed road-crossing structures used in Japan. By comparing Japanese and international case studies, we addressed the possibility of studies on road-kill, barrier effect and mitigation technique development in Japan. The road-studies in Japan were mostly studies of the road-kill of Sika deer, Cervus nippon yesoensis, and Raccoon dog, Nyctereutes procyonoides. There were fewer Japanese studies on roadkill and barrier effect examining species, taxa, and landscapes than international studies. Most of the road-crossing structures were underpasses, box-culverts, and pipe-culverts targeting large and mid-sized mammals. There were fewer eco-bridges targeting arboreal mammals and amphibian tunnels targeting herptiles in Japan. In the future, it will be necessary to analyze the factors influencing road-kill and barrier effect of various species and taxa in order to develop mitigation techniques targeting arboreal mammals and herptiles, and to develop quantitative methods for monitoring wild mammals utilizing road-crossing structures as movement corridors.

Sustainability of hunting, population densities, intrinsic rates of increase and conservation of Papua New Guinean mammals: A quantitative review

New Guinea’s mammalian fauna consists of a unique assemblage of relatively small sized (0.5–13.5 kg) marsupial mammals, the hunting of which provides a major source of protein for local communities. However, the impact of hunting and the influence of the marsupial life-history strategies on the sustainability of hunting are unknown. Anthropological studies of subsistence hunting and published life-history data for Australasian marsupial mammals were quantitatively reviewed to determine the major sources of game and annual harvest, and estimate intrinsic rates of population increase ( r max) and population densities. These data were used to estimate extraction versus maximum sustainable production (MSP) and make a preliminary estimate of the sustainability of hunting. There were significant negative relationships between increasing body size and decreasing r max and decreasing population densities, which were further influenced by phylogeny and diet, and appear very similar to relationships found for placental mammals in Afrotropical and Neotropical forests. The estimated biomass of mid-sized marsupial mammals (923 kg/km 2) in Papua New Guinea is also comparable with densities of placental mammals in other evergreen tropical forests. Intrinsic rates of increase ranged from 0.28 for tree-kangaroos (Macropodidae) and 0.29 for cuscus (Phalangeridae), up to 5.14 for bandicoots/echymipera (Peroryctidae). Estimated population densities ranged from 0.4–4.0 animals/km 2 for long-beaked echidna ( Zaglossus sp.) to 150–340 animals/km 2 for ringtails (Pseudocheridae). Extraction rates of game in three studies averaged 23.5 ± 9.9 kg/km 2/year, with cuscus and bandicoot species numerically comprising the main game, although cuscus are the most important source of protein. Rates of extraction in Papua New Guinea versus rates of production demonstrate that long-beaked echidna, tree-kangaroos and cuscus are likely to be hunted unsustainably. In contrast hunting of bandicoots and ringtails was lower than maximum production levels, and the high intrinsic rate of increase of bandicoots means that they can potentially provide a sustainable source of protein, in preference to scarcer and intrinsically slower breeding species.

Isotopes reveal limited effects of middle Pleistocene climate change on the ecology of mid-sized mammals

To better understand how past climatic change influenced mammalian communities, we used fossils from the Pit Locality of Porcupine Cave, to evaluate how two taxa responded to climatic events spanning two glacial–interglacial transitions of the middle Pleistocene in Colorado. We analyzed the isotopes of carbon, oxygen and strontium in 84 specimens of rabbits and marmots to infer (1) if feeding and habitat preferences differed across glacial–interglacial transitions, and (2) whether these taxa responded similarly and synchronously to climatic events. Our results showed no significant differences in any of the isotopic values within taxa across levels. Stable carbon isotope values revealed a C 3-dominated environment around Porcupine Cave during the middle Pleistocene, similar to what is present around the cave today. Oxygen isotopes did not change significantly across levels suggesting consistent water sources over time and preventing any correlation to the Marine Isotope Stages. Marmots did show significantly more positive oxygen isotope values than rabbits over most of the Pit levels likely indicative of hibernation. Lack of significant change in Sr isotopes indicates similarity in habitat range through time, or homogenization of landscape Sr values due to atmospheric inputs. These results suggest that middle Pleistocene climatic change had a negligible effect on the ecology of the sampled individuals around Porcupine Cave. The effects of climate on mammals are complex and these results cannot be extrapolated globally; research is needed to differentiate how global climate change affects mammals in different regions and of different life history to provide insight into how current global warming will affect extant species.

Effects of Roads on Animal Abundance: an Empirical Review and Synthesis

The authors attempted a complete review of the empirical literature on effects of roads and traffic on animal abundance and distribution. They found 79 studies, with results for 131 species and 30 species groups. Overall, the number of documented negative effects of roads on animal abundance outnumbered the number of positive effects by a factor of 5; 114 responses were negative, 22 were positive, and 56 showed no effect. Amphibians and reptiles tended to show negative effects. Birds showed mainly negative or no effects, with a few positive effects for some small birds and for vultures. Small mammals generally showed either positive effects or no effect, mid-sized mammals showed either negative effects or no effect, and large mammals showed predominantly negative effects. The authors synthesized this information, along with information on species attributes, to develop a set of predictions of the conditions that lead to negative or positive effects or no effect of roads on animal abundance. Four species types are predicted to respond negatively to roads: (i) species that are attracted to roads and are unable to avoid individual cars; (ii) species with large movement ranges, low reproductive rates, and low natural densities; and (iii and iv) small animals whose populations are not limited by road-affected predators and either (a) avoid habitat near roads due to traffic disturbance or (b) show no avoidance of roads or traffic disturbance and are unable to avoid oncoming cars. Two species types are predicted to respond positively to roads: (i) species that are attracted to roads for an important resource (e.g., food) and are able to avoid oncoming cars, and (ii) species that do not avoid traffic disturbance but do avoid roads, and whose main predators show negative population-level responses to roads. Other conditions lead to weak or non-existent effects of roads and traffic on animal abundance. The authors identify areas where further research is needed, but they also argue that the evidence for population-level effects of roads and traffic is already strong enough to merit routine consideration of mitigation of these effects in all road construction and maintenance projects.