Although habitat fragmentation is often assumed to be a primary driver of extinction, global patterns of fragmentation and its relationship to extinction risk have not been consistently quantified ...for any major animal taxon. We developed high-resolution habitat fragmentation models and used phylogenetic comparative methods to quantify the effects of habitat fragmentation on the world’s terrestrial mammals, including 4,018 species across 26 taxonomic Orders. Results demonstrate that species with more fragmentation are at greater risk of extinction, even after accounting for the effects of key macroecological predictors, such as body size and geographic range size. Species with higher fragmentation had smaller ranges and a lower proportion of high-suitability habitat within their range, andmost high-suitability habitat occurred outside of protected areas, further elevating extinction risk. Our models provide a quantitative evaluation of extinction risk assessments for species, allow for identification of emerging threats in species not classified as threatened, and provide maps of global hotspots of fragmentation for the world’s terrestrial mammals. Quantification of habitat fragmentation will help guide threat assessment and strategic priorities for global mammal conservation.
Global positioning system (GPS) telemetry technology allows us to monitor and to map the details of animal movement, securing vast quantities of such data even for highly cryptic organisms. We ...envision an exciting synergy between animal ecology and GPS-based radiotelemetry, as for other examples of new technologies stimulating rapid conceptual advances, where research opportunities have been paralleled by technical and analytical challenges. Animal positions provide the elemental unit of movement paths and show where individuals interact with the ecosystems around them. We discuss how knowing where animals go can help scientists in their search for a mechanistic understanding of key concepts of animal ecology, including resource use, home range and dispersal, and population dynamics. It is probable that in the not-so-distant future, intense sampling of movements coupled with detailed information on habitat features at a variety of scales will allow us to represent an animal's cognitive map of its environment, and the intimate relationship between behaviour and fitness. An extended use of these data over long periods of time and over large spatial scales can provide robust inferences for complex, multi-factorial phenomena, such as meta-analyses of the effects of climate change on animal behaviour and distribution.
There is increasing empirical evidence that the quality of habitat patches (determined by either habitat degradation or natural heterogeneity in the quality of habitat) plays an important role in ...determining species distribution patterns and in regulating spatial dynamics in fragmented landscapes. However, to date, most of the debate has focused on whether or not to include habitat variables in fragmentation studies, and we still lack general conclusions as well as standard and robust research approaches. In this paper we show how a weak conceptualization of “patch quality” and the inappropriate choice of target surrogate variables (e.g., density is often used as an indicator of patch quality) have mainly produced case-specific results, rather than general conclusions. We then identify weaknesses in the inclusion of habitat quality measurements within fragmentation studies. In particular, we focus on: (1) the lack of appropriate experimental design, outlining how few studies have actually included a gradient of habitat quality in their sample; (2) the lack of fundamental information provided (e.g., lack of standard outputs), which in turn hampers the possibility of carrying out meta-analyses. We finally synthesize available knowledge from empirical studies and highlight the different conceptual frameworks needed for patch occupancy versus patch use studies.
The conservation of large carnivores is a formidable challenge for biodiversity conservation. Using a data set on the past and current status of brown bears (Ursus arctos), Eurasian lynx (Lynx lynx), ...gray wolves (Canis lupus), and wolverines (Gulo gulo) in European countries, we show that roughly one-third of mainland Europe hosts at least one large carnivore species, with stable or increasing abundance in most cases in 21st-century records. The reasons for this overall conservation success include protective legislation, supportive public opinion, and a variety of practices making coexistence between large carnivores and people possible. The European situation reveals that large carnivores and people can share the same landscape.
Although mammalian carnivores are vulnerable to habitat fragmentation and require landscape connectivity, their global patterns of fragmentation and connectivity have not been examined. We use ...recently developed high-resolution habitat suitability models to conduct comparative analyses and to identify global hotspots of fragmentation and connectivity for the world's terrestrial carnivores. Species with less fragmentation (i.e. more interior high-quality habitat) had larger geographical ranges, a greater proportion of habitat within their range, greater habitat connectivity and a lower risk of extinction. Species with higher connectivity (i.e. less habitat isolation) also had a greater proportion of high-quality habitat, but had smaller, not larger, ranges, probably reflecting shorter distances between habitat patches for species with restricted distributions; such species were also more threatened, as would be expected given the negative relationship between range size and extinction risk. Fragmentation and connectivity did not differ among Carnivora families, and body mass was associated with connectivity but not fragmentation. On average, only 54.3 per cent of a species' geographical range comprised high-quality habitat, and more troubling, only 5.2 per cent of the range comprised such habitat within protected areas. Identification of global hotspots of fragmentation and connectivity will help guide strategic priorities for carnivore conservation.
Species distribution models (SDMs) are often calibrated using presence‐only datasets plagued with environmental sampling bias, which leads to a decrease of model accuracy. In order to compensate for ...this bias, it has been suggested that background data (or pseudoabsences) should represent the area that has been sampled. However, spatially‐explicit knowledge of sampling effort is rarely available. In multi‐species studies, sampling effort has been inferred following the target‐group (TG) approach, where aggregated occurrence of TG species informs the selection of background data. However, little is known about the species‐ specific response to this type of bias correction.
The present study aims at evaluating the impacts of sampling bias and bias correction on SDM performance. To this end, we designed a realistic system of sampling bias and virtual species based on 92 terrestrial mammal species occurring in the Mediterranean basin. We manipulated presence and background data selection to calibrate four SDM types. Unbiased (unbiased presence data) and biased (biased presence data) SDMs were calibrated using randomly distributed background data. We used real and TG‐estimated sampling efforts in background selection to correct for sampling bias in presence data.
Overall, environmental sampling bias had a deleterious effect on SDM performance. In addition, bias correction improved model accuracy, and especially when based on spatially‐explicit knowledge of sampling effort. However, our results highlight important species‐specific variations in susceptibility to sampling bias, which were largely explained by range size: widely‐distributed species were most vulnerable to sampling bias and bias correction was even detrimental for narrow‐ranging species. Furthermore, spatial discrepancies in SDM predictions suggest that bias correction effectively replaces an underestimation bias with an overestimation bias, particularly in areas of low sampling intensity. Thus, our results call for a better estimation of sampling effort in multispecies system, and cautions the uninformed and automatic application of TG bias correction.
In ecologically pristine ecosystems, top-down effects of apex predators play a fundamental role in shaping trophic cascades and structuring ecosystems, but in human-modified landscapes anthropogenic ...effects may markedly alter the ecological role of predators. In particular, human-provisioned food subsidies represent a serious concern for the conservation of apex predators, even though little empirical attention has been given to this aspect in assessing conservation outcomes. To assess the extent to which anthropogenic food subsidies affected feeding ecology of a protected wolf (Canis lupus) population in a human-modified landscape, we integrated scat-analysis (n = 1141 from 4 packs; Jan 2005–Mar 2009) and winter field inspections of Global Positioning System telemetry re-locations (n = 595 clusters and 96 single locations from 5 wolves in 5 packs and 3 floaters; 2008–2011) of wolves living in a historical national park of central Italy hosting both wild prey and livestock at high densities. We revealed that livestock dominated the wolf diet (mean biomass = 63.3 ± 14.2% SD), secondarily supplemented by wild prey (36.7 ± 5.3%, mostly wild boar Sus scrofa, roe deer Capreolus capreolus, and red deer Cervus elaphus). During winter, we revealed a higher propensity of wolves to scavenge (72.5%; n = 91 feeding events) rather than killing prey, and feeding behavior was affected by prey type (i.e., domestic vs wild ungulates) as the large majority of scavenged carrions (75.8%) were livestock carcasses abandoned on the ground that died for causes different from predation. Feeding behavior of wolves was not affected by social affiliation (i.e., pack members vs solitary wolves), indicating that pack members, even if aided by cooperative hunting, were equally likely than solitary wolves to scavenge rather than killing prey; yet, 27.5% of winter feeding events involved predation, exclusively targeted to wild prey. Our findings indicate that large livestock carrion subsidies may strongly depress predatory behavior in wolves, despite the occurrence of an abundant wild prey community, and have relevant ecological, evolutionary and management implications. Reliance on human-provided livestock carrion subsidies likely alters the ecological role of wolves by reducing their top-down cascading effects on the ecosystem, and this has relevant implications for the conservation of wolves and other apex predators in national parks. Accordingly, we call for more strict regulations to govern livestock management and practices and argue that, at least in national parks, conservation goals of apex predators need to explicitly consider their ecological role.
•Wild and domestic ungulates were comparably consumed by wolves.•Scavenging by wolves was more likely on domestic compared to wild ungulates.•Scavenging predominated both in solitary wolves and pack members.•Large availability of livestock carcasses diverged wolves from predating wild prey.•Conservation of wolves in national parks needs to address their ecological role.
Skin marks occur frequently in many cetacean species across the globe revealing a broad spectrum of causes, including social interactions, infectious diseases and injuries produced by anthropogenic ...factors. The current study used photo-id data from 2005-2014 to estimate the skin mark pattern on resident bottlenose dolphins (Tursiops truncatus) from the Aeolian Archipelago (Italy). Thirteen skin mark types were identified and their origin, prevalence and permanence time were examined. The pattern of skin marks was assessed for the abundance, richness, distribution and severity in six body regions and compared among age classes, sex and degree of dolphins' interaction with trammel nets (DIN). Our results showed higher prevalence, abundance, richness and distribution of skin marks in adults than in the younger age classes, with the exception of black marks and white ring lesions. The prevalence and abundance of skin marks were higher in males than females, with the exception of scratches and white patches. Moreover, gunshot wounds, mutilations and irregular dorsal fin edges were found only on adult males. Since males showed higher DIN than females and, in dolphins with higher DIN, skin marks were more abundant and frequently distributed in different body regions, the skin mark pattern in regard to DIN seems to be sex-related. The more severe marks were observed on adults, males and dolphins with higher DIN, namely skin disorder, tooth rake marks, small shallow indentations, deep indentations and mutilations. On the contrary, the severity of scratches, white patches and dark ring lesions was higher in females than males, but not significantly related to DIN and age of the individuals. Our results showed that photo-id data provide an efficient and cost-effective approach to document the occurrence of skin marks in free-ranging bottlenose dolphin populations, a critical step toward understanding the cause and supporting the conservation strategies.
Global habitat suitability models of terrestrial mammals Rondinini, Carlo; Di Marco, Moreno; Chiozza, Federica ...
Philosophical transactions - Royal Society. Biological sciences,
09/2011, Volume:
366, Issue:
1578
Journal Article
Peer reviewed
Open access
Detailed large-scale information on mammal distribution has often been lacking, hindering conservation efforts. We used the information from the 2009 IUCN Red List of Threatened Species as a baseline ...for developing habitat suitability models for 5027 out of 5330 known terrestrial mammal species, based on their habitat relationships. We focused on the following environmental variables: land cover, elevation and hydrological features. Models were developed at 300 m resolution and limited to within species' known geographical ranges. A subset of the models was validated using points of known species occurrence. We conducted a global, fine-scale analysis of patterns of species richness. The richness of mammal species estimated by the overlap of their suitable habitat is on average one-third less than that estimated by the overlap of their geographical ranges. The highest absolute difference is found in tropical and subtropical regions in South America, Africa and Southeast Asia that are not covered by dense forest. The proportion of suitable habitat within mammal geographical ranges correlates with the IUCN Red List category to which they have been assigned, decreasing monotonically from Least Concern to Endangered. These results demonstrate the importance of fine-resolution distribution data for the development of global conservation strategies for mammals.
We investigated social structure and association patterns for a small population of Mediterranean bottlenose dolphins, Tursiops truncatus, inhabiting the Aeolian Archipelago (southern Italy). ...Specifically we evaluate the role of sex and age composition, residency patterns and interaction with trammel nets on this social organization. Association data for 23 regularly sighted individuals were obtained from summer photoidentification surveys collected from 2005-2012. Using a combined cluster and social network analysis approach, we found associations between dolphins were hierarchically structured, where two mixed-sex social units were subdivided into smaller temporarily dynamic groups. We found non-random and long-term preferred associations in the population; however, the degree of social cohesion, residence pattern and interaction with trammel nets differed considerably between the two social units. Six of eight females occurred in the more resident social unit-1; in addition, social unit-1 individuals had significantly stronger associations, higher preferred associates, lived in larger groups and occurred less frequently with trammel nets. Nine of eleven males were clustered in social unit-2 and five of these males, interacting with trammel nets, formed small groups and preferred associations. We propose that female and male groups associate in the study area during the breeding season and that some males choose to interact with reproductive females forming a distinct but interrelated social unit. Other males may be associating in a larger fission-fusion network, which consists of dolphins that appear to temporarily join the network from the coastal population. We cannot exclude that some males specialized in trammel net foraging, suggesting that this foraging technique may favor a solitary lifestyle. Large group sizes and high degree of social cohesion for females could be an indication of greater protection and more efficiency in detecting, deterring or repelling anthropogenic pressures. Most likely dolphins' social organization depends on a combination of socio-ecological, demographic and anthropogenic factors.
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