Spatial heterogeneity in the local densities of terrestrial carnivores is driven by multiple interacting biotic and abiotic factors. Space-use patterns of large carnivores reflect the competing ...demands of resource selection (e.g., exploitation of habitats with abundant prey) and minimization of risks arising from human interactions. Estimating the relative strength of these drivers is essential to understand spatial variation in densities of large carnivores and there are still key knowledge gaps for many large carnivore populations. To better understand the relative roles of environmental and human drivers of spatial variation in tiger ( Panthera tigris ) densities, we surveyed a 3000 km 2 landscape in North India using camera trap data. Over two years, we photo-captured 92 unique adult tigers. Associating spatial covariates with patterns of detection allowed us to test hypotheses about the relative influence of prey abundance, habitat structure and extent, and proximity to habitat edges on spatial variation in tiger densities across a gradient of anthropogenic disturbance. We documented extensive variation in tiger density within and across management units and protected areas. Spatial variation in prey abundance and proximity to grassland habitats, rather than human use (e.g. extent of human-dominated edge habitat and protection status), explained most of the spatial variation in tiger density in two of the five surveyed sites. The region’s largest tiger population occurred in a multi-use forest beyond protected area boundaries, where wild ungulates were abundant. Our results suggest that tigers can occur at high densities in areas with extensive human use, provided sufficiently high prey densities, and tracts of refuge habitats (eg. areas with dense vegetation with low human use). We argue that tiger conservation portfolio can be expanded across multi-use landscapes with a focus on areas that are adaptively managed as “zones of coexistence” and “refuge habitats”. Advancing this conservation strategy is contingent on greatly strengthening systems to effectively and equitably redress human–wildlife conflict and leveraging existing policies to strengthen local participation in conservation planning and forest stewardship. Our insights into the environmental drivers of spatial heterogeneity in tiger populations can inform both local management and guide to species recovery in working landscapes.
Peat bogs, naturally acidic environments, are extreme habitats for many soil macroorganisms. Soil acidity and reduced calcium availability strongly affect soil invertebrates, which require calcium to ...build exoskeletons. Calcium availability is assumed to limit survival of terrestrial isopods in this nutrient-poor environment. Previous studies, though scarce, have shown that isopods are absent from peat bogs in the north Holarctic. Thus, they were sampled using pitfall traps in the largest and oldest Western Balkans (Croatia) peat bog and at its edges. Isopods were found to maintain stable populations in the Western Balkan peat bogs, despite the extreme soil properties. Species richness did not differ between the centre of the peat bog and its edge, however activity density was higher at the edge, implying that edges provide more favourable habitat for isopods based on microclimatic conditions, food availability, and shelter sites. Calcium concentration is not the key limiting factor for isopod distribution in peat bogs as previously assumed. Environmental variables that impacted isopod spatial distribution include soil moisture and vegetation structure. Thus, presence of isopods in Southern European peat bogs is likely related to warmer climate and successional changes in peat bogs.
•Terrestrial isopods maintain stable populations in the Southern European Đon močvar peat bog.•Despite prior assumptions, high acidity and low calcium availability are not key limiting factors for woodlice distribution.•Occurrence of woodlice in Southern European peat bogs is likely related to successional changes and warmer climate.•Active conservation measures are essential to preserve this fragile ecosystem and its unique soil assemblages.
Primate responses to habitat alteration vary depending on the species’ dietary guild and forest type. Leaves from secondary vegetation can provide nutritious resources to folivorous primates, whereas ...frugivores, burdened with a scattered spatial and temporal distribution of fruiting resources, require larger home ranges, potentially limiting their ability to cope with altered landscapes. Within coastal southeastern Madagascar, we sought to determine whether two lemur species occupying contrasting ecological niches respond differently to the changing features of their degraded and fragmented habitat. We conducted behavioral observations between 2011 and 2013 on frugivorous collared brown lemurs (
Eulemur collaris
) and folivorous southern bamboo lemurs (
Hapalemur meridionalis
). To estimate the ability of lemurs to use pioneer species, we categorized all plants used for feeding and resting as fast growing, mid-growing, or slow growing. We fitted general linear mixed-effects models, one for each plant growth category with monthly proportional use rates as the dependent variable, and included species (
E. collaris
and
H. meridionalis
), activity (feeding and resting), and season (dry and wet) as fixed effects. Our results show that
E. collaris
used both slow- and mid-growing plant species most often, while
H. meridionalis
were more likely to use fast-growing plants, which indicated an ability to use secondary/disturbed vegetation. Frugivorous
E. collaris
appear more limited by climax plants, while folivorous
H. meridionalis
appear to be slightly more adaptable, a finding that is consistent with that for other primate folivores.
In many coastal areas, natural habitats are being fragmented and lost to encroaching human development. These landscape changes can affect the production of recreationally and commercially important ...fisheries because many exploited species of fish and shellfish are estuarine dependent and utilize coastal marshes as nursery grounds. Brown shrimp are an example of a commercially exploited species that may be highly affected by changes in the spatial distribution of habitat types. We used a spatially explicit, individual-based simulation model to explore the role of marsh vegetation and edge habitat in brown shrimp survival. The model simulated shrimp movement, mortality, and growth of individual shrimp from arrival as postlarvae to 70-mm body length, when they emigrate offshore. Simulations were performed on 100 x 100 m spatial grid of 1-m2cells, with each cell labeled as "water" or "vegetation". Predation mortality was influenced by shrimp size, movement, and habitat. Simulated shrimp growth depended on temperature, habitat, and local shrimp density. We examined the relationships between shrimp survival and marsh attributes (amount of vegetation and edge habitat) by simulating a series of four habitat maps that we created from aerial photographs. Biological parameters were derived from published estimates and from field data. We corroborated the model by comparing the simulated shrimp abundance with summary statistics from long-term monitoring data, by comparing the simulated density with fine-scale patterns observed in field studies, and by comparing simulated and measured stable-isotope values. Surviving shrimp grew faster, moved less, spent more time in vegetation, and experienced slightly higher local densities than shrimp that died during the simulation. Habitat maps with more edge habitat invariably produced higher simulated shrimp survival rates. High-edge habitats increased survival by providing shrimp more direct access to vegetation without additional movement-related mortality and density-dependent growth costs associated with low-edge habitats. Model predictions were robust to higher numbers of initial postlarvae and to alterations to the movement rules. The results of this study suggest that the management of brown shrimp should be extended from protecting the spawning stock through catch regulations to also protecting the estuarine life stages through habitat conservation and restoration.
Bistorta vivipara
is a widespread arctic-alpine ectomycorrhizal (ECM) plant species. Recent findings suggest that fungal communities associated with
B. vivipara
roots appear random over short ...distances, but at larger scales, environmental filtering structure fungal communities. Habitats in highly stressful environments where specialist species with narrower niches may have an advantage represent unique opportunity to test the effect of environmental filtering. We utilised high-throughput amplicon sequencing to identify ECM communities associated with
B. vivipara
in Svalbard. We compared ECM communities in a core habitat where
B. vivipara
is frequent (
Dryas
-heath) with edge habitats representing extremes in terms of nutrient availability where
B. vivipara
is less frequent (bird-manured meadow and a nutrient-depleted mine tilling). Our analysis revealed that soil conditions in edge habitats favour less diverse but more distinct ECM fungal communities with functional traits adapted to local conditions. ECM richness was overall lower in both edge habitats, and the taxonomic compositions of ECM fungi were in line with our functional expectations. Stress-tolerant genera such as
Laccaria
and
Hebeloma
were abundant in nutrient-poor mine site whereas functional competitors genera such as
Lactarius
and
Russula
were dominant in the nutrient-rich bird-cliff site. Our results suggest that ECM communities in rare edge habitats are most likely not subsets of the larger pool of ECM fungi found in natural tundra, and they may represent a significant contribution to the overall diversity of ECM fungi in the Arctic.
Following the rediscovery after 200 years of
in 2017, we carried out data collection its habitats regarding vegetation, microclimate, and soil on two prominent dolomite hills of the Eastern Bakony. ...Data collections were carried out in habitat mosaics (xerothermic forest edges on the plateaus, karst shrub forests in south-facing exposure, dry grasslands among forest patches on the plateaus, rocky grasslands in south-facing exposure) of three sampling blocks. Vegetation was examined by phytosociological relevés, microclimate from April to November continuously by TMS-2 dataloggers, and soil by laboratory analyses focused mainly on percentage of different fractions. According to our results a) shrub forests with a south-facing exposure provide a cooler microclimate with temperated fluctuation in the spring–early summer and late summer–early autumn periods; b) plateau grasslands and shrubs are characterised by looser soil structure. Based on our results, heterogeneous habitat character of forest–grassland mosaics of the Pannonicum can mitigate the expected negative effects of climate change on reptiles.
Changes in behavior are often the proximate response of animals to human disturbance, with variability in tolerance levels leading some species to exhibit striking shifts in life history, fitness, ...and/or survival. Thus, elucidating the effects of disturbance on animal behavior, and how this varies among taxonomically similar species with inherently different behaviors and life histories is of value for management and conservation. We evaluated the risk response of three anuran species-southern leopard frog (
), Blanchard's cricket frog (
), and green tree frog (
)-to determine how differences in microhabitat use (arboreal vs ground-dwelling) and body size (small vs medium) may play a role in response to a potential threat within a human-altered subtropical forest. Each species responded to risk with both flight and freeze behaviors, however, behaviors were species- and context-specific. As distance to cover increased, southern leopard frogs increased freezing behavior, green tree frogs decreased freezing behavior, and Blanchard's cricket frogs increased flight response. The propensity of green tree frogs to use the canopy of vegetation as refugia, and the small body size of Blanchard's cricket frogs likely led to greater flight response as distance to cover increased, whereas innate reliance on camouflage among southern leopard frogs may place them at greater risk to landscaping, agricultural, and transportation practices in open terrain. As such, arboreal and small-bodied species may inherently be better suited in human altered-landscapes compared to larger, ground-dwelling species. As land-use change continues to modify habitats, understanding how species respond to changes in their environment continues to be of importance, particularly in ecosystems where human-wildlife interactions are expected to increase in frequency.
Habitat loss and fragmentation have led to a widespread increase in the proportion of edge habitat in the landscape. Disturbance-dependent bird species are widely assumed to benefit from these edges. ...However, anthropogenic edges may concentrate nest predators while retaining habitat cues that birds use to select breeding habitat. This may lead birds to mistakenly select dangerous habitat-a phenomenon known as an "ecological trap." We experimentally demonstrated how habitat shape, and thus amount of edge, can adversely affect nest site selection and reproductive success of a disturbance-dependent bird species, the Indigo Bunting (Passerina cyanea). We did so within a landscape-scale experiment composed of equal-area habitat patches that differed in their amount of edge. Indigo Buntings preferentially selected edgy patches, which contained 50% more edge than more compact rectangular patches. Further, buntings fledged significantly fewer young per pair in edgy patches than in rectangular patches. These results provide the first experimental evidence that edges can function as ecological traps.
The movement patterns of species may affect their susceptibility to modified habitat structure. It is likely that sedentary species perceive habitat features at smaller spatial extents compared to ...mobile species, but there is a lack of experimental research on the effects of fine-scale habitat characteristics on organisms of differing mobility. Spiders display two basic mobility levels based on foraging behavior: web-building species are restricted to specific sites whereas active hunters are mobile. We collected spiders inhabiting sagebrush shrubs with a structurally enhanced, unmodified, or removed understory, to examine (1) whether habitat structure in the immediate vicinity of shrubs affected cursorial and web spiders differently in terms of abundance and species richness and (2) which genera most contributed to changes in community composition. Shrubs without understory had reduced cursorial spider densities and species richness compared to shrubs with added and unmodified understories, whereas web spiders lacked significant responses to treatments. Community-level differences based on relative abundance of genera were detected in cursorial spiders but not in web spiders, despite a strong contribution of the web-building genus Theridion to community dissimilarities. Our results support the hypothesis that sedentary organisms may be sensitive to contiguous habitat at finer spatial scales than cursorial organisms, and highlight the risks associated with only collecting local habitat information when studying mobile species.
Die Bewegungsmuster von Arten können ihre Empfindlichkeit gegenüber modifizierten Habitatstrukturen beeinflussen. Wahrscheinlich nehmen sedentäre Arten Habitatmerkmale in kleineren räumlichen Bereichen wahr als mobile Arten, aber es gibt einen Mangel an experimentellen Untersuchungen zum Einfluss von kleinräumigen Habitatmerkmalen auf Organismen unterschiedlicher Mobilität. Spinnen zeigen zwei grundsätzliche Bewegungstypen in Bezug auf den Nahrungserwerb: die netzbauenden Arten bleiben an einem bestimmten Orte, während die Jäger mobil sind. Wir sammelten Spinnen, die Wüstenbeifuß-Büsche bewohnten. Der Unterwuchs der Büsche wurde mit künstlichen Strukturelementen angereichert, blieb unverändert oder wurde entfernt, um zu untersuchen, (1) ob die Habitatstruktur in der unmittelbaren Nähe der Büsche vagante und netzbauende Spinnen unterschiedlich hinsichtlich Abundanz und Artenreichtum beeinflusste, und (2) welche Gattungen am meisten zu Änderungen in der Zusammensetzung der Gemeinschaft beitrugen. Bei Büschen ohne Unterwuchs waren Abundanz und Artenreichtum der vaganten Spinnen verglichen mit den beiden anderen Behandlungen reduziert, während netzbauende Spinnen keine signifikante Reaktion zeigten. Unterschiede auf der Gemeinschaftsebene ergaben sich für die Dominanz von Gattungen der vaganten Spinnen, nicht aber bei den Netzbauern und das trotz eines deutlichen Beitrags der netzbauenden Gattung Theridion zur Unähnlichkeit der Gemeinschaften. Unsere Ergebnisse stützen die Hypothese, dass sedentäre Organismen auf feineren räumlichen Skalen in einem zusammenhängen Habitat reagieren als vagante Organismen, und sie unterstreichen die Risiken, die damit verbunden sind, bei einer Untersuchung zu mobilen Arten nur lokale Habitatinformationen zu sammeln.
Plant invasions are a current threat to biodiversity conservation, second only to habitat loss and fragmentation. Density and heights of three invasive plants,
Rosa multiflora,
Lonicera japonica, and
...Elaeagnus umbellata, were examined between edges and adjacent interiors of forest sites in southern Illinois. Density (stems
m
−2) and heights (cm) of invasive plants were obtained in plots along transects at edge and interior sampling locations within forest sites. The effect of species, sampling location, and site shape index on invasive plant density was investigated, as well as differences in heights of invasive plants in edge vs. interior sampling locations.
Species, sampling location, and fragment shape index were significant factors influencing invasive plant density at study sites. Density for all three species ranged from 0 to 18
stems
m
−2. All three species invaded interiors of sites, however,
R. multiflora and
L. japonica had significantly greater densities in edge as opposed to interior transects. These two species also had significant differences in density among site shape indices. Density of
E. umbellata was not significantly different between edge and interior sampling locations or among site shape indices. Mean heights of all three invasive plants were higher in edge transects, however, this relationship was only significant for
L. japonica.
These findings suggest that (1) preservation of tracts of forest with less edge can minimize invasion by these three plants in this area. Interiors of forest sites can be protected from invasion by having less edge habitat for invasive species to enter and become established; and (2)
E. umbellata, unlike the other two species, is established in both interior and edges of study sites. Therefore,
E. umbellata may pose the most ecological damage because it is well established throughout sites, and should be given a high priority when implementing management and control efforts in southern Illinois forest ecosystems.
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