Martens in the matrix: the importance of nonforested habitats for forest carnivores in fragmented landscapes

Habitat use by the endangered spotted-tailed quoll in a fragmented landscape

The spotted-tailed quoll (Dasyurus maculatus) is an endangered mesopredator endemic to Australia. It is generally considered a forest-dependent species associated with large, intact forested habitats. In Australia’s mainland, quoll research has typically been conducted in contiguous forest, and consequently, the species’ presumed forest-dependency might reflect sampling bias rather than preferred habitat niche. Recent studies have revealed that quolls also persist in fragmented agricultural landscapes, raising questions about their true habitat requirements and preferences. In this study, we investigated quoll habitat use within a fragmented agricultural landscape in mainland Australia. We deployed 42 lured camera traps to determine quoll habitat preferences across four broad vegetation types (open grassland, grassy woodland, dry sclerophyll forest, and wet sclerophyll forest) based on quoll activity and occupancy. Quolls were detected in all vegetation types, and quoll activity indicated a preference for dry sclerophyll forest and grassy woodlands, although this preference varied depending on the time of year. Our results suggest that quoll habitat use in mainland Australia is more flexible than previously assumed, and we recommend further research on factors that may influence habitat preference such as prey availability and seasonal behavior. Understanding the factors that drive habitat use by quolls outside of contiguous forested landscapes will inform and improve conservation and management strategies to ensure critical habitat for the species is protected and retained in an increasingly fragmented landscape.

Density estimates reveal that fragmented landscapes provide important habitat for conserving an endangered mesopredator, the spotted-tailed quoll

Native predators are increasingly exposed to habitat loss and fragmentation globally. When developing conservation and management strategies, it is important to determine whether fragmented landscapes can still support similar predator densities to intact areas, and thereby constitute important habitat for these species. The spotted-tailed quoll (Dasyurus maculatus) is an endangered Australian mesopredator that is often considered to be forest-dependent. While quolls are known to occur in some fragmented forest landscapes, it is unclear whether these areas represent sub-optimal habitat where quolls merely persist, or whether quolls can still occur at densities similar to those observed in intact forest landscapes. We used camera traps to detect quolls in both a fragmented and intact forested site, over three years. We used each quoll’s unique pelage pattern to identify individual quolls and estimate population density at each site. We were able to assign more than 94% of quoll image sequences across both sites to identify 173 individuals during the study. Density estimates of 0.13–0.66 quolls per km² at the fragmented site were comparable to estimates of 0.28–0.48 quolls per km² at the intact site. Our results highlight the importance of retaining and protecting forest fragments for the conservation of endangered quoll populations.

A framework for integrating inferred movement behavior into disease risk models

Movement behavior is an important contributor to habitat selection and its incorporation in disease risk models has been somewhat neglected. The habitat preferences of host individuals affect their probability of exposure to pathogens. If preference behavior can be incorporated in ecological niche models (ENMs) when data on pathogen distributions are available, then variation in such behavior may dramatically impact exposure risk. Here we use data from the anthrax endemic system of Etosha National Park, Namibia, to demonstrate how integrating inferred movement behavior alters the construction of disease risk maps. We used a Maximum Entropy (MaxEnt) model that associated soil, bioclimatic, and vegetation variables with the best available pathogen presence data collected at anthrax carcass sites to map areas of most likely Bacillus anthracis (the causative bacterium of anthrax) persistence. We then used a hidden Markov model (HMM) to distinguish foraging and non-foraging behavioral states along the movement tracks of nine zebra (Equus quagga) during the 2009 and 2010 anthrax seasons. The resulting tracks, decomposed on the basis of the inferred behavioral state, formed the basis of step-selection functions (SSFs) that used the MaxEnt output as a potential predictor variable. Our analyses revealed different risks of exposure during different zebra behavioral states, which were obscured when the full movement tracks were analyzed without consideration of the underlying behavioral states of individuals. Pathogen (or vector) distribution models may be misleading with regard to the actual risk faced by host animal populations when specific behavioral states are not explicitly accounted for in selection analyses. To more accurately evaluate exposure risk, especially in the case of environmentally transmitted pathogens, selection functions could be built for each identified behavioral state and then used to assess the comparative exposure risk across relevant states. The scale of data collection and analysis, however, introduces complexities and limitations for consideration when interpreting results.

Different increase rate in body mass of two marten species due to climate warming potentially reinforces interspecific competition

Many species show spatial variation in body size, often associated with climatic patterns. Studying species with contrasting geographical patterns related to climate might help elucidate the role of different drivers. We analysed changes in the body mass of two sympatric medium-sized carnivores—pine marten (Martes martes) and stone marten (Martes foina)—across Europe over 59 years. The body mass of pine marten increased with decreasing latitude, whereas stone marten body mass varied in a more complex pattern across its geographic range. Over time, the average body mass of pine martens increased by 255 g (24%), while stone marten by 86 g (6%). The greatest increase of body mass along both martens’ geographic range was observed in central and southern Europe, where both species occur in sympatry. The body mass increase slowed down over time, especially in allopatric regions. The average pine/stone marten body mass ratio increased from 0.87 in 1960 to 0.99 in 2019, potentially strengthening the competition between them. Thus, a differential response in body size to several drivers over time might have led to an adaptive advantage for pine martens. This highlights the importance of considering different responses among interacting species when studying animal adaptation to climate change.

Postrelease movement and habitat selection of translocated pine martens Martes martes

Monitoring postrelease establishment and movement of animals is important in evaluating conservation translocations. We translocated 39 wild pine martens Martes martes (19 females, 20 males) from Scotland to Wales. We released them into forested areas with no conspecifics in 2015, followed by a second release in 2016, alongside the previously released animals. We used radio-tracking to describe postrelease movement and habitat selection. Six martens (15%) were not re-encountered during the tracking period, of which four undertook long-distance dispersal. For the remaining individuals, we characterized two phases of movement, "exploration" followed by "settlement," that differed between releases. In the first release, martens remained in exploration phase for a mean of 14.5 days (SE = 3.9 days) and settled at a mean distance of 8.7 km (SE = 1.8 km) from release sites, whereas martens released in year two, alongside resident conspecifics, traveled away from release sites at a faster rate, settling sooner, at a mean of 6.6 days (SE = 1.8 days), but further, at a mean distance of 14.0 km (SE = 1.7 km) from release sites. Animals released in year one did not exhibit habitat preferences overall but within forests they favored recently felled areas, whereas animals released in year two showed strong selection for forested habitat but did not discriminate between forest types. The presence of conspecifics appeared influential for settlement and site fidelity of translocated martens and was associated with more rapid but more distant dispersal of the later cohort. Releases of animals in close proximity appeared to promote site fidelity and rapid establishment of ranges in the recipient environment.

Home-range size and fidelity of two sympatric Martes species

Determining variation in home-range behavior and the factors shaping this variation is crucial to better understand the biology of species and thus improve their management and conservation. We investigated age and sex variations in the home-range and core-area sizes, as well as fidelity to home range, of the stone marten (Martes foina (Erxleben, 1777)) and the European pine marten (Martes martes (Linnaeus, 1758)) in a rural area (Bresse, France) over several seasons. As expected, pine martens had larger home ranges and core areas than stone martens. Sex differences were also evidenced in both species in accordance with the typical mustelid pattern of socio-spatial organization. Beyond these differences, we found that both species responded to seasonal changes by adjusting seasonally the locations rather than their home-range and core-area sizes, especially stone martens. This difference might come from the higher intensity of perturbation in the preferred habitat of stone martens (human buildings), which explains why stone martens showed lower fidelity than pine martens.

The use of a mixed rubber landscape by tufted-ear marmosets

With the loss and fragmentation of tropical forests, the survival of primates depends on their ability to adapt to human-introduced modifications in their habitat. Marmosets are known for their ecological and behavioral plasticity and have been registered in various agricultural landscapes. Our goal was to describe the ecology of tufted-ear marmosets (Callithrix sp.) in a rubber/forest landscape, monitoring their use of habitat and diet. We followed two groups using radio telemetry and visual observations for nine months at the Michelin plantation Ltd. in Bahia, Brazil. Both groups used mainly pioneer forest and rubber with pioneer vegetation more than expected according to availability, even though they explored all types of vegetation. Rubber monocultures act as corridors for marmoset locomotion among more suitable habitats. Feeding, gummivory and socialization were mainly performed in the pioneer forest (with or without rubber), in which most sleeping sites and food sources were found. Groups of marmosets can incorporate agroforest matrixes to their area of use and activity patterns. Maintenance of marmosets in fragmented landscapes might be favored by their diet flexibility, with the use of resources such as gum and fruit, including exotic plants. Although known for their ecological flexibility, marmosets do require certain resources to be present in native habitat to adapt to agricultural landscapes. Patches of forest within a rubber landscape and pioneer vegetation in the rubber inter-rows should be considered to maintain populations of Callithrix in rubber landscapes.

Modelling the Distribution of Forest-Dependent Species in Human-Dominated Landscapes: Patterns for the Pine Marten in Intensively Cultivated Lowlands

In recent years, the "forest-specialist" pine marten Martes martes has been reported to also occur also in largely fragmented, lowland landscapes of north-western Italy. The colonization of such an apparently unsuitable area provided the opportunity for investigating pine marten ecological requirements and predicting its potential south- and eastwards expansion. We collected available pine marten occurrence data in the flood plain of the River Po (N Italy) and relate them to 11 environmental variables by developing nine Species Distribution Models. To account for inter-model variability we used average ensemble predictions (EP). EP predicted a total of 482 suitable patches (8.31% of the total study area) for the pine marten. The main factors driving pine marten occurrence in the western River Po plain were the distance from watercourses and the distance from woods. EP suggested that the pine marten may further expand in the western lowland, whilst the negligible residual wood cover of large areas in the central and eastern plain makes the habitat unsuitable for the pine marten, except for some riparian corridors and the pine wood patches bordering the Adriatic coast. Based on our results, conservation strategies should seek to preserve remnant forest patches and enhance the functional connectivity provided by riparian corridors.

Scenario-Led Habitat Modelling of Land Use Change Impacts on Key Species

Accurate predictions of the impacts of future land use change on species of conservation concern can help to inform policy-makers and improve conservation measures. If predictions are spatially explicit, predicted consequences of likely land use changes could be accessible to land managers at a scale relevant to their working landscape. We introduce a method, based on open source software, which integrates habitat suitability modelling with scenario-building, and illustrate its use by investigating the effects of alternative land use change scenarios on landscape suitability for black grouse Tetrao tetrix. Expert opinion was used to construct five near-future (twenty years) scenarios for the 800 km2 study site in upland Scotland. For each scenario, the cover of different land use types was altered by 5-30% from 20 random starting locations and changes in habitat suitability assessed by projecting a MaxEnt suitability model onto each simulated landscape. A scenario converting grazed land to moorland and open forestry was the most beneficial for black grouse, and 'increased grazing' (the opposite conversion) the most detrimental. Positioning of new landscape blocks was shown to be important in some situations. Increasing the area of open-canopy forestry caused a proportional decrease in suitability, but suitability gains for the 'reduced grazing' scenario were nonlinear. 'Scenario-led' landscape simulation models can be applied in assessments of the impacts of land use change both on individual species and also on diversity and community measures, or ecosystem services. A next step would be to include landscape configuration more explicitly in the simulation models, both to make them more realistic, and to examine the effects of habitat placement more thoroughly. In this example, the recommended policy would be incentives on grazing reduction to benefit black grouse.

Spatial Niche Segregation of Sympatric Stone Marten and Pine Marten--Avoidance of Competition or Selection of Optimal Habitat?

Coexistence of ecologically similar species relies on differences in one or more dimensions of their ecological niches, such as space, time and resources in diel and/or seasonal scales. However, niche differentiation may result from other mechanisms such as avoidance of high predation pressure, different adaptations or requirements of ecologically similar species. Stone marten (Martes foina) and pine marten (Martes martes) occur sympatrically over a large area in Central Europe and utilize similar habitats and food, therefore it is expected that their coexistence requires differentiation in at least one of their niche dimensions or the mechanisms through which these dimensions are used. To test this hypothesis, we used differences in the species activity patterns and habitat selection, estimated with a resource selection function (RSF), to predict the relative probability of occurrence of the two species within a large forest complex in the northern geographic range of the stone marten. Stone martens were significantly heavier, have a longer body and a better body condition than pine martens. We found weak evidence for temporal niche segregation between the species. Stone and pine martens were both primarily nocturnal, but pine martens were active more frequently during the day and significantly reduced the duration of activity during autumn-winter. Stone and pine martens utilized different habitats and almost completely separated their habitat niches. Stone marten strongly preferred developed areas and avoided meadows and coniferous or deciduous forests. Pine marten preferred deciduous forest and small patches covered by trees, and avoided developed areas and meadows. We conclude that complete habitat segregation of the two marten species facilitates sympatric coexistence in this area. However, spatial niche segregation between these species was more likely due to differences in adaptation to cold climate, avoidance of high predator pressure and/or food preferences by both species than competitive interaction between them.

Landscape genetics for the empirical assessment of resistance surfaces: the European pine marten (Martes martes) as a target-species of a regional ecological network

Coherent ecological networks (EN) composed of core areas linked by ecological corridors are being developed worldwide with the goal of promoting landscape connectivity and biodiversity conservation. However, empirical assessment of the performance of EN designs is critical to evaluate the utility of these networks to mitigate effects of habitat loss and fragmentation. Landscape genetics provides a particularly valuable framework to address the question of functional connectivity by providing a direct means to investigate the effects of landscape structure on gene flow. The goals of this study are (1) to evaluate the landscape features that drive gene flow of an EN target species (European pine marten), and (2) evaluate the optimality of a regional EN design in providing connectivity for this species within the Basque Country (North Spain). Using partial Mantel tests in a reciprocal causal modeling framework we competed 59 alternative models, including isolation by distance and the regional EN. Our analysis indicated that the regional EN was among the most supported resistance models for the pine marten, but was not the best supported model. Gene flow of pine marten in northern Spain is facilitated by natural vegetation, and is resisted by anthropogenic landcover types and roads. Our results suggest that the regional EN design being implemented in the Basque Country will effectively facilitate gene flow of forest dwelling species at regional scale.