David J. Kurz

Out-foxing the red fox: how best to protect the nests of the Endangered loggerhead marine turtle Caretta caretta from mammalian predation?

Recovery plans for the Endangered loggerhead marine turtle Caretta caretta cite mammalian predation as a major threat, and recommend nest protection efforts, already present at many rookery beaches, to protect eggs and hatchlings. Nest protection techniques vary but wire box cages and plastic mesh screens are two common tools used to deter predation by a host of beach-foraging, opportunistic mammalian predators. We empirically tested the efficacy of wire cages and plastic mesh screens in preventing red fox Vulpes vulpes predation on artificial nests. Both techniques averted fox predation (0%), whereas unprotected control nests suffered 33% predation under conditions of normal predator motivation, or a level of motivation stimulated by loggerhead turtle egg scent. However, in side-by-side comparisons under conditions of presumed high predator motivation, 25% of mesh screens were breached whereas no cage-protected nests were successfully predated. In addition to effectiveness at preventing predation, factors such as cost, ease of use, deployment time, and magnetic disturbance were evaluated. Our study suggests that the efficacy of plastic screens and the potential disadvantages associated with galvanized wire should influence selection of mechanical barriers on beaches where fox predation threatens loggerhead nests.

Tropical amphibians in shifting thermal landscapes under land-use and climate change

Land-cover and climate change are both expected to alter species distributions and contribute to future biodiversity loss. However, the combined effects of land-cover and climate change on assemblages, especially at the landscape scale, remain understudied. Lowland tropical amphibians may be particularly susceptible to changes in land cover and climate warming because many species have narrow thermal safety margins resulting from air and body temperatures that are close to their critical thermal maxima (CTmax ). We examined how changing thermal landscapes may alter the area of thermally suitable habitat (TSH) for tropical amphibians. We measured microclimates in 6 land-cover types and CTmax of 16 frog species in lowland northeastern Costa Rica. We used a biophysical model to estimate core body temperatures of frogs exposed to habitat-specific microclimates while accounting for evaporative cooling and behavior. Thermally suitable habitat area was estimated as the portion of the landscape where species CTmax exceeded their habitat-specific maximum body temperatures. We projected changes in TSH area 80 years into the future as a function of land-cover change only, climate change only, and combinations of land-cover and climate-change scenarios representing low and moderate rates of change. Projected decreases in TSH area ranged from 16% under low emissions and reduced forest loss to 30% under moderate emissions and business-as-usual land-cover change. Under a moderate emissions scenario (A1B), climate change alone contributed to 1.7- to 4.5-fold greater losses in TSH area than land-cover change only, suggesting that future decreases in TSH from climate change may outpace structural habitat loss. Forest-restricted species had lower mean CTmax than species that occurred in altered habitats, indicating that thermal tolerances will likely shape assemblages in changing thermal landscapes. In the face of ongoing land-cover and climate change, it will be critical to consider changing thermal landscapes in strategies to conserve ectotherm species.

Evaluating connectivity for tropical amphibians using empirically derived resistance surfaces.

Agricultural expansion continues to drive forest loss in species-rich tropical systems and often disrupts movement and distributions of organisms. The ability of species to occupy and move through altered habitats likely depends on the level of contrast between natural forest and surrounding land uses. Connectivity models, such as circuit theory models, are widely used in conservation biology, and their primary input consists of resistance surfaces representing movement costs associated with landscape features. Cost values are most frequently determined by expert opinion, which may not capture relevant levels of contrast among features. We developed resistance surfaces using experiments that represent different local mechanisms hypothesized to affect connectivity for two Neotropical amphibian species. Response ratios were calculated to translate experimental results to cost values used in connectivity modeling. We used relative abundance data in three land-cover types to generate resistance surfaces for evaluating independent support of models derived from experiments. Finally, we analyzed agreement among movement pathways predicted for each species and among three commonly used connectivity measures: Euclidean, least cost, and resistance distances. Experiments showed that extreme microclimates associated with altered habitats significantly increased desiccation and mortality risk for both species. Resistances estimated from microclimate experiments were concordant with those from survey data for both species. For one focal species, resistance estimates derived from predator encounter rates were also highly correlated with abundance-derived resistances. There was generally low agreement among the three alternative distance measures, which underscores the importance of choosing connectivity models that are most appropriate for the study objectives. Overall, similarity among linkages modeled for each species was high, but decreased with declining forest cover. Our results highlight the value of experiments for drawing inferences about processes in resistance modeling, as well as the need to consider model differences and species-specific responses when developing strategies to maintain connectivity.

Bearded pig (Sus barbatus) utilisation of a fragmented forest–oil palm landscape in Sabah, Malaysian Borneo

Abstract Context. Oil palm plantations have become a dominant landscape in Southeast Asia, yet we still understand relatively little about the ways wildlife are adapting to fragmented mosaics of forest and oil palm. The bearded pig is of great ecological, social and conservation importance in Borneo and is declining in many parts of its range due to deforestation, habitat fragmentation and overhunting. Aims. We assessed how the bearded pig is adapting to oil palm expansion by investigating habitat utilisation, activity patterns, body condition and minimum group size in a mosaic landscape composed of forest fragments and surrounding oil palm plantations. Methods. We conducted our study in Sabah, Malaysian Borneo, in and around the Lower Kinabatangan Wildlife Sanctuary, a protected area consisting of secondary forest fragments (ranging 1200–7400 ha) situated within an extensive oil palm matrix. We modelled bearded pig habitat use in forest fragments and oil palm plantations using survey data from line transects. Camera traps placed throughout the forest fragments were used to assess pig activity patterns, body condition and minimum group size. Key results. All forest transects and 80% of plantation transects showed pig presence, but mean pig signs per transect were much more prevalent in forest (70.00 ± 13.00 s.e.) than in plantations (0.91 ± 0.42 s.e.). Pig tracks had a positive relationship with leaf cover and a negative relationship with grass cover; pig rooting sites had a positive relationship with wet and moderate soils compared with drier soils. Ninety-five percent of pigs displayed ‘good’ or ‘very good’ body condition in forests across the study area. Pigs also aggregated in small groups (mean = 2.7 ± 0.1 s.e. individuals), and showed largely diurnal activity patterns with peak activity taking place at dawn and dusk. Groups with piglets and juveniles were more active during the day and less active at night as compared to overall activity patterns for all groups. Conclusions. Our findings suggest that bearded pigs in our study area regularly utilise oil palm as habitat, as indicated by their signs in most oil palm sites surveyed. However, secondary forest fragments are used much more frequently and for a wider range of behaviours (e.g. nesting, wallowing) than adjacent oil palm plantations. These forests clearly remain the most important habitat for the bearded pig in the Lower Kinabatangan Wildlife Sanctuary, and their protection is a high conservation priority for this species. Implications. Consistent bearded pig presence in oil palm is potentially an indication of successful adaptation to agricultural expansion in the study area. The apparently good body condition displayed by the vast majority of pigs in our study likely results from year-round cross-border fruit subsidies from surrounding oil palm plantations. The consistent diurnal activity displayed by groups containing piglets and juveniles may indicate predator avoidance strategies, whereas the substantial nocturnal activity we observed by other groups could suggest fewer threats for larger individuals. However, the overall effects of oil palm expansion in the region on bearded pig population health, foraging ecology, and movement ecology remain unknown.A

Restored Wetlands Can Support Mammalian Assemblages Comparable to Those in Nonmitigated Reference Wetlands

Abstract Restoration of wetland ecosystems has typically focused on hydrology, soil, and vegetation; taking an, “If you build it, they will come” strategy for the recovery of wetland fauna. We tested this assumption by quantifying mammal richness and abundance in recently restored and nonmitigated reference wetland habitats to determine if mammalian community composition varies with wetland condition. Our study consisted of live trapping and infrared photography at three restored and three reference (“natural”) wetland sites in Northeastern Ohio. After 3000 potential trap nights and 120 potential camera nights, we documented the presence of nine species and nearly 300 unique individuals in reference and restored wetlands. We found no significant differences in mammalian richness, abundance, or species composition between reference and restored wetlands; however, mammal abundance in terms of individual captures was 62% higher in restored wetland patches (n  =  194) than in reference wetlands (n  =  104). Restored wetlands – if managed correctly – can harbor mammalian communities as rich as those found in nonmitigated wetland habitats. Our results support the “Field of Dreams” hypothesis which suggests, among other things, that if the necessary physical conditions are present then desired fauna will subsequently colonize the patch. For small to midsized mammals in our study area, this appears to be the case.