Climate and anthropogenic factors determine site occupancy in Scotland's Northern-range badger population: implications of context-dependent responses under environmental change

Effects of weather and social factors on hormone levels in the European badger (Meles meles)

Animals in the wild continually experience changes in environmental and social conditions, which they respond to with behavioural, physiological and morphological adaptations related to individual phenotypic quality. During unfavourable environmental conditions, reproduction can be traded-off against self-maintenance, mediated through changes in reproductive hormone levels. Using the European badger (Meles meles) as a model species, we examine how testosterone in males and oestrogens in females respond to marked deviations in weather from the long-term mean (rainfall and temperature, where badger earthworm food supply is weather dependent), and to social factors (number of adult males and females per social group and total adults in the population), in relation to age, weight and head-body length. Across seasons, testosterone levels correlated postively with body weight and rainfall variability, whereas oestrone correlated positively with population density, but negatively with temperature variability. Restricting analyses to the mating season (spring), heavier males had higher testosterone levels and longer females had higher oestradiol levels. Spring oestrone levels were lower when temperatures were above normal. That we see these effects for this generally adaptive species with a broad bioclimatic niche serves to highlight that climatic effects (especially with the threat of anthropogenic climate change) on reproductive physiology warrant careful attention in a conservation context.

Sett Use, Density and Breeding Phenology of Badgers in Mediterranean Agro-Sylvo-Pastoral Systems

Simple Summary

Understanding carnivores social structure variation is pivotal for properly addressing conservation challenges and solutions. The European badgers is a social carnivore for which most of the available information regarding how this species is socially organized derives from central west populations. This article describes the group composition, den use patterns and breeding phenology of a Mediterranean population of badgers. We showed that badger live in low density, in relatively small groups, composed by 2–4 adult animals and ca. 2 cubs, born in winter. These patterns, representing a variation of what was described for other populations, show that badgers take advantage of the landscape context, where human-related resources and mild environmental conditions allow badger to reach higher densities than in many southern populations, and to reproduce earlier than their northern counterparts.

Abstract

Carnivores social organization varies widely, from strongly social to solitary predators. European badgers are facultative social carnivores that also shows a geographical variation in social structure. These patterns derive mainly from central/west European regions, with an under-representation of Mediterranean populations that face different conservation challenges, especially regarding group composition, sett use patterns and breeding phenology. We addressed these traits topics for a population inhabiting a Portuguese agro-silvo-pastoral system. Based on monthly monitoring of 34 setts and continuous camera-trapping surveys of 12, we showed that setts surrounded by diversified vegetation and located in sandy sites are more used, a pattern probably linked to food availability and ease of sett excavation and maintenance, respectively. Badgers followed a general pattern regarding group size (2–4 adults), but showed an intermediate population density (0.49–0.73 badgers/km²), with values higher than those estimated for other Mediterranean environments, but lower than for central-western populations. This, together with the breeding (November/January) and cub emergence (1.8 cubs/sett; March/April) periods, indicates an ecological adaptation to the landscape context, where human-related resources and mild environmental conditions allow badger to reach higher densities than in many southern populations, and to reproduce earlier than their northern counterparts.

How far from the road should land cover be assessed? A case study on mesopredator mortality on roads

The methods used to assess the significance of land cover in the vicinity of a road for the mortality of mesopredators are diverse. In assessing the effect of land cover along the road on road causalities, scientists use various buffer sizes, or even no buffer along the road. The aim of this study was to verify how results of land cover effects on the mortality of mesopredators on roads may differ when analyzing various buffer sizes from the road. We assessed road causalities in the Warmian-Masurian voivodeship (Poland) from 3 consecutive years: 2015, 2016, and 2017. The roads were divided into equal sections of 2000 m each with buffer size of radius: 10, 250, 500, and 1000 m. We analyzed the number of road kills of red fox and European badger separately in a generalized linear model, whereas explanatory variables we used land cover types (based on the Corine Land Cover inventory) and traffic volume. Mean annual mortality from road collisions amounts to 2.36% of the red fox population and 3.82% of the European badger population. We found that the buffer size determines the results of the impact of land cover on mesocarnivore mortality on roads. The red fox differed from the European badger in response to land cover depending on the buffer size. The differences we have shown relate in particular to built-up areas. Our results indicate a 500-m buffer as best reflecting the land cover effects in road kills of both species. This was confirmed by model evaluation and a tendency to use or avoid the vicinity of human settlements of the analyzed species. We concluded that buffer size will probably affect mostly the significance of cover types that are spatially correlated with roads, positively or negatively. We suggest that the home range size of given species in local conditions should be assessed before determining the size of the buffer for analysis.

What lies beneath? Population dynamics conceal pace-of-life and sex ratio variation, with implications for resilience to environmental change

Life-history and pace-of-life syndrome theory predict that populations are comprised of individuals exhibiting different reproductive schedules and associated behavioural and physiological traits, optimized to prevailing social and environmental factors. Changing weather and social conditions provide in situ cues altering this life-history optimality; nevertheless, few studies have considered how tactical, sex-specific plasticity over an individual's lifespan varies in wild populations and influences population resilience. We examined the drivers of individual life-history schedules using 31 years of trapping data and 28 years of pedigree for the European badger (Meles meles L.), a long-lived, iteroparous, polygynandrous mammal that exhibits heterochrony in the timing of endocrinological puberty in male cubs. Our top model for the effects of environmental (social and weather) conditions during a badger's first year on pace-of-life explained <10% of variance in the ratio of fertility to age at first reproduction (F/α) and lifetime reproductive success. Conversely, sex ratio (SR) and sex-specific density explained 52.8% (males) and 91.0% (females) of variance in adult F/α ratios relative to the long-term population median F/α. Weather primarily affected the sexes at different life-history stages, with energy constraints limiting the onset of male reproduction but playing a large role in female strategic energy allocation, particularly in relation to ongoing mean temperature increases. Furthermore, the effects of social factors on age of first reproduction and year-to-year reproductive success covaried differently with sex, likely due to sex-specific responses to potential mate availability. For females, low same-sex densities favoured early primiparity; for males, instead, up to 10% of yearlings successfully mated at high same-sex densities. We observed substantial SR dynamism relating to differential mortality of life-history strategists within the population, and propose that shifting ratios of 'fast' and 'slow' life-history strategists contribute substantially to population dynamics and resilience to changing conditions.

Climate and landscape changes as driving forces for future range shift in southern populations of the European badger

Human-Induced Rapid Environmental Change (HIREC), particularly climate change and habitat conversion, affects species distributions worldwide. Here, we aimed to (i) assess the factors that determine range patterns of European badger (Meles meles) at the southwestern edge of their distribution and (ii) forecast the possible impacts of future climate and landcover changes on those patterns. We surveyed 272 cells of 5 × 5 km, to assess badger presence and confirmed its occurrence in 95 cells (35%). Our models estimate that badger’s presence is promoted by the occurrence of herbaceous fields and shrublands (5%–10%), and low proportions of Eucalyptus plantations (<~15%). Regions with >50% of podzols and eruptive rocks, higher sheep/goat density (>4 ind/km²), an absence of cattle, intermediate precipitation regimes (800–1000 mm/year) and mild mean temperatures (15–16 °C) are also more likely to host badgers. We predict a decrease in favourability of southern areas for hosting badgers under forecasted climate and landcover change scenarios, which may lead to a northwards retraction of the species southern distribution limit, but the overall landscape favourability is predicted to slightly increase. The forecasted retraction may affect community functional integrity, as its role in southern ecological networks will be vacant.