Do alternative strategies of space use occur in male Alpine chamois?

Sexual segregation results in pronounced sex-specific density gradients in the mountain ungulate, Rupicapra rupicapra

Sex-specific differences in habitat selection and space use are common in ungulates. Yet, it is largely unknown how this behavioral dimorphism, ultimately leading to sexual segregation, translates to population-level patterns and density gradients across landscapes. Alpine chamois (Rupicapra rupicapra r.) predominantly occupy habitat above tree line, yet especially males may also take advantage of forested habitats. To estimate male and female chamois density and determinants thereof, we applied Bayesian spatial capture-recapture (SCR) models in two contrasting study areas in the Alps, Germany, during autumn. We fitted SCR models to non-invasive individual encounter data derived from genotyped feces. Sex-specific densities were modeled as a function of terrain ruggedness, forest canopy cover, proportion of barren ground, and site severity. We detected pronounced differences in male and female density patterns, driven primarily by terrain ruggedness, rather than by sex-specific effects of canopy cover. The positive effect of ruggedness on density was weaker for males which translated into a higher proportion of males occupying less variable terrain, frequently located in forests, compared to females. By estimating sex-specific variation in both detection probabilities and density, we were able to quantify and map how individual behavioral differences scale up and shape spatial patterns in population density.

Age-specific survival of territorial and non-territorial male chamois

How alternative reproductive tactics (ARTs) are maintained in wildlife populations is one of the major questions in evolutionary biology. As a dominant status, territoriality is typically linked to increased mating opportunities, and one explanation why this behaviour coexists with other tactics is that dominance implies survival costs. Such a trade-off may occur in the Northern chamois Rupicapra rupicapra, as reproductive advantages of territorial males over non-territorial males could be counterbalanced by a reduction in survival mediated through energy expenditure, stress and parasitic infections, ultimately favouring ART coexistence. Here, we analysed age-dependent survival probabilities of territorial (n = 15) and non-territorial (n = 16) adult chamois using information collected over 12 years between 2010 and 2021 in the Gran Paradiso National Park (Western Italian Alps). Survival rates were estimated with a CMR approach using Burnham's joint modelling of live encounter and dead recovery data. The model selection procedure, based on AICc value minimisation, supported a linear decrease of survival with age but the results did not match our predictions, as territorial chamois did not have lower survival rates than non-territorial chamois. In contrast, territorial males appeared to enjoy reproductive success at lower survival costs. This, in turn, supports the role of other factors, such as snow-dependent environmental stochasticity, in the maintenance of ARTs in chamois populations. The limited sample size, however, calls for caution in interpretation, and long-term studies of lifetime reproductive success and survival are necessary to clarify the mechanisms underlying the expression and coexistence of different reproductive behaviours in this species.

Staying close to home: Ecological constraints on space use and range fidelity in a mountain ungulate

Understanding patterns of animal space use and range fidelity has important implications for species and habitat conservation. For species that live in highly seasonal environments, such as mountain goats (Oreamnos americanus), spatial use patterns are expected to vary in relation to seasonal changes in environmental conditions and sex- or age-specific selection pressures. To address hypotheses about sex, age, and seasonality influence on space-use ecology, we collected GPS location data from 263 radio-collared mountain goats (males, n = 140; females, n = 123) in coastal Alaska during 2005-2016. Location data were analyzed to derive seasonal and sex-specific fixed-kernel home range estimates and to quantify the degree of seasonal range and utilization distribution overlap. Overall, we determined that home range size was smallest during winter, expanded coincident with the onset of green-up and parturition, and was largest during summer. Home range size of males and females did not differ significantly during winter, but females had larger home ranges than males during summer, a relationship that was switched during the mating season. Pairwise comparisons involving individual females across subsequent years indicated home ranges were significantly smaller during years when they gave birth to offspring. Mountain goats exhibited a strong degree of range fidelity, and 99% (n = 138) of individual animals returned to their previous year's seasonal range with an average annual Bhattacharyya's affinity utilization distribution overlap index of 68%. Similarity of seasonal home range utilization distributions varied in relation to sex and season in some respects. Home range overlap was highest during the summer vegetation growing season, particularly among females. These findings advance our understanding about how environmental variation and sex- and age-related reproductive constraints influence space use and range fidelity among alpine ungulates. Documentation of the high degree of range fidelity among mountain goats has important conservation implications in landscapes increasingly altered by anthropogenic activities.

Linking alternative reproductive tactics and habitat selection in Northern chamois

In polygynous ungulates, males may achieve fertilization through the use of alternative reproductive tactics (ARTs), discrete phenotypic variations evolved to maximize fitness. ARTs are often associated with different male spatial strategies during the rut, from territoriality to female-following. Although variation in space use patterns of rutting male ungulates is known to be largely affected by the spatial distribution of females, information on the year-round habitat selection of alternative reproductive types is scant. Here, we investigate the seasonal variation in habitat choice of a large mammal with ARTs (territoriality and nonterritoriality), the Northern chamois Rupicapra rupicapra. Global Positioning System (GPS) data on 28 adult males were collected between February 2010 and December 2013 in the Gran Paradiso National Park (Italy) and used to fit resource selection functions to explore the ART-specific use of key topographic features, such as elevation, aspect, and slope, and vegetation phenology expressed as NDVI values. Territorial and nonterritorial chamois profoundly differed in their habitat selection not only during the rutting season. Compared to nonterritorial males, territorial males used lower elevations in summer and autumn, preferred southern slopes in spring and summer, and used steeper areas in summer but not in winter. We found no difference in seasonal selection of NDVI values between males adopting ARTs. Our results suggest that territorial males tend to occupy warmer, lower-food-quality habitats in late spring and summer, whereas nonterritorial males are free to follow and exploit vegetation phenology and more favorable temperatures. Different patterns of habitat selection may reflect different trade-offs between the optimization of energy balances throughout the year and the increase of mating opportunities during the rut in males adopting alternative reproductive tactics.

Weather stochasticity and alternative reproductive tactics in Northern chamois, Rupicapra rupicapra

In polygynous ungulates, male breeding success is often achieved through alternative reproductive tactics (ARTs). The maintenance of ARTs in this taxon is largely explained by condition-dependent selection, a decision rule in which individuals switch their breeding behaviour on the basis of internal factors such as ageing (status-dependent selection), or external factors such as weather conditions during the rut (environment-dependent selection). In some species, however, ARTs are fixed during the mating season, and other forms of selective pressures rather than environment-dependent selection may contribute to the evolutionary maintenance of male types within populations. Assuming female vicinity as a proxy of mating opportunity, we explored the effect of snow depth variations on the elevational overlap between females, and territorial and non-territorial male chamois, Rupicapra rupicapra, in three consecutive rutting seasons. In snow-free periods, females overlapped with non-territorial males, but not with territorial ones. With increasing snow depth, females and territorial males progressively occupied similar elevations. Our results suggest that snow cover variations may impose changes in the spatial distribution of males and females. In turn, weather stochasticity over multiple ruts, rather than within-rut environment-dependent selection, may impose variations in mating opportunities of ARTs, possibly contributing to the coexistence of different phenotypes within populations.

Balkan Chamois (Rupicapra rupicapra balcanica) Avoids Roads, Settlements, and Hunting Grounds: An Ecological Overview from Timfi Mountain, Greece

Balkan chamois (Rupicapra rupicapra balcanica) is a protected species with an Inadequate-Bad (U2) conservation status in Greece. Our study explores its seasonal range use pattern, demography and habitat selection in a site of the Natura 2000 network, Timfi Mountain. To this aim, we examined 1168 observations obtained from six seasonal surveys (2002: four seasons, 2014 and 2017: autumn) and performed an ecological-niche factor analysis (ENFA), using 16 environmental and human-disturbance variables. The species had an annual range of 6491 ha (25% of the study area), followed the typical range-use pattern, and presented the minimum core area during the rutting season (autumn). Timfi Mt hosted 469 individuals in 2017 (the largest population in Greece), increasing by 3.55 times since 2002. The species selected higher altitudes during summer and autumn, pinewoods over broad-leaved woods as winter grounds, and it avoided south-facing slopes. Our results supported the anthropogenic risk avoidance hypothesis; the species always selected remote areas away from roads, human settlements, and hunting grounds. In Greece, 40% of its distribution area falls within hunting ban areas (16.5% of the country). A national conservation policy is needed towards maintaining and increasing roadless areas and hunting-ban areas within Balkan chamois range nationwide.

Predation may counteract climatic change as a driving force for movements of mountain ungulates

Temperature variations are expected to influence altitudinal movements of mountain herbivores and, in turn, those of their predators, but relevant information is scarce. We evaluated monthly relationships between temperature and altitude used by a large mountain-dwelling herbivore, the Himalayan tahr Hemitragus jemlahicus, and its main predator, the snow leopard Panthera uncia, in an area of central Himalaya for five consecutive years (2006-2010). In contrast to expectations, there was no significant direct relationship between altitude of tahr sightings and temperature. The mean altitude of tahr sightings decreased by c. 200m throughout our study. As expected, snow leopard movements tracked those of tahr, although the core area of the snow leopard did not move downwards. Tahr remained the staple of the snow leopard diet: we suggest that the former did not move upwards in reaction to higher temperature to avoid encounters with the latter. Avoidance of competition with the larger common leopard Panthera pardus at lower altitudes could explain why snow leopards did not shift their core area downwards. Apparently, interspecific interactions (predation; competition) influenced movements of Himalayan tahr and snow leopards more than climatic variations.

The effect of snow on space use of an alpine ungulate: recently fallen snow tells more than cumulative snow depth

Snow is one of the most limiting environmental factors for large wildlife of temperate and arctic zones during winter. Snow depth may limit space use, increase energy expenditure related to movement, limit resource availability, and ultimately affect individual survival. Most of the studies on the effect of snow on animal space use have used cumulative snow depth. The amount of recently fallen snow, however, could be more relevant for wildlife, especially in alpine and northern environments, where wind shifts and hardens the snow cover constantly. From 2011 to 2013, we studied space use of mountain goats (Oreamnos americanus (Blainville, 1816)) within Jasper National Park in Alberta, Canada. During winter, daily and weekly movements decreased with the amount of recently fallen snow, but not with cumulative snow depth. These results indicate that recently fallen snow should be included in wildlife space-use studies during winter. Limited movement and range size of mountain goats also highlight the energy-saving tactic used in winter by this species.

The genetic impact of translocations and habitat fragmentation in chamois (Rupicapra) spp

The chamois is a useful species with which to investigate the combined genetic impact of habitat fragmentation, over hunting, and translocations. Genetic variation within and between chamois (genus Rupicapra) populations was analyzed in 259 individuals from 16 sampling sites located in Italy, Spain, Slovakia, and the Czech Republic. Two mitochondrial DNA markers (control region and cytochrome b) and 11 nuclear microsatellites were typed. The principal results of this study can be summarized as follows: 1) high and significant differentiation between almost all chamois populations is observed even on a microgeographical scale, probably caused by the patchy distribution of this species, sharp geographical barriers to gene flow, and drift effects related to recent bottlenecks; 2) historical translocation events have left a clear genetic signature, including interspecific hybridization in some Alpine localities; 3) the Apennine subspecies of chamois, Rupicapra pyrenaica ornata, shows a high and similar level of divergence (about 1.5 My) from the Pyrenean (Rupicapra pyrenaica pyrenaica) and the Alpine (Rupicapra rupicapra) chamois; therefore, the specific status of these taxa should be revised. These results confirm the potential of population genetic analyses to dissect and interpret complex patterns of diversity in order to define factors important to conservation and management.

Disentangling the effects of recombination, selection, and demography on the genetic variation at a major histocompatibility complex class II gene in the alpine chamois

The major histocompatibility complex (MHC) harbours some of the most polymorphic loci in vertebrate genomes. MHC genes are thought to be subject to some form of balancing selection, most likely pathogen-mediated selection. Hence, MHC genes are excellent candidates for exploring adaptive processes. In this study, we investigated the genetic variation at exon 2 of the DRB class II MHC locus in 191 alpine chamois (Rupicapra rupicapra) from 10 populations in the eastern Alps of Italy. In particular, we were interested in distinguishing and estimating the relative impact of selective and demographic factors, while taking into account the confounding effect of recombination. The extremely high d(n)/d(s) ratio and the presence of trans-species polymorphisms suggest that a strong long-term balancing selection effect has been operating at this locus throughout the evolutionary history of this species. We analysed patterns of genetic variation within and between populations, and the mitochondrial D-loop polymorphism patterns were analysed to provide a baseline indicator of the effects of demographic processes. These analyses showed that (i) the chamois experienced a demographic decline in the last 5000-30 000 years, most likely related to the postglacial elevation in temperature; (ii) this demographic process can explain the results of neutrality tests applied to MHC variation within populations, but cannot justify the much weaker divergence between populations implied by MHC as opposed to mitochondrial DNA; (iii) similar sets of divergent alleles are probably maintained with similar frequencies by balancing selection in different populations, and this mechanism is also operating in small isolated populations, which are strongly affected by drift.