Using distance sampling with camera traps to estimate the density of group-living and solitary mountain ungulates

Throughout the Himalaya, mountain ungulates are threatened by hunting for meat and body parts, habitat loss, and competition with livestock. Accurate population estimates are important for conservation management but most of the available methods to estimate ungulate densities are difficult to implement in mountainous terrain. Here, we tested the efficacy of the recent extension of the point transect method, using camera traps for estimating density of two mountain ungulates: the group-living Himalayan blue sheep or bharal Pseudois nayaur and the solitary Himalayan musk deer Moschus leucogaster. We deployed camera traps in 2017–2018 for the bharal (summer: 21 locations; winter: 25) in the trans-Himalayan region (3,000–5,000 m) and in 2018–2019 for the musk deer (summer: 30 locations; winter: 28) in subalpine habitats (2,500–3,500 m) in the Upper Bhagirathi basin, Uttarakhand, India. Using distance sampling with camera traps, we estimated the bharal population to be 0.51 ± SE 0.1 individuals/km2 (CV = 0.31) in summer and 0.64 ± SE 0.2 individuals/km2 (CV = 0.37) in winter. For musk deer, the estimated density was 0.4 ± SE 0.1 individuals/km2 (CV = 0.34) in summer and 0.1 ± SE 0.05 individuals/km2 (CV = 0.48) in winter. The high variability in these estimates is probably a result of the topography of the landscape and the biology of the species. We discuss the potential application of distance sampling with camera traps to estimate the density of mountain ungulates in remote and rugged terrain, and the limitations of this method.

Understanding population baselines: status of mountain ungulate populations in the Central Tien Shan Mountains, Kyrgyzstan

We assessed the density of argali (Ovis ammon) and ibex (Capra sibirica) in Sarychat-Ertash Nature Reserve and its neighbouring Koiluu valley. Sarychat is a protected area, while Koiluu is a human-use landscape which is a partly licenced hunting concession for mountain ungulates and has several livestock herders and their permanent residential structures. Population monitoring of mountain ungulates can help in setting measurable conservation targets such as appropriate trophy hunting quotas and to assess habitat suitability for predators like snow leopards (Panthera uncia). We employed the double-observer method to survey 573 km2 of mountain ungulate habitat inside Sarychat and 407 km2 inside Koiluu. The estimated densities of ibex and argali in Sarychat were 2.26 (95% CI 1.47–3.52) individuals km−2 and 1.54 (95% CI 1.01–2.20) individuals km−2, respectively. Total ungulate density in Sarychat was 3.80 (95% CI 2.47–5.72) individuals km−2. We did not record argali in Koiluu, whereas the density of ibex was 0.75 (95% CI 0.50–1.27) individuals km−2. While strictly protected areas can achieve high densities of mountain ungulates, multi-use areas can harbour meaningful though suppressed populations. Conservation of mountain ungulates and their predators can be enhanced by maintaining Sarychat-like “pristine” areas interspersed within a matrix of multi-use areas like Koiluu.

Climatic changes and the fate of mountain herbivores

Mountains are strongly seasonal habitats, which require special adaptations in wildlife species living on them. Population dynamics of mountain ungulates are largely determined by the availability of rich food resources to sustain lactation and weaning during summer. Increases of temperature affect plant phenology and nutritional quality. Cold-adapted plants occurring at lower elevations will shift to higher ones, if available. We predicted what could happen to populations of mountain ungulates based on how climate change could alter the distribution pattern and quality of high-elevation vegetation, using the “clover community-Apennine chamois Rupicapra pyrenaica ornata” system. From 1970 to 2014, increasing spring temperatures (2 °C) in our study area led to an earlier (25 days) onset of green-up in Alpine grasslands between 1700 and 2000 m, but not higher up. For 1970–2070, we have projected trends of juvenile winter survival of chamois, by simulating trajectories of spring temperatures and occurrence of clover, through models depicting four different scenarios. All scenarios have suggested a decline of Apennine chamois in its historical core range, during the next 50 years, from about 28% to near-extinction at about 95%. The negative consequences of climate changes presently occurring at lower elevations will shift to higher ones in the future. Their effects will vary with the species-specific ecological and behavioural flexibility of mountain ungulates, as well as with availability of climate refugia. However, global shifts in distributional ranges and local decreases or extinctions should be expected, calling for farsighted measures of adaptive management of mountain-dwelling herbivores.

Cooperative defence of female chamois successfully deters an eagle attack

In mountain ungulates, antipredator behaviour is one of the main constraints on foraging behaviour and habitat selection, especially when newborn, vulnerable offspring are present. Golden eagles have been known to prey on ungulates successfully, but predation may be relatively rare on chamois. Here, we report an unsuccessful predation attempt by a golden eagle on a kid of Apennine chamois. The kid was grazing in a female kid mixed herd, and the attack by the eagle was deterred by cooperative defence of females. Chamois are a social species: defending other females’ fawns may be consistent with the importance of cooperative maternal behaviour in kin groups.