- A study from the trans-Himalayan region looked into the spatial genetic pattern of blue sheep and found the gene flow and connectivity between populations to be restricted.
- The absence of physical corridors is believed to be affecting the movement between the populations studied in the Ladakh and Lahaul-Spiti regions of northern India.
- Experts fear this could have a long-term impact on the gene pool of the species and call for re-examination of protected area networks as one of the strategies.
It continues to be a matter of amusement how an ungulate that’s neither blue, nor a sheep, came to be called blue sheep. Morphological, behavioural and molecular analyses have shown that the sheep-like animal that varies in colour from slate gray to pale brown, is more closely related to goats than to sheep. Conservation science has very little information about the species since the blue sheep is mostly studied only as the prey base to the charismatic snow leopard.
A recent study, however, puts the spotlight on blue sheep (Pseudois nayaur), identifying conservation priority areas for the species. This is done by studying the landscape features that determine the distribution, genetic structure, flow and connectivity of the species in the trans-Himalayan region of India. Through field surveys, distribution modeling, genetic analysis and demographic assessments, the researchers found that about 18,775 km2 was suitable for blue sheep in the study area covering Lahaul and Spiti districts of Himachal Pradesh and Leh and Kargil districts of Ladakh.
The lead author of the paper, Stanzin Dolker of the Zoological Survey of India told Mongabay India that blue sheep is one of the least studied ungulates in the region, despite the species, along with the ibex, forming a major prey base for the two apex predators in the Himalayas — snow leopard and the Himlayan wolf.
While there is interest and funding support to study snow leopard, the blue sheep that maintains the snow leopard population is neglected, Dolker said, as a reason why she chose the species for the genetic study. Nepal-based researcher Kamal Thapa who has studied blue sheep, welcomed the effort saying that up until now, there is very little information about the genetic diversity of mountain goats. Conventionally, researchers study species through observation since genetic study, that provides information as unique as fingerprints, is expensive and impossible without funding, which is hard to come by for ungulate studies, Thapa, who was not associated with this study, maintained.
The study, that used faecal samples for the DNA analysis of the animal, analysed how the largely xeric (dry) trans-Himalayan region, with low resources, supports the blue sheep population which is feared to be on the decline in the last few decades. It also looked into the spatial genetic pattern of the species including the genetic flow and connectivity between two regions of Lahaul-Spiti and Ladakh. The study also looked into the bioclimatic influence on the species population and distribution.
Conducted in Leh, Kargil, Lahaul and Spiti districts, the study found that even though these are trans-Himalayan habitats, Leh and Spiti are more xeric with low precipitation and vegetation, while Kargil and Lahaul, at a slightly lower elevation, have high precipitation and more vegetation.
Blue sheep demands better corridors for better gene flow
Listed as “Least Concern” on the IUCN Red List of Endangered Species, experts dedicate this categorisation largely to its wide distribution, a presumably large global population and a lack of documented severe population declines. Globally, they are distributed across India, China, Bhutan, Nepal and northern Pakistan. In India, they are mostly found in Ladakh, Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh. A study in 2021 reported that blue sheep and other mountain ungulates have been increasingly threatened by human pressures as well as climate change. In India, it is a Schedule I species, enjoying the highest protection under the Wildlife Protection Act 1972.
Mukesh Thakur, a scientist with the Zoological Survey of India who co-authored the study said that in the absence of population estimation, it is hard to say how many blue sheep exist in the area though it is expected to be around 10,000-15,000. However, the study has shown that the population is genetically stable even though the genetic flow and connectivity among the two populations is limited, potentially due to limited physical corridor and patchiness in vegetation. The Zanskar range that divides the two regions is found to be such a barrier between the two populations. Experts maintained that genetic flow and connectivity between populations are important for the long-term health and sustenance of the species.
“If there is a restricted gene flow of a free ranging population in a landscape, over the years or over the generations, the population could resort to inbreeding, and may undergo severe demographic changes, which can affect the long-term survival of the species,” Dolker explained. Landscape barriers restrict gene flow and create regional genetic signatures in the future. A population is considered viable only if the gene flow is maintained, she said.
The researchers also found that the populations move downwards during winter and the probability of the exchange of the males and females between the groups is high during this transition. “This is a kind of a behavioural phenomenon that keeps enriching their gene pool by exchanging the male and female between the groups during migration,” said Thakur.
Global warming threatens the population stability
Since the study was conducted in areas with low human habitation, the anthropogenic pressures were insignificant, but the paper reported that the bioclimatic variables are a concern. Earlier studies have shown that snow leopards in the Himalayan region are moving upwards owing to global warming. Scientists say that blue sheep too have been found to scale heights, probably in search of food resources. “Blue sheep are now found at 5800 m altitude from 5600 m earlier,” said Thapa. He informed that apart from climatic variables, the spread of exotic invasive species replacing native species in the Himalayas is another cause for the upward movement of the blue sheep population.
Of about the 106,014 km2 of the study area, only 18,775 km2 (<20%), that lies primarily in Leh region of Ladakh (LA) and Spiti region of Lahaul-Spiti, was found to be suitable for the blue sheep, the study notes. The study calls for a reexamination of protected area networks as most of the suitable habitat as well as geographical corridors for blue sheep were found to fall outside the current protected area networks. “We need a better understanding on how the protected area network can be made efficient for conserving the blue sheep as the species depends a lot on indigenous vegetation,” Thakur said. The study underscores the importance of maintaining geographic corridors for the populations to maintain a healthy gene pool of the species.
Banner image: A camera trap image of a blue sheep with its lamb. Experts believe there is a need for a re-examination of protected areas network in the trans-Himalayan region as suitable habitats for the animal. Photo by NMHS