When we speak of the ‘snow leopard range’, we’re talking about a huge area – almost 2 million square kilometers, or roughly the same size as Mexico.
But how do we actually know where these cats live, and where they don’t?
In certain areas, we know snow leopards are present because we’ve seen the cats (or their signs). In other parts, there are reliable accounts from local people. But vast stretches of what we call snow leopard habitat haven’t ever been studied systematically, so nobody really knows if there are any snow leopards.
Instead, we put our faith in geophysical models. We look at things such as location, altitude, climate or terrain. If these factors match, we assume an area to be suitable for snow leopards – and so it becomes part of the 2 million square kilometer range of this cat.
Of course, this approach has its limits. We may well be missing some good habitat, perhaps because it’s at a lower altitude than what we think is typical. On the other hand, we may also be considering areas as snow leopard habitat that don’t actually have any cats – or where they may have gone locally extinct.
If our assumptions of where snow leopards occur are inaccurate, any population estimate built on these assumptions – whether it’s for a region or globally – will be inaccurate as well.
To reduce the uncertainty, researchers in India wanted to get a more accurate picture of where these cats really live, and how that may have changed over time. They published their surprising results in the scientific journal Oryx this month.
“We systematically interviewed local people across the state of Himachal Pradesh to find out where snow leopards occur today, and where they used to occur 30 years ago”, says Abhishek Ghoshal, a researcher with NCF and Wildlife Institute of India.
“We found that snow leopards only use 75% of what we presumed to be snow leopard habitat in the state”, Abhishek says. “In the remaining 25%, there don’t seem to have been any cats in the last 30 years.”
While the interviews Abhishek and his team conducted give reliable information on whether snow leopards occur in a certain area, they don’t provide information about how many cats there are – so it’s impossible to say whether the population has grown or declined. But the researchers at least found out that the snow leopard distribution in Himachal Pradesh hasn’t changed significantly since the mid 1980s. “It’s unlikely that the snow leopard has disappeared from any sites in Himachal Pradesh in the last three decades, which is a positive sign”, added Kulbhushansingh Suryawanshi, a co-author on the paper and director of the Snow Leopard Trust’s India Program. “But we also need to be mindful of the fact that the snow leopard range hasn’t expanded to any new areas in that time.”
Prey is key factor
While Abhishek’s work revealed that existing global habitat models for snow leopards do not fit Himachal Pradesh very well, his research also showed one possible better way to predict where snow leopards occur at vast spatial and long temporal scales: “the actual snow leopard habitat in Himachal Pradesh seems to overlap exactly with the distribution of prey species like ibex and blue sheep. Wherever we found one of the prey species, we found snow leopards as well.”
This result confirms earlier research that suggested prey was the most important condition for snow leopards to thrive. “Where there is no prey, there can be no predator. And at the scale of this work, whether the prey is ibex or blue sheep doesn’t seem to matter for snow leopards. As long as ibex or blue sheep are there, the snow leopard has a chance to persist in the long term”, Abhishek says.
However, the list of threats to the cat remains long, according to Yash Veer Bhatnagar, a senior scientist with NCF: “Traditional threats, such as intense migratory livestock grazing and hunting by local communities, continue to persist in some areas, while new threats related to an unprecedented thrust on infrastructure development in the region poses some largely unknown impacts on wildlife. Such development is likely to bring in related issues such as degradation, fragmentation of habitat and immigration of laborers in large numbers, some of whom may get involved in poaching and excessive natural resource extraction.”
Main insight: habitat maps should be improved with real-life data
First and foremost, the fact that a quarter of the potential snow leopard habitat of Himachal Pradesh doesn’t appear to contain any snow leopards is remarkable. It raises important questions about the reliability of maps and models predicting the cat’s distribution. “The study shows that we need to use caution when we rely on habitat and population models to assess how snow leopards are doing. Such maps are valuable tools to help fill in gaps – but we clearly need a lot more detailed data to make them reliable”, Abhishek says. “For instance, information on the densities of key prey species in various areas, or insights into the types of terrain snow leopards actually use within their habitat, could help make distribution maps more precise.”