We are happy to see the comprehensive book on snow leopards and their biology that was published earlier this summer (1).
However, a group of authors state in a chapter of this book (2) that the global snow leopard population may be significantly higher than prevailing estimates. This claim and its implications, which have been highlighted in a press release (3) and have been covered in several media articles, are scientifically unconvincing.
We believe that conservation of endangered species should be guided by the best possible science. In the case of the snow leopard, only few rigorous population and distribution studies exist, and most of the population estimates are based on extrapolations.
Any such extrapolation must be applied with utmost care and a thorough understanding of its limitations and pitfalls. An uncritical use of survey methodologies, on the other hand, can lead to incorrect conclusions, and, as a result, a slackening of conservation efforts, with potentially grave consequences for the species.
The prevailing range of global estimates of the snow leopard population varies between 3920 and 7500. These estimates have come from various local and regional sources. In the above-mentioned book, on the other hand, the authors estimate that in just 44% of their global range, there may be between 4,678 and 8,745 cats – implying there could be twice as many in the total range.
This estimate, which is largely based on data assembled for a conservation meeting in 2008, has significant flaws.
- The authors arrive at their global population estimate by adding up regional population estimates for 68 so-called ‘Snow Leopard Conservation Units’, or SLCUs; making up 44% of the possible global snow leopard range. Only 6 of these 68 regional estimates are based on solid survey methods such as camera trapping using the mark-recapture framework or genetic data, which are considered scientifically acceptable. The rest are based on sign surveys (which can be very useful tools for the detection of a species’ presence, but are of limited value for an estimate of population numbers); interviews with local communities; and ’expert opinion’. Abundance estimates based on sign surveys have long been rejected by the Snow Leopard Network. The authors don’t provide more detailed sources on the snow leopard numbers for the different conservation units, so we have to assume that a large part of the data they used to arrive at their overall population estimate are extrapolations based on untested assumptions, and have not been scientifically peer-reviewed or published.
- The suggestion in the chapter that that there may be between 4,678 and 8,745 snow leopards in only 44 percent of their global range is highly misleading. The total surface area of the Snow Leopard Conservation Units (SLCUs) used in this estimate may only represent 44% of the possible snow leopard range (i.e. any area that has the necessary ecological features to contain snow leopards, 1,670,906 km2), but they represent more than 100% of the definitive (i.e. areas where the cat’s presence is confirmed; 892,435 km2) and probable ranges (i.e. areas with a high likelihood and recent records of snow leopards, but no definitive proof; 214,969 km2). In simpler terms, the area within which the authors have estimated the population contains the entire confirmed and likely snow leopard habitat.
Even if the population estimates for these SLCUs were scientifically sound (which, as shown above, they are not – they are, in fact, highly inadequate in their coverage), it would still be inadmissible to assume comparable densities across the entire ‘possible’ snow leopard range.
- Population studies of large carnivores, even if sampling is done across several hundred square kilometers, tend to be done in high-quality habitats with relatively high densities of the species of interest. Studies in smaller areas don’t represent density, but rather intensity of use, and can thus be misleading.
- While this allows efficient data collection, it poses significant statistical challenges for extrapolations, even if the base study’s methodology were scientifically sound. The snow leopard occurs in a vast range, where a large variety of more or less suitable habitats and threats exist. Simply assuming a stable density across this range is highly problematic, especially when study areas are not randomly selected, but biased towards areas with high density. Another challenge for estimating snow leopard numbers is the fact that only about 1.5% of the total possible snow leopard range has been sampled rigorously for snow leopard abundance, and only 14% has been covered by any form of field research at all, according to a literature review by the WWF (in preparation).
- The authors did not consider in their assessment recent studies that indicate major declines in snow leopard populations. In Pakistan, recent surveys based on camera trapping and fecal genetics in more than 70% of the country’s high quality snow leopard habitat (4) have yielded a much lower snow leopard population number in the country than previously believed. For the Alay range of Kyrgyzstan, based on interviews of local stakeholders, Taubmann et al (5) have reported significant declines in the snow leopard distribution. The aforementioned authors, in the new book, on the other hand, assume stable snow leopard populations in these areas.
The authors claim that “as more research is undertaken in snow leopard range and more technologies such as camera traps and noninvasive genetics are employed, it is becoming clear that there are likely more snow leopards than previously thought”. While it is correct that research efforts have greatly increased and have led to more available data on these cats, there is no valid, scientific evidence in this data of a greater overall population.
The fact that we now have more snow leopard studies and photos doesn’t mean that we have more snow leopards. On the contrary: results from large landscapes (e.g. Pakistan and Nepal) where robust surveys on snow leopard population have been carried out suggest that current guesstimates of snow leopard populations are either too high, or that there has been a significant decline in the populations.
Claims about populations of endangered species that aren’t based on solid science can be a disservice to conservation
While we still don’t know enough to make reliable statements on their global populations and trends, we do know that the threats to these cats are not decreasing. In fact, many new threats to snow leopards and their habitats have emerged, such as large-scale linear developments, mining, and climate change. While immense conservation efforts are being undertaken by many organizations, including the Snow Leopard Trust, there remain significant gaps and unaddressed threats. We must not grow complacent in our efforts to address these threats.
In the ‘Bishkek Declaration’ of 2013, the range country governments have committed to securing the snow leopard’s future through the ‘Global Snow Leopard & Ecosystem Plan’. To achieve the plan’s ambitious goal of securing 20 snow leopard landscapes by 2020, we must continue to partner with research institutions as well as the public and private sectors to scale our research and conservation efforts across the snow leopard’s range. Rather than distracting ourselves by speculating over the number of snow leopards left in the wild, we must expand reliable scientific surveys of global snow leopard populations, so we can continue to make informed decisions based on the best available science.
In 2017, the President of Kyrgyzstan is hosting a global summit on snow leopards and their conservation. This will be a unique opportunity for the conservation community, governments, and international donors to not only renew their commitment to saving this cat, but to also assess what we know, what we don’t know, and how to close those knowledge gaps.
Several staff members of the Snow Leopard Trust and its partner organizations have contributed chapters to the same book. They were not part of the team of authors who wrote the chapter in question. The content of book chapters not co-authored by Snow Leopard Trust staff members do not necessarily reflect the views of the organization.
(1 & 2)
McCarthy, T., Mallon, D., Sanderson, E.W., Zahler, P. and Fisher, K.: Chapter 3: What is a Snow Leopard? Biogeography and Status Overview. In: (1) Nyhuis, P.J., McCarthy, T., and Mallon, D. (Eds.): Biodiversity of the World: Conservation from Genes to Landscapes. 1st Edition. Snow Leopards. Elsevier Press, 2016, p. 22-42.