Determining whether a snow leopard population is thriving, stable or declining isn’t as simple as counting how many cats you see. Scientists must track the complete life cycle, from birth to death, to get the full picture. You need to know if enough cubs are surviving to replace the adults that die. This is one of the reasons we use GPS collars and camera traps to track individual snow leopards and their families over many years, gathering detailed data to make smart conservation decisions. Survival vs. Reproduction Balance Imagine you’re tracking a group of 20 adult snow leopards (10 males and 10 females) in the wild. To understand if this population is healthy, you need to look at two key numbers: How many die each year (death rate) How many new cubs survive to adulthood (birth rate) Let’s compare two different areas in a real-world example: Area A (Worse survival): 20% of cats die each year (4 out of 20) 80% survival rate Area B (Better survival): 10% of cats die each year (2 out of 20) 90% survival rate At first glance, Area A looks like it’s in trouble with twice as many deaths. But here’s the key question: Are enough snow leopards being born to replace the ones that die? The Reproduction Factor We currently do not know exactly how many surviving cubs a female snow leopard produces in a year. (Cubs typically stay with their mothers for two years.) But if each female snow leopard raises an average of 0.6 cubs per year that survive to independence, then: 10 females × 0.6 cubs = 6 new snow leopards per year The Math: Area A loses 4 cats but gains 6 = net gain of 2 cats Area B loses 2 cats but gains 6 = net gain of 4 cats Both populations are actually growing, even though Area A has a higher death rate. The Waiting Game There’s one important catch: snow leopards don’t start having their own cubs until they’re 3-4 years old. So there’s always a delay between when adults die and when the cubs can replace them by reproducing. The Hidden Danger: Sink vs. Source Populations Sometimes, a population can look stable on the surface but actually be in serious trouble. Imagine an area that consistently has 20 snow leopards year after year. This might seem healthy, but what if eight cats die annually while only four cubs survive to adulthood? The population may stay at 20 because four new snow leopards are moving in from other areas each year. Scientists call this a ‘sink population’ – it’s like a leaky bucket that needs constant refilling from somewhere else. Conversely, some areas produce more cubs than they lose adults, creating a ‘source population’ of surplus cats. Such source-sink systems help maintain larger overall populations and add to population stability. The problem is that sink populations are relatively unsustainable – if the source areas stop producing extra cats, the sink will quickly collapse. That’s why simply counting snow leopards isn’t enough; we need to understand whether each population is truly self-sustaining or secretly dependent on others. Why This Matters This research is vital for assessing species vulnerability. Mathematical models, used by organizations like the IUCN to create the ‘Red List’ that assigns protection status to species worldwide, need accurate data for these critical decisions. That’s why every collared snow leopard and every cub monitored matters for the species’ future. Check out this simplified version of one of four matriarchal lines documented in our long-term ecological study in Tost, Mongolia.  Sign up for our monthly E-News to get all the latest updates from the field delivered to your inbox. Photo credits: SLCF-Mongolia, SLF-Kyrgyzstan, Snow Leopard Trust and Kesang Chunit Acknowledgements: This long-term ecological study is in collaboration with Snow Leopard Conservation Foundation in Mongolia and Snow Leopard Trust, with special thanks to the Ministry of Nature, Environment and Tourism, the Government of Mongolia, and the Mongolian Academy of Sciences for their support. We would also like to acknowledge: Acton Family Giving, Bioparc Zoo de Doue la Fontaine, David Shepherd Wildlife Foundation, Idaho Falls Zoo at Tautphaus Park, John Ball Zoo, Kolmårdens Zoo, Korkeasaari Zoo, National Geographic Society, Nordens Ark, Parco Zoo Punta Verde, Play for Nature, Tierpark Berlin, The Big Cat Sanctuary/Wildlife Heritage Foundation, Tulsa Zoo, Whitley Fund for Nature, Zoo Basel, Zoo Dresden, Zoo New England and the many incredible partners who have supported programs like our Long-term Ecological Study and research in Mongolia since it began in 2008. We could not do this work without you. The post Cracking the Code: Calculating Snow Leopard Survival appeared first on Snow Leopard Trust.