Signs at the Top: Habitat Features Influencing Snow Leopard Uncia uncia Activity in Sagarmatha National Park, Nepal

1. What they did

Snow leopards disappeared from the Mount Everest region of Nepal in the 1960s. They have recently come back to Sagarmatha (Mount Everest) National Park, apparently following the recovery of Himalayan tahr, their main prey. The authors asked what shapes where these returning cats are active: the land itself, their prey, or people. They predicted that snow leopards would be most active where tahr were plentiful and less active near busy human areas.

• Finding signs. Over three field seasons (2004, 2005 and 2006), two people trekked the four main valleys of the park, visiting every place where they judged snow leopards and tahr to occur. They followed the standard methods of the Snow Leopard Information Management System. They recorded scrapes, feces, footprints, spray or scent marks and places where the cats had rubbed against rock, with a Global Positioning System (GPS) location for each. Signs within 50 m of each other in the same year were counted as one site.
• Describing the habitat. For each sign site, and for five times as many randomly chosen sites in surveyed areas with no sign, they measured elevation, slope, winter snow depth, distance from rivers, distance from trails and from settlements, using a Geographic Information System (GIS).
• Mapping prey. They counted tahr herds from vantage points with binoculars and spotting scopes, and turned the herd locations into a map of where tahr spend their time.
• Modelling. They compared sign sites with the available sites using logistic regression, chose the best model with the Akaike Information Criterion (AIC), and checked it by rebuilding it four times, each time with a quarter of the data held back.

2. What they found

The signs

• 223 sign locations were found: 131 scrapes, 55 feces, 23 pugmarks (footprints, 15 of them in 2005), 7 spray or scent marks and 7 rubbing sites.
• The models did not differ between years or sign types, so all signs were pooled. After joining signs within 50 m of each other, 177 sites were left for analysis.

What predicted where signs were found

The best model included every variable and explained the data well (area under the curve 0.934).

• Elevation: signs were more common at lower elevations, which surprised the authors, since snow leopards are generally thought to prefer high ground.
• Snow depth: signs were more common where winter snow was shallower.
• Slope: signs were somewhat less common on steep ground, a weaker effect. The authors note this may come from averaging slope over each 50 x 50 m cell.
• Rivers: the paper reports a significant positive relationship with distance from rivers but reads it as a preference for being near rivers or valleys.
• People: signs were more common farther from trails, a strong effect. Distance from settlements stayed in the best model but was not significant.
• Prey: signs were more common where tahr herds were denser, but this effect was weaker than elevation, snow depth and distance from rivers.

3. What they concluded

• Terrain and human activity were the most important factors in where snow leopards were active; tahr had a more moderate effect.
• The cats seem to trade off between milder conditions at lower elevations and avoiding people. Being more active low down puts them in the areas most likely to bring them close to humans.
• Most trails carry tourists, guides, porters and yak caravans, which may disturb these secretive cats, even though hunting is not common in the area. Humans may be a substantial factor in where snow leopards are active.
• The effect of prey was probably underestimated. One possible reason the authors give is that snow leopards might leave fewer scrapes and feces where prey could detect them.
• The study shows where snow leopards are likely to leave sign, not habitat selection itself, but areas the cats find attractive should collect more sign. Because scrapes and spray sites are territorial markings placed near those of other snow leopards, not every site was fully independent.
• Footprint analysis from the same study (Ale 2007) suggests at least 10 different individuals were represented.
• Sign surveys are less accurate than sightings or radio telemetry, but they are cheaper and easier, and remain a valuable way to study rare carnivores when other methods are not feasible.

4. How tracking was or was not used

The whole study rests on tracks and signs. Two people searched for and identified snow leopard sign across the park: scrapes, feces, pugmarks, spray or scent marks and rubbing sites on rock. Each sign site became a “use” site in the habitat model. No trailing was reported. The paper also mentions that the footprints found were analysed in another study (Ale 2007) to estimate that at least 10 individuals were present.

5. Tracker or observer certification

Not reported. The paper says two people searched for signs following the Snow Leopard Information Management System methods, but does not say who they were or how their sign identification was checked. Because the only large predator known in the area was the snow leopard, the risk of confusing their sign with another large predator’s may have been small, but the paper does not discuss this.

6. Other technologies, skills or innovations

• Garmin eTrex Venture GPS receivers (20 m accuracy) for sign and tahr locations.
• ArcGIS 9.1 and Hawth’s Tools for random site selection, distance layers and habitat values at 50 x 50 m cells, from a digital elevation model.
• Tahr counts by scanning opposite slopes with 8 x 21 binoculars and Nikon 15-60x spotting scopes, recording calves, yearlings, adult females and adult males.
• A use-versus-available logistic regression, a method usually applied to radio telemetry locations, adapted here to sign locations.

7. Implications for conservation (from the paper)

• Most large predators are at risk or endangered, so knowing how physical habitat, human activity and food together shape where they live is critical to conserving them.
• Most habitat studies of large predators look at either prey or people. This study suggests carnivores face trade-offs between physical habitat, human activity and food.
• Understanding how this newly re-established population uses its habitat, in relation to the land, people and prey, is an important step toward its long-term survival.
• Sign surveys are a valuable, low-cost way to assess carnivore presence when more costly monitoring is not feasible.