This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Nepal has a lofty goal: The country wants to have at least 250 Bengal tigers (Panthera tigris tigris) within its borders by the year 2022. They’ve already made pretty amazing progress, growing the population from 121 in 2009 to 198 in 2013. Earlier this week conservation groups praised Nepal for its efforts to reduce poaching, which previously had caused tiger populations to plummet. Only one tiger has been poached in Nepal since the beginning of 2011.
But anti-
poaching efforts may not be enough. According to a paper published January 26 in Ethology Ecology & Evolution, Nepal’s tigers lack both the necessary food and space to grow their populations much further.
On supporting science journalism
If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.
It all boils down to math. Tigers must eat about five kilograms of meat a day. Achieving that requires fairly dense prey levels of more than 150 animals per square kilometer. Meanwhile tigers also live mostly solitary lives and defend their territories from other tigers. Each cat requires 54 square kilometers of territory. That means a population of 250 tigers would require 13,500 square kilometers of territory. The five current protected zones for tigers in Nepal only add up to about 5,200 square kilometers and have a prey density of just 56 animals per kilometer.
According to the paper—which was written by researchers from New Zealand’s Massey University, Nepal’s Kathmandu University and other institutions—the tigers would need another 8,282 square kilometers of protected territory if they are to achieve and maintain the goal of 250 animals.
So where would that land come from? Well, it turns out that there’s a lot of it. As you can see in the map below, the five protected tiger zones are surrounded by more than 22,000 square kilometers of forests and grassland as well as another 16,000 square kilometers of agricultural land, all of which historically had been tiger habitat.
The researchers wrote that expanding the protected tiger territory into some of these currently unprotected forests would give the cats more room to roam. Meanwhile the tigers’ prey would also flourish in the newly protected zones, says lead author Achyut Aryal, a conservation biologist at Massey.
Now these forests aren’t necessarily free for the taking—Aryal says they contain numerous human settlements. Some of the land is privately held; other tracts belong to local communities or the Nepalese government. But that still leaves a lot of land for tigers.
Any new protected zones would also require buffer zones—the area between people and tigers that safely separates the two species. Nepal has a long history of tiger–human conflict typical of any region that is inhabited by people and large predators. That results in both human and tiger fatalities. Twelve people were killed by tigers in the buffer zone around Nepal’s Bardia National Park between 1994 and 2007. During the same period, local households each lost an average of one livestock animal to tiger predation every four years, according to a paper published last March in Oryx. Tigers are often killed in retaliation for these attacks.
Deaths for both species could increase, the authors of the new paper warned, writing that as tiger populations increase the animals will expand their ranges outside of their existing protected territories and result in more human–wildlife clashes. Establishing new protected zones as well as buffer zones and an in-depth monitoring program would help to minimize this risk to both humans and tigers.
Despite human–carnivore conflict, the Oryx paper found that the Nepalese people actually have a positive attitude toward tiger conservation efforts. Nepal has spent the past several years working with villages near tiger populations to build fences and increase tourism, bringing both safety and revenue to local communities. Villages that once protected poachers have even started to turn them in, Tikaram Adhikari, Nepal’s director general of its Department of National Parks and Wildlife Conservation, told AFP this week, as the country hosts a five-day anti-poaching summit.
Timing is of the essence. As the authors of the new paper warned, agriculture in the potential tiger habitats is rapidly increasing while the amount of forests is decreasing. With Nepal’s 2022 goal looming high on the horizon, now is definitely the time to act.
Photo: Tigers at Kathmandu Zoo, by S. Pakhrin, via Flickr. Used under Creative Commons license