Lions have experienced a shocking decline; that much is clear. They’ve disappeared from well over 90 percent of their historic range in Africa in the last 120 years. And in the past quarter century alone, their population has declined by about half.
But just how many lions are left in Africa? The answer is surprisingly fuzzy. The most commonly cited estimate is 20,000, but many lion researchers aren’t entirely comfortable with that number.
It’s “based largely on guesswork rather than science,” says Nic Elliot, a lion researcher at Oxford University. “We just don’t know how many there are in Africa.”
Lions are difficult to count because they have low population densities, are mostly active at night, blend in with their surroundings, and sometimes hide from humans, especially where poaching is common.
But counting them accurately is critical. Effective conservation requires reliable population estimates over time because those numbers give a sense of the extent, urgency, and geographical locations of a species’ decline—and what may be causing it.
You have to know there’s a problem, and what it is, before you can solve it, says Alexander Braczkowski, a researcher at Griffith University’s Resilient Conservation Laboratory in Queensland, Australia.
A relatively new technique could better spot warning signs and estimate lion populations more accurately, Elliot, Braczkowski, and other scientists argue in a paper in Frontiers in Ecology and Evolution. Called spatially explicit capture-recapture (SECR), it’s already routinely used for counting other species of big cats. This technique uses field observations to generate a detailed portrait of a population’s estimated size, density, and movement patterns, Braczkowski says. Moreover, it can allow scientists to track trajectories of lion populations in a level of detail that often isn’t possible with older methods.
The approach has been slow to catch on with lion researchers, however. It’s more time-intensive and only works with discrete populations of lions that can be photographed, say researchers who are critical of it.
Not using SECR, however, is a “missed opportunity,” Baczkowski, Elliot, and colleagues argue in their paper. The more traditional methods “can often produce spurious trends in lion population dynamics, which can…mislead conservation investments.”
Soundtracks and foot tracks
In the 1970s and 1980s, researchers would often lure lions with bait before darting them and marking them with a hot iron, to indicate they’d been counted and to keep track of them in the future.
“This technique still remains one of the best to survey a relatively finite area, but in this day and age, [it] would tend to be frowned upon,” says Paul Funston, who leads lion research for Panthera, a global wild cat conservation organization.
More common today are call-up surveys and track counts. The first involves driving into the bush and broadcasting distress calls of a prey species, such as a Cape buffalo, over a loudspeaker—then noting how many lions show up. The second consists of counting lion tracks along a set of transects.
“Both methods pose serious methodological flaws and statistically are pretty flimsy,” Elliot says. They can double-count lions and involve making assumptions, he says, such as about how far sound travels and how likely lions are to respond, or about how lions move in their environment.
But Frans Radloff, an ecologist at Cape Peninsula University of Technology in South Africa, defends their use in certain circumstances—as does Funston. When done correctly, for example in areas where it’s well-known where to find lion tracks, they can provide reasonable estimates of lion abundance, Radloff says.
Elliot and Braczkowski argue that SECR is better because it’s more precise, is less prone to over- or underestimation, and allows scientists to build up a fluid, evolving picture of a population.
For it to work well, however, scientists need a way to recognize individual animals, says Braczkowski, who’s also a National Geographic Explorer. With tigers, for example, each has a unique stripe pattern, allowing researchers to more readily tell them apart. With lions, researchers photograph individuals—either from a vehicle or using camera traps—and study their faces for distinctive markings.
After researchers assemble a large catalog of GPS-tagged images over time, the SECR modeling technique uses this information to mathematically estimate population density, total population, and other parameters.
SECR has been used to count lions successfully several times. For example, Braczkowski teamed up with Musta Nsubuga, a biologist with the Wildlife Conservation Society, and others to estimate lion numbers in Uganda’s Queen Elizabeth Conservation Area in 2017 and 2018. Over three months they drove nearly 5,000 miles throughout the area, taking photos of the lions’ faces.
With a scientific record of each individual’s location at a specific time, SECR allowed them to determine the overall population—71. That research, published this summer in Ecological Solutions and Evidence, also provides new information about their range. Males, for example, now roam over an area five times larger than they did a decade prior, likely because they need to travel farther to find food. It seems the number of prey animals has decreased as a result of increased snaring for bushmeat in the area, Braczkowski says. That insight likely wouldn’t have been possible with older techniques, he says.
Some researchers say that traditional techniques are still useful when handled correctly, and that newer techniques are not appropriate everywhere. Indeed, SECR is easiest when individual animals can be approached with cameras or photographed using camera traps.
“It is not a one-shoe-fits-all issue. Lions cannot be counted in the same way across Africa as each area is unique,” Radloff says. “The only way to get an estimation of the remaining number of lions in Africa is to embrace all [scientifically valid] techniques.”
As to what the total population of lions is, researchers agree that a perfectly accurate lion count is less important than whether lion numbers are going up or going down. And nobody thinks numbers are going up overall. “Regarding your question on how many lions there are left in Africa—I can simply conclude that there are not enough,” Radloff says.