Stalking, chasing, and taking down prey like high-leaping springbok or giant elk is a hard day’s work. But over the course of thousands of years, cheetahs and pumas have polished their hunting strategies down to a precise science, according to two studies published in Science this week. They’re much less energetically constrained by resources and competition than we thought.
Carnivores must balance the energy spent seeking and subduing prey with what they get back when they finally kill something. It’s essential that they carefully calculate calorie costs and gains. Researchers used to think prey loss to theft and the extra energy expenditure from having to trek across rugged terrain might be weakening the wild cats, but perhaps not.
To study the energetics of mid-size predators in the wild, David Scantlebury from Queen’s University Belfast and colleagues used radio collars to track 19 cheetahs (Acinonyx jubatus) in southern Africa for two weeks. They recorded how much time the cats spent lying down, sitting, walking, and chasing. They also injected heavy (isotope-laden) water into the cats, so by analyzing urine and feces, they could determine how much water the cats lose each day as well as track energy expenditure.
They found that cheetahs were in motion for about 12 percent of the day, and there’s a direct correlation between the distance cheetahs travel and the mass of their prey. They spend more energy searching for prey than they do in spectacular outbursts of running, which are actually infrequent. "Cheetahs may be Ferraris but most of the time they are driving slowly,” Scantlebury says in a news release.
These resilient wild cats are also victims of kleptoparasitism: Larger carnivores like lions and hyena steal their meals. But they’re well-adapted to being exploited. Even when 25 percent of their meals were stolen, cheetahs only had to hunt for an extra 1.1 hours, upping their daily energy expenditure by just 12 percent.
In a related study, a team led by Terrie Williams from University of California, Santa Cruz, monitored energy expenditure of four wild pumas (Puma concolor) prowling in the Santa Cruz Mountains using Species Movement, Acceleration and Radio Tracking, or SMART, collars. These cryptic cats -- also known as cougars, panthers, and mountain lions -- employ more patient approaches like sit-and-wait and stalk-and-ambush. That’s because they don’t have the aerobic capacity for sustained, high-energy activity.
The pumas, the team found, spend about 2.3 times more energy locating prey than researchers previously predicted. But the cats balance this expenditure by lying in wait and precisely matching the force of their pounce to the size of their prey. During the actual attack, the cats invest a lot of energy in a short time to overpower their prey, adjusting for full-grown bucks or fawns accordingly.
"They are power animals. They have a slow routine walking speed and use a burst of speed and the force of the pounce to knock down or overpower their prey," Williams says in a university statement. "What's really exciting is that we can now say, here's the cost of being a mountain lion in the wild and what they need in terms of calories to live in this environment."
Images: Michael G.L. Mills (top), T.M. Williams, UCSC (middle)
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