A test of the pumas pounce on an elk leg at normal speed and slow motion demonstrates the power of these cats. - Hunting Cats Energy Balance Could Be Disrupted by Humans Human activity may cause cheetahs and pumas to expend more energy than usual in finding and stalking prey. aaas.org/news/science-hunting-cats-energy-balance-could-be-disrupted-humans Mid-sized carnivores like cheetahs (1) and pumas (2) spend more energy searching for prey than chasing it, according to two new studies of the animals in their natural habitats. But, this energetic balance could be upset by human disruptions of the cats hunting grounds, such as fencing, that threaten the cats survival in the wild. David Michael Scantlebury from Queens University Belfast in Northern Ireland and colleagues from around the world studied cheetahs in Africa while Terrie Williams from the University of California, Santa Cruz, and her team focused their attention on pumas hunting in the mountains. Together, the researchers paint a vivid picture of these mid-sized predators hardscrabble lives. Their results, based on years of field work and detailed data from sensitive radio collars, appear in the 3 October issue of the journal Science and reveal how finely-tuned these hunters really are. Olympic sprinters expend a lot of energy to stay fit and maintain their bodies, and youd imagine that cheetahs have to do the same, said Scantlebury. But we looked at their energy expenditures, based on their behaviors, and the main correlation to energy was how far they walked to find prey. So if you disturb a cheetah on its hunt or if anthropogenic factors change its landscape to a field with fences or a farm with dogs and a shotgun-toting farmer, you figure a cheetah is going to have to walk around more to avoid these nuisances and, in doing so, expend a lot more energy, he said. Scantlebury and his colleagues studied 19 cheetahs in Africa for weeks at a time, recording their behaviors such as lying, sitting, walking, and chasing prey throughout the day. Using ratios of hydrogen and oxygen isotopes in the cats excrement, the researchers were able to estimate the cheetahs daily energy expenditures. We have behavioral data because we followed these cheetahs every day for two weeks at a time and saw what they killed, what they ate, whether they fought over the meal or if a female was in heat, said Scantlebury. We went out every day, hour after hour in the baking sun, and watched these animals, wondering, When are you going to poop? Surprisingly, the researchers found that cheetahs dont spend much more energy than other similarly-sized mammals — and that their biggest energy drain doesnt come from their infrequent sprints, but simply from walking around in search of prey. Scantlebury and his colleagues were also concerned about the effects of kleptoparasitism, or the theft of meals by larger carnivores, on cheetahs energy budget. The researchers discovered that cheetahs were extremely well-adapted. Even when 25% of their meals were stolen, cheetahs only had to go back out and hunt for another 1.1 hours, upping their daily energy expenditure by just 12%. Pumas, on the other hand, have adopted a more patient approach to hunting over the years, according to Williams and her team. The researchers developed a new SMART collar (which stands for species movement, acceleration and radio tracking) that follows the predators movements while measuring oxygen consumption and monitoring GPS information. Williams and her colleagues calibrated the collars with three captive pumas that they trained to walk on treadmills — a tricky and time-consuming task — before they fixed SMART collars to four wild pumas in Californias Santa Cruz Mountains to collect data on the cats hunting behavior. The researchers findings show that pumas spend about 2.3 times more energy locating prey than researchers had predicted. The cats balance out this expenditure by lying in wait and then precisely matching the force of their attack, or pounce, to the size of their prey. The pounce provides a remarkable, powerful kill that enables these individual pumas to bring down prey that is two to three times their size, she said. The more time that the animals could spend in low activity level behaviors, such as stalking, sitting and waiting, and slowly walking, the greater the relative benefit of the kill. But if the pumas habitat is altered and it becomes more difficult for them to hide, the cats could have a much harder time hunting, according to the researchers. In that way, humans have the potential to offset the delicate balance that these wild cats have struck with nature over thousands of years of evolution, they say. We are hoping that these new SMART collars will give us greater insights into the biological needs of these unique cats, and that conservation measures and habitat plans will incorporate their species-specific biology into management schemes, said Williams. - Study of mountain lion energetics shows the power of the pounce High-tech collars enable scientists to record the energetics of mountain lion hunting behavior, showing why cats use stalk and pounce and how they overpower large prey news.ucsc.edu/2014/10/puma-energetics.html Scientists at UC Santa Cruz, using a new wildlife tracking collar they developed, were able to continuously monitor the movements of mountain lions in the wild and determine how much energy the big cats use to stalk, pounce, and overpower their prey. The research teams findings, published October 3 in Science, help explain why most cats use a stalk and pounce hunting strategy. The new SMART wildlife collar--equipped with GPS, accelerometers, and other high-tech features--tells researchers not just where an animal is but what it is doing and how much its activities cost in terms of energy expenditure. Whats really exciting is that we can now say, heres the cost of being a mountain lion in the wild and what they need in terms of calories to live in this environment, said first author Terrie Williams, a professor of ecology and evolutionary biology at UC Santa Cruz. Understanding the energetics of wild animals moving in complex environments is valuable information for developing better wildlife management plans. The researchers were able to quantify, for example, the high energetic costs of traveling over rugged terrain compared to the low cost of cryptic hunting behaviors such as sit-and-wait or stalk-and-ambush movements. During the actual pounce and kill, the cats invest a lot of energy in a short time to overpower their prey. Data from the collars showed that mountain lions adjust the amount of energy they put into the initial pounce to account for the size of their prey. They know how big a pounce they need to bring down prey that are much bigger than themselves, like a full-grown buck, and theyll use a much smaller pounce for a fawn, Williams said. Cats on treadmills Before Williams and her team could interpret the data from collars deployed on wild mountain lions, however, they first had to perform calibration studies with mountain lions in captivity. This meant, among other things, training mountain lions to walk and run on a treadmill and measuring their oxygen consumption at different activity levels. Those studies took a bit longer than planned. People just didnt believe you could get a mountain lion on a treadmill, and it took me three years to find a facility that was willing to try, Williams said. Finally, she met Lisa Wolfe, a veterinarian with Colorado Parks and Wildlife, who had three captive mountain lions (siblings whose mother had been killed by a hunter) at a research facility near Fort Collins, Colorado. After eight months of training by Wolfe, the mountain lions were comfortable on the treadmill and Williams started collecting data. Power animals According to Williams, the treadmill data showed that mountain lions do not have the aerobic capacity for sustained, high-energy activity. 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, she said. In addition to the treadmill studies, the captive cats were videotaped wearing the collars while doing a wide range of activities in a large outdoor enclosure. This provided a library of collar acceleration signatures specific for different behaviors, from resting and grooming to running and pouncing. We got all the different behaviors videotaped and analyzed with the corresponding accelerometer traces, Williams said. Meanwhile, coauthor Chris Wilmers led a team that deployed the collars on wild cats in the Santa Cruz mountains. Wilmers, an associate professor of environmental studies at UC Santa Cruz, leads the Santa Cruz Puma Project, which has been tracking mountain lions in the area to study the effects of habitat fragmentation and developing new technology for understanding the animals behavior and energetics. Because mountain lions are a cryptic animal, we cant really observe them hunting and killing prey. With the SMART collars, we can see how they go about doing that, what their strategies are, and how many calories they are expending to do it, Wilmers said. The ability to estimate the field energetics of animals in the wild opens up a whole new suite of questions we can ask about the ecology of these animals, which ultimately informs not only our basic understanding of them but also their conservation and management. State-of-the-art collars Coauthor Gabriel Elkaim, professor of computer engineering at UCSCs Baskin School of Engineering, worked on signal processing of the accelerometer data and is continuing to develop the state-of-the-art tracking collars. The prototype used in this study, called the Species Movement, Acceleration, and Radio Tracking (SMART) wildlife collar, was developed by computer engineering graduate student Matthew Rutishauser. The collars include a GPS unit, accelerometers, and a magnetometer to provide detailed data on where an animal is and what it is doing. We hope this will be an enabling technology to allow a much greater depth of understanding of animals in the wild, Elkaim said. The researchers now want to look at mountain lion energetics in a range of different habitat types. In particular, Wilmers said, he is interested in how human land use and habitat fragmentation may be influencing the energetic demands on mountain lions in the wild. Williams and her students also have projects using the new collar technology to study other large carnivores, including wolves, polar bears, and Weddell seals. A lot of these large carnivore species are threatened or endangered, and understanding their physiological limitations has been a big missing piece in conservation planning, Williams said. This technology gives us a whole new level understanding of what these animals are doing and what it costs them to live in the wild, and that can really help move the science of conservation forward. In addition to Williams, Wilmers, Wolfe, and Elkaim, the coauthors of the paper include Tracy Davis at Colorado Parks and Wildlife; program manager Traci Kendall and head trainer Beau Richter in Williamss lab at UC Santa Cruz; and UCSC graduate students Yiwei Wang and Caleb Bryce. This research was funded by the National Science Foundation. - New study suggests humans to blame for plummeting numbers of cheetahs alphagalileo.org/ViewItem.aspx?ItemId=145875&CultureCode=en A new study led by Queen’s University Belfast into how cheetahs burn energy suggests that human activity, rather than larger predators, may force them to expend more energy and thus be the major cause of their decline. Wild cheetahs are down to under 10,000 from 100,000 a century ago with conventional wisdom blaming bigger predators for monopolising available food as their habitat becomes restricted. The traditional thinking has been that cheetahs no longer have sufficient access to prey to fuel their enormous energy output when engaging in super-fast chases. But, in the first study of its kind, published today in the international journal Science, academics from Queen’s, other Universities and conservation institutions have made the surprising discovery that, in the main, cheetahs do not use significantly more energy than other, similar-sized mammals. The scientists also discovered that, in searching for prey, cheetahs incur more energy loss than in outbursts of running which, although spectacular, are infrequent. So, where their prey have been reduced or re-distributed through human impacts, their ability to balance energy budgets has been severely curtailed. Lead researcher Dr Michael Scantlebury from Queen’s School of Biological Sciences said: “We studied 19 free-roaming cheetahs each for two weeks across two sites in southern Africa, one in the Kalahari desert and the other in a wetter area. We injected heavy water into the animals before tracking them continuously and collecting their faeces. From these samples, we could determine how much of this heavy water they were losing each day and calculate their energy expenditures. “What we found was that the cats’ energy expenditure was not significantly different from other mammals of similar size – cheetahs may be Ferraris but most of the time they are driving slowly. What our study showed was that their major energy costs seem to be incurred by travelling, rather than securing prey. If you can imagine walking up and down sand dunes in high temperatures day in, day out, with no water to drink you start to get a feel for how challenging these cats’ daily lives are, and yet they remain remarkably adapted and resilient. “They can even withstand other species, such as lions and hyenas, stealing their prey. The reality may be that human activities – for example erecting fences that inhibit free travel or over-hunting cheetah prey – are forcing cheetahs to travel ever-increasing distances and that this may be compromising their energy more than any other single factor. Our study, which is the result of ten years’ of research, seriously questions previously held assumptions about the factors affecting population viability in large predators threatened by extinction.” Co-researcher Dr Nikki Marks, also from Queen’s University Belfast said: “Research of this type helps improve our understanding of the challenges facing cheetahs as they strive to survive and helps inform future decisions on conservation strategies for cheetahs and other threatened animals.” Manuscript co-author Dr John Wilson of North Carolina State University said: “Too often we blame lions and hyenas for decimating cheetah populations when in fact, it is likely to be us humans that drive their declines. Imagine how hard it must be for a small cub to follow its mother further and further through the desert to look for food, while she herself is fighting for survival.” Another key member of the research team, Dr Gus Mills from The Lewis Foundation said: “Having spent the best part of six years studying these animals in the Kalahari you get a good understanding at first hand of the challenges they face in order to survive, even without the detrimental impact of human activity.” The Queen’s-led research was carried out in partnership with Oxford University, Swansea University, Ohio State University, North Carolina State University, the University of Aberdeen, the University of Pretoria, the Chinese Academy of Sciences, The Lewis Foundation (South Africa), the South African Wildlife Research Expedition and the Zoological Society of London. It was supported by awards from the Natural Environment Research Council (NERC) and the Royal Society. - Wild cats need to count calories, too news.sciencemag.org/plants-animals/2014/10/wild-cats-need-count-calories-too A sleek cheetah races with legs outstretched, leaping with a great burst of energy to bring down a fast-moving antelope. That iconic image of this African wild cat needs a footnote. The world’s fastest runner actually spends very little time and energy at full speed, a new study finds. Instead, its most strenuous activity is simply walking around in the hot sun, looking for potential prey (1). Its much the same story for the cheetah’s American cousin, the puma, which spends more than twice as much energy locating prey than researchers had predicted (2). Scientists have long wanted to know how large carnivores spend their days and how many calories they need to survive. Until now, researchers have had only rough estimates of the animals’ total daily energy expenditure. Yet this information is key to managing wildlife, says Terrie Williams, a wildlife physiologist at the University of California (UC), Santa Cruz. For these animals, the bottom line is do you have enough calories to live and to reproduce? That’s been a missing piece of information. Her group and another independent research team have taken some innovative steps to quantify energy use in wild cats. Williams and her colleagues developed a collar that monitors the movement and activity of pumas living in Californias Santa Cruz Mountains, and they calibrated the collar by testing captive pumas on a treadmill. A different team spent weeks tracking cheetahs from dawn to dusk, analyzing the animals feces to determine energy use. As a result, they were able to more finely divide up the day in terms of the different types of activity the animals were engaged in, says John Laundré, a large carnivore ecologist at UC Riverside, who was not involved in either study. Cheetah populations have plummeted in the last century, from about 100,000 in 1900 to about 10,000 today. Some researchers think lions and hyena are in part to blame for the decline. They are able to steal dead prey from the cheetahs, forcing them to spend what seems like an inordinate amount of energy in high-speed chases after more food. To figure out if food theft was really a big problem, Michael Scantlebury, a conservation physiologist at Queens University Belfast in the United Kingdom, and colleagues studied 19 cheetahs in two South African reserves. His team put radio collars on the animals, injected them with water with heavy hydrogen and oxygen atoms so these elements could be traced, recorded the animals behaviors, and collected their feces to check for how fast those atoms were used, an indicator of metabolic rate. We knew exactly where they were, what they were doing, and what they were eating, he says. The cheetahs spent about 3 hours a day walking around—which uses up about 42% of their energy budget. They chase prey less than twice a day, about 38 seconds per sprint, Scantlebury and colleagues report online today in Science. That [time for] energy expenditure is really short, Laundré says. Either they catch them or they give up. And the cheetahs are successful catching prey about half the time. Only four out of 43 times did the cheetahs lose their catch to hyenas or lions—not enough to put a strain on the cheetahs, Scantlebury says. He calculates that even if 25% of the prey were stolen, the cheetahs could compensate by just adding about an hour to the time they spent wandering around. He worries, however, that in an effort to please tourists, game managers will increase the numbers of large predators in reserves, putting the cheetahs at greater risk of having their meals stolen out from under them. He found that cheetahs dont hunt when lions are nearby, or they move away—which could be energetically costly. Also, the data indicate that life would be tough on these animals if prey were scarce or inaccessible because of boundary fences that break up the landscape, forcing the cheetahs to spend a lot more time searching. Williams and UC Santa Cruz ecologist and co-author Christopher Wilmers had long wanted to study the energetics of the local pumas. Unlike cheetahs, which hunt by day in very open landscapes, pumas are active at night in rugged territory and so are hard to watch. To monitor the movements of the cats, Williams and their colleagues developed collars equipped with GPS and devices that measure changes in acceleration and magnetic fields. By analyzing collar data for captive pumas walking or running on a treadmill, pouncing on dead prey, and going through their daily routines in a fenced yard, the researchers learned how to use the collar to figure out an animals activity as well as its location. It gives you information about a very secretive animal, Scantlebury says. The pumas spend about 2 hours a day looking for food. Some wander around quite a bit—and it takes a fair amount of energy for them to traverse the rugged terrain, Williams and her colleagues report online today in Science. Others just sit and wait. Of that time, the actual kill—a powerful pounce that can take down animals larger than the puma itself—takes just seconds in a high energy burst. And the pumas moderate the power of the bounce depending on the size of the prey, the researchers discovered. Ultimately the animals are using strategy to keep the [energy] cost as low as possible, Williams says. However, their results indicate that she and others have underestimated by 2.5 times what it costs these animals to make a kill. And wildlife managers should take heed. If we’re going to have carnivores in a system we’ve got to provide what they need to live, she adds. Those provisions should include not just enough prey, but the right landscape for capturing that prey, Laundré says. In that terrain, predators will expend less energy. “The better they are able to balance their energy needs, the better they will do. Video: Wild cats need to count calories, too video.sciencemag.org/News/3817875203001/1 A sleek cheetah races with legs outstretched, leaping with a great burst of energy to bring down a fast-moving antelope. That iconic image of this African wild cat needs a footnote. The world’s fastest runner actually spends very little time and energy at full speed, a new study finds. Instead, its most strenuous activity is simply walking around in the hot sun, looking for potential prey. Its much the same story for the cheetah’s American cousin, the puma, which spends more than twice as much energy locating prey than researchers had predicted. References 1. Flexible energetics of cheetah hunting strategies provide resistance against kleptoparasitism Science 3 October 2014: Vol. 346 no. 6205 pp. 79-81 DOI: 10.1126/science.1256424 sciencemag.org/content/346/6205/79 Editors Summary The costs and benefits of stalking and chasing Organisms live under a constant balance between getting and using energy. Large carnivores may feel this balance more acutely because of the large amounts of energy needed to capture and subdue their prey. Williams et al. and Scantlebury et al. used remote measures of physiology and behavior to identify the hunting strategies of the stalking North American puma and the speedy African cheetah (see the Perspective by Laundré). In both cases the cats hunting strategies are well matched to produce a balance between the energy they spend on the hunt and the energy they acquire from their prey, despite their very different strategies and levels of competition. Science, this issue p. 81 (2), p. 79 (1); see also p. 33 (3) Abstract Population viability is driven by individual survival, which in turn depends on individuals balancing energy budgets. As carnivores may function close to maximum sustained power outputs, decreased food availability or increased activity may render some populations energetically vulnerable. Prey theft may compromise energetic budgets of mesopredators, such as cheetahs and wild dogs, which are susceptible to competition from larger carnivores. We show that daily energy expenditure (DEE) of cheetahs was similar to size-based predictions and positively related to distance traveled. Theft at 25% only requires cheetahs to hunt for an extra 1.1 hour per day, increasing DEE by just 12%. Therefore, not all mesopredators are energetically constrained by direct competition. Other factors that increase DEE, such as those that increase travel, may be more important for population viability. Supplementary Materials sciencemag.org/content/suppl/2014/10/01/346.6205.79.DC1/Scantlebury.SM.pdf 2. Instantaneous energetics of puma kills reveal advantage of felid sneak attacks Science 3 October 2014: Vol. 346 no. 6205 pp. 81-85 DOI: 10.1126/science.1254885 sciencemag.org/content/346/6205/81 Editors Summary The costs and benefits of stalking and chasing Organisms live under a constant balance between getting and using energy. Large carnivores may feel this balance more acutely because of the large amounts of energy needed to capture and subdue their prey. Williams et al. and Scantlebury et al. used remote measures of physiology and behavior to identify the hunting strategies of the stalking North American puma and the speedy African cheetah (see the Perspective by Laundré). In both cases the cats hunting strategies are well matched to produce a balance between the energy they spend on the hunt and the energy they acquire from their prey, despite their very different strategies and levels of competition. Science, this issue p. 81 (2), p. 79 (1); see also p. 33 (3) Abstract Pumas (Puma concolor) live in diverse, often rugged, complex habitats. The energy they expend for hunting must account for this complexity but is difficult to measure for this and other large, cryptic carnivores. We developed and deployed a physiological SMART (species movement, acceleration, and radio tracking) collar that used accelerometry to continuously monitor energetics, movements, and behavior of free-ranging pumas. This felid species displayed marked individuality in predatory activities, ranging from low-cost sit-and-wait behaviors to constant movements with energetic costs averaging 2.3 times those predicted for running mammals. Pumas reduce these costs by remaining cryptic and precisely matching maximum pouncing force (overall dynamic body acceleration = 5.3 to 16.1g) to prey size. Such instantaneous energetics help to explain why most felids stalk and pounce, and their analysis represents a powerful approach for accurately forecasting resource demands required for survival by large, mobile predators. Supplementary Materials sciencemag.org/content/suppl/2014/10/01/346.6205.81.DC1/Williams.SM.pdf 3. How large predators manage the cost of hunting Science 3 October 2014: Vol. 346 no. 6205 pp. 33-34 DOI: 10.1126/science.1260170 sciencemag.org/content/346/6205/33 Being a large carnivore is not easy. First, there is the food, the energy they need to survive, which by definition consists mainly of other animals. This means that meeting daily energetic needs is not as easy as just going out and gathering plants that are waiting around to be found and eaten. Large carnivores often prey on animals that are bigger than themselves and that try to avoid being killed. Foraging by carnivores becomes a two-player game of stealth and fear (1), making it more difficult and thus energetically costly for carnivores to catch enough to stay alive. Large carnivores must balance the energy spent seeking and subduing prey with the energy they get back when they catch something—which does not happen as often as one might think (2–4). Two reports in this issue, by Scantlebury et al. (5) on page 79 and by Williams et al. (6) on page 81, look at how two carnivores, cheetahs (Acinonyx jubatus; see the first photo) and pumas (Puma concolor; see the second photo), tread the fine line of energy losses and gains in order to survive.
Posted on: Sun, 05 Oct 2014 18:55:17 +0000
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