Study of mountain lion energetics shows the power of the pounce

The SMART wildlife collar is equipped with GPS, accelerometers, and a magnetometer to provide detailed data on where the animal is and what it is doing.

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 team's 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.

"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," 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 they'll 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 didn't 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 can't 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 UCSC's 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 Williams's lab at UC Santa Cruz; and UCSC graduate students Yiwei Wang and Caleb Bryce. This research was funded by the National Science Foundation.

Source: University of California - Santa Cruz

Boy moms more social in chimpanzees: Watching adult males in action may help youngsters prepare

Infant chimpanzee in Gombe National Park, Tanzania. Nearly four decades of observations of Tanzanian chimpanzees has revealed that the mothers of sons are about 25 percent more social than the mothers of daughters. Boy moms were found to spend about two hours more per day with other chimpanzees than the girl moms did. Credit: © Impala / Fotolia

Nearly four decades of observations of Tanzanian chimpanzees has revealed that the mothers of sons are about 25 percent more social than the mothers of daughters. Boy moms were found to spend about two hours more per day with other chimpanzees than the girl moms did.

Chimpanzees have a male-dominated society in which rank is a constant struggle and females with infants might face physical violence and even infanticide. It would be safer in general to just avoid groups where aggressive males are present, yet the mothers of sons choose to do so anyway.

"It is really intriguing that the sex of her infant influences the mother's behavior right from birth and that the same female is more social when she has a son than when she has a daughter," said Anne Pusey, chair of Evolutionary Anthropology at Duke.

The researchers believe that the mothers are giving the young males the opportunity to observe males in social situations, even while still clinging to their mothers. This gives the youngsters a start on developing the social skills they'll need to thrive in the competitive world of adults.

The findings are based on an analysis of 37 years of daily observations of East African chimpanzeess from the Gombe National Park in Tanzania. Duke University houses all of the data from the famous Kasekela chimpanzee community in the Jane Goodall Institute Research Center, which contains more than 50 years of observational data all the way back to Jane Goodall's first hand-written observations from the early 1960s.

The data largely consist of "follows," in which a researcher focuses on one chimpanzee and notes her behaviors and interactions with others throughout the day. Duke scholars led by Pusey are now working on digitizing the entire collection of Gombe data in the Goodall archive to enable more longitudinal studies of this kind.

"Drawing from the long-term datasets, we were able to investigate patterns within the same mother, examining how she behaved with her sons versus with her daughters," said lead author Carson Murray, an assistant professor at George Washington University, who was a PhD student under Pusey. "These results are even more compelling than a general pattern, demonstrating that the same female behaves very differently depending on the sex of her offspring."

For this study, researchers measured gregariousness based on three kinds of analyses. They looked at how much time a mother spent with other adults who were not immediate family members; the average size of the mother's party and its composition; and the proportion of time a mother spent in mixed-sex and female-only parties.

For the most part, mothers with offspring spend their time alone or with adult daughters and other dependents. Adult males are the more gregarious sex, forming coalitions with other males to assert rank, defend their territory and hunt as a group.

Mothers with sons were found to spend more time with others and to associate with more of their kin. During the first six months of an infant's life, mothers with sons spend significantly more time in mixed-sex parties than mothers with daughters.

At 30 to 36 months, chimpanzee infants start moving around more on their own without being carried and spend most of their time out of mother's reach. At this age, the male infants start having more interactions with unrelated chimpanzees, especially adult males. Their female counterparts are significantly less social.

As the offspring get older and range further from their mothers, the young males have more social partners over the course of the day. Juvenile and adolescent males watch their adult counterparts carefully and often mimic the behaviors they see, including charging displays and copulation.

"Mothers obviously increase social exposure for their young male infants," Murray said. "This finding leads to a larger question about how social exposure might shape gender-typical behavior in humans as well."

This study also suggests it is possible the sons themselves are driving the increased gregariousness later in life. In early infancy, the boy mothers spend about the same time in female-only groups that the girl moms do. But as their sons become older, boy moms spend more time in female-only, nursery groups, probably because the young males are attracted to the offspring of other females as playmates.

"One of the most surprising results to me was that mothers with young females still have lower association with their relatives," Murray said. "As we argue in the paper, this suggests that social exposure is less critical to females in general."

Social exposure has a potential downside too. Females with low rank are known to experience more social stress in large groups, and there is always a risk of infanticide against the young chimpanzees. Perhaps the best way to avoid having infants killed is to steer clear of groups, which the mothers do up to 70 percent of the time.

"Mothers with infant daughters were likely to be avoiding competitive and stressful situations," Murray said. "While mothers with sons seem willing to incur those costs for the benefit of having their sons socialized."

Source: Duke University.

On a safari through the genome: Genes offer new insights into the distribution of giraffes

Three young, male Angola giraffes. Credit: © Julian Fennessy, GCF

The Giraffe (Giraffa camelopardalis), a symbol of the African savanna and a fixed item on every safari's agenda, is a fascinating animal. However, contrary to many of the continent's other wild animals, these long-necked giants are still rather poorly studied. Based on their markings, distribution and genome, nine subspecies are recognized -- including the two subspecies Angola Giraffe (Giraffa c. angolensis) and South African Giraffe (Giraffa c. giraffa).

South African Giraffes occur farther north than previously assumed

Like most other giraffes, these subspecies are now mainly found in nature reserves. Until recently, scientists assumed a clear demarcation of their ranges: Angola Giraffes occur in Namibia and northern Botswana, while South African Giraffes reside in southern Botswana and South Africa. "However, according to our studies, the distribution areas prove to be much more complex. South African Giraffes also occur in northeastern Namibia and northern Botswana, and Angola Giraffes can be found in northwestern Namibia and southern Botswana, as well," explains the study's author, Friederike Bock from the Biodiversity and Climate Research Center (BiK-F). A look at the new distribution map reveals the presence of a population of Angola Giraffes in the Central Kalahari Game Reserve, the world's second-largest national park, quasi nestled between two populations of the South African Giraffe, with both subspecies living side by side.

Subspecies were the result of early geographic separation

According to the research team, the fact that two genetically distinct subspecies could develop within the same region may be explained by the local geographic conditions that prevailed approximately 500,000 to two million years ago. Back then, the mountain range along the East African Rift Valley was sinking, creating vast wetlands and lakes, such as the paleo lake Makgadikgadi. According to Professor Dr. Axel Janke from the BiK-F, "these large bodies of water may have separated the populations for long periods of time. Moreover, female giraffes likely do not migrate across long distances, thereby contributing to a clear separation of the maternal lines." Today, there no longer exist any barriers that prevent the possible mingling of both subspecies; an investigation of these processes is however subject to further genetic analyses.

Angola and South African Giraffes can be uniquely identified by their maternal gene profile

For the study, the researchers created a profile of the subspecies' mitochondrial DNA, using tissue samples from about 160 giraffes from various populations across the entire African continent. On the basis of this genetic material, inherited from the maternal side, the often similarly marked subspecies can be uniquely identified genetically and the relationships between various populations can be clearly demonstrated. "Our focus was on giraffes in southern Africa, in particular in Botswana and South Africa. There, we sampled populations that had not been genetically analyzed before," says Bock.

New insights enable improved protection measures for the giraffe

According to estimates by the World Conservation Organization IUCN, the world's giraffe population is about 100,000 individuals -- showing a decreasing trend. In Botswana alone, the population has dwindled by more than half in recent years. In order to achieve effective protection measures that will preserve the majority of the giraffe's subspecies, it is indispensable to gain knowledge that allows their reliable identification as well as detailed information regarding their distribution. The surprising results concerning the distribution of the two subspecies in Namibia and Botswana emphasize the importance of additional taxonomic research on all giraffe subspecies.

Source: Senckenberg Research Institute and Natural History Museum