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Tracking Urban Lions

From NPR, an excellent radio spot about our puma project.  The online version has a bonus video to accompany it.

 

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Research Ties Human Acts to Harmful Rates of Species Evolution

From the NY Times, a Science Times article on our recent PNAS paper.

Human actions are increasing the rate of evolutionary change in plants and animals in ways that may hurt their long-term prospects for survival, scientists are reporting.

Hunting, commercial fishing and some conservation regulations, like minimum size limits on fish, may all work against species health.

The idea that target species evolve in response to predation is not new. For example, researchers reported several years ago that after decades of heavy fishing, Atlantic cod had evolved to reproduce at younger ages and smaller sizes.

The new findings are more sweeping. Based on an analysis of earlier studies of 29 species — mostly fish, but also a few animals and plants like bighorn sheep and ginseng — researchers from several Canadian and American universities found that rates of evolutionary change were three times higher in species subject to “harvest selection” than in other species. Writing in The Proceedings of the National Academy of Sciences, the researchers saythe data they analyzed suggested that size at reproductive maturity in the species under pressure had shrunk in 30 years or so by 20 percent, and that organisms were reaching reproductive age about 25 percent sooner.

Click here to read the full article at nytimes.com.

 

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The Fastest Way to Change a Species: Start Eating It

From Science magazine, more coverage on our PNAS article.

From the dwindling Atlantic cod to the increasingly rare American ginseng plant, species are racing to adjust to relentless human exploitation. According to a new analysis, the rate at which hunted and harvested species are changing their size and breeding schedules is unmatched in natural systems. Ecologists say the results point to errors in the way we manage fisheries and other harvested populations.

Researchers have noted rapid changes in heavily exploited fish and other species since the 1970s. To name one famous example, adult Atlantic cod (Gadus morhua) have decreased 20% in size over the past 30 years, and females now reproduce a year earlier than they used to (ScienceNOW, 31 January 2007). Although such hunting-induced alterations seem rapid, evolutionary biologist Chris Darimont of the University of Victoria in Canada, and colleagues wanted to determine whether they outpace changes in nonharvested organisms.

Read the full article here.

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Tracking mountain lions – for their own good

From the San Francisco Chronicle, a Sunday front page article on our recently launched puma project.

The tired, sweaty trackers scrambled up a steep, muddy slope in a remote canyon in the Santa Cruz Mountains to the towering madrone tree where the hounds were barking.

Poised on a thick, bare branch on a brilliant day in late December was a panting, snarling mountain lion.

“There she is, straight up above us,” said Paul Houghtaling, a 33-year-old researcher for the Bay Area Puma Project, as he dug his boots into the soft leaf matter on the nearly vertical hillside.

The muscles in the tawny lion’s back legs rippled 30 feet above him. The cougar’s mouth was open and her nose was working, sniffing, perhaps, for her cub, which had darted off in another direction.

Led by researchers from UC Santa Cruz, the project is the first attempt to track Bay Area mountain lions, which are being seen in greater numbers as urban areas spread into the region’s wildlands.

For the next three years, the team will track their behavior and movements in the Santa Cruz Mountains – including mating habits, favored prey, survival needs and travel routes. Researchers hope to expand the study for several more years after that to include the Diablo Range and the North Bay.

The 90-pound cat turned her gaze from the dogs to the humans, staring first at Houghtaling, then at each of the other five humans as they clambered into view on this brilliant sunny day just before the New Year.

“It is an intense feeling to be in the presence of such a powerful animal,” Houghtaling said. “I think they feel somewhat safe being in a tree, but they know they are cornered and they are looking for a way out. I feel a sense of awe and also a sense of responsibility that the animal is being captured and collared for a good reason – namely, that we are increasing our understanding of them and contributing to their long-term conservation.”

The researchers were after the mother lion because they wanted to replace a device called an accelerometer in her collar. The specially designed gizmo, which uses software similar to that found in interactive video games, will allow researchers to plot movements like running, stalking, pouncing or even mating at any given time.

Since May, four mountain lions – two males and two females – have been captured, darted and fitted with collars that have Global Positioning System devices and an accelerometer. The other female recently lost her collar during a violent struggle with a deer, the remains of which were later found along with the collar.

Chris Wilmers, the lead investigator for the project, said the data from collars – which can be retrieved every couple of weeks using a remotely triggered radio uplink – will be used to calculate daily calorie consumption and energy demands. The ultimate goal, he said, is to determine how vulnerable pumas are to environmental and habitat disturbance.

Click here to read the full article SF chronicle article.

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Wolves Buffer Scavengers Against Climate Change

From Conservation Magazine, a story about our PLoS Biology article documenting the influence of wolves on scavengers as the climate changes.

Wolves and other top predators may help other species cope with climate change. Milder winters in Yellowstone National Park mean fewer elk (Cervus elaphus) die late in the season, which is tough on bald eagles (Haliaeetus leucocephalus), grizzly bears (Ursus arctos), and other scavengers that depend on the carcasses.

New research shows that wolves help scavengers by killing elk and thus providing more late-winter carrion. “Wolves act to retard the effects of a changing climate on scavenger species,” say Christopher Wilmers and Wayne Getz of the University of California, Berkeley, in PLoS Biology.

Many scavengers — from ravens (Corvus corax) and bald eagles to grizzly and black bears (Ursus americanus) — rely on carrion to get them through the winter in Yellowstone. However, without gray wolves (Canis lupus), carrion got scarcer as late winters got milder because deaths of elk depended primarily on snow depth. But after wolves were reintroduced in 1995, they once again became the primary cause of elk death and thus carrion availability.

To see whether wolves could buffer the impact of climate change on late-winter carrion, Wilmers and Getz analyzed 55 years of weather data from northern Yellowstone National Park, which has the park’s largest elk herd (at perhaps 10,000) and nearly 100 wolves. The researchers then estimated carrion availability with and without wolves by using models that accounted for factors including snow depth, wolf pack size, and elk kill rate as well as changes in the wolf and elk populations.

The weather analysis showed that Yellowstone’s winters have gotten shorter and milder, with shallower snow in the late winter months of March and April. The models confirmed that wolves do buffer the impact of milder winters on carrion availability: late-winter carrion drop-ped sharply as temperature increased without wolves but largely rebounded with them. Specifically, March elk deaths declined 27 percent without wolves vs. only four percent with wolves; April elk deaths declined 66 percent without wolves vs. only 11 percent with wolves.

“Late winter carrion in Yellowstone will decline with or without wolves, but by buffering this reduction, wolves extend the timescale over which scavenger species can adapt to the changes,” say Wilmers and Getz. They are now testing whether scavenger populations are in fact higher in areas where wolves have been reintroduced.

This work also shows that there is no substitute for intact ecosystems. “Their conclusions challenge the notion that human hunting serves as a surrogate to wild carnivore predation. Wolves distribute carrion widely in time and space, whereas modern human hunters do not,” says Douglas Smith of the National Park Service, who leads the Yellowstone Wolf Project.

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Wolves’ Leftovers Are Yellowstone’s Gain

From National Geographic, a nice article about our recent work on the effects of gray wolves on scavengers in Yellowstone NP.

Amid controversy, gray wolves (Canis lupus) were reintroduced to Yellowstone National Park in 1995. Now, new studies are hinting at the added benefits that the once-spurned carnivore have rapidly brought to the preserve.

Research published last month revealed that—unlike other top predators—Yellowstone’s wolves routinely leave unfinished elk (Cervas elephas) and moose (Alces alces) carcasses. These provide essential scraps for scavenging coyotes (Canis latrans), eagles, and other animals. Related work suggests that these carcasses provide dinner more consistently, and for more species, than remains discarded by human hunters.

Other recently published findings show that wolves may also be rebalancing Yellowstone’s ecosystems. Some streamside trees, such as species of cottonwood (Populus) and willow (Salix) are growing vigorously once more in areas overgrazed for much of the last century, researchers wrote.

“Part of the integrity of the ecosystem has been restored,” said Christopher Wilmers, an ecologist of the University of California, Berkeley, and lead author of two of the studies. The findings vindicate the decision to bring wolves back, he said.

Wiped Out

Wolves were systematically hunted in Yellowstone and much of the Western United States from the 1800s onwards. Yellowstone’s last pack was eliminated in 1926.

“In the early 1900s no one stopped to consider the ecological role of wolves,” commented Robert Beschta, a forestry scientist at Oregon State University in Corvallis. “Wolves were considered a predator with no value and seen as a huge constraint on allowing a productive ecosystem to flourish,” he said. Wolves, mountain lions (Puma concolor), and coyotes (Canis latrans) were all targeted as threats to livestock and game, he said.

When the National Park Service first considered reintroducing wolves in the late 1980s, critics warned that the predators might seriously impact elk, deer, and moose herds. Nevertheless, 31 wolves were re-introduced in 1995 and 1996 to Yellowstone, which spans portions of Idaho, Montana, and Wyoming. That population, now living in the vast park and its surroundings, had swelled to 220 animals in 21 packs by the end of 2001.

While elk numbers have been reduced by around 18 percent since the mid-1990s, few devastating impacts associated with the reintroduction program have yet been recorded, said Wilmers.

Feeding the Masses

Instead, the park is now enjoying some wolf-related benefits. According to Wilmers and colleagues’ study, published in the November Journal of Animal Ecology,wolves may be providing other scavengers with more regular meals than they’ve had since the early 20th century.

Mountain lions and grizzly bears (Ursus arctos) have a habit of sticking close by their kills, even when full. Wolves, on the other hand, tend to move away to “sleep off their meal,” said Wilmers, making meat available for scavengers.

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