What wolves’ teeth reveal about their lives

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Biologist Blaire Van Valkenburgh has spent more than three decades studying the skulls of large carnivores. Here she displays a replica of a saber-toothed cat skull. At left are the skulls of a spotted hyena (in white) and a dire wolf (the black skull). Photo credit: Christelle Snow/UCLA.

UCLA evolutionary biologist Blaire Van Valkenburgh has spent more than three decades studying the skulls of many species of large carnivores — including wolves, lions and tigers —  that lived from 50,000 years ago to the present. She reports today in the journal eLife the answer to a puzzling question.

Essential to the survival of these carnivores is their teeth, which are used for securing their prey and chewing it, yet large numbers of these animals have broken teeth. Why is that, and what can we learn from it?

In the research, Van Valkenburgh reports a strong link between an increase in broken teeth and a decline in the amount of available food, as large carnivores work harder to catch dwindling numbers of prey, and eat more of it, down to the bones.

“Broken teeth cannot heal, so most of the time, carnivores are not going to chew on bones and risk breaking their teeth unless they have to,” said Van Valkenburgh, a UCLA distinguished professor of ecology and evolutionary biology, who holds the Donald R. Dickey Chair in Vertebrate Biology.

For the new research, Van Valkenburgh studied the skulls of gray wolves — 160 skulls of adult wolves housed in the Yellowstone Heritage and Research Center in Montana; 64 adult wolf skulls from Isle Royale National Park in Lake Superior that are housed at Michigan Technological University; and 94 skulls from Scandinavia, collected between 1998 and 2010, housed in the Swedish Royal Museum of Natural History in Stockholm. She compared these with the skulls of 223 wolves that died between 1874 and 1952, from Alaska, Texas, New Mexico, Idaho and Canada.

Yellowstone had no wolves, Van Valkenburgh said, between the 1920s and 1995, when 31 gray wolves were brought to the national park from British Columbia. About 100 wolves have lived in Yellowstone for more than a decade, she said.

In Yellowstone, more than 90% of the wolves’ prey are elk. The ratio of elk to wolves has declined sharply, from more than 600-to-1 when wolves were brought back to the national park to about 100-to-1 more recently.

In the first 10 years after the reintroduction, the wolves did not break their teeth much and did not eat the elk completely, Van Valkenburgh reports. In the following 10 years, as the number of elk declined, the wolves ate more of the elk’s body, and the number of broken teeth doubled, including the larger teeth wolves use when hunting and chewing.

The pattern was similar in the island park of Isle Royale. There, the wolves’ prey are primarily adult moose, but moose numbers are low and their large size makes them difficult to capture and kill. Isle Royale wolves had high frequencies of broken and heavily worn teeth, reflecting the fact that they consumed about 90% of the bodies of the moose they killed.

Scandinavian wolves presented a different story. The ratio of moose to wolves is nearly 500-to-1 in Scandinavia and only 55-to-1 in Isle Royale, and, consistent with Van Valkenburgh’s hypothesis, Scandinavian wolves consumed less of the moose they killed (about 70%) than Isle Royale wolves. Van Valkenburgh did not find many broken teeth among the Scandinavian wolves. “The wolves could find moose easily, not eat the bones, and move on,” she said.

Van Valkenburgh believes her findings apply beyond gray wolves, which are well-studied, to other large carnivores, such as lions, tigers and bears.

Extremely high rates of broken teeth have been recorded for large carnivores — such as lions, dire wolves and saber-toothed cats — from the Pleistocene epoch, dating back tens of thousands of years, compared with their modern counterparts, Van Valkenburgh said. Rates of broken teeth from animals at the La Brea Tar Pits were two to four times higher than in modern animals, she and colleagues reported in the journal Science in the 1990s.

“Our new study suggests that the cause of this tooth fracture may have been more intense competition for food in the past than in present large carnivore communities,” Van Valkenburgh said.

She and colleagues reported in 2015 that violent attacks by packs of some of the world’s largest carnivores — including lions much larger than those of today and saber-toothed cats — went a long way toward shaping ecosystems during the Pleistocene.

In a 2016 article in the journal BioScience, Van Valkenburgh and more than 40 other wildlife experts wrote that preventing the extinction of lions, tigers, wolves, bears, elephants and the world’s other largest mammals will require bold political action and financial commitments from nations worldwide.

Discussing the new study, she said, “We want to understand the factors that increase mortality in large carnivores that, in many cases, are near extinction. Getting good information on that is difficult. Studying tooth fracture is one way to do so, and can reveal changing levels of food stress in big carnivores.”

Co-authors are Rolf Peterson and John Vucetich, professors of forest resources and environmental science at Michigan Technological University; and Douglas Smith and Daniel Stahler, wildlife biologists with the National Park Service.

The research was funded by the National Science Foundation and National Park Service.

This article originally appeared in the UCLA Newsroom.

UCLA historian Kelly Lytle Hernández awarded MacArthur Fellowship

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Kelly Lytle Hernández, a 2019 MacArthur Foundation Fellow, is one of 14 UCLA faculty to be chosen for the honor. Photo credit: John D. & Catherine T. MacArthur Foundation

UCLA professor Kelly Lytle Hernández, an award-winning author and scholar of race, mass incarceration and immigration, was announced today as a recipient of a prestigious MacArthur Fellowship from the John D. and Catherine T. MacArthur Foundation.

Lytle Hernández, who is a professor of history and African American studies, is the director of UCLA’s Ralph J. Bunche Center for African American Studies, which under her leadership has focused on supporting research into two critical themes in the modern black world — work and justice. The Bunche Center is home to Million Dollar Hoods, which maps the fiscal and human cost of mass incarceration in Los Angeles. Lytle Hernández is the director and principal investigator on the project.

“Lytle Hernández’s investigation of the intersecting histories of race, mass incarceration, immigration, and cross-border politics is deepening our understanding of how imprisonment has been used as a mechanism for social control in the United States,” the foundation said.

The MacArthur Fellowship is a $625,000, no-strings-attached award to people the foundation deems “extraordinarily talented and creative individuals.” Fellows are chosen based on three criteria: exceptional creativity, promise for important future advances based on a track record of accomplishments, and potential for the fellowship to facilitate subsequent creative work. Lytle Hernández is one of 26 individuals the foundation selected for fellowships in 2019.

“As a scholar, I both work deeply alone and deeply in community, but until very recently the scholarly communities I’ve worked in — immigration and the carceral state — have been fairly separate,” said Lytle Hernández, who holds the Thomas E. Lifka Chair in History at UCLA. “I hope my work has helped people understand immigration as another aspect of mass incarceration in the United States and that my award further helps people understand that these two regimes are intertwined. This award will help us continue this work across communities and shine a light on this kind of thinking that unites these two crises that others often see as distinct.”

Lytle Hernández, 45, received a her bachelor’s degree from UC San Diego in 1996 and earned her doctorate in 2002 from UCLA.

For her first book, “MIGRA! A History of the U.S. Border Patrol,” Lytle Hernández pored over historical records to illuminate the border patrol’s nearly exclusive focus on policing unauthorized immigration from Mexico.

In “City of Inmates: Conquest, Rebellion, and the Rise of Human Caging in Los Angeles,” she began zeroing in on another dimension of race and law enforcement, specifically what forces shaped Los Angeles so that it came to operate the largest jail system in the United States.

“What I found in the archives is that since the very first days of U.S. rule in Los Angeles — the Tongva Basin — incarceration has persistently operated as a means of purging, removing, caging, containing, erasing, disappearing and otherwise eliminating indigenous communities and racially targeted populations,” Lytle Hernández said in an interview about the book.

The MacArthur Fellowship, which is commonly referred to as the “genius grant,” is according to the foundation, intended to encourage people of outstanding talent to pursue their own creative, intellectual and professional inclinations. Recipients may be writers, scientists, artists, social scientists, humanists, teachers, entrepreneurs, or those in other fields, with or without institutional affiliations.

Lytle Hernández joins 13 other UCLA faculty as MacArthur fellows, including mathematician Terence Tao, choreographer Kyle Abraham, director Peter Sellars, astrophysicist Andrea Ghez and historian of religion Gregory Schopen.

While unsure of her specific plans for the award, Lytle Hernández said that she will continue to expand the scope and scale of her social justice scholarship, including with partners outside of UCLA.

“I’d like to create a space for myself and others — especially community organizers and movement-driven scholars — to write,” she said, noting that these people’s calendars tend to be jammed by the “urgency of their work.” “I’d like to create space that allows myself and others to process the work that we’re doing and to share it.”

This article originally appeared in the UCLA Newsroom.