Natural Science

A local great blue heronry provides a natural spectacle

Anonymous — Tue, 13 Apr 2021 18:03:33 +0000

A local great blue heronry provides a natural spectacle Anonymous (not verified) Tue, 04/13/2021 - 12:03

Jeff Mitton

Social systems of great blue herons vary dramatically, from solitary nests to large heronries, and some heronries include nests of great egrets and cattle egrets

Crane Hollow Road, one mile southwest of Hygiene, provides a view of about 50 nests in a great blue heron rookery, or more precisely, heronry. Massive nests made of sticks, up to 4 feet in diameter and 3.5 feet deep, can be seen high in the cottonwoods along Saint Vrain Creek. Great blue herons (Ardea herodias) up to 4.5 feet tall with wingspans of 6.6 feet, can be seen standing beside or sitting in their nests.

A heronry is an entertaining site, for the herons are constantly active. Birds leave to feed or gather nesting materials and soon return. A female on the nest becomes attentive as her mate glides in and lands softly. They may mate, or go through an elaborate welcome ceremony that involves mutual displays of affection such as standing with chests appressed, necks embracing one another, erecting their head and chest plumes and clappering their bill tips.

In addition to dark plumes on the head, neck and back, great blue heron adults have down feathers that grow continuously from the chest. These specialized feathers fray constantly but never molt, so the tips turn to powder down that the heron combs from these feathers and applies to other feathers to keep them dry and free of slime.

Living in a heronry involves many close neighbors. Photo by Jeff Mitton.

Early settlers called herons cranes, suggesting that the heronry was occupied in the 1800s when Crane Hollow Road was named. It has not been occupied continuously since then, but it is mentioned by bird ecologists working in several decades, suggesting it has been occupied much of the time. In a study in 2014, CU Professor Alexander Cruz (deceased) and his graduate students identified 51 heronries along rivers in Colorado. But that number changes frequently as new heronries are established and others are abandoned.

Social systems of great blue herons vary dramatically, from solitary nests to large heronries, and some heronries include nests of great egrets and cattle egrets. This range of variation drives curious minds to wonder if there are advantages to placing nests in dense colonies.

Herons may also walk slowly in shallow water, occasionally flicking their wings repeatedly out and back."

A large study of great blue heronries along the Pacific coast in British Columbia tested the hypothesis that a colony of nests serves as an information center that helps the residents find food. That study showed that birds left the heronry in groups that foraged in different sites every day. As the herons left the colony, they would stop to join other heron feeding flocks and even joined feeding flocks of gulls. Finally, they showed that herons in feeding groups caught fish more quickly and efficiently than solitary herons. This study concluded that heronries provided advantages for fishing when prey were locally abundant but moving unpredictably in space and time--birds benefitted substantially when many others helped search for prey. Conversely, herons nested solitarily and defended feeding territories when food was reliably available in that territory.

While the study in British Columbia showed the advantage of nesting in dense groups when birds had to search for food each day, it does not explain why the birds in other heronries fly to private fishing territories that they defended against other herons. Why are some colonially nesting herons solitary fishers?

My local experiences with great blue herons are with birds nesting in heronries that forage and fish alone. I usually see a great blue heron standing motionless at the edge of the water, waiting for fish to approach. Herons may also walk slowly in shallow water, occasionally flicking their wings repeatedly out and back. In the water, the resulting flickering shadows may cause fish to panic and flee.

This is not a criticism of the BC study explaining advantages of nesting colonies and group hunting. But that study was conducted in cold coastal rain forest and it would not be astounding to note that different strategies were needed to adapt the same species to a shortgrass prairie with an arid, temperate climate. We certainly have much to learn about great blue herons.

How long might the heronry in Crane Hollow be entertaining naturalists this year? When I visited last week, some nests were under construction, but other nests had an adult sitting serenely, perhaps incubating eggs. Females lay one egg about every other day to produce a clutch of 2 to 6 eggs. Adults begin incubation when the last egg has been added, and eggs will begin hatching in 27 to 29 days. Nestlings need 49 to 81 days to grow feathers, increase in size and learn to fly. So, the nests will be active and this magnificent spectacle will continue for at least another 2.5 months.

Living in a heronry involves many close neighbors. Photo by Jeff Mitton.

Social systems of great blue herons vary dramatically, from solitary nests to large heronries, and some heronries include nests of great egrets and cattle egrets.

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Human activity degrading world’s large river deltas

Anonymous — Tue, 23 Feb 2016 07:00:00 +0000

Human activity degrading world’s large river deltas Anonymous (not verified) Tue, 02/23/2016 - 00:00

Jim Scott

Photo of Mississippi River Delta taken by NASA’s Space Shuttle Discovery in early 1985. Photo courtesy NASA.

From the Yellow River in China to the Mississippi River in Louisiana, researchers are racing to better understand and mitigate the degradation of some of the world’s most important river deltas, according to a University of Colorado Boulder faculty member.

CU-Boulder Professor James Syvitski said more than two-thirds of the the world’s 33 major deltas are sinking and the vast majority of those have experienced flooding in recent years, primarily a result of human activity. Some 500 million people live on river deltas around the world, a number that continues to climb as the population increases.

"Deltas are sinking at a much greater rate than sea levels are rising.”

“These deltas are starved of the sediments they need for stability because of upstream dams that trap the material,” said Syvitski, a professor in geological sciences who also is executive director of the international Community Surface Dynamics Modeling System (CSDMS), which is based in Boulder. “We are seeing coastal erosion increasing in many places across the planet.”

Syvitski presented new research findings on changing deltas around the world at the 2016 Ocean Sciences meeting held in New Orleans Feb. 21-26.

River deltas are land areas created by sediment that collects at the mouths of rivers as they enter slow-moving or standing water like oceans and estuaries. Human effects on river deltas range from engineering tributaries and river channels, extracting groundwater and fossil fuels, trapping sediments behind dams, reducing peak flows of rivers and varied agricultural practices, he said.

“Deltas are sinking at a much greater rate than sea levels are rising,” Syvitski said.

One positive action was taken on the 3,395-mile-long Yellow River recently when some major dams were flushed of their sediments and sent rushing downstream, said Syvitski. “This might be the first time that dam operators on the Yellow River have worked with people in the coastal zone to solve a problem.”

But looming threats to the Yellow River Delta include the sinking, or subsidence of land, caused in large part by a move from rice farming to aquaculture – raising fish and shrimp, he said. The land in some areas there is sinking by 10 inches per year as groundwater is pumped to the surface.

“The rate of subsidence there is amazingly – the ground can sink 3 feet in four years and affect infrastructure like buildings and roads,” Syvitski said. “But more importantly, lowering the land surface makes it much more exposed to the ocean environment, including storm surges from hurricanes and tsunamis.”

The two major river deltas in the United States are the Mississippi River Delta in Louisiana and the Sacramento-San Joaquin River Delta in California. While the Sacramento-Joaquin Delta has significant issues with agricultural, industrial and urban pollution and subsidence, things are more dire in the Mississippi River Delta, where a football field-sized chunk of wetlands disappears every hour, said Syvitski. There are more than 40,000 dams 20 feet or higher on the Mississippi River system.

The Community Surface Dynamics Model System is a global, interdisciplinary program involving hundreds of researchers and students now in 500 institutes in 68 countries. Cross-disciplinary research groups develop integrated software modules that predict the movement of water, sediment and nutrients across landscapes and into the oceans. Major funding for CSDMS comes from the National Science Foundation.

“We are interested in how landscapes and seascapes change over time, and how materials like water, sediments and nutrients are transported from one place to another,” he said. “The CSDMS effort gives us a better understanding of Earth and allows us to make better predictions about areas at risk to phenomena like flooding, deforestation, forest fires, land-use changes and the impacts of climate change.”

Jim Scott is senior science editor for the CU Office of News Services.

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Temperature changes wreak havoc in deforested areas

Anonymous — Mon, 22 Feb 2016 07:00:00 +0000

Temperature changes wreak havoc in deforested areas Anonymous (not verified) Mon, 02/22/2016 - 00:00

Trent Knoss

A clear-cut forest area near Eugene, Oregon. Photo by Calibas / Wikipedia.

The newly exposed edges of deforested areas are highly susceptible to drastic temperature changes, leading to hotter, drier and more variable conditions for the forest that remains, according to new research from the University of Colorado Boulder.

The findings suggest that thermal biology—an emerging discipline that examines the effects of temperature on biological and ecological processes—could be an effective tool for understanding how temperature changes in fragmented habitats can potentially wreak havoc on species activity and other critical ecosystem functions.

A study outlining a framework for applying thermal biology to deforestation research was recently published in the journal Ecology Letters.

Previous research has shown that widespread deforestation is a threat to global biodiversity, but scientists are only just now beginning to examine the role that temperature may play when trees are removed from an ecosystem—especially near the newly-cut edges of forests.

Kika Tuff

“When you chop down trees, you create hot spots in the landscape that are just scorched by the sun,” said Kika Tuff, a PhD candidate in the Department of Ecology and Evolutionary Biology at CU-Boulder and the lead author of the new paper. “These hot spots can change the way that heat moves through the landscape.”

In some cases, this creates a phenomenon known as the ‘vegetation breeze,’ where low air pressure in the cleared areas pulls the cool, moist air out of the forest and feeds hot, dry air back in.

“So now the cleared areas get all the rain and the forests gets sucked dry,” said Tuff.

The warming effect is most pronounced between 50 and 100 meters of a forest edge, the study reports, where temperatures can be anywhere from 4 to 18 degrees Fahrenheit warmer than in the forest interior.

“This is like climate change on steroids,” Tuff said, “and it happens over much more rapid time scales.”

Biologists estimate that 20 percent of the world’s remaining forests lie within 100 meters of an edge, while more than 70 percent lie within a kilometer of one. This means that much of the world’s forests may be experiencing the vegetation breeze and other warming effects.

Increased temperature variation near forest edges could affect species’ ability to regulate their body temperatures, resulting in behavioral changes that could alter the local ecosystem.

One such example, Tuff said, could be the feeding patterns of animals living at the forest edge. Animals are very temperature sensitive, so they hunt for food when they have sufficiently warmed up in the morning and stop hunting for food when it is too hot in the afternoon. If temperatures are higher at the forest edge, species may respond by retreating to hunt in the cooler, deeper forest, where they become dependent on new types of food, sparking a domino effect in the food chain.

Another example might be the timing and duration of species activity. If temperatures were to increase due to tree loss, predators may start foraging later in the day to avoid the heat. Such a change could increase how frequently predators come across their prey, intensifying predation events and resulting in localized prey population crashes in some cases.

Such effects should also apply in instances of natural treefall, Tuff said. In Colorado, for example, high winds, wildfires and beetle kill can create edges in the treeline where greater sunlight exposure would subsequently increase the solar radiation and temperature in localized areas.

The sensitivity of animals and plants to temperature could have implications for future conservation strategies as deforestation and habitat fragmentation continue worldwide.

“Applying thermal biology on the scale of landscapes is a fairly new idea,” Tuff said. “Thermal biology presents a new imperative for forest conservation and makes the value of forests all the greater because of what they do for thermal regulation. Trees aren’t just habitat for animals, they are the world’s insurance for a thermally stable and habitable planet.”

The study was co-authored by Assistant Professor Kendi Davies and graduate student Ty Tuff, both of the Department of Ecology and Evolutionary Biology (EBIO) at CU-Boulder.

Trent Knoss is a science editor at the CU Office of News Services.

The newly-exposed edges of deforested areas are highly susceptible to drastic temperature changes, leading to hotter, drier and more variable conditions for the forest that remains, according to new research from the University of Colorado Boulder.

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Giant flightless bird strolled Arctic 50 million years ago

Anonymous — Fri, 12 Feb 2016 07:00:00 +0000

Giant flightless bird strolled Arctic 50 million years ago Anonymous (not verified) Fri, 02/12/2016 - 00:00

Jim Scott

A new study involving CU-Boulder and the Chinese Academy of Sciences has confirmed that a flightless bird weighing several hundred pounds roamed Ellesmere Island in the high Arctic about 50 million years ago. Its name is Gastornis. Illustration by Marlin Peterson

It’s official: There really was a giant, flightless bird with a head the size of a horse’s wandering about in the winter twilight of the high Arctic some 53 million years ago.

The confirmation comes from a new study by researchers from the Chinese Academy of Sciences in Beijing and the University of Colorado Boulder that describes the first and only fossil evidence from the Arctic of a massive bird known as Gastornis. The evidence is a single fossil toe bone of the 6-foot tall, several-hundred-pound bird from Ellesmere Island above the Arctic Circle. The bone is nearly a dead ringer to fossil toe bones from the huge bird discovered in Wyoming and which date to roughly the same time.

The Gastornis (formerly Diatryma) fossil from Ellesmere Island has been discussed by paleontologists since it was collected in the 1970s and appears on a few lists of the prehistoric fauna there, said Professor Thomas Stidham of the Chinese Academy of Sciences in Beijing. But this is the first time the bone has been closely examined and described, he said. Gastornis fossils also have been found in Europe and Asia.

“We knew there were a few bird fossils from up there, but we also knew they were extremely rare,” said Eberle, an associate professor in geological sciences who conducts research on fossil mammals, reptiles and fishes. In addition to the Gastornis bone from Ellesmere, another scientist reported seeing a fossil footprint there, probably from a large flightless bird, although its specific location remains unknown, Eberle said.

A paper by Stidham and Eberle appears in the most recent issue of Scientific Reports, an open access, weekly journal from the publishers of Nature.

About 53 three million years ago during the early Eocene Epoch, the environment of Ellesmere Island was probably similar to cypress swamps in the southeast U.S. today, Eberle said. Fossil evidence indicates the island, which is adjacent to Greenland, hosted turtles, alligators, primates, tapirs and even large hippo-like and rhino-like mammals.

Today Ellesmere Island is one of the coldest, driest environments on Earth, where temperatures can drop to minus 40 degrees Fahrenheit in winter, said Eberle, also the curator of paleontology at the University of Colorado Museum of Natural History.

Originally thought to be a fearsome carnivore, recent research indicates Gastornis probably was a vegan, using its huge beak to tear at foliage, nuts, seeds and hard fruit.

A second Ellesmere Island bird from the early Eocene also is described by Stidham and Eberle in the new paper. Named Presbyornis, it was similar to birds in today’s duck, goose and swan family but with long, flamingo-like legs. The evidence was a single humerus, or upper wing bone, collected by the same paleontology team that found the Gastornis bone.

Like Gastornis, Presbyornis was mentioned in several lists of Ellesmere Island fauna over the years but the bone had never been described, said Stidham.

Stidham compared casts of Presbyornis bones excavated in ancient Wyoming to the single bone from Ellesmere Island, including all of the marks for muscle attachments. “I couldn’t tell the Wyoming specimens from the Ellesmere specimen, even though it was found roughly 4,000 kilometers (2,500 miles) to the north,” he said.

While the diversity of plants and animals on Ellesmere was surprisingly high in the early Eocene, one of the biggest challenges to life on the island may have been the Arctic winters, said Eberle. “Since Ellesmere Island is high above the Arctic Circle, the lights still went out there for several months of the year, just as they do today.”

It is not known whether Presbyornis migrated north to Ellesmere Island every year or lived there year-round, said Stidham. “Given the fossils we have, both hypotheses are possible,” he said. “There are some sea ducks today that spend the winter in the cold, freezing Arctic, and we see many more species of waterfowl that are only in the Arctic during the relatively warmer spring and summer months.”

The paleontology team working on Ellesmere Island in the 1970s and who found the Gastornis and Presbyornis bones in the 1970s included Mary Dawson, Robert “Mac” West, Howard Hutchinson and Malcolm McKenna.

The new study has implications for the rapidly warming Arctic climate, primarily a result of greenhouse gases being pumped into Earth’s atmosphere by humans.

“Permanent Arctic ice, which has been around for millennia, is on track to disappear,” Eberle said. “I’m not suggesting there will be a return of alligators and giant tortoises to Ellesmere Island any time soon. But what we know about past warm intervals in the Arctic can give us a much better idea about what to expect in terms of changing plant and animal populations there in the future.”

The study was funded in part by the U.S. National Science Foundation, the Chinese Academy of Sciences and the Chinese Natural Science Foundation.

Jim Scott is senior science editor for the CU Office of News Services.

It’s official: There really was a giant, flightless bird with a head the size of a horse’s wandering about in the winter twilight of the high Arctic some 53 million years ago.

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Gene controlling skin stem-cell self-renewal is found

Anonymous — Fri, 05 Feb 2016 07:00:00 +0000

Gene controlling skin stem-cell self-renewal is found Anonymous (not verified) Fri, 02/05/2016 - 00:00

Paul Muhlrad

Image credit: Science

A University of Colorado Boulder research team, in collaboration with a researcher at the CU School of Medicine, has discovered how skin stem cells know when to stop dividing.

The findings, published as the cover story in the Feb 5 issue of the journal Science, suggest new avenues for controlling stem cells in regenerative medicine, and should further our understanding of how stem cells may go awry in cancer, says Rui Yi, associate professor of molecular, cellular, and developmental biology at CU-Boulder, who led the study along with first author Li Wang, who recently completed his PhD in Yi’s lab.

"It is now widely accepted that skin cancers originate from stem cells. Hair-follicle stem cells are especially prone to develop into invasive cancers such as basal cell carcinoma and squamous cell carcinoma.”

By some estimates, Yi says, adults replace all the cells in their skin every month. To maintain such constant cell turnover, the skin has to exert tight controls over which cells may divide and when any particular cell divides.

Fortunately, Yi says, most cells within our body do not divide, or we would grow unrestrained. But stem cells, such as those responsible for replenishing skin, have the potential to divide unlimited times, given the opportunity.

How does a stem cell know when to divide and when to stop? That question is important, not only for understanding how skin controls its normal growth, but for developing strategies to fight skin cancer, the unfettered tissue growth that ensues when these controls run amok.

Biologists understand many details of how molecular signals secreted by surrounding skin tissue communicate with stem cells to stimulate them to divide. For example, when the skin suffers a cut, it musters stem cells in the area to divide and repair the injury.

But until now, not much has been known about whether a stem cell, itself, has any internal sense of when to divide or when it should lay in wait.

Using genetically engineered mice provided by co-author Julie Siegenthaler, an assistant professor in the department of pediatrics at CU-Denver, the researchers discovered that a transcription factor called Foxc1 acts within hair follicle stem cells to keep them from dividing until the appropriate time.

A transcription factor is a protein that controls when genes are turned on or off, and the Colorado team identified more than a hundred genes that Foxc1 turns on. Enforcing a two-pronged control strategy, Foxc1 activates genes that prevent stem cells from dividing, and as a result also turns off genes that stem cells need to divide.

When Yi’s team inactivated Foxc1 in hair-follicle stem cells, the cells lost their inhibition toward dividing, allowing them to divide prematurely. Yi’s team noticed that Foxc1 is also turned on in the stem-cell niche, a cluster of neighboring cells that supports the stem cells. When the researchers inactivated Foxc1 in the niche, it led to hair loss. As Yi observes, “It seems that this factor has different roles in the stem cells and in the niche.”

The most intriguing finding about Foxc1, Yi notes, is that it appears in a stem cell only once the cell has divided. In effect, he says, Foxc1 serves as a switch that notifies a stem cell that it has divided and should stop dividing until further notice.

This way, he explains, every hair follicle stem cell gets to divide at least one time so that it can replenish itself, but once that happens, Foxc1 in the newly divided daughter cells contols whole networks of genes to keep the cells from dividing further unless absolutely necessary.

What turns on Foxc1 in newly divided stem cells? Yi says that question is still an unsolved mystery.

Now that Yi’s team has pinpointed Foxc1 as the key control point for hair follicle skin stem-cell division, team members are eager to learn how the dozens of Foxc1’s target genes carry out its orders to prevent cell division.

This is a profoundly important question, Yi says, because it is now widely accepted that skin cancers originate from stem cells. And hair-follicle stem cells in particular, he adds, are more prone to develop into invasive cancers, such as basal cell carcinoma and squamous cell carcinoma.

In addition to Wang, Yi, and Siegenthaler, MCDB assistant professor Robin Dowell co-authored theScience paper and supervised bioinformatics analyses.

Paul Muhlrad is science communications manager at the CU-Boulder Department of Molecular, Cellular and Developmental Biology. Read more about this work here and here.

A University of Colorado Boulder research team, in collaboration with a researcher at the CU School of Medicine, has discovered how skin stem cells know when to stop dividing.

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Ancient extinction of giant bird points to humans

Anonymous — Thu, 28 Jan 2016 07:00:00 +0000

Ancient extinction of giant bird points to humans Anonymous (not verified) Thu, 01/28/2016 - 00:00

Jim Scott

An illustration of the giant flightless bird known as Genyornis newtoni, surprised on her nest by a 1 ton, predatory lizard named Megalania prisca in Australia roughly 50,000 years ago. Illustration by Peter Trusler, Monash University.

The first direct evidence that humans played a substantial role in the extinction of the huge, wondrous beasts inhabiting Australia some 50,000 years ago — in this case a 500-pound bird — has been discovered by a University of Colorado Boulder-led team.

Gifford Miller

The flightless bird, known as Genyornis newtoni, was nearly 7 feet tall and appears to have lived in much of Australia prior to the establishment of humans on the continent 50,000 years ago, said CU-Boulder Professor Gifford Miller. The evidence consists of diagnostic burn patterns onGenyornis eggshell fragments that indicate humans were collecting and cooking its eggs, thereby reducing the birds’ reproductive success.

“We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian megafauna,” said Miller, associate director of CU-Boulder’s Institute of Arctic and Alpine Research. “We have documented these characteristically burnedGenyornis eggshells at more than 200 sites across the continent.”

A paper on the subject appears online Jan. 29 in Nature Communications.

In analyzing unburned Genyornis eggshells from more than 2,000 localities across Australia, primarily from sand dunes where the ancient birds nested, several dating methods helped researchers determine that none were younger than about 45,000 years old. Burned eggshell fragments from more than 200 of those sites, some only partially blackened, suggest pieces were exposed to a wide range of temperatures, said Miller, a professor in CU-Boulder’s Department of Geological Sciences.

Optically stimulated luminescence dating, a method used to determine when quartz grains enclosing the eggshells were last exposed to sunlight, limits the time range of burned Genyorniseggshell to between 54,000 and 44,000 years ago. Radiocarbon dating indicated the burnt eggshell was no younger than about 47,000 years old.

The blackened fragments were likely burned in transient, human fires — presumably to cook the eggs — rather than in wildfires, he said.

Amino acids — the building blocks of proteins –decompose in a predictable fashion inside eggshells over time. In eggshell fragments burned at one end but not the other, there is a tell-tale “gradient” from total amino acid decomposition to minimal amino acid decomposition, he said. Such a gradient could only be produced by a localized heat source, likely an ember, and not from the sustained high heat produced regularly by wildfires on the continent both in the distant past and today.

Miller also said the researchers found many of the burnt Genyornis eggshell fragments in tight clusters less than 10 feet in diameter, with no other eggshell fragments nearby. Some individual fragments from the same clusters had heat gradient differences of nearly 1,000 degrees Fahrenheit, conditions virtually impossible to reproduce with natural wildfires there, he said.

“We can’t come up with a scenario that a wildfire could produce those tremendous gradients in heat,” Miller said. “We instead argue that the conditions are consistent with early humans harvestingGenyornis eggs, cooking them over fires, and then randomly discarding the eggshell fragments in and around their cooking fires.”

Another line of evidence for early human predation on Genyornis eggs is the presence of ancient, burned eggshells of emus — flightless birds weighing only about 100 pounds and which still exist in Australia today — in the sand dunes. Emu eggshells exhibiting burn patterns similar to Genyorniseggshells first appear on the landscape about 50,000 years ago, signaling they most likely were scorched after humans arrived in Australia, and are found fairly consistently to modern times, Miller said.

The Genyornis eggs are thought to have been roughly the size of a cantaloupe and weighed about 3.5 pounds, Miller said.

Genyornis roamed the Australian outback with an astonishing menagerie of other now-extinct megafauna that included a 1,000-pound kangaroo, a 2-ton wombat, a 25-foot-long-lizard, a 300-pound marsupial lion and a Volkswagen-sized tortoise. More than 85 percent of Australia’s mammals, birds and reptiles weighing over 100 pounds went extinct shortly after the arrival of the first humans.

The demise of the ancient megafauna in Australia (and on other continents, including North America) has been hotly debated for more than a century, swaying between human predation, climate change and a combination of both, said Miller. While some still hold fast to the climate change scenario — specifically the continental drying in Australia from about 60,000 to 40,000 years ago — neither the rate nor magnitude of that change was as severe as earlier climate shifts in Australia during the Pleistocene epoch, which lacked the punch required to knock off the megafauna, said Miller.

Miller and others suspect Australia’s first inhabitants traveled to the northern coast of the continent on rafts launched from Indonesian islands several hundred miles away. “We will never know the exact time window humans arrived on the continent,” he said. “But there is reliable evidence they were widely dispersed across the continent before 47,000 years ago.”

Evidence of Australia megafauna hunting is very difficult to find, in part because the megafauna there are so much older than New World megafauna and in part because fossil bones are easily destroyed by the chemistry of Australian soils, said Miller.

“In the Americas, early human predation on the giant animals in clear — stone spear heads are found embedded in mammoth bones, for example,” said Miller. “The lack of clear evidence regarding human predation on the Australia megafauna had, until now, been used to suggest no human-megafauna interactions occurred, despite evidence that most of the giant animals still roamed Australia when humans colonized the continent.”

Co-authors on the new study include Research Professor Scott Lehman, doctoral student Christopher Florian and researcher Stephen DeVogel of CU-Boulder; Research Fellow John Magee of the Australian National University; and researchers from seven other Australian institutions. The study was funded in part by the U.S. National Science Foundation and the Australian Research Council.

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Microbiologist Pace retiring after illustrious career

Anonymous — Thu, 30 Apr 2015 06:00:00 +0000

Microbiologist Pace retiring after illustrious career Anonymous (not verified) Thu, 04/30/2015 - 00:00

Magdalena Rost

Norm Pace has no plans to leave the city after his retirement. ‘I will leave Boulder only in an urn!” he says.

Winner of ‘Genius Award,’ vanguard of extremophile research, pioneer in RNA study, bicycle-loving prof eyes life at a slower pace

Norman Pace, a University of Colorado Boulder distinguished professor in molecular, cellular, and developmental biology (MCDB), is retiring after this semester.

His research and teaching career has been punctuated with prestigious awards, including election to the National Academy of Sciences in 1991 and the MacArthur Fellowship “Genius Award” in 2001. Pace first came to CU-Boulder in 1999 and was named distinguished professor in 2008. Pace has authored or contributed to more than 267 published works.

Over the years, Pace has done groundbreaking work in RNA processing. He discovered new microbes by extracting genetic information from samples unable to be cultured in labs, tracing their genetic relatives.

He was among the vanguard of scientists who discovered the existence of extremophiles, which live in areas long thought to be inhospitable to life—in extremely hot, cold or acidic environments, for instance. Most recently, he studied the prevalence of microbes within the human environment—showers, swimming pools and municipal water.

Pace became interested in microbiology while in high school in the small, farming town in southern Indiana where he grew up. Science education had received a big boost in funding due to the success of Russia’s Sputnik satellite in 1957, and Pace benefited from the proliferation of programs.

He attended a summer institute between his junior and senior year of high school hosted by Indiana University. Along with 60 other students, Pace attended lectures and labs on the campus for two weeks. At the end of the two weeks, 18 students were chosen to work over the next eight weeks in a university lab.

“At that stage of the game, I was planning on attending Purdue and becoming a chemical engineer,” says Pace.

But something changed during Pace’s eight-week lab experience.

“I was meted out to the laboratory of a scientist by the name of Dean Fraser, who at that time was in the Department of Bacteriology,” explains Pace.

The lure of molecular biology

Pace worked with a graduate and post-doctoral fellow on a project that resulted in a published paper—the very first of his long list of publications. More importantly to Pace, he learned about laboratory work and molecular biology. “I was enthralled.”

Pace attended Indiana University for his bachelor’s degree and worked at labs throughout his undergraduate career. He attended the University of Illinois for his Ph.D., and says that’s where he became really interested in RNA, a nucleic acid most widely known for its ability to act as a messenger, carrying instructions from DNA to control the synthesis of proteins in cells.

After his post-doctoral fellowship (also at the University of Illinois), Pace accepted a job in Denver at the University of Colorado Medical Center. With his move to Denver came the inception of his lab—the Pace Lab, which he later brought to CU-Boulder. His lab focuses on RNA processing.

His lab has spent considerable time studying the process of using the structure of ribosomal RNA to infer evolutionary patterns. Pace explains this molecule is particularly suited for conservation, making it great for mapping species and traits.

Pace and the others working in his lab realized that most bacterial life is not able to be cultured and studied within a lab setting, but that by tracing RNA sequencing, microbes would be identifiable. This would also enable them to make correlations between organisms and environments.

Pace says that his lab was doing quite well studying RNA processing, but many other scientists were interested in the same topic. They became attracted to work begun by a scientist named Carl Woese, who was responsible for the three-kingdom model of biological life. This model discards the popular term “prokaryotes,” and its phylogenetic tree consists of Bacteria, Archaea, and Eucarya.

Pace and the others working in his lab realized that most bacterial life is not able to be cultured and studied within a lab setting, but that by tracing RNA sequencing, microbes would be identifiable. This would also enable them to make correlations between organisms and environments.

This discovery led to Pace’s MacArthur Fellowship in 2001. He was able to identify microbial species in areas like underwater hydro-thermal vents (which were thought to be uninhabitable by microbes until then) and hot springs at Yellowstone National Park.

Because the microbes could not be cultured in the labs, Pace and his assistants extracted nucleic acids from large amounts of water and used RNA sequencing to trace relations to the microbes they discovered.

“I knew the next bunch of years was going to be committed to this,” says Pace. “We had found a way to figure out what all this stuff was.”

Pace’s lab published the first metagenomic library. Metagenomics is the study of genetic material taken directly from environmental samples. Over the next decade, the field of metagenomics took off among other scientists, but Pace is proud he was key in its inception.

The bugs in your shower

In recent years, the Pace Lab moved on to another interest: the biology of the human environment. Under funding from the Alferd P. Sloan Foundation, Pace studied human microbiology like non-tuberculosis microbacteria present in moist environments such as saunas and swimming pools—even home showers.

These opportunistic bacteria are non-communicable but abundantly present in indoor, human environments.

Pace studied microbacteria in subway stations in New York City and determined that the microbiology there is essentially the same as the concentration outside the subway.

Pace acknowledges that the New York City subway generally makes people think the microbacteria found would be extensive and “weird,” but credits the normal microbacteria levels to the excellent ventilation system within the stations, driven only by the forced air of the moving subways.

Pace studied microbacteria in subway stations in New York City and determined that the microbiology there is essentially the same as the concentration outside the subway.

Most recently, Pace and his lab studyied microbacteria within municipal water systems. The most striking thing to Pace was the detail. Members of the lab travelled from Salida, Colo., down the Arkansas River to Mississippi, taking samples of water along the way. Some places had high instances of microbacteria, but others were relatively low, sometimes for unclear reasons.

Pace has been pleased to watch members of his lab develop through their innovative research experiences alongside him. The Pace Lab, which hosted 18 members at its prime, has slowed down over the past few years and decreased its members to just a few individuals. The lab will close officially after Pace’s retirement.

Mark Winey, professor and chair of the MCDB department, says it’s been an honor to have Pace on the faculty. “He’s been a leader in the community of microbiologists. He’s served the college by delving into our core curriculum, and he has been an advisor, mentor and fine colleague to so many members of university community, faculty and students alike.”

Pace says that he plans to stay involved with science after his retirement, but that he’ll be slowing down his work substantially.

“It’s going to be very low key,” says Pace. “I have lots of writing yet to do, but I have no specific plans. I don’t play golf.”

Pace is on the board of directors for the Monterey Bay Aquarium Research Institute and sits on the Space Studies Board Committee on Origin and Evolution of Life. He also continues to be involved with his colleagues’ work, some of which involves projects delegated from his closing lab.

Pace also hopes to pursue one of his great—and less well-known—passions after his retirement. Another interest from a young age, Pace is interested in mapping and exploring caves.

A member of the National Speleological Society, Pace was awarded the Bicking Award—widely considered to be the most prestigious award for a “caver” to receive—in 1987 for his work coordinating mapping of cave systems.

The mapping of caves and mapping of biological evolution are both what Pace calls “aesthetically pleasing to do,” and he jokes that “they even pay you money to do the latter!”

He notes that he has stayed with the University of Colorado Boulder longer than he has taught at any other university. An avid bicyclist, Pace attributes making Colorado his home to the beautiful mountains and many biking trails and has no plans to move after his retirement. Pace says he bought a new car three years ago and only recently broke the 7,000-mile-mark.

“I believe in cycling as a way of life,” says Pace. “As I jokingly tell my friends, I will leave Boulder only in an urn!”

Magdalena Rost, a student majoring in classics and English, is an intern for Colorado Arts & Sciences Magazine.

Norman Pace, a University of Colorado Boulder distinguished professor in molecular, cellular, and developmental biology (MCDB), is retiring after this semester. He has done pioneering research on RNA and on extremophiles, microbes that live in inhospitable environments.

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Naval pilot earns soaring praise for honors’ research

Anonymous — Thu, 30 Apr 2015 06:00:00 +0000

Naval pilot earns soaring praise for honors’ research Anonymous (not verified) Thu, 04/30/2015 - 00:00

Clint Talbott

Courtnie Paschall is the Outstanding Graduate for the College of Arts and Sciences for spring 2015. Photo by Laura Kriho.

Before Courtnie Paschall touched down at the University of Colorado Boulder, she’d graduated from the Naval Academy (‘08), attained the rank of lieutenant in the U.S. Navy and undergone years of flight training.

Paschall graduates on May 9 with a degree in neuroscience and a minor in electrical engineering. She earned the distinction of graduating summa cum laude and was named the Outstanding Graduate for the College of Arts and Sciences for spring 2015.

Paschall graduated from the Naval Academy in 2008 with a bachelor of science in physics and a minor in Mandarin Chinese. She went immediately into flight school, where she learned to pilot fixed-wing planes and helicopters.

"The blood rushed from my face. I had to walk outside and take a deep breath and just make sure that I was really willing to commit to an unknown future and give up everything this path meant.”

She was two weeks from “winging”—a graduation ceremony in which military pilots celebrate completing flight school and sign an eight-year service contract—when the Navy downsized its forces.

This was a major crossroads for Paschall, given her history with the U.S. military: her father and mother are both Marines, and her dad is still active duty.

Also, the Navy had made a large investment in Paschall’s training, both in the Naval Academy and in flight school. But with the Navy downsizing, she had the option to stay or go.

She left.

“It was terrifying,” Paschall said, recalling when her flight instructor told her commanding officer that the decision to leave or stay was hers.

“The blood rushed from my face. I had to walk outside and take a deep breath and just make sure that I was really willing to commit to an unknown future and give up everything this path meant.”

She was 23.

Paschall knew she wanted to do something else but was not sure what or where.

Still, there were signposts. She had always wanted to study neuroscience. Also, her dad, who was from Colorado, described the state this way: “God stood in Colorado and created everything else from the leftovers.”

So she picked CU-Boulder. Her arrival coincided with the semester that the university approved a new major in neuroscience.

In her thesis, Paschall’s original aim was to study the morphological impacts of schizophrenia. But the dataset she was studying “didn’t have a great representation of schizophrenic patients.”

As an alternative, she studied the morphological effects of marijuana on three subcortical brain structures often shown to be impacted by drug use in human adults.

An interesting scientific question, the scientific literature currently demonstrates conflicting results regarding the long-term effects of marijuana use on brain structure. In addition, marijuana use and the eventual development of schizophrenia have been linked.

Marie Banich, professor of psychology and neuroscience and Paschall’s thesis advisor, noted that Paschall made use of a recently released public dataset culled from more than 500 individuals.

Paschall found that the duration of marijuana use over one’s lifetime affected the shape of brain structures critical for emotion, memory and reward. Paschall is now in the process of revising her thesis for submission to a scholarly journal.

Banich described Paschall as an exceptionally bright and motivated young scholar who finished her honors’ thesis in nine months—half the time of an average honors’ student.

Paschall plans to enroll in an MD-PhD program and to focus her clinical and research efforts on mental illness.

“I could be a student the rest of my life—without exaggeration. There’s so much to know, and there’s so much interconnection that is required, moving forward in science. We’ve scattered, and connecting the pieces in each of these [scientific] tracks is so important.”

Clint Talbott is director of communications and external relations for the College of Arts and Sciences and editor of the College of Arts and Sciences Magazine.

Before coming to CU, Courtnie Paschall had graduated from the Naval Academy, attained the rank of lieutenant and undergone years of flight training. Now, she’s graduating summa cum laude with a degree in neuroscience and a minor in electrical engineering. She is also the Outstanding Graduate for the College of Arts and Sciences for spring 2015.

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Python lab course helps students chart the future

Anonymous — Thu, 30 Apr 2015 06:00:00 +0000

Python lab course helps students chart the future Anonymous (not verified) Thu, 04/30/2015 - 00:00

Magdalena Rost

Leslie Leinwand examines a python with Ryan Doptis, an undergraduate participant in the Python Project.

‘Python Project’ helps undergraduates see if grad-school laboratory research, medical school or other alternatives are right for them; it also helps the university effectively allocate graduate-school funds

At the University of Colorado Boulder, 16 undergraduate students are gaining valuable lab experience that will help them determine if they should pursue the sciences in graduate or medical school, work in private laboratories, or even follow other educational paths.

The course, called the “Python Project,” allows undergraduates to pursue research in a laboratory setting—an experience that is normally available to very few undergraduate students and is usually reserved for graduate students.

Students in the Python Project participate in poster sessions, as graduate students and other researchers do.

With the cooperation of the Leslie Leinwand Lab (the course’s first instructor) within the BioFrontiers Institute, students measure RNA sequences of genes in Burmese pythons. The pythons, after feeding, undergo rapid growth and increased function in many organs and cellular functions, such as the heart and metabolism.

It is the hope that by studying these physiological changes scientists might be able to understand beneficial (physiological) heart growth and harmful growth (such as heart disease) in humans, and ways to treat the latter.

Unfortunately, the python genome is not as well annotated as other species’, so the sequences that control growth in python organs are not well-known. That’s where the students come in:

“The student’s job is to use a similar sequence like the same protein in a chicken or lizard, compare it to a python and try to assemble a transcript close to it,” Harvey explains. Transcription is the process by which the biological information stored in DNA is used to produce a complementary strand of RNA.

Experimenting with lab life

This experience aids students in deciding their future educational and career goals, assists the Leinwand Lab in gathering data, and points students toward an informed decision about spending money on graduate or medical school. The current course helps to avert a much larger cost in the future should less-informed students pursue post-grad studies and later realize it’s not what they expected.

Feeding’s effect on python hearts is significant, as seen here in two cross sections of python hearts before feeding and three days after feeding (of two different, size-matched snakes). Image courtesy of Leinwand lab.

Pam Harvey, the instructor of the Python Project course, believes the class is important for both students and the university. It helps students discern their career paths by giving them a snapshot of what working in a real lab doing research that may be used outside of the campus is like, and it aims to keep students in the sciences.

“There’s something between undergraduate and graduate school where we’re losing a ton of students,” says Harvey, adding, “even between freshman and senior year.” Harvey believes students aren’t given a realistic idea of what graduate school will be like before they commit.

The class was started about eight years ago and funded by a professorship awarded by Leslie Leinwand, now chief scientific officer of the BioFrontiers Institute at CU-Boulder, and by the Howard Hughes Medical Institute. Once the initial funding ran out, an anonymous donor contributed an additional $50,000 for the class to continue.

“The course comes and goes depending on funding,” says Harvey. The class does not currently receive supply money from the CU-Boulder Department of Molecular, Cellular and Developmental Biology. However, the MCDB department is covering the instructor’s salary for the course—a cost that previously had to be absorbed by the grant and donations. Harvey says that development is “really big,” and frees money for the necessary materials for the course, and helps it to run longer.

The course is pricey: Most MCDB courses cost $32 per student, but the Python Project requires just under $300 per student to cover the materials.

However, as data are collected about the success of the course in helping retain students to continue in their pursuit of studies and careers in science, the MCDB department is becoming more open to the idea of funding the project

Harvey published a research article last fall with data on the success of the course and the current activities of the former students of the class. She found that not only are the data in the student lab helpful to the Leinwand Lab’s projects, but the course was also successful in retaining students in the sciences, with a majority of students continuing either their science research or medical school.

“The department is really warming up to the course,” says Harvey.

Most students who take the class have never had lab experience. Before enrolling, however, they complete a survey indicating whether they want to go to graduate school to earn a Ph.D., go to medical school or have yet to decide. Students who aren’t given the benefit of a research experience like in the Python Project class can be more costly in time and money down the road.

Harvey puts it this way: “Graduate school for a university is a huge investment, so if I’m going to invest $200,000 in you for five years, how do I know that you can tolerate being in a lab? That you can tolerate failure, which students in a regular class don’t typically get?”

At the end of the class, some students who were considering medical school decide they really liked doing research and decide to pursue graduate school instead.

Similarly, many students who were initially planning on graduate school shift into the unknown category because doing research wasn’t exactly what they expected. Lastly, the majority of the students who considered their future in science as unknown filter into the medical school and graduate school categories after they receive the benefit of a trial period pursuing one of the established career paths.

In a large department like MCDB, Harvey says it’s hard for students to get information: “Students aren’t thinking ahead to post-doctoral fellowships, or what to do to become a full professor,” Harvey explains.

“In the class we do a lot of talking about Ph.D. programs, and the students learn about the process and their options. For instance, students never think about becoming patent lawyers, but it is often a career where holding a Ph.D. is viewed as highly desirable.”

The students learn about graduate school and practical lab knowledge as well. One of the first exercises is to ensure students can properly pipette, a process that sometimes takes 12 to 15 hours for students to learn. And then there are the pythons.

A rigorous examination of pythons

Near the beginning of the course, students can attend an optional dissection of a Burmese python conducted by a member of the Leinwand Lab. “No students actually come into direct contact with the pythons,” says Harvey.

Each semester, Harvey, collaborating with the Leinwand Lab, comes up with a list of genes thought to be responsible for a specific function within the pythons. The class is somewhat fluid: Something new is researched each semester, from growth hormone signaling to mitochondria biogenesis.

“The overriding goal is to understand how the genes change,” says Harvey: “what proteins are responsible for some specific function, like making the heart big.”

All students focus on a similar process each semester but approach it in their own ways. Since they study 16 to 20 genes as a class, they function as a mini-screening lab for the Leinwand Lab, which is also interested in relating processes in the python’s hearts to human hearts.

"They’re not being graded day-to-day on research, but they are being ‘graded’ in a sense on how they maintain their lab notebookand how they present their information.”

Each semester, students present a public poster session to the MCDB department and BioFrontiers Institute. The environment is very similar to graduate studies, especially at the poster presentations, when students display their work for critique by colleagues and peers.

The assignments during the semester resemble what students would be expected to do if they were in graduate school or working in a lab.

“To me, the important things are the same things that would be important for a graduate student,” says Harvey. “They’re not being graded day-to-day on research, but they are being ‘graded’ in a sense on how they maintain their lab notebookand how they present their information.”

There are many similarities between the Python Project class and research as a graduate student. The most dreadful of these to an undergraduate: failure.

“About halfway through the semester, I start getting panicked emails,” says Harvey. “‘I think I’m failing the course.'”

Harvey offers a lot of encouragement to students and often tells them that success isn’t always measured in advancing a correct hypothesis, but rather in what conclusions can still be gleaned from a hypothesis that was proved incorrect.

Most students leave the Python Project with tangible lab skills that will help them get internships, jobs and acceptance to graduate programs. After the class, 95 percent of students agreed with the statement, “I prefer the structure of lab courses similar to the Python Project.”

Furthermore, 88 percent of students indicated that they had gained critical-thinking skills through the class.

Harvey, who tried to forgo a salary for the class to continue its run when funding dried up at one point, is excited that tangible results of student satisfaction and learning gains can be measured and reported.

“We would love for it to be offered every semester,” Harvey says.

With more helpful research being done on student retention, and as students spread word of their positive learning experience in the Python Project, that just may happen.

Magdalena Rost, a student majoring in classics and English, is an intern for Colorado Arts & Sciences Magazine.

The ‘Python Project’ helps undergraduates see if grad-school laboratory research, medical school or other alternatives are right for them; it also helps the university effectively allocate graduate-school funds.

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Spruce bark beetle outbreaks hurt squirrel populations

Anonymous — Mon, 16 Mar 2015 06:00:00 +0000

Spruce bark beetle outbreaks hurt squirrel populations Anonymous (not verified) Mon, 03/16/2015 - 00:00

Magdalena Rost

The spruce bark beetle kill in the Gore Range stretches from Dillon many miles to the north.Photo by Jeff Mitton

Bryan Hankinson, a fall 2014 CU-Boulder student who graduated magna cum laude, developed hishonors thesis by investigating the relationship between an increase in spruce bark beetle population and a decrease in American red squirrel population.

Hankinson found that squirrel populations decrease in areas with an increase in beetle-kill trees. The squirrels, primarily seed-consumers, were observed eating beetle larvae from infected Engelmann spruce trees. However, the squirrels weren’t able to glean enough nutritional substance from feeding on the beetle larvae to maintain their population.

Bryan Hankinson

The geography student who minored in technology arts and media became interested in this question while assisting geography Ph.D. student Julia Hicks as she explored how avian species in Colorado were being affected by spruce bark beetle outbreaks.

Why squirrels? Hankinson says it’s because “They actually do play a vital role in the ecosystem, especially when it comes to bird species, because they’ve been known to prey upon bird nests, nestlings, and smaller bird species. A lot of people don’t think about squirrels,” chuckles Hankinson.

Hankinson sought to address whether or not American red squirrels were affected by the spruce bark beetle outbreaks in Engelmann spruce forests in Colorado, but he also wanted to study whether the squirrels were successfully adapting to include the beetles in their diet. Hankinson also observed whether the fluctuations in squirrel populations affected cavity-nesting bird populations.

Hankinson and his colleagues gathered their data last summer in the San Juan and Gunnison national forests. They divided the areas into four transects of eight square kilometers of land. The transects were individuated by the relative health of the Engelmann spruces they contained, from containing little to no spruce bark beetle outbreaks to containing high levels of activity, as evidenced by diseased trees.

Those transects were further subdivided into nine point-count stations—areas an observer can record all the pertinent species from for a set amount of time. Starting at 4:30 in the morning, the researchers took around 10 minutes at each station and counted squirrels based on sight and auditory cues. The extensive data collection lasted from the beginning of June to mid-July.

"These habitats are these animals’ homes, and a lot of these animals rely on these habitats in order to live and for their populations to thrive.”

Hankinson counted 76 squirrels throughout the four transects. Only 27 of the squirrels inhabited the diseased, treatment transects—roughly 35 percent of the total squirrels. Hankinson discovered a negative correlation between the red squirrel counts and the number of infected Engelmann spruces, suggesting that the spruce bark beetle outbreaks were in fact negatively affecting American red squirrel populations.

The American red squirrel population probably drops in infected areas of forest because the squirrels in Colorado largely rely on a seed-based diet, according to Hankinson. As the beetles damage the trees, the food source of the squirrels decreases.

This caused Hankinson and his team to question whether the squirrels could adjust using beetles as a replacement food source. Unfortunately, “larvae don’t provide enough caloric substance,” says Hankinson. “Even though the squirrels feed, it doesn’t sustain the population.”

This indicates significant behavioral change in the American red squirrel. The only other study that has observed red squirrels preying on spruce bark beetle larvae was conducted in Canada’s Yukon Territory. No other studies have shown similar behavioral changes in squirrels within Colorado.

Hankinson also used the point-count stations to record the number of birds such as the American three-toed woodpecker. His research demonstrated a negative correlation between squirrel counts and woodpecker counts in the healthy transects, as well as a higher abundance of woodpeckers in the diseased transects. This suggested that the squirrels were preying on woodpecker eggs and nestlings within the nests, decreasing the nest success rate of the birds and lowering their overall population in those areas.

Although he admits it was a lot of work, Hankinson says the research for his thesis was ultimately worth it. Initially, Hankinson didn’t know what the data would indicate. He was satisfied to find that spruce bark beetle outbreaks were actually having an effect on species in Colorado.

“I love the fact that I did this study, and I can put it out there so people know it’s not only affecting us,” says Hankinson. “These habitats are these animals’ homes, and a lot of these animals rely on these habitats in order to live and for their populations to thrive.”

Hankinson notes that spruce bark beetle outbreaks are often reported in the news, and the effects they have on trees, landowners and homeowners are often discussed at length, but creatures like the humble American red squirrel are often neglected. Over time, spruce bark beetle outbreaks have the potential to highly influence entire chains of ecosystems within Engelmann spruce forests.

Hankinson, pursuing a career as a park ranger or wildlife forestry technician with the U.S. Forest Service or National Park Service, found his research as a CU-Boulder undergraduate rewarding. “To be able to write a thesis and put it out there so people know is really satisfying,” remarks Hankinson.

Magdalena Rost, a student majoring in classics and English, is an intern for Colorado Arts & Sciences Magazine.

In an undergraduate research effort, recent graduate Brian Hankinson found that squirrel populations decrease in areas with an increase in beetle-kill trees. The squirrels, primarily seed-consumers, were observed eating beetle larvae from infected Engelmann spruce trees. However, the squirrels weren’t able to glean enough nutritional substance from feeding on the beetle larvae to maintain their population.

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