NSF : Discovery Feeding birds in your local park? If they're white ibises in Florida, think twice .- La alimentación de las aves descubrimiento en su parque local? Si son los ibis blancos en Florida, piense dos veces

Hola amigos: A VUELO DE UN QUINDE EL BLOG., En el folklore nativo americano, el ibis blanco era el último animal a buscar refugio antes de un huracán, y los primeros en salir después de la tormenta. Por consiguiente, el ibis simboliza el peligro de una tormenta que se aproxima, y también la seguridad después de la vorágine pasado.
Pero ahora ibis pueden más a menudo señal de peligro - al menos en los parques públicos.
Las personas que alimentan los ibis blancos en esos lugares están recurriendo aves silvestres en los más dóciles, dicen los científicos. Los investigadores creen que la práctica puede propagar la enfermedad entre los ibis, y entre ibis y los seres humanos.
Los biólogos están estudiando como parte de la lactancia está cambiando la salud, la ecología y el comportamiento de los ibis blancos en el sur de Florida, donde el desarrollo está allanando sobre los hábitats de humedales naturales de las aves.

More information..........

http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=137557&WT.mc_id=USNSF_51&WT.mc_ev=click

White ibises may transmit diseases like salmonelosis
ibis blancos pueden transmitir enfermedades como la salmonella

White ibises congregate in flocks in urban parks, where they're inappropriately fed by people. Credit and Larger Version

February 3, 2016

The following is part 17 in a series on the NSF-NIH-USDA Ecology and Evolution of Infectious Diseases (EEID) Program. See parts: one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15 and16.

In Native American folklore, the white ibis was the last animal to seek shelter before a hurricane, and the first to emerge after the storm. The ibis therefore symbolized the danger of an approaching storm, and also the safety after the maelstrom passed.

But now ibises may more often signal danger -- at least in public parks.

People feeding white ibises in such places are turning wild birds into tame ones, scientists say. The researchers believe the practice may spread disease among ibises, and between ibises and humans.

The biologists are studying how hand-feeding is changing the health, ecology and behavior of white ibises in south Florida, where development is paving over the birds' natural wetland habitats.

 

Shift in ibis behavior

 

White ibises usually prey on aquatic animals such as fish, snails and crayfish, but they're becoming accustomed to bread, fast food and popcorn from people, says Sonia Hernandez, a veterinarian and ecologist at the University of Georgia (UGA).

The shift in behavior could have serious consequences not just for the ibises, says Hernandez, but also for people. It may allow pathogens transmitted through feces, like salmonella, to build up and pose risks for both birds and humans.

"We found that the strains of salmonella bacteria white ibises are infected with are the same ones people get sick from, especially in Florida," Hernandez says. "Because white ibises fly from urban to natural environments fairly easily, they could move these strains across large distances."

 

White ibis infectious disease ecology

 

Hernandez is working with other UGA researchers on a white ibis project funded by the National Science Foundation (NSF) Ecology and Evolution of Infectious Diseases (EEID) Program. Additional UGA researchers involved are Jeff Hepinstall-Cymerman, Sonia Altizer, Richard Hall and Kristen Navara.

The findings will ultimately apply to other wildlife species that live alongside humans in public parks and similar landscapes, the scientists say.

"Our interactions with wildlife can enliven our cities, but they also carry the potential for increasing disease risk to wildlife and to us," says Sam Scheiner, EEID program director at NSF. 

"This study will provide important information on the consequences of our interactions with ibises -- and serve as a model for managing urban wildlife," says Scheiner. "The research is the most comprehensive to date on how food resources in human-dominated habitats influence wildlife responses to infectious diseases."

 

Global urbanization: the risks it carries

 

Urbanization is expanding across the globe, with two-thirds of the world's people expected to live in cities within the next 40 years.

Development is causing many wildlife species to decline. Some species, however, are capitalizing on new urban resources, especially food provided by humans.

Shifts in wildlife ecology in response to intentional or accidental feeding by people can alter animals' susceptibility to infectious diseases, says Hernandez.

"Human-altered diets might change the makeup of these species' gut bacteria and increase their susceptibility to infection," adds Scheiner.

 

Easier in a park

 

In their NSF EEID project, the researchers are focusing on white ibises in Palm Beach County, Florida, where Hernandez has monitored the birds since 2010.

White ibises live along the Atlantic coast as far north as North Carolina and on the Gulf Coast west to Louisiana. The birds are usually nomadic and spend much of their days searching for food.

Why expend energy searching for food when humans in parks will provide it? Because it's an easy meal. "If white ibises have a reliable food source, they often form large flocks that stay year-round in one place," says Altizer.

Increasing numbers of ibises in urban parks facilitate contact with animals the ibises wouldn't normally encounter, like mallard ducks, gulls and other city birds that are disease reservoirs.

 

Urban vs. natural áreas

 

The researchers are comparing six urban and six natural areas in Palm Beach County. They're placing identification bands on captured birds before releasing them, tracking movements using GPS devices, recording basic data about each ibis marked, taking blood samples and collecting feces for salmonella testing.

The scientists are focusing on salmonella because it causes one of the most significant diarrheal diseases in people and results in mortality in young wading birds such as ibises.

"Urban ibises have extremely high levels of stress hormones and weak immune systems compared with other birds," Navara says. "Ultimately, this could affect how pathogens, including salmonella, are transmitted among individual ibises and between the birds and humans."

To date, the biologists have found that GPS-tracked ibises at urban sites move very little compared to those at natural sites. The prevalence of salmonella in ibises at urban sites, as well as salmonella in city water and soil, is higher than that in ibises and in the environment at natural sites, says Hernandez.

Soon the scientists will have further insights to offer. Their next field work is planned for Feb. 10 to March 10, 2016. They will place GPS tracking devices on as many as 50 ibises in urban parks and 50 in natural areas.

The researchers hope the project will raise awareness about how "helping" wildlife species by feeding them may have unintended consequences. The findings will also lead to improved ways people and wildlife can share habitats in cities.

The result? Less danger in human-bird disease connections -- and more optimism for our co-existence with wild species.

--	Cheryl Dybas, NSF (703) 292-7734  cdybas@nsf.gov
--	Sandi Martin, UGA (706) 542-2079  smartin@warnell.uga.edu

Investigators Richard Hall
Sonia Altizer
Kristen Navara
Sonia Hernandez
Jeffrey Hepinstall-Cymerman

Related Institutions/Organizations University of Georgia Research Foundation Inc
Related Programs Ecology and Evolution of Infectious Diseases
Related Awards #1518611 Consequences of Anthropogenic Resources for the Cross-Scale Dynamics of an Enteric Pathogen in an Avian Host
Total Grants $1,222,344
Related WebsitesNSF Special Report: Ecology and Evolution of Infectious Diseases: http://www.nsf.gov/news/special_reports/ecoinf/
NSF News: To slow the spread of infectious diseases, NSF, NIH, USDA support new research: http://www.nsf.gov/news/news_summ.jsp?cntn_id=136044&org=NSF

White ibises with spoonbills, wood storks and other wading birds in Florida's Fisheating Creek.
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White ibises are abundant in Florida; the species has become synonymous with the Everglades.
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Biologists secure a backpack-style harness for a GPS transmitter on a white ibis.
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Researchers release a white ibis outfitted with a GPS transmitter as part of the NSF EEID project.
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Scientists take blood from an ibis for stress hormones, immune function, antibodies to pathogens.
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the National Science Foundation (NSF)
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nsf.gov - National Science Foundation - National Science Foundation awards $9.47 million for research on coupled natural and human systems

Studies will lead to better understanding of how humans and the environment interact

The spread of insects such as mountain pine beetles has devastated forests in the Western U.S. Credit and Larger Version

August 20, 2014

Mountain pine beetles, tiny bark beetles the size of grains of rice, have become widespread pests. The insects infest tree after tree in western North America, killing off entire swaths of forests during outbreaks.

The effects of climate change and other factors have led to the unprecedented epidemic. Tens of millions of acres of trees have been killed over the past 20 years.

Scientist Christopher Bone of the University of Oregon is using the power of computing to inform the response to the mountain pine beetle epidemic, thanks to a grant from the National Science Foundation's (NSF) Dynamics of Coupled Natural and Human Systems (CNH) program.

The award addresses how humans and the environment interact--and where mountain pine beetles fit into the picture.

The grant is one of 11 NSF CNH awards made this year. Total funding for 2014 CNH grants is $9.47 million; the program has made awards nearly continuously since 2001.

CNH is co-funded by NSF's Directorates for Biological Sciences (BIO); Geosciences (GEO); and Social, Behavioral & Economic Sciences (SBE).

"This year's CNH awards address, among other topics, how humans affect and respond to changing environmental conditions in large metropolitan areas, how natural predators combat disease, how noise from a range of sources affects humans and wildlife, and the complex interactions between wind turbines and local environments," says Tom Baerwald, CNH program director for SBE.

"The project results will be useful for all of us," says Baerwald, "as we work to maintain and improve environmental quality over the long run."

This year's grantees will look at the way in which people deal with environmental processes in a range of settings, including cities, mountains, grasslands and forests.

Findings from the CNH projects, scientists believe, will enhance our understanding of, and increase our capabilities to improve, environmental quality and the well-being of people.

Among 2014 research subjects are the coupled health and human dynamics of schistosomiasis; feedbacks between local democracy and large-scale biodiversity conservation; bridging communities through mountain sustainability networks; the interactions among economic development, urbanization and forest degradation; drinking water quality and food security in arsenic-affected Southeast Asia; and increasing the resilience of grasslands in the Southern Great Plains.

"We now live in a world where wildlife and its habitats are strongly affected by human societies, but where societies still depend on nature--a world of coupled natural and human systems," says Peter Alpert, CNH program director for BIO.

"CNH is uniquely devoted to advancing our ability to understand this mutual dependence."

The CNH program considers humans and the environment as one interconnected system.

Research funded by CNH awards will provide a better understanding of natural processes and cycles and of human behavior and decisions--and how and where they intersect.

"Each of the new projects brings together teams of researchers from across the social and natural sciences," says Sarah Ruth, CNH program director for GEO, "to help us better understand how complex systems function, and ultimately, how we might best manage finite environmental resources."

NSF 2014 CNH Awards

Paul Armsworth, University of Tennessee, Knoxville,

CNH-Ex: Synergies and Feedbacks Between Local Direct Democracy and Large-Scale Biodiversity Conservation Efforts

Jesse Barber, Boise State University,

CNH: Sound as an Element in Coupled Natural and Human Systems

Christopher Bone, University of Oregon-Eugene,

 CNH: Forest Governance and Climate Change in Driving Native Insect Outbreaks

Hallie Eakin, Arizona State University,

CNH: The Dynamics of Multi-Scalar Adaptation in Megacities

Julia Klein, Colorado State University,

 CNH-RCN: Bridging Communities and Scales Through a Global Transdisciplinary Mountain Sustainability Network

Armand Kuris, University of California, Santa Barbara,

 CNH: The Coupled Human Health and Environmental Dynamics of Schistosomiasis

Zhulu Lin, North Dakota State University-Fargo,

CNH-Ex: A Model for Groundwater Allocation and Management at the Bakken Shale in Western North Dakota

Julie Lundquist, University of Colorado Boulder,

CNH-Ex: Legal, Economic, and Natural Science Analyses of Wind Plant Impacts and Interactions

Julie Silva, University of Maryland, College Park,

 CNH-Ex: Investigating the Dynamic Intersections Among Economic Development, Urbanization, and Forest Degradation

Alexander van Geen, Columbia University,

CNH: Competing Demands and Future Vulnerability of Groundwater: Drinking Water Quality and Food Security in Arsenic-Impacted South and Southeast Asia

Bradford Wilcox, Texas A&M University-AgriLife Research,

CNH: Slowing the Expansion of Woodlands and Increasing the Resilience of Grasslands in the Southern Great Plains

-NSF-

Media Contacts Cheryl Dybas, NSF, (703) 292-7734, cdybas@nsf.gov

Related WebsitesCNH: Summertime: Hot Time in the City:

 http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=128204&org=NSF
CNH: Cooking Up Clean Air in Africa:

 http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=126403&org=NSF&from=news
CNH: Studying Nature's Rhythms: Soundscape Ecologists Spawn New Field:

 http://www.nsf.gov/discoveries/disc_summ.jsp?cntn_id=123046&org=NSF
CNH: Scientists chart a baby boom--in southwestern Native Americans from 500 to 1300 A.D.:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=131869
CNH: Eradicating invasive species sometimes threatens endangered ones:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=131478
CNH: Climate of Genghis Khan's ancient time extends long shadow over Asia of today:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=130669
CNH: Human Disease Leptospirosis Identified in New Species, the Banded Mongoose, in Africa:

 http://www.nsf.gov/news/news_summ.jsp?cntn_id=127914

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2014, its budget is $7.2 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives about 50,000 competitive requests for funding, and makes about 11,500 new funding awards. NSF also awards about $593 million in professional and service contracts yearly.

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CNH scientists hope to balance woodland expansion and grassland resilience in the Great Plains.
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A parasitic worm causes schistosomiasis, a disease that threatens people across the globe.
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CNH grantees will study the human and environmental effects of wind plants.
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Groundwater allocation at the Bakken Shale in western North Dakota is the subject of a CNH award.
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Well polluted with arsenic; 100 million people in Southeast Asia are threatened by such wells.
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nsf.gov - National Science Foundation: Cool Cat in a Hot Zone

 As winter comes to Colorado, a bobcat at dusk makes its way along a well-trod path.
Credit: Colorado State University
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 Areas in California and Colorado where bobcats frequent were studied by scientists.
Credit: Scott Carver et al.
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 Bobcats are on-the-move from sunset until midnight, and again before dawn until sunrise.
Credit: Colorado State University
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Largely unseen, the secretive bobcat is in fact our next-door neighbor.
Credit: USDA Forest Service
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Hollow logs, brush piles and thickets, and the undersides of rock ledges: homes to bobcats.
Credit: Wikimedia Commons
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 In Boulder, a city along Colorado's Front Range, bobcats and humans cross paths.
Credit: Colorado State University
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What do Ventura County, Calif., and the Front Range of Colorado's Rocky Mountains have in common?

Ventura, which encompasses the city of Los Angeles, has a Mediterranean climate and habitat; the Front Range surrounding Denver is cooler, drier and is lined with tall conifers instead of low, dense shrubs.

Both, however, have people. Lots of them.

But it's what else they have in common that tells the real tale of these urban areas.

Alley cat of the wild

It's on the move from three hours before sunset until midnight, and again before dawn ‘til three hours after sunrise. Each night it roams two to seven miles, mostly along the same route.

Like humans, it visits known locales along the way. In this case, though, those places are a hollow log or two, a brush pile or thicket and the underside of a rock ledge.

It also shares something far more personal with the people it quietly lives alongside: gastrointestinal diseases.

It's a bobcat, and we gave it our afflictions rather than the other way around, say scientists Sue VandeWoude, Kevin Crooks, Mike Lappin and Andrea Scorza of Colorado State University at Fort Collins; Scott Carver of the University of Tasmania; Sarah Bevins of the U.S. Department of Agriculture and Seth Riley of the U.S. National Park Service.

The researchers published results of their study of the parasites bobcats and humans share in a recent issue of the Journal of Clinical Microbiology.

Their work is funded by the joint National Science Foundation (NSF) and National Institutes of Health (NIH) Ecology and Evolution of Infectious Diseases (EEID) Program.

"The growing interaction of humans and wildlife means that we now share our diseases with each other at an ever-increasing rate," says Sam Scheiner, EEID program officer at NSF.

NSF's EEID program is funded by the agency's Division of Environmental Biology and Division of Ocean Sciences.

"This study demonstrates that we and our wild animal neighbors," says Scheiner, "are closely interconnected in ways that affect the health of us all."

The spillover effect

Pathogen spillover, as it's known, is a major source of disease in humans and in wildlife.

Indeed, bobcats are more likely to pick up parasites such as Giardia when the cats are closer to urban areas, VandeWoude and colleagues found.

They collected bobcat fecal samples in Ventura County and on the Front Range and tested them for Toxoplasma gondii, Giardia duodenalis and Cryptosporidium spp. All are disease-causing parasites found in wildlife and in people. Contact with the latter two results in diarrhea and other gastrointestinal upsets.

The scientists compared samples from bobcats in the two urban areas with those from rural areas of Colorado.

The findings show that city bobcats are more likely than country bobcats to carry parasites.

"Bobcats are exposed to and shed more zoonotic [i.e., may be transmitted between species] parasites near human-occupied landscapes," says Crooks.

But how did the cats, which are smaller relatives of threatened Canadian lynx, acquire the parasites?

"They were probably exposed to the water supply around cities," says VandeWoude. Parasites all-too-often lurk there.

Cryptosporidium parvum and Giardia duodenalis account for the majority of waterborne disease outbreaks in humans, with hundreds of thousands of cases in the United States alone every year.

Studies have long suggested that wild cats such as bobcats might contribute to a spillover of pathogens to humans, and vice-versa. But with the cats' secretive natures, few researchers have been able to draw conclusions about wild cats' "shedding" of disease-causing microbes. This study is the first.

A disease continuum

Bobcats are widespread in North America. They traverse a continuum of natural to urbanized habitats, often living side-by-side with humans, domestic animals and other urban-adapted wildlife species.

"Along these boundaries," says VandeWoude, "close living quarters make it easy for one species to transmit diseases to another."

In a city or suburb, pathogens travel from human to bobcat, and bobcat to human, the scientists found, almost as fast as a virus that infects one human family member runs through an entire household.

Whether that household lives in a two-story A-frame or a two-story log pile, there's not much difference, it turns out, in the spread of diseases.

It must be something in the water

It's when everyone heads for the water that things really begin to ramp up.

One group of bobcats in Ventura County, says Carver, the paper's lead author, left its calling card in the Malibu Creek watershed: Cryptosporidium and Giardia. Malibu Creek's environs are heavily populated by bobcats--and humans.

"Our results suggest that humans transmitted these pathogens to bobcats," says Carver, "likely through contaminated water or other environmental sources."

At the time of the study, there was no evidence that bobcats carrying the parasites were ill. But for these cool cats that roam along our streets and through our backyards, life in the ‘burbs can be a chancy existence. Simply crossing an urban stream may be walking through a hot zone.

For bobcats. And for humans.

--	Cheryl Dybas, NSF (703) 292-7734 cdybas@nsf.gov

Related Programs Ecology and Evolution of Infectious Diseases

Related Websites
NSF News Release: Domestic Cats, and Wild Bobcats and Pumas, Living in Same Area Have Same Diseases: http://www.nsf.gov/news/news_summ.jsp?cntn_id=123011
NSF Special Report: Ecology of Infectious Diseases: 

http://www.nsf.gov/news/special_reports/ecoinf/index.jsp

 The National Science Foundation (NSF)

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SCIENCE: Study of Yellowstone Wolves Improves Ability to Predict Their Responses to Environmental Changes

Hi my Friends: A VUELO DE UN QUINDE EL BLOG., Methods developed in this study may ultimately improve predictions of wildlife responses to environmental changes in various ecosystems. Yellowstone wolves at play.
A study of the wolves of Yellowstone National Park recently improved predictions of how these animals will respond to environmental changes.
The study, which was partially funded by the National Science Foundation, appears in the Dec. 2, 2011 issue of Science.
Part of the Yellowstone Wolf Project, researchers tracked changes in various characteristics of wolves living in the national park between 1998 and 2009. They found some tracked characteristics--such as population size--are related to population ecology, while other tracked characteristics--such as coat color--are genetically determined through evolution.
The project also involved using a new model to compare data collected on Yellowstone wolf characteristics to environmental conditions through the years covered by the study. Researchers defined conditions in the park during each year of the study along a continuum from "good years" to "bad years"--with good years more favorable to wolf survival than bad years.
Tim Coulson of Imperial College London, the study's lead author, explains, "The novelty of the new model is that it looks at how the frequencies of changes in environmental conditions along the 'good to bad' year continuum simultaneously impact many wolf characteristics."
Study results indicate:
1.- Environmental changes will inevitably generate simultaneous ecological and evolutionary responses in the Yellowstone wolves.
2.- Changes in mean environment conditions will impact the size of the Yellowstone wolf population more than will changes in the variability of environmental conditions.
3.- A single environmental change may impact various wolf characteristics differently, depending on which particular aspects of wolf biology it impacts.
Researchers say to understand their conclusions, suppose environmental conditions in a "good year" helped increase the population size of Yellowstone wolves by increasing their survival rates. Also, suppose that a grey coat color would confer a survival advantage to wolves. Then, under those particular "good" conditions, an increase in the size of the wolf population would be expected to produce an increase in the prevalence of grey coats among the wolves.
By contrast, suppose that certain environmental conditions in a "good year" helped increase the population size of Yellowstone wolves by increasing the availability of their prey. Because the availability of prey and coat color are not related to one another, under those particular "good" conditions, an increase in the size of the wolf population would not be expected to produce an increase in the prevalence of grey coats among the wolves.
Coulson says increasing the specificity of the model's predictions requires collecting more data on the ecological and evolutionary responses of Yellowstone's wolves to various environmental conditions and on the relationships of these responses to one another.
As part of this effort, the Yellowstone Wolf Project research team currently is studying the differential impacts of various environmental changes on ecological and evolutionary characteristics of Yellowstone wolves during various stages of their life cycles. The team also is working to identify the types of environmental conditions--such as the sizes of various populations of prey species and the amount and residence time of snow on the ground--that define good, bad and intermediary years for wolves.
The researchers hope once the methods developed through this study are refined, they may be applicable to other types of species, such as insects or crop pests, that live in other types of ecosystems. What's more, Coulson suggests that these methods may ultimately help answer questions about human populations. As just one example, the methods developed through this study might ultimately be used to help predict the impacts of the ongoing obesity epidemic on survival and fertility rates and the resulting influence of those variables on the growth rate of selected human populations.
The National Science Foundation provided funding to all of this paper's co-authors: Daniel R. MacNulty of the University of Minnesota at St Paul, Daniel Stahler of the National Park Service, Bridgett vonHoldt of the University of California at Irvine, Robert K. Wayne of the University of California at Los Angeles and Douglas Smith of the National Park Service.
-NSF-
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Science:Large Ice-Age Mammal Extinctions: Humans and Climate the Culprits

Hi my Friends: A VUELO DE UN QUINDE EL BLOG., The histories of six large herbivores--the woolly rhinoceros, woolly mammoth, wild horse, reindeer, bison and musk ox--are linked with climate fluctuations and human activity, especially at the end of the last ice age, scientists find in a new report.Many, but not all, ice-age mammals went extinct due to climate change and human influences.

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Research led by evolutionary biologist Eske Willerslev of the Centre for GeoGenetics at the University of Copenhagen along with an international team of paleontologists, geologists, geneticists and climate modelers suggests early humans and changing climate were responsible for the extinction of some cold-adapted animals, and the near-extinction of others.
The journal Nature published the results of the study this week. It was the first to use genetic, archaeological and climate data to infer the population history of large-bodied ice age mammals.
"The combination of approaches in this study--including the most modern molecular tools and painstaking fieldwork--sheds a powerful light on the complex interactions of humans, ecosystems and climate," said Hedy Edmonds, arctic natural sciences program director in the National Science Foundation's (NSF) Office of Polar Programs, Division of Arctic Sciences.
The results carry a message about the possible fates of living mammals as Earth continues to heat up.
"Our findings put a final end to single-cause theories of these extinctions," said Willerslev.
"Our data suggest care should be taken in making generalizations regarding past and present species extinctions," he said. "The relative impacts of climate change and human encroachment on species extinctions really depend on which species we're looking at."
"We couldn't pinpoint what patterns characterize extinct species, despite the large and varying amount of data analyzed," said scientist Eline Lorenzen of the University of Copenhagen, the first author of the paper.
"This suggests that it will be challenging for experts to predict how existing mammals will respond to future global climate change--to predict which species will go extinct and which will survive."
Beth Shapiro, a biologist at Penn State University whose research for the project was funded by NSF, explained that all six of the studied species flourished during the Pleistocene Epoch--the period of geologic time that lasted from about two million to 12,000 years ago.
"During this time, there were lots of climate ups and downs--oscillations between long, warm intervals called interglacial periods, during which the climate was similar to what we have today, followed by long, cold intervals called glacial periods, or ice ages.
"Although cold-adapted animals fared better during the colder glacial periods, they still managed to find places where the climate was just right--refugia--to survive during warmer interglacial periods.
"Then after the peak of the last ice age around 20,000 years ago, their luck started to run out."
What changed?
To find answers, Shapiro and colleagues tested hypotheses about how, when and why the woolly rhinoceros, woolly mammoth and wild horse went extinct after the last ice age and why the reindeer, bison and musk ox were able to survive--albeit in more restricted ranges than during the ice ages.
"One source of information we used was DNA from the animals themselves," Shapiro said. "With genetic data, it's possible to estimate when and how much populations were able to grow and shrink as the climate changed and their habitat started to disappear."
The scientists also collected climate data--temperature and precipitation patterns--from both glacial and interglacial periods, as well as archaeological data, which they used to study the extent to which early humans may have influenced the survival of these species.
"For example, in locations where animal bones had been cooked or converted into spears, we know that humans lived there and were using these mammals as a resource," Shapiro said.
"Even where we didn't find evidence that humans were using the animals, if they lived in the same place and at the same time, humans could have had some influence on whether the animals survived or not."
In the case of the now-extinct woolly rhinoceros, the scientists found that in Europe the ranges of humans and woolly rhinoceros never overlapped.
"These data suggest that climate change, and not humans, was the main reason why this particular species went extinct in present-day Europe," Shapiro said.
"We expect, though, that humans might have played a role in other regions of the world where they did overlap with woolly rhinos."
Much clearer was the evidence that humans influenced, and not always negatively, the population sizes of the five other species in the study--the woolly mammoth, wild horse, reindeer, bison and musk ox.
Population fluctuations for all six species continued until around 14,000 years ago when many of the species simply disappeared at the end of the last ice age.
"The take-home message is that during the most recent warming event, when the last ice age faded into the warm interval we have today, something kept these animals from doing what they had always done, from finding alternative refugia--less-than-ideal, but good-enough chunks of land on which to keep their populations at a critical mass," Shapiro said.
"That 'something' was probably us."
During the time when the animals were declining, the human population was beginning its boom, and was spreading out across not only the large-bodied mammals' cold-climate habitats, but across their warm-climate refuges, changing the landscape with agriculture and other activities.
Many large-bodied, cold-adapted mammals, including the horse--which is considered extinct in the wild and now survives only as a domesticated animal--suddenly had no alternative living spaces, and, as such, no means to maintain their populations.
"The results of our study suggest that although past warm periods caused these animal species to go through periodic bottlenecks--evolutionary events during which the size of a population diminishes substantially and stays small for a long time--they always seemed to bounce back, and to return to their previous habitats as soon as Earth became cooler again," Shapiro said.
"Then, during the most-recent warming cycle, the trend changed."
As the climate became warmer after the last ice age, the woolly rhinoceros, woolly mammoth and wild horse went extinct, but the reindeer, bison and musk ox survived.
Reindeer managed to find safe habitat in high arctic regions where today they have few predators or competitors for limited resources.
Bison are extinct in Asia, where their populations were extensive during the ice ages, and now are found only in North America, although a related species survives in small numbers in Europe.
Cold-adapted musk oxen live only in the arctic regions of North America and Greenland, with small introduced populations in Norway, Siberia and Sweden.
Interestingly, if humans had any impact on musk ox populations, it may have been to help sustain them. Musk ox populations first became established in Greenland around 5,000 years ago, after which they expanded rapidly, despite having been a major food resource for the Paleo-Eskimo population.
Today, the species survives in large numbers.
These findings could help predict the fate of mammal populations threatened by present-day climate change and habitat alteration.
"The results provide direct evidence that something changed between the most-recent glacial cycle, when many of these species went extinct, and previous glacial cycles, through which they all managed to survive," said Shapiro.
"Although it's clear that climate change drives the dynamics of these species, we, as humans, have to take some of the blame for what happened during this most recent cycle."
Our ancestors, it seems, were able to change the landscape so dramatically, said Shapiro, that these animals were effectively cut off from what they needed to survive, even when the human population was small.
"There are many more humans today," she said, "and we have changed, and are continuing to change, the planet in even more important ways."
In addition to Shapiro, Willerslev and Lorenzen, many other scientists contributed to the research. They are from Denmark, Australia, Sweden, Spain, the United Kingdom, the Netherlands, Germany, Norway, Russia, China, Canada and the United States. U.S. co-authors are from institutions in Utah, California, Texas, Missouri, Maryland, Colorado, Massachusetts, Oregon and Kansas.
The Leverhulme Trust, the Awards Fund, the Danish National Research Foundation, the Lundbeck Foundation and the Danish Council for Independent Research also funded the research.
-NSF-
Guillermo Gonzalo Sánchez Achutegui
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