Pictures - Animal Winners and Losers of Summer's Heat Waves

Losers: Marmots
Photograph by Erin Huber, National Geographic My Shot
A marmot takes a snack break in front of Washington State's snow-capped Olympic mountain range. Like most species, these burrowing rodents—cousins of the squirrel—have a limited range of weather they can adjust to.
Usually found in cool high-altitude locations, marmots rely on a thick, insulating blanket of snow during hibernation to stay warm—and on summer vegetation to stay rotund. A long winter or a lack of snow can be a roadblock to survival, as can dry summers, which produce little food, or too much spring rain, which deters mating.
Much to the marmot's dismay, the western U.S. this year saw minimal snowfall, followed by record heat and prolonged drought. (Related: "Warm Spring May Mean Drought and Wildfires in West.")
Such extreme conditions, especially in the Rocky Mountains, have made a significant dent in marmot populations, according to Daniel Blumstein, chair of the Ecology and Evolutionary Biology Department at the University of California-Los Angeles, who runs a marmot research site in Colorado.
Blumstein warns that it won't be global warming's gradual temperature increases that will cause massive population die-offs in the animal world. Instead, it will be the increased frequency of extreme weather events.
Unfortunately, those extremes may be the new normal. As Earth heats up, there will likely be more heat waves, droughts, even rain—due to higher rates of ocean evaporation and more moisture in the atmosphere. (Read "Weather Gone Wild" in the latest issue of National Geographic magazine.)
While this year started off bad for marmots, it may actually end up OK, Blumstein explained. Recent rain in the Rockies has encouraged edible plants, helping marmots add weight and focus more on breeding.
—Tasha Eichenseher
Published September 11, 2012
Winners: West Nile Mosquitoes
Photograph by Robin Loznak, ZUMA Press/Corbis
Heat waves are all the buzz among Culex mosquitoes—a species that carries the West Nile virus.
During this summer's western U.S. heat wave, these larvae (pictured) were killing time in a cattle watering trough on a ranch near Roseburg, Oregon, before they hatched.
While spells of hot weather generally dry up mosquito breeding grounds, Culex, and West Nile, seem to thrive in warmer temperatures. (Related: "Heat Waves 'Almost Certainly' Due to Global Warming?")
The number of U.S. West Nile cases documented this year hovers around 2,000, with nearly 90 deaths, making the outbreak one of the worst to hit the country since the virus was first detected there in 1999, according to the Centers for Disease Control and Prevention (CDC).
Public health officials have said this summer's drought may have played a role in the increased number of cases. "Hot weather, we know from experiments done in the laboratory, can increase the transmissibility of the virus through mosquitoes and that could be one contributing factor," Lyle Petersen, director of CDC's Division of Vector-Borne Infectious Diseases, said during an August press conference.
In the worst cases the West Nile virus can enter the nervous system, causing meningitis or encephalitis. But the majority of people who are infected will have few or no symptoms.
(See more pictures of the "Surprising Effects of the U.S. Drought.")
Published September 11, 2012
Winners: Hedgehogs
Photograph by Roger Tidman, Corbis
A hedgehog searches for slugs near Norfolk, England.
Mild, frost-free winter weather followed by a record wet spring and summer doubled and even tripled the number of slugs in some regions of the U.K., according to local news reports. The Daily Mail reported in May that researchers were finding up to a thousand slugs per square meter (11 square feet).
The slimy deluge was feared by gardeners and farmers but embraced by hedgehogs, which rely on slugs and snails as a food source. (See extreme weather pictures.)
"Hedgehogs have done really well with lots of slugs and snails to eat and badgers did well, too, with plenty of earthworms," Marina Pachesco of Britain's Mammal Society told The Times of London.
Published September 11, 2012
Winner: Anthrax
Image by Dennis Kunkel Microscopy, Inc., Visuals Unlimited/Corbis
Spores of the potentially fatal Bacillus anthracis bacterium—which causes the disease anthrax—sit in a lung.
Once inhaled, spores may germinate and release toxic substances that have been known to cause internal bleeding, swelling, and tissue death. The disease can also enter the bloodstream when spores are ingested or make contact with an open wound.
Anthrax outbreaks this summer have killed more than a hundred farm animals on ranches in Colorado and Texas, with some experts pointing to drought as a culprit. The extended warmth, they say, could expedite the production of more spores and help them survive for years in the soil. Livestock may also be forced to root around more for food in dry conditions, unsettling soil and releasing spores.
But the primary concern about drought is the stress it inflicts on animals, weakening their immune systems, said Martin Hugh-Jones, professor emeritus of epidemiology at Louisiana State University and coordinator of the World Health Organization's Working Group on Anthrax Research and Control.
"The animals are less efficient in hot weather when dealing with an infection, and therefore a smaller dose [of the pathogen] can result in a deadly case," said Hugh-Jones, who has investigated many outbreaks.
Despite the numbers, Hugh-Jones said it actually has been a "mellow" year for anthrax. "There have been very few outbreaks so far this summer, but the ones that have happened have been severe."
Once a member of a herd is infected, it is easy for the disease to spread if animals are corralled together or carcasses and blood are left out in the open. A wet spring can also bring swarms of biting flies that help to transmit anthrax.
"This season's outbreaks have more to do with management than ecology," Hugh-Jones added. "If you control [anthrax] correctly, you also eradicate it."
Livestock can be vaccinated for the infectious disease. Humans contract anthrax most commonly through contact with infected animals and can usually be treated with antibiotics.
Published September 11, 2012
Winners: Bark Beetles
Photograph by Stephen Dalton, Minden Pictures/Corbis

Adult and larval large elm bark beetles nestle into the innards of a tree trunk. The beetles carry Dutch elm disease, a fungus that causes a tree to shut down and stop delivering water and nutrients to its branches.
Just as heat stress makes animals more susceptible to disease, it makes trees more vulnerable to infestation, weakening their defenses against Dutch elm and other diseases, reports the U.S. Forest Service.
Bark and pine beetles of all varieties have attacked and killed billions of trees across the U.S., but the 2012 outbreaks—some of the largest on record—have been associated with accelerated climate change and persistent drought. (Related: "Earth Day Pictures: Ten Most Threatened Forests.")
In Georgia the rice-size black turpentine beetle and southern pine beetle have wreaked havoc on certain species of pine trees. In Indiana the emerald ash borer is destroying ash trees. And prolonged drought in the western U.S. has helped mountain pine beetles turn enormous swatches of green into brown.
Historic levels of destruction are due, in part, to underlying global warming trends as well, with more mild winters possibly allowing the beetles to survive from year to year and claim more territory, reports the forest service. Other factors include forest-management trends that have suppressed fire, so that trees in many forests are around the same age—all old enough to fall prey to the beetles.
Published September 11, 2012
Losers: Deer
Photograph by Tom Bean, Corbis
With scant rainfall this spring and early summer, ungulates (deer skull pictured in file photo) and other wildlife suffered as they tried to find sagebrush, bitterbrush, and grasses in a parched landscape.
In Utah, the Wildlife Board has approved more than a thousand additional hunting licenses for elk in an effort to help prevent the elk population from dying of starvation and to ensure enough food for the coming winter's deer population, according to local news reports.
The difficult food situation is mirrored on many farms. Cattle ranchers across the country have had a hard time feeding their herds as drought conditions have boosted corn and other feed prices—at a time when the U.S. Bureau of Land Management has reduced livestock grazing on federal lands. (Related: "Drought Withers U.S. Corn Crop, Heats Debate on Ethanol.")
Published September 11, 2012
Losers: Zebra Mussels
Photograph by Gary Meszaros, Visuals Unlimited/Corbis
Invasive zebra mussels may find the waters of Lake Erie a bit warm for their liking these days. The invasive species—which has been credited with sucking the life out of many U.S. lakes, including the Great Lakes—may be on the decline if warming trends continue.
Zebra mussel numbers dwindled this summer in some places, in part because of a midwestern U.S. heat wave.
Missouri Department of Conservation fisheries biologist Greg Stoner recently told a local paper that declines in the Lake of the Ozarks have likely been aided by warmer-than-usual water temperatures this year—maxing out at 90 degrees Fahrenheit (32 degrees Celsius).
Published September 11, 2012
Losers: Penguins
Photograph by Gavin Emmons, National Geographic My Shot
A pair of gentoo penguins wade through icy waters off Sea Lion Island in the Falklands. The charismatic creatures also call Antarctica home, but prefer its ice-free areas, including coastal plains, sheltered valleys, and cliffs.
Recent months have been particularly tough on penguins, according to Stuart Pimm, a professor of conservation ecology at Duke University and president of the nonprofit Saving Species. Pimm said much of Antarctica has seen wetter weather and heavier-than-usual snow, which can bury penguins.
"They aren't adapted to warmer, snowier conditions. Eventually it may get so wet that their eggs cool or get flooded," Pimm said.
He added that Antarctica is warming faster than any other region thanks to global climate change.
Pimm has spent a significant amount of time researching the migration of species both to higher altitudes and latitudes as temperatures become too hot for critters that do best in alpine or colder-weather conditions.
"I worry about biodiversity, about species going extinct," he said. "The thing about these weather extremes is that they are really sort of idiosyncratic. You can only die once. When a species is wiped out over large areas, it could take years or decades for it to recover."
Will species adapt? "Yes, there will be some adaptation, but to blindly think that adaption will take care of everything is wrong," Pimm added.
To prevent extinctions, he said, we'll have to get serious about stopping greenhouse gas emissions. (See our global carbon footprint map.)
Published September 11, 2012
Next Up: Weather Gone Wild>>
Panorama composed of four images; Sean R. Heavey, Barcroft Media/Landov
Published September 11, 2012