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发表于 2014-11-11 20:18:29
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Part II: Speed
5 Surprising Facts About Squirrels (Hint: They Make Jerky)
by Jason Bittel | 26 Sep 2014
[Time 2]
Right now, across much of the Northern Hemisphere, squirrels are doing what they do best: squirreling away seeds and nuts for the approaching winter.
But there’s a lot more about these rodents that you might not realize. So we talked to Richard Thorington, curator of mammals at the Smithsonian Museum of Natural History, who presides over one of the world’s largest collections of the squirrel family, or Sciuridae. In all, the Smithsonian is home to more than 30,000 squirrel specimens.
Thorington started studying squirrels almost 50 years ago as a boy who just wanted to keep the varmints off his bird feeder. Since then, he’s co-authored two books on the subject, Squirrels: The Animal Answer Guide and Squirrels of the World, each of which probes the hidden lives of these seemingly everyday creatures and investigates their myriad roles across ecosystems.
Here are some of Thorington’s surprising squirrel facts:
Squirrels exist in nearly every habitat on Earth.
There are 285 species scattered across the globe, ranging from the half-ounce pygmy tree squirrels of western Africa to the nearly 20-pound (9-kilogram) gray marmots of Kazakhstan.
You’d basically have to venture to the planet’s Poles to escape them.
Squirrels can help trees.
Take the gray squirrel (Sciurus carolinensis) and its penchant for burying acorns for later use. A single gray squirrel can create several thousand buried caches of food each season, not all of which it can hope to rediscover. This is called scatter hoarding.
“In some cases the burying of nuts is good for the trees,” said Thorington.
“You have squirrels taking the acorns from directly underneath an oak tree and burying them somewhere else. That gives the trees more of a dispersal.”
Squirrels can hurt trees.
In other cases, the relationship between squirrels and trees is less harmonious.
North American red squirrels (Tamiasciurus hudsonicus) and Douglas squirrels (T. douglasii) are seed predators that live almost entirely on the cones of conifer trees. They either eat the seeds immediately or store pine cones by the score in secret larders where the seeds remain moist and have little chance of germinating.
Obviously, this is great for the squirrels, because the preserved food supply allows them to survive the winter. The trees, on the other hand, lose their chance at reproducing.
[377words]
[Time 3]
Interestingly, a study published in 1995 in the International Journal of Organic Evolution showed that the trees may have ways of fighting back. The research revealed that in the Rocky Mountains, where red squirrels were prominent, the cones of limber pine trees had thicker seed coats and more resin.
“This makes it difficult for the squirrels to get between the pine cone’s scales,” said Thorington.
But that’s not all. The researchers also found the cones had fewer seeds than normal and less energy per seed. So not only do the squirrels have to put in more work to access the pine cone’s innards, but they also got less of a reward for doing so.
Squirrels make mushroom jerky.
Perhaps one of the most intriguing things you’ll find in Thorington’s books are the lengths to which some squirrels will go to take advantage of a food source.
For instance, did you know that some squirrels eat mushrooms? Not only that, but red squirrels will hang fungi out to dry between tree branches so that it keeps better over the winter.
Mushroom jerky is also less likely to infect their larder with insect larvae and nematodes.
Squirrels can “garden”—and know their food sources well.
Gray squirrels have also evolved a few rather impressive storage strategies. Thorington explained that the squirrels can tell the difference between red oak acorns and white oak acorns and store them accordingly.
Whites germinate quickly, almost as soon as they hit the ground, said Thorington, and the squirrels tend to eat them immediately since a germinated acorn loses nutritional value. Conversely, reds don’t germinate until spring, so the squirrels prefer to bury those for winter snacking.
And now for the twist. A 1996 study in the journal Animal Behavior observed some squirrels biting through the embryo of white oak acorns, essentially paralyzing the seed’s ability to sprout. The squirrels then buried the modified white oak acorns as they would have with the reds.
What’s more, the scientists witnessed the squirrels digging up red oak acorns that they didn’t need to eat over the winter, nipping off their embryos, and re-burying the food for later use.
“It’s really interesting,” said Thorington. “If you watch squirrels, they are actually doing so much more than you might anticipate
If only humans were half as efficient with our leftovers.
[388words]
Source: National Geographic
http://voices.nationalgeographic.com/2014/09/26/squirrels-animals-fall-winter-science-united-states-surprising-facts/
Mysterious Flying Squirrel Could Get Endangered Species Protection
by John R.Platt | 24 Sep 2014
[Time 4]
The squirrels gliding amid the mountains east of Los Angeles have been, for the most part, flying under the scientific radar. There has never been a single scientific paper published specifically about the San Bernardino flying squirrel (Glaucomys sabrinus californicus), even though hundreds of papers about squirrels in general are published every year.
Despite this scientific oversight, the San Bernardino flying squirrel—a subspecies of the northern flying squirrel—has become very popular among some conservationists, who have been fighting to get it protected under the Endangered Species Act (ESA) since at least 1985. This week they finally made progress: the U.S. Fish and Wildlife Service (FWS), in response to a 2010 petition from the Center for Biological Diversity (CBD), agreed that the squirrels may deserve ESA protection. The agency said it will make a recommendation, either for or against protection for the subspecies, by April 2016.
Of course protecting a rare species depends on possessing detailed scientific information about its ecology, habitat use, threats and behaviors. We don’t have much of that for the San Bernardino squirrel. Here’s what we do know: They are medium-sized gray-brown squirrels which, like others in their family, possess wing-like skin flaps between their legs, which allows them to jump and glide up to 90 meters from tree to tree. They live in high-elevation forests exclusively on the San Bernardino Mountains. They used to be found on the San Jacinto Mountains as well, but the squirrels haven’t been seen there since at least 1980. Their remaining habitat is completely isolated by the Mojave Desert and several deep passes, so they can’t expand their range. The most recent estimate of their population put it at less than one squirrel per hectare, but that was from a trapping survey of the entire region conducted way back in 1998.
[302 words]
[Time 5]
FWS started looking into the status of the squirrel in 2012 when, prompted by the CBD petition, they opened a public-comment period on the animals. That should have been followed within months by a decision to propose an endangered listing or not—but that next step never happened. CBD threatened to sue. The agreement this week was part of a settlement with CBD under which FWS promised to move forward on the squirrel and nine other species that have been stuck in a backlog of ESA decisions.
According to CBD’s petition, the squirrels face multiple threats. The San Bernardino Mountains are warming and drying due to climate change and drought, making the lower elevations too dry for truffles (the squirrels’ favorite food). Meanwhile, forest management practices the CBD calls “misguided” have removed too many of the high forest canopy limbs the squirrels use to traverse the mountains. More people are moving into the area, which could result in more habitat loss. To top it all off, those people are bringing more domestic animals such as cats, which are apparently preying upon the squirrels.
The next 18 months could make or break the fate of the rare squirrels. We can hope that FWS biologists and others will be able to dig up enough information to protect the subspecies. Maybe someone will even get a scientific paper out of the process.
[229 words]
Source: Scientific American
http://blogs.scientificamerican.com/extinction-countdown/2014/09/24/mysterious-flying-squirrel/
This Massive Squirrel Has Been Saved from Extinction
by John R. Platt | 23 Sep 2014
[Time 6]
It only took about half a century, but the once-rare Delmarva fox squirrel (Sciurus niger cinereus) now has a healthy population once again, placing it in a position to finally leave the protection of the Endangered Species Act (ESA). If that happens, this giant squirrel—which can reach an astonishing 75 centimeters in length—would join just 29 other species that have been declared recovered under the ESA.
The Delmarva fox squirrel has enjoyed legal protection since 1967, predating the Endangered Species Act of 1973. At the time it was declared endangered, the subspecies had lost 90 percent of its historic range, which once included almost the entire 274-kilometer Delaware peninsula for which it is named as well as areas of Pennsylvania and New Jersey. Deforestation and other habitat loss during the first half of the twentieth century pushed the squirrel out, while hunting also took a heavy toll. By the 1960s the subspecies could only be found in a few Maryland counties.
Endangered-species protection brought an end to the squirrel hunting season, but the real key toward recovering the Delmarva squirrel turned out to be private landowners. Biologists with the U.S. Fish and Wildlife Service (FWS) relocated squirrels onto several large Maryland farms where they thrived. Other reintroductions took place on national wildlife refuges, but today 80 percent of the squirrel’s expanded habitat consists of private lands. The squirrel has now regained approximately 28 percent of its historic range and its population (estimated at between 17 and 20,000) is stable, widely distributed and, according to the FWS, healthy enough to withstand any future threats that might arise from disease or habitat loss, or even sea-level rise (which, FWS predicts, will result in some deforestation along the Chesapeake Bay and Atlantic Coast).
The process to delist the squirrel from the ESA isn’t quite over. The public is invited to submit comments or other supporting information on the proposal to delist the species. Comments are due by November 24. Assuming no new information about previously unassessed threats comes in during that process, it would then take another few months before the squirrels were delisted. Even then, FWS would continue to monitor the squirrels for several years to make sure their populations remain healthy outside the protection of the ESA.
It has been a long road to recovery for the Delmarva fox squirrel, but hopefully the journey is just about completed.
[399 words]
Source: Scientific America
http://blogs.scientificamerican.com/extinction-countdown/2014/09/23/massive-squirrel-saved/
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