Feb. 1, 2008 at 11:25 AM ET
| Official groundhog handler Bill Deeley holds |
Punxsutawney Phil on Feb. 2, 2006.
Groundhogs have their day in the sun on Saturday, when Punxsutawney Phil, Grady, Jimmy, Sir Walter Wally and other furry rodents across the country are dragged out to judge whether there will be six more weeks of wintry weather. If the weather is sunny enough on Feb. 2 for the groundhogs to see their shadow, they supposedly pop back down into their lairs and wait out the prolonged chill.
Is there anything to the purported predictive power of Groundhog Day? Not much.
But is there anything at all to the idea that animals can "predict" the weather? You bet.
First, about those groundhogs: When you look back at the historical record, the Groundhog Day story appears to be a blend of several weather-related folktales. Long before the days of Doppler radar, Europeans put great stock in Feb. 2, or Candlemas Day on the church calendar, as a weather indicator at the halfway point between the winter solstice and the spring equinox.
Clear weather on Candlemas was seen as a harbinger of snowy weather to come, while cloudy weather held the promise that things would get better in the weeks ahead. Some have speculated that there was a shred of meteorological truth behind the folktale: Clear skies in early February could be associated with persistent masses of cold, dry air that would prolong low temperatures, while cloudy skies could hint at wetter, more temperate days ahead.
The Germans added animal lore to their Candlemas story, saying that if the weather was sunny enough to scare a badger back into its hole, there were more wintry days to come. When German immigrants came to America (and settled in places like Punxsutawney, Pa.), the groundhog took the place of the badger.
Whether we're talking about badgers or groundhogs, the correlation between sunshine on Feb. 2 and extended cold weather appears to be shaky. A Canadian study found that shadow-fearing groundhogs would have a 37 percent accuracy rate at predicting late-winter weather anomalies, or just slightly above chance.
The science of hibernation
Some folks have wondered whether there might yet be something scientific behind the groundhog tale. After all, the groundhog is a hibernating species that occasionally rouses itself during the winter, and perhaps the creature can sense something that tells it whether to wake up for the warm weather or go back into its torpor in early February.
"There's a little bit of truth to that, but with modifications," said Hannah Carey, a professor of veterinary medicine at the University of Wisconsin at Madison. Carey specializes in the study of hibernating animals.
"For hibernators like groundhogs and the ground squirrels that we study, they're on a biological clock that tells them when to start [to hibernate] in the fall and when to finish in the spring, regardless of external conditions," she told me. "They do arouse periodically throughout the winter. They do this spontaneously while they're underground, but there are no external signals."
During hibernation, Carey's ground squirrels lower their internal temperature to near the freezing point "Our squirrels right now are hibernating in a walk-in cold room that's really like a refrigerator in your kitchen," she said.
Carey said some Arctic ground squirrels can actually bring their temperature down below freezing, "so they somehow supercool in ways that are not fully understood."
Scientists also have puzzled over what controls a hibernating animal's cycle of torpor and arousal. The arousal periods come more frequently as spring approaches - but sunshine and shadows have nothing directly to do with it, since the animal doesn't leave its burrow. "They don't come outside at all," Carey said.
Temperature could conceivably play a part. "It's possible that later in the spring, the warming of the soil around them is one of many signals that tell them spring is coming," Carey said. But the primary factors appear to be body fat levels and the brain's hard-wired biological clock, she said.
Over the long term, that clock could end up being reset to reflect different climatic conditions. Carey said that may be the reason why ground squirrels tend to wake up for the spring earlier in Ohio (February-March) than in Wisconsin (March-April). But Carey said such differences could be explained by an evolutionary response to environmental factors.
If that hypothesis is correct, it would have implications for future Groundhog Days.
"If the climate changes, and we have fewer extended cold spells, those animals that are spending more time above ground might be doing better when it comes to having babies," Carey explained. "Hibernating animals might be bellwethers for how climate affects animal populations."
If you look beyond groundhogs, you can find a number of cases where animal folklore contains a grain of scientific truth. An oft-cited example is this saying: "A cow's tail to the west is weather coming at its best; a cow's tail to the east is weather coming at its least."
It turns out that the saying encapsulates animal behavior as well as regional meteorology, at least according to North Carolina's State Climate Office. Animals tend to turn their backs into the wind, so that they have a chance of catching the scent of a predator that's sneaking up behind them. In New England, where the saying is thought to have originated, a west wind is likely to bring fair skies, while the onshore easterly breeze is associated with nasty weather.
Thus, the cow's tail could serve as a weathervane of sorts, indicating which way the wind is blowing and eventually giving rise to the folk saying.
This Web page at NASA does a reality check on other bits of weather folklore, ranging from high-flying geese to oft-biting flies. Crickets are among the most intriguing weather indicators: If you count the number of cricket chirps in 14 seconds, then add 40 to your tally, you supposedly come up with a good approximation of the temperature in Fahrenheit degrees. The Old Farmer's Almanac even provides a formula for Celsius cricket conversion.
In most of these cases, it's not really a case of animals predicting the weather. Instead, animal behavior reflects the meteorological phenomena that in turn give rise to the weather. For example, researchers have found that a cricket's metabolism varies with temperature, leading to the differences in the chirp rate.
In their studies of seismic activity, a fair number of scientists suspect that animals are more sensitive to the relatively harmless P waves that precede an earthquake's strong S waves by a matter of seconds. Chinese and Japanese researchers have gone even further, looking into claims that animal behavior can be a tip-off well in advance of a large-scale earthquake. The evidence on that score is far from conclusive, however.
If you have further examples of the folklore surrounding natural phenomena, feel free to add them as comments below. In the meantime, here's hoping that Punxsutawney Phil, Sir Walter Wally and the rest of the groundhog gang miss seeing their shadows - after this week's weather, we all could use an excuse to start thinking about spring.