Each February 2, the most famous of the groundhogs, Phil, of the town Punxsutawney in the US, it disrupts their hibernation and comes out of its burrow. According to popular belief, your reaction immediately after will help to predict the duration of what is left of winter. How? If the day is cloudy and the animal does not see his shadow, winter will soon end; but if you see it, again to enter his hole because the cold weather will last six more weeks.
Like Phil, hundreds of these little mammals come out each winter in their dens to celebrate Groundhog Day in the U.S. and Canada. But though the tradition is well entrenched in numerous locations in north america, the reliability of the bizarre prediction method leaves much to be desired at a scientific level.
“In general, most of the beliefs weather they do not have a real basis. The famous Groundhog Day in some places of USA and Canada, or the places they choose bears to hibernate, among others, that supposedly predict the time during the winter, are all false beliefs”, declares to Sinc Juan Antonio Fargallo, a researcher at the National Museum of Natural Sciences (MNCN-CSIC) in Madrid, leaving settled any possible doubts.
According to the scientist, the animals cannot predict the time that is going to do in the winter or in the summer or long term. But, although the predictions of the Groundhog Day respond to superstitions, the behavior of animals and humans can vary in function of changes of temperature and precipitation with physiological responses more or less rapid, that is to say, in the very short term.
Advance relative to the time
For Fargallo it is a response to the present conditions: “We have little ability to anticipate the weather that is coming. The chaotic nature of the weather, highly unpredictable, it prevents you may be created of adaptations in animals to predict the weather,” he says.
But if you take into account some factors, certain animals themselves are able to perceive the variation in the atmospheric pressure. “The phenomena that generate low pressures, such as storms or hurricanes, can be perceived by the animals, but only minutes or hours before”, explains the expert of the department of Evolutionary Ecology.
In this case, the animals have adapted to react with a few hours of anticipation of environmental conditions that can affect the availability of food or ability to maintain their internal conditions is optimal state (homeostasis). An escape, a shelter, or eating behaviors are signs that they are anticipating any way, and these behaviors vary according to each group’s animal.
The birds in front of the pressure drops
The arrival of storms can pose a serious challenge to the birds. When the temperature drops and the winds low can increase your energy expenditure and inhibit the search for food. To avoid these risks and increase their chances of survival, one of the mechanisms that the birds use is the early detection of the atmospheric pressure, which decreases with inclement weather.
In a study, published in the Journal of Experimental Biology, a team from the University of Montana in the USA examined the behavior of the sparrows white crown (Zonotrichia leucophrys) north America in an experiment in the laboratory that decreased barometric pressure.
The results showed that despite the change of pressure, is not produced in birds a response in their physiology of the stress, but they stimulated the search, the collection and intake of food. “These data suggest that the sparrows of the white crown can feel and respond to the drop in barometric pressure. This ability may be common in vertebrate wild, especially in the small, the storms may be events life-threatening”, stress the authors of the work.
Another case is that of the swifts, a bird that feeds on insects which they hunt by flying. When approaching a storm, these birds “disappear from the towns and cities into places with weather more stable,” reports Fargallo. If this occurs during the period of breeding, the chickens can go several days without being fed until the return of the parents.
“It seems that the sensitive organ to the variations of external pressure is called the body paratimpánico, also provided by hair cells and located in the middle ear of birds,” explains the scientist of the MNCN.
Insects that are protected
In the species of birds that feed on insects in the air, like swifts, swallows, airplanes and nightjars, it has further been observed that in the moments leading up to the storm flying more under. This is because the insects also perceive the variation of pressure, and “are kept closer to the vegetation to seek shelter and avoid the strongest winds that are generated in the higher layers of the air”, emphasizes the expert.
These observations have been made by naturalists, “but there is no scientific study that describes it”, certifies the researcher. However, it is known that there are indeed fewer insects in the higher layers of air in the moments prior to the storm compared with a sunny day.
There are many examples of insects that describe similar behaviors. “The insects reduce their activity moments before the storm“, confirms Fargallo, who recalls the well-known case of bees that are kept in the vicinity of the hive or even take refuge in it when the air pressure is low.
The songs of amphibians
Other animals, like amphibians, are sensitive to precipitation. “In some species of frogs and toads has been detected an increase in the frequency of singing in the hours preceding the arrival of rains,” says the scientist.
The frequency of the songs of the tree frog gray (Hyla versicolor), for example, increases with rising temperatures and rainfall in the previous two weeks, according to a study published in Environmental Monitoring and Assessment. During ten years, scientists from Wilfrid Laurier University in Canada, recorded data on nine species of frogs.
Hyla versicolor and Pseudacris crucifer, for example, were affected by the volume and timing of precipitation, although in different ways, say the authors. “The tree frogs gray seem to prefer drier conditions, when the temperatures are significantly warmer, while other prefer to call during or after the precipitation”, point.
To perceive in advance the arrival of the rains is an adaptation strategy that, in the case of amphibians, to increase the reproductive success through the increase of the songs that will attract the potential partners. “The precipitation will form pools of water or allow moisture conditions necessary to be able to leave the shelter and embark on the conquest”, explains Juan Antonio Fargallo. To achieve this, the mechanism of the amphibians is the same: the perception of low atmospheric pressures.
Fish in search of depth
If for terrestrial animals, the atmospheric pressure is an indicator of the change of time, in fish it is vital to the detection of the hydrostatic pressure in order to anticipate the ups and downs of tides that could leave them trapped in the ponds. For this reason, many species of fish in the coastal have developed some organs such as the hair cells in the vestibular apparatus of the inner ear, sensitive to the pressure changes.
“Some species of fish that possess these sensory organs perform movements to deeper areas when the atmospheric pressure lowers drastically, radical enough to affect the hydrostatic pressure of the sea,” describes the scientist. This occurs in the moments that precede the arrival of hurricanes or tropical storms of great magnitude.
Among the species that have this type of behavior is the shark black-tip (Carcharhinus limbatus). In the study, published in the Journal of Fish Biology, scientists from the Mote Marine Laboratory in Florida they observed a group of juveniles swim into deeper water before the arrival of a tropical storm.
“The movement of the sharks was triggered by a drop in barometric pressure associated with the arrival of the storm. All returned to the breeding area a little deep after the passage of the storm, suggesting that it is an innate behavior”, reveal the authors of the research.
The behaviors of birds, fish, amphibians, or mosquitoes, among others, in the end it does not describe more than the present. “Don’t predict the time”, insists Fargallo. In this sense, they might be certain and have a certain sense of expressions such as “when the rook flies low, makes it cold as hell”. “On cold days does not produce rising currents of air used by birds such as crows and ravens to pick height”, explains the expert. But still have to prove scientifically.