A sound more commonly heard in the spring was prevalent in some areas during the late-February warm spell. The northern spring peeper, a frog perhaps best identified by its voice, chirps every spring when it warms up enough. This frog's mating call can be loud, yet at the same time, a soothing noise for people who associate it with warmer weather.Mating ChantsWood Frogs, Too

"It certainly is unusual to hear them in late February. We had some extremely warm weather for several days and that's enough to get them awake and a little confused," said Jenny Dickson, a wildlife biologist with the Connecticut Department of Energy & Environmental Protection (DEEP). "They kind of went, 'Oh, spring is here.'"

When there are unseasonable temperatures in the winter only to have the thermometer drop back to near or below freezing, humans shake off the return to frigid conditions, bundle back up, adjust the thermostats, and wait patiently for the true start of spring.

But what about those peepers who were tricked into thinking spring was really here and started voicing themselves a bit prematurely - understandably so - during this winter's warm spell?

"If it stays cold, they're going to go back down into the mud layer," said Ms Dickson, explaining that the northern spring peeper will weather the cold for a couple of days before having to go back into hibernation mode.

"They do have a substance in the blood that acts kind of like antifreeze," said Ms Dickson, adding that the frogs will only have problems if they get caught out in the cold too long before finding moist shelter.

"They've got a little bit of wiggle room, but not a lot," said Ms Dickson, noting that the frogs adjust to changes quite well and we can still expect to hear peepers in full force when the time comes.

That said, it is possible that some of the eggs laid during that balmy stretch last month might not hatch if the water temperature gets too low again, Ms Dickson said. "Like most things in nature, it's complicated."

Peepers generally start their chorus of mating chants in late March and April; or if the air and water temperature take some time to warm up, sometimes in May and early June, Ms Dickson said. The chirps are quick when it is warmer and chirps drop in tone and slow down when temperatures drop, she said.

The peepers overwinter in bogs, small ponds, and vernal pools, and can also spend time where there is damp moss and leaves, and where they can find soft mud.

"They just need to be someplace where they're going to stay moist enough but not freeze," Ms Dickson said.

It is the male peepers who do a bulk of the chirping. The females have less noticeable chirps, and use them in response to other things in their lives, Ms Dickson said. Peepers go to breeding grounds, sometimes the same location where they have hibernated. Those areas are shallow water spots free of fish, which put frog eggs at risk. Peeper frog eggs can hatch in six to 12 days, depending on the weather, said the biologist.

"A combination of factors get them going: warmer temperatures, a significant thaw, and some heavy rain - all of which we had within a few days when we had our prolonged warm spell," Ms Dickson said.

"The other thing that helps is night temperatures that remain above freezing. So, 55 degrees for a few days may not help much if it gets below freezing at night and is fairly dry. With daytime temps in the 60s or 70s, nights only dropping to the 40s, and a rain event, you've got the perfect conditions to get them thinking about breeding," she added.

Peepers are considered tree frogs and are the earliest active member of their group, Ms Dickson said.

The DEEP website describes the peeper as "an arboreal frog distinguished by its brown dorsum with an X-shaped marking and small suction cups on the tips of its toes. Very small, females larger than males, adults 20-35 mm body length."

These are not the only frogs to shake off the winter slumber and make lots of noise to attract mates when the temperature warms up each spring. Wood frogs are similar to peepers, but larger, growing from 40 to 60 mm. They hibernate in the late October to March range and head to breeding pools in March, much like peepers. They prefer the vernal pools, whereas peepers will use shallow, shrubby areas of larger water bodies as well, Ms Dickson explains.

Ms Dickson said it is not unusual to hear wood frogs slightly before peepers in a typical year, but that she had many reports of peepers in February.

"Wood frogs are noted for moving over some ice to reach breeding pools and have been recorded breeding while there is still some ice on the water surface," Ms Dickson said.

For wood frogs, egg hatching also depends on water temperature, but the hatching range is longer - as it can take up to 30 days. "Like the peepers, they have some built-in antifreeze that helps them survive dips in temperatures. Also like peepers, their call rate and pitch will change a bit with the temperatures," Ms Dickson said.

A noticeable difference between the frogs is their call. The wood frog's sound is similar to a duck quack, Ms Dickson notes.

Soon enough, we will be able to hear these calls with regularity. A sure sign that spring has sprung is when we hear these frogs chanting - unless, of course, these chirps occur during unusual warm stretches in February.

"I think some of us are just as confused as the amphibians out there," Ms Dickson said.