NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/417216
them through the winter by making it difficult for ice to form in their tissues. Unable to read a calendar, amphibians and reptiles need to recognize environmental cues to know winter is just around the corner. A drop in temperature is a great cue. But sometimes temperatures stay warm through the fall and into the first weeks of winter. Thus another important cue is photoperiod: the length of time daylight is available. As winter approaches, daylight availability becomes shorter. Although it might be warm out, the shorter days will warn animals to prepare for the cold that will inevitably come. Where these animals spend winter is dependent on their life history, but two key criteria determine their location: oxygen and above-freezing temperatures. Amphibians and turtles are mostly aquatic and will spend winters buried in the mud below and around water bodies and survive by breathing through their skin. They can extract oxygen from water, and with metabolic activity being reduced at colder temperatures, they can obtain enough oxygen to stay alive while completely submerged. Box turtles are non-aquatic so they dig themselves deep into the soil for the winter, but like chorus frogs, they too produce a biological antifreeze to protect their cells. Lizards and snakes have to be more selective about their overwintering sites. They still have to breathe and remain at above-freezing temperatures, so their best course of action is to get underground below the frost line. This is easier said than done. Lizards can actually dig, and in places with loose soils, they bury themselves deep enough to keep from freezing. In other places, they can simply burrow beneath large rocks for the winter. Snakes, however, have the most difficulty finding a winter home. In areas with rocky ledges they can crawl deep into crevices and stay cozy, especially if these rocks face to the south. Places like this are rare, so usually snakes of multiple species share the most optimal sites. But what most snakes depend on are the burrows of other animals: crayfish, rodents, badgers and prairie dogs all dig burrows that go deep underground, and snakes are opportunists. When they find a nice burrow, they use it. After a six-month nap or so, most amphibians and reptiles emerge and start their new season of feeding and breeding. Sadly, some will not survive the winter. But this ensures that only those with the best survival skills will live to pass on their skills to future generations. ■ DECEMBER 2014 • NEBRASKAland 35 As fall days grow shorter, timber rattlesnakes may travel miles to return to the safety of an overwintering den which they share with other snake species. Strong legs and claws help the ornate box turtle dig to a safe level for the winter, but as a backup plan they also produce a biological antifreeze in their body tissues.