How do Central Oregon Reptiles and Amphibians Stay Alive in the Winter?
Winters in Central Oregon can be brutally cold for some of our native wildlife. Compared with the warmer months, wildlife sightings are much less common when the temperatures drop and the days shorten. It may seem like some species just disappear during the colder months, such as reptiles and amphibians. You may be wondering what happens to these species during the winter? How do they survive?
Unlike mammals, reptiles and amphibians are ectothermic (cold blooded), meaning they can’t regulate their own body temperature. Central Oregon reptiles and amphibians are often seen basking in the sunshine during a warm spring and summer day in order to heat their bodies and are found hiding in the shade when they get too hot. But when the external temperature drops to freezing, what do these animals do to avoid suffering from the cold?
One strategy reptiles and amphibians use to survive the winter is a dormant state called brumation. Similar to hibernation, brumation is a type of torpor in which the animal slows down their heart rate, metabolic rate, and respiration rate as their body temperature drops. Unlike hibernation, during this dormant state, the animal will occasionally emerge on warmer days before going back into brumation. Reptiles and amphibians will typically brumate in burrows, piles of logs or leaf litter, or partially buried in the mud at the bottom of ponds (many aquatic frogs such as the Oregon spotted frog do this).
Another strategy that some frogs use is delayed metamorphosis, in which the animal overwinters as a tadpole so they can metamorphosize at a larger size when it warms up again. This option can be beneficial for frog species as it improves their chance of survival during colder months. Some frogs can also produce their own biological antifreeze to prevent them from freezing to death in the winter. These frog species produce high amounts of glucose and urea to act as an antifreeze that protects essential organs and cells from damage until temperatures rise again.
Reptiles and amphibians are also evolved to have more efficient heat transfer systems and use either freeze avoidance or freeze tolerance methods. Freeze avoidance or supercooling is a state where body fluids remain liquid when temperatures drop below the freezing point. This metastable state prevents ice formation within the cells all over the body and is promoted by physiological responses and behaviors. For example, the pygmy short-horned lizard will bury itself 4-5 inches into the sand or soil and allow themselves to freeze for months at a time. Their bodies keep ice crystals from forming in their cells while in this “frozen” state using freeze avoidance so that they can become active again when it warms up. Some reptiles and amphibians use a freeze tolerance which is a metabolic and enzymatic adaptation allowing key organs and cells to resist freezing. Both freeze avoidance and freeze tolerance are helpful in avoiding freezing, and some reptiles and amphibians can even alternate between the two methods.
Other reptiles and amphibians will keep their eggs in their bodies and give live birth instead of laying their eggs as an adaptation to shorter breeding seasons. This strategy is called ovovivipary. Central Oregon’s pygmy short-horned lizards and garter snakes are two reptiles that are ovoviviparous.
Another unique adaptation seen in side-blotched lizards is the ability to stay active during colder months. These lizards heat up quickly due to their small size and stay active during warmer days of the winter. Since this lizard is able to remain active during the winter, they are able to restore the fat reserves in their bodies to give them the energy they need to survive.
Between brumation, reproduction alterations, and efficient heat and energy transfer systems, reptiles and amphibians are well equipped to survive even a harsh winter here in Central Oregon.
Learn more about antifreeze methods in amphibians and reptiles here:
https://www.deschuteslandtrust.org/news/blog/2017-blog-posts/amphibians-in-winter
Learn more about Central Oregon’s native reptiles and amphibians here: https://www.thinkwildco.org/identify-central-oregon-wildlife/
