Hibernation in frogs

During the cold, frigid and bitterly bleakly conditions of the winter season, humans protect themselves by staying indoors while completely shrouded and heavily insulated by comfy sweaters and soft cloth, animals like whales, caribou, bats and monarch butterflies migrate away to warmer environments in order to safely guarantee their winter survival, arctic dwelling mammals like polar bears and walruses develop fist-sized blubbers to stay warm and cozy for the most part, and smaller sized mammals like chipmunks and squirrels along with some species of Northern bears retire mostly into partly insulated dens and actively repress their bodily functions to conserve energy.

But what exactly do frogs do? How do they cope with the immensely emotional and dramatic atmosphere of the winter season? How do they find food and where do they drink water?

Well, the answer is simple.

They remain ‘involuntarily’ dormant for the most part of winter, a method fairly similar to the way squirrels and bears actively repress their physcological activities to conserve energy.

We didn’t use the term ‘hibernate’ because based on scientific convention and beliefs, frogs actually cannot hibernate.

They have no control over their internal body temperatures and therefore cannot actively down-regulate it or suppress other physiological activities like metabolic rates and heart beat.

They’re only triggered into winter dormancy by the plunging ambient temperatures which automatically drags their body temperatures alongside other physiological processes with it.

Hibernation in frogs

Humans may be the smartest or perhaps the most advanced living creatures of the animal kingdom but frogs alongside other hibernators are definitely the high and mighty when it comes to winter.

We hide snuggly in the expanse of our sweaters and bedrooms when winter come knocking impatiently on our doors, but frogs stand firmly at ease and face winter boldly with no cloths on!

Heres how frogs do it.

Remain dormant in water

Aquatic frog species observe their seasonal leave in water bodies. This can be in the bottom of lakes, ponds or other running waters. Frogs actually sit at the bottom of water muds or partly submerged into it rather than completely submerging.

The reason for this lies in the low oxygen contents of water muds. If a frog completely buries itself underneath water muds for prolonged periods, it would end up suffocating due to lack of oxygen. So frogs must leave part of their bodies exposed in water so they can breath through their permeable skins.

Speaking of skin, all aquatic frogs that become dormant during winter respire or breathe using their skin. They exchange oxygen with carbon dioxide using thin permeable membranes spread all over the surface of their skins.

They require water bodies with adequate amount of oxygen to be able to survive throughout winter. Dormant aquatic frogs can be observed sometimes swimming their way under the bottom of lakes to properly breath and circulate oxygen within their bodies. Some can even wake to feed and drink.

Aquatic frogs overwintering underwater have greatly reduce metabolic rates, heart rates, breathing rates and body temperatures as a result of the low ambient  temperatures of their environments not because they actively decide to repress them. They cant.

Because of this enormous reductions in physcological activities, frogs only need very little energy reserve to make it through winter. They rely mostly on the little fat reserves they acquired pre-hibernation to survive.

They have many adaptations that enable them to be able to cope with the drastic drop in body tempreatures and physiological activities within their bodies.

On bare ground

Terrestrially based frog species observe their winter dormancy above water levels. Those that are unable to dig safely below the frost line of soils (depth where their bodies naturally remain un-frozen) opt to take shelter in the peeling barks of tropical trees, downed tree logs, caves, cracks, cervices, or in the piled up depths of tropical leaf litters.

These environments naturally offer very little insulation to their inhabitants (but frogs don’t care anyway), so individuals observing winter dormancy in these places usually get frozen to some degree.

Areas like their body cavities, bladder and under their skins can be observed to turn rock solid from freezing, but vital organs like the hearts and lungs are often kept below freezing conditions. About 65 percent of a frogs body can be said to freeze under the outlined condition.

The vital organs don’t free because at the time when other body parts begin to give in to ambient temperatures, the frogs liver begins to produce glucose in excess amount and surrounding vital organs like the heart and lungs using this glucose. This cause their cells to maintain firm structure and resist freezing. So the glucose secretion acts somewhat like an antifreeze within their bodies.

While spending the winter in this semi-frozen condition, frogs may have their breathing rate, heart rate and brain activities completely stopped. Oxygen consumption becomes low and metabolic rate decreases too. This in short means very low energy consumption and therefore (unless one hungry predator says otherwise) survival till spring.

When the fierce claws of the sun arrives early spring, the frogs’ body parts thaw out and they resume normal breeding and feeding activities.

In burrows

Terrestrial frogs do this. Those able to dig deeply below the frost line in bare soils. They may shift upwards or downwards in accordance with the changing position of the frost line.

Burrows may be anywhere from 6 inches to 3 feet deep depending on snow cover, temperature and period in winter.

Most frogs that opt for this usually cannot endure freezing of their organs or do not have any adaptations to prevent such from occurring. So by digging below the frostline and constantly changing position in accordance with the changing line, they may effectively keep their bodies below freezing point.

Species of frogs that become dormant in winter include:

  • American tree frogs (terrestrial)
  • Wood frogs (terrestrial)
  • Leopard frogs (aquatic)
  • American bull frog (aquatic)

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Cite this Article (APA Format)

Bunu. M. (2020, June 25). Hibernation in frogs. Retrieved from http://emborawild.com/hibernation-in-frogs/

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