With over 7,500 known frog species, it’s no surprise that they can sleep in a wide variety of places and at different times. Frogs that live in trees generally sleep on branches or in the canopy, aquatic frogs sleep underwater and terrestrial frogs bury themselves underground. Frogs that live in cold or high altitude regions hibernate or estivate during winter and dry seasons respectively.
When it comes to frogs and sleep, there is a lot of controversy over whether or not they actually do sleep. It all started with Pieron’s study in 1913 where he proposed that mammals, birds and reptiles all have a clear sleep behaviour pattern. This theory was rejected by the scientists of the time due to a lack of evidence that this is actually true for all other animals.
Frogs are cold-blooded amphibians so they don’t have the same kind of behaviour that mammals and other reptiles do when it comes to rest and sleep. Frogs do however experience prolonged periods of immobility that could be considered a form of sleep. Libourel et al (2015) found that even while a frog is in this state of rest, it is still able to respond to stimuli such as a hungry predator or the presence of food.
In 1982, Ida Gavrilovna Karmanova conducted a study to understand the evolution of sleep in vertebrates (animals with a spine). She established that amphibians and fish enter into three forms of rest or sleep-like states – protosleep 1, cataleptic sleep and paradoxical sleep. It is during this phase that the eyes are open and the heart rate decreases.