Do Frogs Sleep?

Frog sleep is a fascinating topic that is hardly covered by scientific research. Some older studies report that frogs do not sleep at all, yet more recent studies have clearly outlined the reasons why frogs do sleep and how.

Frogs generally sleep based on intermediate period of Non-REM, Primary and Cataplectic Sleep. Frogs do not sleep like humans other mammals, yet few scientific studies have been carried out on the topic of frog sleep, and many existing studies are based on a mammal-centric definition of sleep.

Put simply, humans define sleep in ways that do not apply to frogs, yet much of the science studying frog sleep is based on how humans and mammals sleep. Therefore, there remains a lot of confusion about how frogs rest due to lack of quantity and quality scientific studies on the topic.

Let’s dive into what we know about how frogs sleep and the limitations to what science has provided us thus far.

Do Frogs Go to Sleep?

Frogs employ a Slow-Wave sleep pattern, also called Non-REM Sleep or Quiet Sleep. Karmanova (1982) found that amphibians display 3 different types of rest or sleep-like states called: Primary, Catatonic and Cataplectic Sleep.

Scientists agree that all animals including insects, vertebrates and frogs show some forms of sleep or rest-like states. Let’s have a look at how we define sleep from a human standpoint, and how our sleep differs from how frogs sleep.

A Simplified Human Definition of Sleep

Human sleep is defined by a number of factors including a period of immobility, rapid eye movement, variation in brain waves, specific brain activity, motor automatisms, muscle atonia, lower metabolic rate, lower brain temperature, and slower breathing and heart rate (WebMD).

Scientists have uncovered two types of sleep in humans, birds and other mammals:

  • Slow-wave sleep: Non-REM sleep, quiet sleep
  • Paradoxical sleep: REM sleep, or active sleep

In the 1960’s, scientists applied this mammal-centric definition of sleep to frogs. But frogs are cold-blooded (ectotherms) amphibians, and so many of the ways we define human sleep may or may not apply to frogs.

Although frogs also display a prolonged period of immobility that can be considered a sleep-like state, they regulate their temperature differently to humans and do not have the same brain structure as us. 

Frogs also hibernate when located in high-latitude environments, and estviate when located in environments with Dry Seasons. These are unique periods of rest that humans do not experience.

The Current Definition of Frog Sleep

In 1982, Karmanova found that amphibians display 3 different types of rest or sleep-like states called:

  1. Primary Sleep: A rest state during the day when the eyes are open
  2. Catatonic Sleep: Takes place at night, frogs may have rigid muscles
  3. Cataplectic Sleep: Takes place at night, frogs may have atonia

Karmanova’s study (1982) suggested that amphibians display intermediate sleep between Primary Sleep and Cataplectic Sleep (Libourel et al, 2015).

How frogs sleep is very important for us to understand our own evolution of sleep. Such findings can lead us to study our own sleep patterns since we may also have slept intermittently with a period of activity at night (segmented sleep, WebMD). 

Why we sleep is still highly debated among scientists, but it has generally been found to be important to preserve and replenish energy, for optimal brain function and memory, as well as development for newborn and young individuals. And, although scientists are still working on the subject of why we sleep, these principles certainly apply to animals as well (CTNF).

How Do Frogs Sleep?

Observing how frogs sleep or rest can be fairly easy from a non-scientific standpoint. I am going to set aside the scientific studies this article is based on to give you some personal observations of how frogs sleep.

Behaviorally, frogs sleep by doing the following:

  • Resting immobile for long periods of time
  • Tucking their limbs under their body
  • Keeping their chin and stomach very close to the ground
  • Covering their eyes with their nictitating membrane

Although resting, frogs that are sleeping or in a sleep-state can quickly respond to external stimuli (food, predator). Frogs generally close their nictitating membrane (third eyelid) during sleep so they can still see and react to their surroundings.

Frog’s Nictitating Membrane

But with over 7,400 known frog species that live all over the world on land, in water and in trees, you can imagine that frogs probably display different sleep behaviour patterns depending on their immediate environment and possibly the species. Yet, such theories have not been sufficiently studied.

When And Where Do Frogs Sleep?

Tree frogs generally sleep in trees, aquatic frogs in water and terrestrial frogs underground. Frogs located in high-latitude and cold regions also hibernate in Winter, and frogs in low-latitude or desert regions generally estivate during Dry seasons. 

When and where frogs sleep depends on the type of frog (arboreal, aquatic, terrestrial), their environment and the time of year (Winter, Dry Season). I have personally observed different patterns of rest or sleep in frogs depending on the species. 

Although I can read scientific articles, I am not a scientist myself, so these are based on personal observations of a few species around where I live, as well as other research carried out on this blog.

  • Terrestrial Frogs: Toads generally burrow during the day and probably experience low activity periods of rest while underground. Toads are ambush predators that are active at night. They are capable of remaining immobile during long periods of time while hunting, yet can immediately respond to food or a predator.
  • Aquatic Frogs: Aquatic frogs can generally be found along the water’s edge among vegetation during the day and often seem to be resting in my opinion. Aquatic frogs are generally active at night when they can sometimes be found on land yet near water looking for food.
  • Arboreal Frogs: Grey Tree Frogs are often found in sleep-like positions during the day on horizontal branches in trees (limbs tucked under body, chin and belly close to the branches). Spring Peeper are difficult to find during the day but actively call during Mating Season between sundown and 3 to 5 am, after which they may also experience periods of rest.

Types of frogs I have observed: 

Limitations of Scientific Findings on Frog Sleep

Libourel et al (2015) found that most studies on frog sleep were focused on the human definition of sleep or only contained mature, adult individuals, and lacked nuance with regards to temperature and lighting. 

The study’s authors explain that mammal-centric sleep may not apply to amphibians, that younger individuals may have different sleep patterns and that temperature and lighting can influence results.

Not only that, but only 9 frog species had been studied in the context of sleep at the time they published their article. The studies were generally based on short observation periods of 24h, and did not use the same protocols or instruments to draw conclusions. Libourel et al (2015) also argue that location (natural environment or laboratory) can influence sleep study results.

So you can imagine that the lack of consistency and data makes it very difficult to draw viable conclusions as to how frogs sleep. However, despite conflicting results from some studies, Libourel et al (2015) concluded that “the amphibian species studied to date display behavioural characteristics of sleep” as do “virtually all animals, including insects, nematodes, scorpions, spiders, and vertebrates” that “show some form of sleep, or at least sleep-like states.”

More About Frog Sleep

Although the definition of how frogs sleep and the influences of these conditions is unclear, it is clear that frogs do experience periods of rest that can be considered sleep.

Learn more about frogs and how they sleep in the guides on our site:

Common Questions About How Frogs Sleep

How to Tell if a Frog is Sleeping? You can tell if a frog is sleeping by observing its behaviour for resting immobile for long periods of time, tucking their limbs under their body, keeping their chin and stomach very close to the ground and covering their eyes with their nictitating membrane.

How Long do Frogs Sleep? No studies have scientifically observed how long frogs sleep, but from a behavioural and non-scientific standpoint, it is possible that frogs spend 12 to 16 hours resting or sleeping, yet are active part of the night, generally from sunset to 3 am to 5 am before other predators like birds wake up.

Do Frogs Sleep With Their Eyes Open? Frogs generally close their nictitating membrane or third eyelid during sleep so they can still see and react to their surroundings. This third eyelid keeps their eyes moist and is transparent so frogs can detect movement even if they are resting.

Sources

Libourel PA, Herrel A. Sleep in amphibians and reptiles: a review and a preliminary analysis of evolutionary patterns. Biol Rev Camb Philos Soc. 2016 Aug;91(3):833-66. doi: 10.1111/brv.12197. Epub 2015 May 29. PMID: 26031314.

Hobson, J. Allan, et al. “Sleep Behavior of Frogs.” Quarterly Journal of the Florida Academy of Sciences, vol. 30, no. 3, 1967, pp. 184–186. JSTOR, www.jstor.org/stable/24314832

Karmanova, I. G., Evolution of Sleep: Stages of the Formation of the “Wakefulness-Sleep” Cycle in Vertebrates. 1982. Karger, Basel, Originally Published in Russian by Nauka Publishers, Leningrad.

J. Allan Hobson, Electrographic correlates of behavior in the frog with special reference to sleep, Electroencephalography and Clinical Neurophysiology, Volume 22, Issue 2, 1967, Pages 113-121, ISSN 0013-4694, https://doi.org/10.1016/0013-4694(67)90150-2

WebMD, What is Segmented Sleep

WebMD, Sleep