Do Warm Blooded Snakes Exist?

Snakes are stereotypically thought of as cold blooded reptiles that bask in the sun to regulate their body temperature. However, some snake species have adapted the ability to raise their temperature through muscle contractions rather than relying solely on external heat sources, leading some to characterize them as ‘warm blooded’.

If you’re short on time, here’s a quick answer: While no snakes are truly warm blooded like mammals and birds, some snake species have evolved mechanisms that allow them to raise their body temperature higher than their environment through muscle contractions rather than relying solely on external heat.

In this comprehensive article, we will analyze the mechanisms that allow some snakes to control their body temperature, compare them to true warm blooded animals, look at the evolutionary advantages this provides, and profile snake species capable of these temperature increases.

Muscle Contractions Allow Some Snakes to Raise Body Temperature

Shivering and Muscle Flexing

Some snake species like pythons and rattlesnakes have been observed to use muscle contractions to raise their body temperatures (Source). Through actions like shivering or muscle flexing, these snakes can generate heat via cellular respiration and temporary spikes in metabolic rate.

This allows cold-blooded snakes to increase their body heat substantially above air temperature, though they still cannot self-regulate temperature like mammals.

Chemical Reactions and Heat Generation

Another way snakes temporarily increase body temperature is through heat released from chemical reactions. Some species that have recently eaten meals high in fat and protein can experience rising body heat through digestive processes.

The heat increment of feeding or specific dynamic action (SPD) from digestion may allow some snakes to raise body temperatures by up to 7℃C above ambient levels.

Limits on Sustainable Temperature Increases

Though impressive, the internal heat generation capabilities of snakes do have limits. Without a true endothermic physiology, most snakes cannot maintain an elevated body temperature for extended time periods. Bhullar et al.

(2020) found that the heat increment from digestion in snakes only lasted around 24 hours before body temperature returned to ambient levels. So while muscle contractions and digestion offer temporary respite from cooler external environments, most snake species ultimately must return to behavioral thermoregulation and basking.

Comparing Snake Thermoregulation to Warm Blooded Animals

Generating Body Heat Internally

Unlike mammals and birds, snakes do not have the ability to generate their own body heat internally. Snakes are ectothermic, meaning they rely on external heat sources like the sun to regulate their body temperature.

When a mammal or bird eats food, that food is metabolized and used to produce heat that warms their body from the inside out. Snakes lack this internal heating system and must behaviorally thermoregulate by moving between hot and cool environments.

Maintaining Stable Body Temperatures

Warm-blooded animals like mammals and birds maintain a constant internal body temperature, despite changes in the external environment. For example, humans maintain an average body temperature around 98.6°F whether they are relaxing in the shade or running a marathon under the hot sun.

Snakes, on the other hand, have body temperatures that fluctuate widely depending on their environment. When it’s cold out, a snake’s body temperature will drop dramatically, sometimes as low as 40°F. In hot conditions, their body temperature can spike to over 100°F.

This variability allows snakes to conserve energy by not having to constantly produce internal heat, but it also means they are more vulnerable to extreme temperatures. Mammals and birds maintain safe body temperatures in hot or cold weather by internally regulating heat production and loss.

Energy Requirements and Metabolism Rates

Generating internal body heat requires a lot of energy and a high metabolism rate. Mammals and birds have very active metabolisms to support their warm-blooded lifestyles. Snakes, as ectotherms, have much lower energy requirements.

Their metabolic rates are a fraction of the rates of similarly-sized mammals. For example, a snake might have a metabolism of just 10% of the rate expected for a mammal of the same weight. This slow metabolism allows snakes to survive on less food and go longer between meals.

The downside is that snakes have less stamina and energy reserves compared to warm-blooded animals. While a mammal or bird can sustain activity like running, flying, or foraging for hours, snakes tire quickly and must rest and recharge their low energy supplies.

So although snakes save energy by not producing internal heat, their overall energy budgets and activity levels are still quite different from warm-blooded species.

The Evolutionary Advantages of Temperature Control

Expanded Habitats and Geographical Ranges

The ability to regulate body heat provides warm-blooded animals access to a wider range of habitats and geographical locations than cold-blooded animals (ectotherms). Warm-blooded species (endotherms) can thrive in extreme cold temperatures that would be fatal to ectotherms relying on external heat sources.

For example, birds and mammals inhabit polar, temperate, and tropical regions around the world. In contrast, ectothermic reptiles are mostly limited to tropical and temperate habitats. Very few ectothermic vertebrates live in polar habitats year-round.

The expanded habitat range gives endotherms more access to resources like food, shelter, and mates.

Increased Speed, Agility and Response Times

Warm-blooded animals also have faster reaction times and greater speed and stamina than cold-blooded creatures because they maintain elevated bodily temperatures and oxygen circulation. Muscle contraction rates are much quicker when body tissues are warm.

Higher and more stable body temperatures allow mammals and birds to react faster to stimuli like predators or prey (fight-or-flight response). Quick muscular reflexes and maximum exertion is maintained better in warm conditions.

Ability to Hunt in Cold Conditions

Finally, warm-blooded creatures can hunt for food effectively in cold weather when ectotherms are sluggish and slow. Birds and mammals have high energy demands fueling their inner furnace and must eat much more frequently than reptiles.

Endothermy supports active lifestyles even in frigid environments. Polar bears, arctic foxes, reindeer, seals, penguins and other vertebrates thrive around cold northern and southern latitudes thanks largely to their evolved temperature control.

To learn more, visit these sites:

• amnh.org – Ectotherm vs. Endotherm Exhibit
• bbc.co.uk – Advantages of Being Warm-blooded

Snake Species Capable of Significant Temperature Increases

Rattlesnakes

Rattlesnakes are well-known for their ability to raise their body temperature significantly above ambient levels. They achieve this through a process called facultative endothermy, where they can increase their metabolic rate to generate heat internally.

Some key facts about rattlesnake thermoregulation:

• Rattlesnakes rely on external heat sources like the sun to warm up. They can raise their body temperature by coiling their bodies and exposing maximum surface area to the sun.
• By shivering and increasing their metabolic rate, they can raise their body temperature by as much as 8-10°C above ambient levels.
• This allows them to maintain optimum body temperatures of 30-35°C required for digestion and other physiological processes.
• Their ability to “burn calories” to produce heat allows them to be active at night and in cooler weather when other snakes may be dormant.

Pythons and Anacondas

Like rattlesnakes, large constrictor snakes like pythons and anacondas are capable of raising their body temperatures higher than their surroundings. Here are some key facts:

• Pythons and anacondas rely heavily on external heat sources and will bask to absorb heat from the sun.
• They can raise their body temperature by around 7°C compared to ambient air temperature through muscular thermogenesis – generating heat by increasing metabolic activity in their muscles.
• This allows them to reach optimal body temperatures of 30-35°C needed for digestion and other physiological functions.
• Their large size also helps them retain heat more efficiently than smaller snakes.

So pythons and anacondas, though not quite as specialized at thermoregulation as rattlesnakes, also display significant capacities for raising their body temperatures higher than their surroundings. Their sheer bulk also grants them thermal inertia to retain heat for longer.

This grants them expanded habitats and greater ability to be active at night.

Mambas and Cobras

Mambas and cobras have also evolved some noteworthy thermal capacities:

• Mambas are able to raise their body temperatures by around 5°C above ambient air temperature through muscle contractions and increasing metabolic rate.
• Cobras can elevate their body temperatures by a few degrees higher than ambient levels by expanding their neck hoods and exposing more surface area to the sun.
• Both types of snakes rely heavily on basking and choosing warm microhabitats to raise their temperatures.

So while mambas and cobras do not have the same level of endothermic capacity as rattlesnakes, they do display the ability to raise their body heat significantly above their environment through behavioral adaptations like basking.

This allows them to thrive in a variety of habitats and extend their activity cycles.

Conclusion

While no snakes are truly warm blooded in the same way as mammals and birds that can constantly maintain high body temperatures, some snake species have evolved impressive mechanisms to raise their temperatures through muscle contractions rather than relying solely on external heat.

This allows them to expand their habitats, improve hunting capabilities in cold conditions, and increase speed and response times. By analyzing the muscle contractions and chemical reactions snakes use to heat their bodies, comparing them to true warm blooded animals, and profiling species capable of significant temperature control, we can appreciate the innovative survival adaptations of these reptiles.