The sight of a crocodile lying with its mouth wide open is a familiar one, but why exactly do crocodiles engage in this peculiar behavior? As apex predators that emerged over 200 million years ago, crocodiles have evolved some fascinating adaptations that enable them to survive and thrive in their environments.
If you’re short on time, here’s a quick answer to your question: Crocodiles open their mouths to thermoregulate, or control their body temperature. The mouths contain many blood vessels that can release heat when open.
In this article, we’ll take a deep dive into the reasons behind this crocodilian quirk, exploring topics such as thermoregulation, communication, prey luring, and more. With insights from experts and the latest scientific research, you’ll gain a comprehensive understanding of the purposes and mechanisms behind crocodile mouth gaping.
Thermoregulation
Crocodiles are ectothermic creatures, meaning they rely on external sources to regulate their body temperature. As reptiles, crocodiles have developed behavioral adaptations like basking in the sun with mouths agape as a means of thermoregulation.
Their mouths contain a dense network of blood vessels that allow crocodiles to release excess heat when they’re too hot or absorb heat when they’re too cold.
Mouths Contain Many Blood Vessels
A crocodile’s mouth is filled with blood vessels that are very close to the surface. When the reptile opens its jaw, the blood in these vessels becomes easily exposed. So a gaping crocodile mouth serves as an effective heat exchange system.
There can be as many as 60 to 240 blood vessels per square centimeter lining a crocodile’s mouth and tongue. That dense vascular surface makes the mouth an ideal place for crocodiles to regulate body temperature. Blood flowing through the vessels quickly takes on or expels heat.
Releasing Excess Heat
To cool down on hot days, crocodiles will orient their open mouths toward breezes. This allows hot blood from the body core to circulate through the mouth vessels, dissipate built-up heat, and then cycle back through the body as cooler blood.
A crocodile may even pant with its mouth open to increase air flow and evaporation.
Scientists have recorded temperature differences of up to 8°C (14°F) between blood flowing into and out of the mouth. So heat transfer through mouth gaping can provide significant thermoregulation.
Absorbing Heat When Cold
When it’s chilly, crocodiles seek out sunny basking spots on the banks of rivers and lakes. With mouths wide open, the blood vessels efficiently collect the sun’s warmth. The crocodile may even orient itself broadside to maximize solar heat absorption capacity.
The mouth also gives off heat itself through metabolic processes. So unlike many reptiles that are sluggish in cold weather, gaping allows crocodiles to remain active when temperatures drop. Though their bodies cool below room temperature, graceful mouth gaping lets crocodiles maintain higher functioning brains and muscle coordination even as ambient conditions chill.
Communication
Visual signals
Crocodiles open their mouths for a variety of visual signals to communicate information. One key reason is to regulate their body temperature. As crocodiles are cold-blooded, they rely on external heat sources like the sun to warm their bodies.
By gaping with their mouths open towards the sun, crocodiles can maximize heat absorption.
Crocodiles may also open their mouths to show dominance and establish territory boundaries. An open mouth is a clear visual signal demonstrating the formidable teeth and power of a crocodile. It communicates “back off” to rival crocodiles encroaching on their domain.
Interestingly, the wider the open mouth, the more dominant the signal conveyed.
Establishing dominance
Gaping mouths are an important part of ritualized combat between male crocodiles. By standing in the water with mouths agape, they size up their opponent while clearly communicating their fighting capabilities. This allows the crocodiles to often resolve conflicts without physical violence.
The croc with the greatest display of teeth and strength usually wins.
Baby crocodiles also open their mouths during tussles over hierarchy and access to the best basking spots. Their communication is crucial in avoiding injuries within the crocodile social structure.
During courtship
Interestingly, the male crocodile’s gaping display takes on a whole new meaning during mating season. He will boldly approach the female while slowly opening and closing his mouth and inflating his body to demonstrate his suitability as a mate.
If receptive, the female will respond with a gaping display of her own. This bonding activity helps reinforce pair loyalty during courtship. Mating usually follows to fertilize her eggs for the nesting season ahead.
Prey Luring
Inviting Birds
Crocodiles have a sneaky way of luring birds into their mouths for an easy meal. They will often float in the water with their mouths wide open, appearing motionless. This attracts curious birds that come to investigate the strange sight.
Little do the birds know, they are being tricked into landing right inside the crocodile’s trap!
Research shows that crocodiles can stay perfectly still with mouths agape for up to an hour. Their patience usually results in succulent bird flesh. Ducks, herons, storks, and other waterfowl often cannot resist exploring the mysterious open croc jaws.
This morbid curiosity seals their fate when the jaws slam shut.
Experts believe crocodiles use this deceptive technique because birds have highly developed vision suited for detecting movement. By staying still, the crocodiles avoid triggering the birds’ alarm systems. Only when it is too late do the birds realize their mistake.
One minute you are peering into a bizarre void, the next you are being swallowed by razored teeth.
Trapping Fish
Crocodiles also use their gaping mouths to snare delicious fish. The mighty reptiles will submerge themselves just below the water’s surface with their jaws wide open. This creates an underwater death trap that fish cannot resist swimming into.
The lure of the open mouth is two-fold. First, fish are attracted to the shade and protection offered by the interior of the jaws. Second, small fish will actually swim inside seeking parasite removal. Certain species of fish, like bluestreak cleaner wrasse, eat parasites off the teeth and tongue of larger open-mouthed predators.
However, one false move and they become meals themselves.
Studies show that up to 45 species of fish have been known to vanish into the mouths of waiting crocodiles. The most frequent visitors are probably seeking dental work. But eventually the crocs snap their jaws shut and gulp, no flossing required.
Just a fatal case of mistaken identity and crossed wires in the symbiotic relationship between fish and croc.
Buoyancy and Balance
Water displacement when floating
When crocodiles float in water, their bodies displace a certain volume that counterbalances their weight (Archimedes’ principle). This allows them to float effortlessly with most of their bodies submerged.
Interestingly, crocodiles can alter their floating stance by swallowing stones and holding air in their lungs. This shifts their center of buoyancy and rotation axis for better control in water.
Young crocodiles tend to float higher in the water with more of their bodies exposed. Their small size means less water displacement compared to large adult crocodiles. The remarkable ability to alter buoyancy enables crocodiles to ambush prey from below without being noticed.
Counterbalance when walking on land
On land, balance while walking poses a different challenge without the benefit of flotation. Crocodiles must prevent themselves from toppling over sideways or pitching forward/backward excessively. To achieve this, they often let their mouths hang open.
This has the counterbalancing effect of shifting the center of gravity backwards.
Crocodile Status | Mouth Position | Effect on Balance |
---|---|---|
Standing still | Fully open | Shifts center of gravity rearwards for sideways stability |
Walking | Partially open | Prevents excessive front/back pitching |
Additionally, the open mouth sticking out forwards acts as a counterweight against the heavy tail dragging behind. This clever bilateral balance mechanism is crucial for locomotion on land. It allows crocodiles to walk steadily without tipping over (contrary to initial perceptions of clumsiness).
Their sprawled posture also aids stability just like other reptiles.
In short, letting their mouth hang open is an ingenious trick used by crocodiles both in and out of water. It helps with floating, underwater stealth, walking balance, and dynamic body weight distribution. Truly a multi-purpose adaptation for these ancient apex predators!
Breathing
Mouth Breathing
Crocodiles primarily breathe through their nostrils, which are located on the tip of their snout. However, they can also breathe through their mouths when necessary. Here are some reasons why crocodiles may open their mouths to breathe:
- To regulate body temperature – Crocodiles do not have sweat glands and rely on their mouths to release heat. By gaping their jaws, evaporation occurs, cooling the blood vessels in the mouth.
- To enhance smell – Opening the mouth allows odors and scents to reach the Jacobson’s organ (a sensory receptor organ) located on the roof of their mouth. This helps them better detect prey or threats.
- When stressed or exerted – During strenuous activity like hunting, crocodiles can supplement nasal breathing by opening their mouths. More oxygen can enter, meeting their increased metabolic demands.
- To threaten or intimidate – An open-mouthed crocodile is a clear warning sign. This aggressive display exposes their dangerous teeth and sends a message to back off.
Underwater Breathing
Crocodiles have special valves in the back of their throat that seal off their air passageways when underwater. This allows them to open their mouths without water flooding in. Here’s how they breathe when submerged:
- The palatal valve closes off the nasal passageway to the throat.
- The muscular flap seals the glottis (opening to the lungs).
- With these barriers in place, crocodiles can open their jaws underwater while keeping their lungs protected.
- Muscles contract to force air from the lungs out through the nostrils.
- When they resurface, the valves reopen, allowing them to breathe again.
This unique anatomical adaptation allows crocodiles to lie in wait for prey while mostly submerged. Only their eyes, ears, and nostrils are above the waterline. When they strike and drag prey underwater, they can hold their breath for an hour or more before needing to surface for air.
Conclusion
In summary, crocodilians open their jaws for a number of important reasons related to thermoregulation, communication, hunting, locomotion, and respiration. Their mouths contain vascular structures that allow them to regulate body temperature, signal to other crocodiles, lure prey, displace water, and even breathe underwater.
The next time you see a lazily gaping crocodile, you’ll have a much deeper appreciation for the evolutionary adaptations behind this behavior. While it may seem like simple basking, there are in fact complex physiological processes and survival strategies at play.
Understanding crocodilian behavior provides fascinating glimpses into successful evolutionary designs that have persisted for eons.