The gular region in animals refers to the exterior area of the throat, situated beneath the lower jaw and extending towards the neck. This anatomical feature is present across various animal classes, including birds and reptiles, where it can manifest in diverse forms. While its appearance varies, the gular region often plays a role in specialized behaviors and survival mechanisms unique to each species.
Types of Gular Structures
The gular region exhibits several distinct anatomical variations across different animal species. One common form is the gular pouch, a distensible sac of skin observed in birds like pelicans and cormorants. Cormorants also possess gular skin, which can display bright coloration, particularly during breeding seasons.
Another specialized structure is the inflatable gular sac, found in the male magnificent frigatebird. This sac is a large, balloon-like red pouch on the throat that males inflate during courtship displays. The inflation process can take approximately 20 minutes, transforming the gular skin into a visual signal.
Reptiles, such as anole lizards, feature a gular flap, often called a dewlap. This is an extensible flap of skin folded beneath the throat. Anole dewlaps vary in color, including shades of yellow, red, and blue, and are extended through movements of the hyoid apparatus and associated muscles. Other reptiles, such as snakes and lizards, may also feature specialized gular scales on the ventral surface of the neck or throat.
Role in Mating and Territorial Displays
Gular structures serve as visual signals in animal communication, particularly during mating and territorial interactions. Male magnificent frigatebirds use their large, red inflatable gular sacs to attract females. During courtship, the male inflates this sac to its full, balloon-like size while pointing its bill upwards, creating a display for females flying overhead. This inflated pouch signals fitness and readiness to mates.
Anole lizards use their colorful gular dewlaps in both courtship and territorial warnings. Both male and female anoles extend these throat flaps in combination with head-bobbing displays. This behavior communicates ownership of a territory, deterring rivals and preventing physical confrontations. The specific color and pattern of a dewlap can also help anoles distinguish between members of their own species and other species, refining signals.
Adaptations for Feeding and Thermoregulation
Beyond communication, the gular region also features adaptations for obtaining food and regulating body temperature. The pelican’s large gular pouch is primarily adapted as a temporary scooping device for capturing fish from the water. After scooping, the bird tilts its bill downwards to drain excess water before swallowing the fish, which then slides into the gullet. This pouch is not used for long-term food storage; it functions more like a net, capable of holding up to three gallons or approximately 24 pounds of fish.
Certain bird species use a behavior known as gular fluttering for thermoregulation, especially in hot conditions. This involves rapidly vibrating the muscles and bones in the throat, which increases airflow over the moist, highly vascularized membranes of the gular region. This rapid movement facilitates evaporative cooling, similar to how mammals pant, allowing heat to dissipate from the blood vessels near the surface of the gular skin. Species such as owls, nighthawks, and cormorants use gular fluttering to reduce their internal body temperature, preventing overheating with minimal water loss.