Lithobates grylio (Stejneger, 1901)

Coloration and Markings

Lithobates grylio, commonly called the pig frog, is green or grey-green with brown or black blotches.

External Morphology

It has fully webbed feet, a sharply pointed nose, and large eardrums (tympana).

Sexual Dimorphism Traits

This species shows sexual dimorphism in size and coloration: males have larger tympana than females, and males also have a distinctive bright yellow throat that sets them apart from females.

Adult Size Range

Pig frogs grow to a snout to vent length (SVL) of 85 to 140 millimeters (3 1/4 to 5 1/2 inches).

Growth Rate Patterns

Males and females have similar growth rates until their snout-vent length reaches roughly 100mm; after this point, females grow faster and eventually reach a larger adult size than males.

Wild Population Demographics

Because adult females are larger, they generally have higher survival rates than males and are therefore likely more abundant in the wild.

Similar Congeneric Species

Pig frogs are easily confused with other species in the genus Lithobates that share their geographic range, including the American bullfrog (Lithobates catesbeiana).

Common Name Origin

The species gets its common name from the loud, deep grunting or snorting call males produce, which resembles the oinking sound of a pig.

Male Call Function

Males use this low grunting call during the breeding season to attract females and establish territory.

Habitat Preferences

Pig frogs are almost entirely aquatic, and are most often found along the edges of lakes, or in vegetation-heavy cypress swamps and marshes.

Activity Pattern

They are nocturnal, and their pig-like grunts can be heard during the warm months of the year.

Breeding Season Timing

Their breeding season runs from April to August.

Fertilization Method

Fertilization is external: males release sperm over eggs as the eggs are laid.

Egg Laying Characteristics

Females lay eggs in large surface masses of up to 10,000 eggs at a time, usually positioned over vegetation on the water surface.

Development Timeline

The eggs hatch within several days, and tadpoles may take a full year to complete metamorphosis into adult frogs.