Keeled Sepia Snake

This is a small to medium-sized dipsadid snake, typically reaching total lengths between 15 to 24 inches (40 to 60 cm). Its body is slender and slightly laterally compressed, giving it a very agile and streamlined appearance. The dorsal coloration consists of a pale brown, yellowish-gray, or tan background, distinctly marked with dark longitudinal stripes running along the length of its body, including a prominent dark postocular stripe extending from the eye to the neck. The head is distinct from the neck, featuring a short snout and relatively large eyes with vertical elliptical pupils, which are highly adapted for low-light vision. It possesses an opisthoglyphous dentition, meaning it has enlarged, grooved fangs located at the rear of the upper jaw connected to Duvernoy´s glands; while its venom is highly effective at immobilizing prey, it is considered of mild clinical significance to humans, causing only localized pain and mild swelling in rare cases of defensive bites.

Geographical distribution: It is widely distributed across the southern and central regions of South America, including southeastern and southern Brazil, eastern Paraguay, throughout most of Uruguay, and the northeastern provinces of Argentina, reaching its southernmost distribution limit in the humid Pampean grasslands of Buenos Aires province.

Habitat: This species primarily inhabits open and transitional environments, displaying a strong affinity for wetlands, flooded grasslands, marshes, riparian forests, and the margins of permanent or temporary freshwater bodies. It is highly abundant within the Cerrado, Chaco, and Pampas ecoregions, showing a remarkable tolerance for mildly disturbed agricultural landscapes as long as sufficient vegetative cover and moisture are preserved.

Feeding: It is a specialized carnivore with a diet dominated by amphibians, particularly anurans from the Hylidae and Leptodactylidae families. It actively hunts frogs and toads, but will opportunistically consume small lizards, nestling rodents, and occasionally small fish or invertebrates in its semi-aquatic habitat. The snake utilizes an active foraging strategy, relying on its mild venom to rapidly sedate and subdue struggling prey before ingestion.

Behavior: It exhibits a primarily crepuscular and nocturnal activity pattern, although it can be observed active during overcast or cooler days. This snake is mostly terrestrial and semi-aquatic, capable of swimming gracefully and navigating through dense aquatic vegetation. When threatened, it employs distinctive anti-predator displays, such as lateral body compression to appear larger, tail vibrating, and executing rapid defensive strikes if cornered or handled.

Reproduction: This species employs a viviparous reproductive strategy, which is highly advantageous in highly dynamic wetland ecosystems where egg-laying could risk flooding. Mating occurs during the warmer spring months, and after a gestation period of several months, females give birth to live, fully developed young during mid-to-late summer. Litter sizes typically range from 5 to 15 offspring, which measure about 5 to 6 inches (12 to 15 cm) at birth and are immediately independent, feeding on tiny frogs or insects after their initial shed.

Conservation status: It is currently assessed as Least Concern (LC) on global red lists due to its expansive geographic range and stable overall populations. Nonetheless, localized declines occur due to wetland drainage, agricultural expansion, intensive pesticide use that depletes amphibian prey bases, and direct persecution stemming from human ignorance and fear of snakes.