Green Basilisk, Basilisk plumifrons

Green Basilisk, Basilisk plumifrons. Photograph taken within the Caño Negro Wetlands National Wildlife Refuge in northwestern Costa Rica, February 2023. Photograph and identification courtesy of Dr. Tom Bartol, Carlsbad, California.

The Green Basilisk, Basiliscus plumifrons, is a member of the Corytophanidae family of Basilisk Lizards, a subfamily of the Iguanidae family. The Corytophanidae family consists of nine members placed in three genera. There are four global species in the Basiliscus genus. The Green Basilisk is also known as the Double-crested, Green-crested, and Plumed Basilisk. They can run across water on their hind limbs at up to 1.5 meters (5 feet) per second for a distance of approximately 4.5 meters (15 feet), giving them the name “La Gartija de Jesus Cristo” or Jesus Christ Lizard.

Off the four basilisk species, the Green Crested Basilisk is the only one that is bright green in color. They have white and gray or light-blue markings on their body, and some populations also have black markings. Their ventral surface is a lighter green than their sides and their tail may be unmarked or have thin black bands. Their head is triangular in profile with ear openings that are slightly larger than their eyes. They have round eyes with yellow irises. Their body is laterally compressed and their skin is covered with small granular scales. Their hind limbs are much longer than their front limbs, and their toes are long and flattened. Their tail is laterally compressed with a crest running its length. Sexual dimorphism is displayed with males possessing four vertebral crests: a tiny crest just behind their eyes, a much larger crest on the back of their head, a dorsal crest, and a tail crest. Females and juveniles only have a greatly reduced second head crest and a feeble tail crest. Green Basilisks may grow to reach 0.9 m (3 feet 0 inches) in total length (including their tail) and weigh up to 200 grams (7 oz).

Green Basilisks are diurnal, spending much of their time basking in the sun or foraging for food. Males are highly territorial and a single male may keep land containing a large group of females, with whom he mates. Mating occurs in March and pregnant females become visibly plump one or two weeks after mating. During the third week, females begin looking for a suitable site to lay their eggs. Females lay between 15 to 17 eggs and bury them under warm, damp soil or sand. Clutch size depends mostly upon the age, size, and health of the female and multiple clutches are typically laid during a breeding season. Four to five clutches per season have been observed. Eggs hatch after approximately 8 to 10 weeks over a 1 to 2 day period. Hatchlings emerge as fully independent lizards and they do not receive any parental care. Juveniles reach sexual maturity in 18 to 24 months. Green Basilisks have life spans of five to six years in the wild and eight to ten years in captivity. 

Green Basilisks are semi-arboreal and semi-aquatic. If frightened on land, they can sprint on their hind legs, moving at speeds of over 11.3 km (7 mph) per hour. Their speed combined with specialized scales on the bottom of their feet allow them to run across water for a fair distance without breaking the surface tension. Fringes of skin on their rear feet unfurl in the water, increasing their surface area. As they rapidly churn their legs, they slap their splayed feet against the water. This creates a tiny air pocket that keeps them from sinking, provided they maintain their speed. When gravity eventually takes over, after 5 m (15 feet) or more, the Green Basilisk resorts to its exceptional swimming abilities to continue its flight. They can remain submerged for more than 10 minutes at a time. Green Basilisks are omnivores and consume insects, spiders, small mammals, small birds, small nonvenomous snakes, smaller species of lizards, amphibians, crustaceans, fruits, flowers, and leaves. In turn, they are primarily preyed upon by snakes, large birds, and other reptiles. 

The Green Basilisk may be confused with the Brown Basilisk, Basiliscus vittatus (brown or olive brown in color with yellow cross banding on their flanks and dorsal crest).

From a conservation perspective the Green Basilisk is currently considered to be of Least Concern due to their wide range and large overall population. They are currently threatened by the loss of primary forest habitat resulting from expanding human populations.