During a 10-day Biology/Forestry field course in Costa Rica, attended by NAU students over the recent Thanksgiving break, we saw more snakes than in my seven previous trips to the country combined. Their great diversity of feeding habits shows that snakes do not confine their culinary endeavors to mice. Here are the eight species we had the good fortune to see.
Green vine snake: These slender, bright green snakes with yellow stripes on the face eat mice, lizards, and birds. They follow their prey and wait for an opportunity to bite its head and inject venom into it.
Cat-eyed snake: These nocturnal snakes have a zigzag pattern made of black spots on their brown or yellowish back and large eyes with vertical elliptical pupils. They eat frogs (including poisonous ones), tadpoles, frog eggs, salamanders, small lizards, and fledgling birds.
Caracolera: The rings of this snake alternate between thick black and thin pale ones, with a collar of bright red or orange. “Caracol” is Spanish for “snail”, and as the name suggests, these snakes eat snails. The one we saw had a snail in its mouth that looked far too big for the snake to swallow, especially since its neck abruptly narrows behind the head.
Mussurana: Juveniles have a light pink back that turns bluish-black as they mature, though the belly is a pale yellow in snakes of all ages. They eat other snakes — a behavior called ophiophagy — and are immune to the venom of many snakes, including pit vipers. Some farmers keep them as pets to remove snakes that can harm and kill livestock or farm workers.
Fer-de-lance: The deadliest snake (to humans) in Costa Rica has a triangular head and a series of black-edged diamonds bordered by a lighter color; they also have a yellow chin. Their diverse diet includes lizards, centipedes, insects, frogs, lizards, other snakes, rodents, opossums, and birds.
Hog-nosed pit viper: This grayish-brown snake with dark rectangular or triangular blotches on the sides and a pale narrow strip along its back has a characteristic scale on its nose that extends upward. It eats lizards, frogs, rodents, and small birds.
Parrot snake: These snakes are bright green on the top, and yellow or white on the belly with a black stripe through the eye. Many of their scales have black edges. Tree frogs are their primary prey, but they also eat lizards, grasshoppers, bird eggs, and nestlings.
Eyelash pit viper: The most spectacular of the snakes we saw is famous for having modified scales above the eyes, resembling eyelashes. We saw two bright yellow snakes, but they can also be pink, red, green or brown. They eat lizards, frogs, bats, small rodents, and can even catch hummingbirds!
Snakes are disliked and even feared by many, but luckily, all the students were happy to encounter these gorgeous animals in the wild. Each time the call “Snake!” went out during one of our walks in the rain forest, everyone came running to get a good look—and perhaps to see what the creature was eating.