Costa Rica: Ground Anole

Very common in Costa Rica but can be hard to pin down; they are fast and elusive when they need to be.

When Theresa and I weren’t out in the field we were at our villa relaxing and enjoying the warm sunny weather. Our front yard was lush in vegetation and everything looked like it was on steroids. Every so often I’d see movement out of the corner of my eye, but by the time I focused on that area, it was empty. The cause? A small, shy, rocket fast reptile which turned out to be the Ground Anole Lizard.

Habitat: This lizard prefers shady areas on the forest floor or near the base of large trees, particularly ones with large buttresses holding deep leaf litter. The ground anole can live in virgin rainforest as well as overgrown cacao plantations; lowland to premontane to lower montane zones; and moist to wet to the rainforest.

Range: From eastern and southern Honduras down to central Panama, this animal can live from 2 to 1,500 m in elevation.

Physical Description: A small brown lizard, Ground Anole (Norops humilis) can have a broad dark band down its back and a lighter brown underside. The eyes are a bronze-speckled light brown. Males have a dewlap—a flap of skin on the throat—that is bright orange in this species. Other species have differently colored dewlaps. Females do not have a dewlap, although they may still have a patch of reddish skin on the throat; they might have a white stripe or row of spots on the back as well.

This lizard has a deep auxiliary pore or pocket in the armpit of each front leg. This pore is inhabited by parasitic mites.

Biology and Natural History: There are 21 species of Norops lizards in Costa Rica and 7 live in the southwestern region. This species, Ground Anole, is the most likely to be seen. An abundant, small, arboreal creature, Ground Anole is diurnally active and commonly glimpsed perching on tree trunks, tree buttresses, or deep leaf litter on the forest floor. This is not basking behavior like other lizards—this species is a thermoconformer and maintains its body temperature without relying on taking sun and shade. When perching, one often clings to the bark of a tree about 1.5 m off the ground with its head pointed down. When startled, this lizard will take an evasive route before diving under the leaf litter.

Much of the day’s energy is spent searching for prey. From its perch, the anole watches the leaf litter for small invertebrates, sprints after them, and returns to the perch. They may eat as often as once an hour. Nearly all of a female’s energy is spent looking for food. Males are more preoccupied with social behaviors, particularly defending territory and attracting females. Males, therefore, perch higher off the ground than females. An adult male spends several hours of his day showing off his dewlap. He stretches out the dewlap and bobs his head up and down. If this display coincides with a female’s entrance into his territory, the male will court her by flashing his dewlap just for her before chasing her across the forest floor. If another male is bold enough to intrude, the resident male’s display may escalate to chasing and biting. A male is fiercely territorial towards other males to ensure his access to the females (1 to 3) that overlap his territory. A female defends her territory solely to ensure food supply.

Rainfall brings an increase in courtship and reproduction, although these lizards may mate all year. A female will lay one large egg once a week through the rainy season, and once every two weeks in the dry. This ability to reproduce so often is one reason this lizard is prolific in the forests of Costa Rica. Few norops lizards live longer than a year. They are common prey for many larger animals, from larger lizards, vine snakes (and other serpents), to motmots and trogons. Young, small anoles become food for large invertebrates, such as mantids and katydids.

Diet: Norops eat quite the variety of arthropods, including but not limited to spiders, cockroaches, crickets, caterpillars, beetles, flies, termites, hemipterans, and centipedes. They do not like ants.

Height/Weight: An average total length for this species is 114 mm, the snout-vent portion of which is 40 mm. The tail is approximately 60% of its total length. Females tend to be smaller than males by a few millimeters.

You can read more about the various animals we encountered here. Please your own personal observations or encounters in the comments.

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