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| Green Iguana - Muelle, Costa Rica |
Costa Rica contains around 250 species of reptile (compared to only six in my native Great Britain). While many of these are snakes, which tend to keep themselves to themselves, the ones that you are most likely to encounter are certainly the lizards. Unsurprisingly, it's the big lizards that are the most obvious.
And there are some real whoppers. This blog post looks at the two most conspicuous groups - the large iguanas and basilisks.
Iguanas are the biggest of them all. Costa Rica hosts three species from the iguana family, of which two fall within the scope of this blog post. (The third, the Dwarf Spiny-tailed Iguana, is a secretive and endangered species only found in the extreme north of the country.)
Top of the tree, sometimes literally, is the Green Iguana (below - and at the start of this blog post). This is the archetypal iguana, indeed its scientific name is actually Iguana iguana. You cannot get more iguana-ish than that! They range across much of Central and South America and are native to some of the southern Caribbean islands, as well as having been introduced to Florida, where they're making a bit of a nuisance of themselves.
Some authorities have split the Central and South American Green Iguanas into two separate species, but I'm sticking here with the name used by international conservation body the IUCN.
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| Green Iguana - Sarapiqui, Costa Rica |
Green Iguanas are huge - adult males can exceed two metres in length. They can crop up across much of lowland Costa Rica, although are more likely to be encountered in protected areas. If you're in northern Costa Rica then the place to head for is the town of Muelle on the road up to Los Chiles. And specifically to the café next to the Puente de las Iguanas - which is a good sign.
Here, the Green Iguanas are an established tourist attraction: although wild, the café owners (and probably visitors) feed them (cabbage seemed a favourite), and we saw plenty hanging around. Green Iguanas are fairly strict vegetarians, although they do look capable of taking a chunk out of your thigh - if only they could be bothered to stop snoozing.
Other places to see Green Iguanas include the excellent rainforest reserve at Tirimbina (web link here). When we arrived there, one was perched high in a tree above the car park (below). They are excellent climbers.
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| Green Iguana in a tree - Tirimbina, Costa Rica |
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| Green Iguana - Muelle, Costa Rica |
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| Ctenosaur - near Chomes, Costa Rica |
The second group of lizards that I'm looking at in this blog posts are the Basilisks, of which there are three Costa Rican species. These are a bit confusing, as all have a broadly similar body pattern. It doesn't help that there is no consistency in their naming; these are species where it pays to keep an eye on the formal scientific names. For example, all three species have been called the 'Jesus Christ Lizard' owing to their ability to run over the water on their hind legs. I witnessed a juvenile do this on a small stream on the Pacific coast, and can vouch for the fact that it's a startling and effective method of escaping from potential predators. It doesn't help to distinguish between the three species, though.
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| Brown Basilisk - Tirimbina Rainforest Reserve, Costa Rica |
We only encountered two of the three species on our trip in November 2024, the first of which was the Brown Basilisk Basiliscus vittatus (above) in Tirimbina rainforest reserve. It was our guide Pat O'Donnell (website link here) who first spotted the lizard, which at first was doing an excellent job of blending in with the leaf litter on the forest floor. But perhaps as a result of being noticed, it decided to climb up onto a low branch allowing me to get this lovely portrait. This species is less associated with streams and watercourses than the other two, and can be found at higher altitudes - although it's still able to do the running-over-water trick if it needs to.
As in all three basilisks, Brown Basilisk has a prominent, pointed crest (or casque) on the head. But, unlike the other two species, adults have only a low crest on the back and a line of enlarged scales (looking like small spines), rather than a crest, along the top of the tail. Helpfully, it is only found on the eastern (Caribbean) side of Costa Rica's central mountain chain. Costa Rica is at the southern end of this species' distribution; heading north, its range extends into Mexico.
Both of my field guides (I've listed them at the end of this post) use the name 'Striped Basilisk' for this species (although Henderson also mentions Brown Basilisk). This is unhelpful, to put it mildly! As can be seen from my images, both this and the next species show prominent stripes. And, of course, both are mostly brown! In writing this blog, I have used the IUCN nomenclature for the sake of clarity.
So, let's look at basilisk number two:
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| Common Basilisk - near Golfito, Costa Rica |
This is the Common Basilisk Basiliscus basiliscus. We found this one basking on a tree trunk above a stream in the Golfito Wildlife Refuge on the Pacific coast. In contrast to the previous species, the Common Basilisk is only found on the western side of Costa Rica's central mountains, although its range extends into the Central Valley where suitable habitat is available. In contrast to the previous species, Costa Rica lies at the northern end of its range, which extends south into Colombia and Venezuela. These two reptiles provide a nice illustration of one of the reasons why this small country is such a diverse wildlife destination; it sits at the cross-roads where Central American species meet those from tropical South America.
Common Basilisks have a similar pointed crest or casque to Brown Basilisks. The key difference is that adults have conspicuous sail-like crests on both the back and the tail, as is shown in the one pictured below, which we also found in the Golfito area of Costa Rica's southern Pacific lowlands.
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| Common Basilisk - near Golfito, Costa Rica |
One of my field guides (Twan Leenders) refers to this species as the Brown Basilisk, which as I've explained above can only add to the confusion between these two reptiles. If you stick to the accepted international terminology it's a lot clearer.
Unfortunately we didn't encounter Costa Rica's third basilisk species - the Green Basilisk Basiliscus plumifrons - so I can't provide a photograph. What I can do is refer you to websites that do, such as its page on the IUCN Red List site (link) and this rather excellent article on the Tetrapod Zoology blog (link) which contains a feast of basilisk-related information.
Within Costa Rica, Green Basilisks are mainly found on the eastern (Caribbean) side of the mountains, although there is also a population on the Osa peninsula in the Pacific-side lowlands - which is the southern end of their global range. As this only extends as far north as Honduras, these basilisks have by far the most restricted range of our three species. The bright green colours is their main identification feature, along with bright yellow eyes and (in adult males) a generally more prominent crest (casque) on the head. But be warned: this species is also known as Emerald Basilisk and Double-crested Basilisk. Once again, I've used the IUCN nomenclature.
(For the sake of completeness, I should add that there is a fourth basilisk species that doesn't make it to Costa Rica. This is the Western Basilisk which is found in Colombia and Ecuador. They are green, have a rounded casque and serrated scale along the back. Sadly, I haven't encountered any on my travels.)
As an aside, it's worth noting that the basilisk has long been referred to in European literature as a mythical beast, going back at least as far as Roman times (for example the works of Pliny the Elder). It always seems to be some sort of reptile, but generally in snake rather than lizard form. Both its gaze and venom were meant to be lethal, its only weakness being (wait for it) the scent of a weasel. It popped up as a massive snake-like monster in Harry Potter and the Chamber of Secrets, where our heroes had to resort to a non-weasel-related method of basilisk disposal. None of which explains why the name has been bestowed upon a genus of entirely non-venomous Neotropical reptiles.
I'll leave you with a close-up of a particularly prehistoric-looking Common Basilisk that we found in a small area of remnant rainforest near Alajuela in Costa Rica's Central Valley.
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References & Websites:
Halliday, T. and Adler, K. ed (2002) The New Encyclopedia of Reptiles and Amphibians. Oxford: OUP
Henderson, C.L. (2010) Mammals, Amphibians and Reptiles of Costa Rica. Austin: University of Texas Press.
Leenders, T. (2023) Pocket Guide to the Amphibians and Reptiles of Costa Rica. Hellbender-Zona Tropical: Cornell University Press.
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