We are unapologetic Death in Paradise fans. So when we got to Guadeloupe, where the show is filmed, we did the film sites tour: the harbor at Deshaies, the police station, the beach bar, the whole fictional island of Saint Marie laid over a real one.
Somewhere along the way, our guide pointed out to sea at the little island that sits just off the coast, the one you see in the background of shot after shot if you watch the show. He mentioned, almost in passing, that the islands around Guadeloupe each had their own kinds of lizards. He called them lizards, sometimes geckos. All these different species, he said, on these little islands.
It was a throwaway line on a tour. It stuck with me anyway.
It turned out to be a real mystery, the kind the show would build an episode around, with a clue hiding in plain sight in the opening shots. The island in the background is Îlet à Kahouanne, about a mile and a half off Deshaies, uninhabited and protected. It covers about half a square kilometer, and it is home to one of the rarest lizards in the Caribbean, a species that lives there and on one neighboring rock and nowhere else on Earth.
And Harry, the station’s resident lizard? He’s CGI, but the anole researchers who have looked into it agree: if he were real, he’d be a Guadeloupe anole, Anolis marmoratus. Given that real anoles live about five years in the wild and Harry has been on the show for more than a decade, he is either immortal or on his third understudy.
So I did what a GIS analyst does with a mystery: I pulled the records and built a map. This is ANOLE-WATCH, and it turns out our guide was exactly right.
One lizard, many faces
Guadeloupe is really two islands pinned together by bridges: Basse-Terre, volcanic, wet and mountainous, and Grande-Terre, flat limestone. Around them sit smaller islands: Marie-Galante, Les Saintes, La Désirade, the two low islets of Petite Terre, and a scrap of rock called Îlet à Kahouanne.
For most of the twentieth century, scientists saw one anole across all of it: Anolis marmoratus. But it never looked like one species. In the Basse-Terre rainforest the males are apple-green shading to blue on the tail. On Grande-Terre one form has a sky-blue ring around the eye. On the northwest coast lives the “hairy anole,” with conical scales on its neck. In 1964 the Harvard herpetologist James Lazell sorted this riot of color into a string of named subspecies, many of them pinned to a single coastline or a single island.
Five of Lazell’s island forms are now treated as full species of their own:
- A. ferreus, Marie-Galante. The heavyweight: males grow to about 12 cm from snout to vent, nearly twice the size of females, with tall crests along the tail.
- A. terraealtae, Les Saintes. The name is Latin for Terre-de-Haut, the main island.
- A. desiradei, La Désirade, a long, dry limestone ridge.
- A. chrysops, Petite Terre. “Golden eye”: males have a red-gold ring around the eye and a bright yellow belly.
- A. kahouannensis, Îlet à Kahouanne and neighboring Tête à l’Anglais. Two rocks. That’s the whole range.
A channel a few kilometers wide can be as much of a wall as a mountain range.
Why islands make species
Caribbean anoles are to evolutionary biology what Darwin’s finches were to Darwin. On the big islands of the Greater Antilles, Jonathan Losos and colleagues showed that the same set of body plans evolved over and over, independently, on Cuba, Hispaniola, Jamaica and Puerto Rico: a twig anole, a trunk-ground anole, a crown giant. Evolution, given the same problems, kept arriving at the same answers.
Guadeloupe tells the other half of that story. Small islands usually hold only one or two anole species, so instead of many species splitting up one island, you get one lineage splitting up many islands. Each population, cut off by open water that a small tree lizard does not cross, drifts and adapts on its own: to rainforest on Basse-Terre, to dry scrub on La Désirade, to a windswept rock on Kahouanne.
And it isn’t only ancient history. After Hurricanes Irma and Maria in 2017, Colin Donihue’s team re-measured anoles they had surveyed on two islands in the Turks and Caicos just days before the storms. The survivors had bigger toe pads and longer front legs. The hurricane had done the selecting, in a single afternoon.
Mapping them
ANOLE-WATCH pulls every georeferenced record of all six species from the Global Biodiversity Information Facility: museum specimens, field surveys, and a flood of iNaturalist sightings. A GitHub Action refreshes it every Monday.
The first run brought in 2,914 records. The mainland A. marmoratus dominates with more than 2,000. The Kahouanne anole has 21. That’s every usable record of it in the world’s biggest biodiversity database.
See the map. Every record plotted, colored by species, with a card for each lizard, plus an explorer map where you can click any dot through to its GBIF record.
Read the story map → Explorer map → GitHub →The data had its own mysteries
This is the part I enjoyed most, because it’s my day job.
Every species, even the ones confined to tiny islets, had a little cluster of records at the same spot: 16.20°N, 61.54°W, near Pointe-à-Pitre. No lizard lives on all six islands. That point is where records land when the only locality anyone wrote down was “Guadeloupe.” Sixty-nine records were parked there.
Then the golden-eyed anole of Petite Terre turned up on Les Saintes, 60 km away. Eleven records of it. The answer is a place-name collision. Petite Terre’s two islets are called Terre-de-Haut and Terre-de-Bas. So are the two main islands of Les Saintes. Somewhere along the chain from a collector’s label to a database, “Terre-de-Haut” got georeferenced to the wrong one.
What I did about it: nothing gets deleted. ANOLE-WATCH flags records parked on the centroid, and island species recorded far from their home island, then leaves them out of the counts. The explorer map still draws them as hollow circles, so you can see exactly what was set aside and why. Ninety-six of 2,914 records were flagged.
That matters most for the rarest species. More than half the raw A. chrysops records were in the wrong place. A naive map would have shown Petite Terre’s golden-eyed anole living on three different islands.
A lizard found only on two small islets, placed on the wrong island by two identical names.
What comes next
The next layer comes from orbit: Sentinel-2 imagery classifying forest, scrub and bare rock on every islet, to ask what kind of world each lizard has been shaped by. Is the Marie-Galante giant a product of flat limestone forest? Is the golden-eyed anole’s scrub on Petite Terre as open as it looks from the air?
The lizards have been answering those questions for a very long time. The map is just starting to ask.
Go deeper
Anoles are one of the best-studied groups of animals on Earth, so there is a lot to read. Start with the podcast.
Does Evolution Repeat Itself? — Scientific American Science Talk, 27 September 2017. Jonathan Losos on contingency versus convergence, with Caribbean anoles as Exhibit A. The companion to his book Improbable Destinies.
Anoles Get a Grip — EarthDate, episode 182, 16 October 2020. A short one on hurricanes and cities selecting for bigger, stickier toe pads.
Lazell, J.D. (1964). The anoles (Sauria, Iguanidae) of the Guadeloupéen Archipelago. Bulletin of the Museum of Comparative Zoology 131, 359–401. Open access. — where the island forms got their names.
Losos, J.B. & Ricklefs, R.E. (2009). Adaptation and diversification on islands. Nature 457, 830–836. — the big-picture review of why islands are evolution’s laboratories.
Donihue, C.M. et al. (2018). Hurricane-induced selection on the morphology of an island lizard. Nature 560, 88–91. — natural selection caught in the act. The behind-the-paper post is a great read too.
Losos, J.B. (2009). Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles. University of California Press. — the reference book, if you want everything.
Anoles on TV: Harry the Lizard in Death in Paradise — Anole Annals. Yes, the anole researchers have weighed in on Harry.
The Anoles of Guadeloupe — Anole Annals. A field tour of the A. marmoratus color forms, with photos.
The Reptile Database — species accounts for A. chrysops, A. kahouannensis and the rest.
If you only read one, make it Lazell’s 1964 monograph. It’s free, it’s the origin of every island name on the map, and it’s a reminder that a lot of modern biodiversity data starts with one person, a notebook and a boat.