The lizards basking on the wall beside your sun lounger and the near-mythical giant lizards of El Hierro are the same thing — members of Gallotia, a family of lizards that exists nowhere on Earth except these islands, and which on some islands grew to the size of a small cat. One of them was declared extinct, mourned in print, and then found alive on a cliff ledge in 1974 by a goatherd who had known about it all along.

The basics first. Millions of years ago an ancestral lizard arrived from North Africa, almost certainly rafting on floating vegetation, and found islands with no mammals, no snakes and nothing much that ate lizards. Freed of predators and left to fill roles that elsewhere belong to rodents and tortoises, it did what island animals often do: it got bigger, it started eating fruit and leaves, and it diversified into a different species on almost every island.

Then people arrived, and with them cats, rats and dogs. The large species crashed. What survives is a spectrum, from small, abundant lizards that will come and sit on your foot to a handful of critically endangered giants clinging to cliffs that cats cannot reach.

The ones you will actually meet

Every visitor sees lizards, usually within an hour of arriving. They are often called wall lizards, which is technically wrong and worth correcting, because the real point is more interesting: the European wall lizard does not live here. What you are looking at is a small member of the same endemic genus as the giants, found nowhere else in the world.

The lizard that came back from the dead

El Hierro once had a spectacular lizard, Gallotia simonyi, known from the sea stack of Roque Chico de Salmor off the island's north coast. Specimens were collected for European museums in the late nineteenth century, in the way Victorian natural history tended to do things, and the Salmor population was gone by the middle of the twentieth. Scientific opinion wrote the species off.

In 1974 it turned up alive. A small population was confirmed on the Fuga de Gorreta, a nearly vertical face below the Tibataje cliffs on the north side of the island — terrain so steep that the feral cats which had cleared the accessible ground could not work it. Local shepherds, reportedly, had never regarded the animal as mysterious in the slightest. The lizard was immediately one of the rarest reptiles in Europe, and it has been on life support ever since: a captive breeding programme, the lagartario at Guinea in the El Golfo valley, has released animals into fenced and cat-controlled enclosures, and the total wild population is still counted in the hundreds rather than the thousands.

The Guinea lagartario, next to the restored village museum in the El Golfo valley, is the only place most people will ever see one of these animals — and seeing a metre-long-looking lizard with a dinosaur's profile next to a photograph of a Victorian collecting trip is a strange, bracing experience. It sits naturally into a day taking in Manrique's clifftop viewpoint at La Peña and the rest of El Hierro's small list of sights.

Then it happened twice more

El Hierro turned out not to be a one-off. In 1996 a giant lizard was confirmed on Tenerife — Gallotia intermedia, the speckled giant — surviving on cliffs in the far west of the island around the Teno massif. In 1999 another was found on La Gomera, on the sheer face of La Mérica above Valle Gran Rey, having been presumed extinct for centuries. A claimed rediscovery on La Palma in 2007 remains disputed and unconfirmed.

The pattern is identical every time: a large, slow-breeding, ground-dwelling lizard wiped out everywhere a cat can walk, hanging on in a few hectares of cliff. Each has a recovery centre, each is legally protected at the highest level, and each is one bad introduction away from finishing.

Why the giants got so big

Island gigantism in reptiles usually reflects the absence of competitors and predators. With no native mammals to eat fruit and seeds and nothing on the ground hunting adult lizards, size paid: bigger animals can eat tougher plant material, survive lean seasons, defend territory and shrug off temperature swings. The archipelago's extinct species went further still — subfossil bones show lizards substantially larger than anything alive today, animals the Guanches hunted and ate, and whose remains turn up in the same middens as goat bones and shells.

The Guanches clearly ate a lot of lizard, and the pressure of a human population on an island with limited protein is probably where the decline actually began — long before cats.

The job they do: lizards as gardeners

Here is the detail that changes how you look at them. In a normal ecosystem, fleshy fruit exists to be eaten by birds and mammals so the seeds get carried and dropped somewhere useful. The Canaries have relatively few native fruit-eating mammals — effectively none of the usual suspects — so a striking number of endemic plants have ended up depending on lizards instead. Gallotia are seriously frugivorous; they eat the fruit, walk off and deposit viable seed, and studies of island shrubs have found lizard-passed seeds germinating better than uneaten ones.

Which means the collapse of the giant lizards was not just a loss of charismatic animals. It was the loss of the seed dispersal service that a slice of the islands' endemic flora evolved around, and some of those plants are now themselves rare, propagating poorly, on cliffs that lizards no longer patrol.

What is killing them, in order

  1. Feral and domestic cats. The single biggest factor everywhere. A cat colony fed by well-meaning residents at the foot of a cliff is a lizard extinction engine.
  2. Rats. They take eggs and juveniles, and they reach places cats do not.
  3. Habitat loss. Coastal building has removed most of the flat, sunny, scrubby ground the giants originally occupied.
  4. Introduced competitors. California kingsnakes, released or escaped from the pet trade, have established on Gran Canaria and eat lizards enthusiastically. Their spread is one of the most serious active conservation problems in the archipelago.

Please do not feed them

Lizards at miradors, picnic areas and restaurant terraces get fed constantly — bread, crisps, chips, biscuits. It is charming and it is bad for them. Bread is nutritionally useless to a lizard; fed populations become unnaturally dense, which spreads disease and parasites; and animals that associate cars and people with food spend more time on roads and car parks, which is where a surprising number die. If you want to watch them, sit still for five minutes and let them get on with hunting insects, which is far more interesting anyway.

Where to see them properly

Anywhere warm, rocky and sunny between about nine in the morning and mid-afternoon, and especially on dry stone walls and old lava. For the giants, the recovery centres are the honest option: the lagartario on El Hierro, and the reptile collection at Reptilandia on Gran Canaria, which keeps and breeds Canarian species alongside its international collection. The Jardín Botánico Canario outside Las Palmas is a reliable place to watch large stehlini going about their business among the endemic plants they help to propagate — the whole relationship, visible in one garden.

The bottom line

The Canaries have their own lizards, found nowhere else, running from pocket-sized to genuinely alarming, and the story of the big ones — collected to near-extinction, written off, found again on a cliff nobody could climb, bred back by hand — is the best wildlife story in the archipelago. It belongs alongside the rest of the islands' wildlife, and it is one more argument for spending a couple of days on the smallest and least visited island, where the whole drama played out.