Malpelo on land

A true land crab that lives its adult life out of the water, sheltering in cracks and hollows between the rocks and coming out to feed. Carapace widths run from 5 to 82 mm. It is an opportunistic omnivore and eats more or less whatever is available: plants, guano, dropped fish, dead birds, and other crabs.

Numbers: A mark-and-recapture study that tagged 909 crabs put the island population at roughly 833,000, at densities of about 0.41 adults and 0.55 juveniles per square metre. They are spread across most of the main island and avoid only the steepest faces. That makes the crab the hinge of the land food web: it converts bird waste into crab, and the galliwasps eat the crab.

Breeding: Like other land crabs it has to return to the sea to breed. Females release their larvae on high tides around the new moon, at least during the rainy season.

A note on the name: It is malpilensis, not malpelensis — an odd spelling that goes back to Walter Faxon's original 1893 description and has stuck. You will also see it under its old genus, Gecarcinus malpilensis.

GBIF · López-Victoria & Werding 2008, Pacific Science

A heavy, glossy, almost snake-like lizard reaching about 50 cm and 500 g, black with hundreds of small white dots. It is the flagship animal of the island's land ecoregion and, along with the crab, the thing most visitors have actually heard of.

How it feeds is the remarkable part. Groups of galliwasps gather at the booby colonies and mob adult birds coming back from the sea, harassing them until they regurgitate their catch — food meant for their own chicks — which the lizards then take. They also eat crabs, eggs, dead and dying chicks, carrion and guano. For a lizard, that is a very strange living.

They give birth to live young rather than laying eggs, and they can swim short distances, which is unusual enough to invite comparisons with the marine iguana, though it has nothing to do with how they feed. They are common on the island and listed as Least Concern.

Wikipedia · One Earth — Malpelo Island xeric scrub

A grey-brown anole, the males 89–114 mm from snout to vent and the females a little smaller at 79–84 mm. Females and some males have spotted heads; the larger males carry a black nuptial crest. It lives on moist rock and in the scrub, from the waterline up to the summit at 376 m.

It eats mostly insects, beetles above all, and will take young land crabs and probably booby eggs. Its own main predator is the galliwasp.

Worth knowing: Most anoles are famously territorial, and this one is not. Malpelo anoles share perches and feeding spots without much argument, and their territories overlap freely — a difference researchers link to living on a small island where the food arrives in unpredictable pulses from the sea.

Wikipedia · López-Victoria et al. — ecology of the Malpelo lizards

The least known of the four, and the hardest to find: it is nocturnal, spends the day wedged in cracks in the rock, and reaches about 15 cm. Its name comes from its markings — roughly eight broad chocolate-brown bars running across the body from the back of the head to the base of the tail. It eats insects.

It was described by Huey in 1975 and is known only from Malpelo. The IUCN lists it as Least Concern.

Reptile Database · López-Victoria & Rozo — notes on its ecology