Introduced snakes on snake-free islands are bad news. The California Kingsnake on Gran Canaria devastates the local lizard populations

Did you know that an introduced snake is having a devastating effect on the three endemic lizards of Gran Canaria? No, me neither but a paper published this month spells out what has been happening.

The California Kingsnake (Lampropeltis californiae) became one of the most popular snakes kept and bred in captivity from the 1970s. The story from Gran Canaria, where there are no native snakes, states that they were first found in the wild in 1998 after ‘the release or mass escape of individuals bred in captivity’. Since 2007 it has been found in first one, then two and then three distinct areas and various efforts have been made to control the population.

The research described in the new paper has estimated the effects of the snake’s presence by comparing areas where it is known to occur and those in which it does not (yet). There are three species of reptile on Gran Canaria, all endemic to the island. One, the Gran Canaria Giant Lizard, Gallotia stehlini, was reduced in numbers by 90% in the sites where the snake was present; the second, the Gran Canaria Skink, Chalcides sexlineatus, by 80%; the third, Boettger’s Wall Gecko, Tarentola boettgeri, by 50%.

Lizards are not the only prey. The endemic birds of the Canary Islands are also eaten as are feral mice and rats. Not surprisingly, efforts have been—and continue to be—made to eradicate the snake from the island.

This California Kingsnake I kept in the early 1970s. Kingsnakes are
famous for killing and eating other, often venomous, snakes.
I had to put this one in a vivarium holding a much heftier Royal
Python for a couple of minutes. When I returned I found the
kingsnake trying to constrict the python. Had I not intervened
would it have succeeded?

Gallotia stehlini is a magnificent lizard, reaching 80 cm in length.
I had a pair in the 1980s but passed them on to somebody with
more room. They breed readily in captivity and are omnivorous.
Photo: Juan Emilio from Las Palmas de Gran Canaria - on Wikipedia

Piquet JC, López-Darias M. 2021 Invasive snake causes massive reduction of all endemic herpetofauna on Gran Canaria. Proc. R. Soc. B 288: 20211939. https://doi.org/10.1098/rspb.2021.1939