September 1, 2017

On remote Deserta Grande Island in the eastern Atlantic Ocean, a very rare and endangered spider is fighting for survival. A single valley on the island is home to the Deserta wolf spider (Hogna ingens), a stout and hairy burrowing spider found nowhere else on Earth. Deserta Grande is a small island among Portugal’s Madeira Islands. Deserta Grande once had a large population of these unique spiders, but habitat loss has reduced their numbers to an estimated 4,000 in the wild—a shockingly small population for an entire species of invertebrates (animals without backbones). The island, uninhabited by people, has fallen victim to an invasive grass that binds the soil so tightly that the spiders cannot burrow into it. This deprives the spiders of home and shelter, and their numbers have been greatly reduced. Help is on the way, however. At Bristol Zoo Gardens in the United Kingdom, Curator of Invertebrates Mark Bushell has begun raising his own Deserta wolf spiders, and he is part of a wider plan to replenish the spiders’ numbers on little Deserta Grande.

Mark Bushell shows off a tiny Deserta wolf spiderling at Bristol Zoo Gardens in the United Kingdom. Credit: © Bristol Zoo

In 2016, Bushell and Bristol Zoo veterinarian Richard Saunders traveled to Deserta Grande, where they collected 25 of the impressive black-and-white wolf spiders. The spiders are quite large, measuring up to 4 ¾ inches (12 centimeters) across, with a body size of 1 ½ inches (4 centimeters). Bushell and Saunders brought the spiders back to the zoo and have since successfully bred them. Tiny spiderlings, about 3/20 of an inch (4 millimeters) wide, emerged from tiny eggs, and the original 25 spiders have now multiplied to more than 1,000. The young spiders are incredibly delicate, however, and require committed and faithful care. In early 2018, Bushell will begin returning some of the spiders to their native island. Other young Deserta wolf spiders will go to other zoos to set up further safety net populations.

A conservation strategy to restore the native habitat on Deserta Grande is also in the works, a collaborative effort of the Bristol Zoo, the Instituto das Florestas e Conservação de Natureza of Madeira, and the International Union for Conservation of Nature in Switzerland. Working with local park rangers, the aim is to control or eradicate the invasive grass and restore the full breadth of the spider’s habitat. The Deserta wolf spider is listed as critically endangered, but it is not yet protected by any legislation.