These newly discovered 'pelican spiders' resemble pelicans for a good reason

January 15, 2018, 11 a.m.
Pelican spider, Eriauchenius milajaneae
Photo: Hannah Wood

If something seems strange about the tiny pelican pictured above, that's because it isn't a pelican. It's a "pelican spider," one of 18 newly discovered arachnid species from Madagascar that bear an uncanny resemblance to their namesake seabirds.

The 18 previously unknown species are described in a new study, published this week in the journal Zookeys. The spider above, Eriauchenius milajaneae, is known only from one remote mountain in the southeast of Madagascar.

Pelican spiders were introduced to science in 1854, when one of the bizarre-looking creatures was found preserved in 50 million-year-old amber. With a long neck-like structure and mouthparts protruding like an angled "beak," the comparisons to a pelican were probably inevitable. Scientists initially thought pelican spiders were extinct, but then live specimens were found a few decades later — and that's when the purpose behind their pelican-esque appearance became clear.

Pelican spiders, aka assassin spiders, evolved to look like this for good reason: They eat other spiders, and need a way to subdue their potentially dangerous prey from a safe distance. They're active hunters, skulking through the night in search of silk draglines created by other spiders. When they find one, they follow the silk to its source, sometimes plucking on the spider's web to trick it into coming closer. And once the unsuspecting prey is within range, a pelican spider will impale it with her long, fang-tipped "jaws" (actually appendages called chelicerae), as the Smithsonian Institution explains. She then uses her chelicerae to hold the prey away from her body, keeping herself safe from potential counterattacks until the captured spider dies (see photo below).

pelican spider with prey A pelican spider dangles its spider prey upside-down with its chelicerae after capturing it. (Photo: Nikolai Scharff)

"They're kind of like these little wolves in the forest capturing other spiders," study lead author and Smithsonian entomologist Hannah Wood tells National Geographic.

Although their diet of fellow spiders has inspired some to call them "cannibals," pelican spiders actually don't seem to prey on their own species. Wood says she has never seen one eat another pelican spider of any kind — even when she puts them together in a petri dish, they just politely give each other space. "If I had three, they'd make a triangle pattern," she says. "Four make a square."

These arachnids are "living fossils," Wood says in a statement, noting that they're remarkably similar to ancient species preserved in the fossil record, some of which lived 165 million years ago. And in addition to Madagascar, modern pelican spiders have also been found living in South Africa and Australia, a curious distribution that suggests their ancestors inhabited these landmasses when they were all still part of the supercontinent Pangaea.

Eriauchenius bourgini pelican spider Eriauchenius bourgini is a tiny species of pelican spider from the central eastern part of Madagascar. (Photo: Hannah Wood)

Pelican spiders are especially diverse in Madagascar, and that biodiversity was the main focus of the new study. It provides detailed descriptions of 26 different species, 18 of which had never been identified before, across two separate genera. Madagascar is famed for its strange and wide-ranging wildlife, but many native species are increasingly threatened by habitat loss due to deforestation. Researchers like Wood hope to fight that trend by shedding more light on the ecological legacy at stake.

Because they often live in remote and hard-to-explore habitats, only a few species of pelican spiders had been well-studied until recently. These new descriptions represent a big leap forward, but Wood says they probably still only scratch the surface. "I think there's going to be a lot more species that haven't yet been described or documented," she says. Unveiling them should help rally support for conserving what's left of Madagascar's ancient forests — and the unique wildlife that relies on them.

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