How do you know when a species is extinct? It’s a tricky question and one which Re:wild are interested in having run their Search for Lost Species program for the last five years. In that time, they’ve found eight of their "25 most wanted" lost species to science, demonstrating that species aren’t always as lost as they first seem.

One such species that “returned from the dead” was the Somali sengi, also known as the elephant shrew, which pulled off the comeback of the (half) century in 2020 when it was found after being lost to science for 50 years. Rediscovered in the Horn of Africa, the mouse-sized, wibbly-nosed shrew was thought to be lost after its last sighting in 1968.

Hoping for further successes such as this one, Re:wild is updating its 25 most wanted list to include eight new little-known and unusual species that will replace those who were found. The new additions span 17 countries and have each been lost to science for at least 10 years, some considerably longer.

"The closest a fish could get to the Michelin Man” has now joined the list, says Re:wild, a fish that’s the only known catfish in the world to be packing rings of fatty tissue along its body. The portly runaway is aptly named the fat catfish and has been missing from Colombia since 1957.

Hunting with hearing might help Re:wild track down the South Island k?kako bird from New Zealand, which hasn’t been seen since 2007. This bird has a distinctive call similar to that of a flute. New Zealanders: ears at the ready.

A tapdancing spider joins the notable new names on the list, known as the Fagilde’s trapdoor spider from Portugal who’s been MIA since 1931. This elusive arachnid is something of a performer, shuffling its feet in an effort to win a mate. Trapdoor spiders perhaps present an unusually complex lost species owing to the fact they reside in horizontal traps that are designed to go unnoticed by passing prey.

"Recovering the South Island k?kako, one of New Zealand’s ancient wattlebird species, is a duty of care we have to ourselves as Kiwis and to global biodiversity," said Nigel Babbage, chair of the South Island K?kako Charitable Trust, in a statement. "Our immediate priority is to determine where it might survive in our vast southern forests. We want to restore its transcendently beautiful calls to the chorus of native birdsong."

The search isn’t specific to animals either, with the big puma fungus from South America and the Pernambuco holly from Brazil. The fungus hasn’t been seen since 1988, while the Pernambuco holly has been on the lamb for two centuries, last seen in 1838.

“When we launched the Search for Lost Species, we weren’t sure if anyone would rediscover any of the wildlife on our most wanted list,” said Barney Long, Re:wild’s senior director of conservation strategies and a Search for Lost Species program lead, in a statement.

“Each new rediscovery has reminded us that we can find hope in even the most unlikely situations and that these stories of overlooked – but fascinating – species can be a powerful antidote to despair.”