Stories from Christmas Island – The elusive Labuanium vitatum

Somewhere in Christmas Island resides a cryptic tree-climbing crab (Labuanium vitatum), commonly known as the white-stripe crab. With bright purple claws, a purplish body and neon-yellow eyes, it should not be hard to spot. However, even the most seasoned crab catcher has had no luck finding it.

The head of the museum, Prof. Peter Ng, is a man on a mission — to see the crab in the flesh, and obtain a fresh specimen. After all, he was the person who described and named it, with Dr. Peter Davie from the Queensland Museum in Brisbane, Australia.

Their paper, published in the journal Zootaxa in 2012, described the new species based on specimens that were collected on Christmas Island in the late 1970s and 1980s. Since then, no new specimen of Labuanium vitatum has been collected from Christmas Island for study.

Searching for the crab has proved to be a test of endurance and patience — with numerous unsuccessful attempts by Prof. Ng and his team since the year 2010.

“It has been a consistent failure,” said Prof. Ng.

Even the former chief ranger of Christmas Island, Max Orchard, who has lived on the island for more than 25 years, has not had much luck either. He has only spotted the crab just once, on the rainy night of April 15, 2010 near Anderson’s Dale, a seaside cavern on Christmas Island.

“I was walking back up along the stream in pouring rain and edging around a tree when I caught a glimpse of a crab with bright yellow eyes and brownish carapace on a tree about 1.5 metres above the ground,” recounted Mr. Orchard. Knowing the importance of having a fresh specimen, he tried to obtain it – but the crab vanished as he circled the tree to get a better view of it.

On the contrary, people who are not actively searching for the crab have ironically bumped into it in the strangest ways.

Australian Geographic photographer Chris Bray was on a safari photography recce trip to Christmas Island in May 2013, when he came across the elusive white-stripe crab and snapped a photograph of it. Unknown to him, that random photograph was the first taken of the crab in 25 years, since its last formal collection in 1989.

A few months later in February 2014, Taiwanese crab ecologist Liu Hung Chang and his team spotted three female white-stripe crabs releasing their eggs in the shallow waters of Dolly Beach. They stopped and took photographs of the crabs, but did not collect them.

Dr. Liu, a superb crab hunter in his own right who has collected tree-climbing crabs with Prof. Ng in Taiwan and Guam, searched the surrounding forest after seeing the females, but failed to see any others in the trees or anywhere else. When they backtracked to Dolly Beach to find the female crabs, they were gone.

“People who are not looking for it just happen to chance upon it,” said Prof. Ng with a hint of frustration, “It’s just fate.”

However, Prof. Ng is determined to find the white-stripe crab, no matter what it takes.

“It’s the thrill of the hunt,” said Prof. Ng, “Nothing is known about its biology and habits, and that’s why it’s so hard to find it.”

“Seeing it in the flesh gives you insights about its habits and behaviour, such as where it probably lives and how it moves, which cannot be gleaned from a dead specimen,” he added.

On the expedition to Christmas Island last September, Prof. Ng and his team searched every nook and cranny, including all the areas where the crab has been seen recently, in the hope to spot it.

LKCNHM Crustacean Curator Jose C. E. Mendoza, who was part of the expedition team, recounted Prof. Ng leading a 2.5-kilometre trek through thick vegetation to Dolly Beach, searching for the crab. The trek, which spanned over two hours, forgoing rest and lunch, was unfruitful.

“Food is a secondary concern when you’re after a rare crab,” said Dr. Mendoza.

Prof. Ng agreed. “When you’re after a rare crab, nothing else matters,” he said.

Unfortunately, during this latest expedition, Prof. Ng and his team were yet again unsuccessful in their search for Labuanium vitatum. However, he is still hopeful — after all, he successfully managed to find another crab, Geosesarma foxi, after 30 years of relentless searching. But of course, that’s a story for another time. 😉

References:

Ng PKL & Davie PJF (2011) Labuanium vitatum (Crustacea: Decapoda: Brachyura: Sesarmidae), a new Indo-West Pacific species of arboreal crab. Zootaxa, 2889: 35–48.

Ng PKL (2017) On the identities of the highland vampire crabs, Geosesarma foxi (Kemp, 1918) and G. serenei Ng, 1986, with description of a new phytotelmic species from Penang, Peninsular Malaysia (Crustacea: Decapoda: Brachyura: Sesarmidae). Raffles Bulletin of Zoology, 65: 226–242.