Crayfish climbing trees

Author
by Blair
Publish date
22 November 2011
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Comments (5)

Roll over Drop Bears, there's a new, real threat in the trees of Wilsons Promontory - freshwater crayfish!

I reckon the best story from the recent Prom Bioscan for Parks Victoria is the discovery of freshwater crayfish climbing trees. Forget that a huge whale washed ashore nearby, forget the species found that had never been recorded from the area, and ignore all the hype around helicopters, it should be all about these partly arboreal crustaceans that are only known from the Prom.

Engaeus australis at Wilsons Prom. Freshwater crayfish Engaeus australis at Wilsons Prom.
Image: Adnan Moussalli
Source: Museum Victoria
 

Our freshwater ecologist Dr Richard Marchant was among the researchers to see the Engaeus crayfish on tree trunks and branches. He's worked around streams and rivers throughout Victoria for over 25 years and this is the first time he's seen this.

"It's a mystery why this mainly burrow-dwelling species would be in the trees when their food is on the ground. Clearly there's something new here that we didn't know about this Prom population. Unfortunately on this trip there wasn't time to find out more." said Richard.

"It has been only recently appreciated that from an evolutionary point of view insects are just 'flying crustaceans'. While tree-climbing crayfish suggest a hankering for an aerial existence among crustaceans there is no evidence that this is how they took to the skies and evolved wings!" said Dr. Gary Poore, another of the museum's crayfish experts, when he heard of the finding.

When I heard the story, my thoughts went immediately to the mythical Drop Bear - a furry clawed beast the size of a dog that, legend has it, lives in trees in Australia and drops down on people as they walk below. At only a finger-length long, perhaps 8cm or so, these little crustaceans wouldn't do much damage if they did drop on someone, but you still might be at risk of a nip from their tiny claws on your shoulder if they did.

Normally sticklers for poking around in rivers and digging burrows with mini mountains of mud as entrances, the aquatic Engaeus crayfish were seen in a remote area of the Prom off limits to the public, so rest assured – hikers and campers this summer will be safe.

Engaeus australis at Wilsons Prom. Freshwater crayfish Engaeus australis at Wilsons Prom.
Image: Adnan Moussalli
Source: Museum Victoria
 

The species in the trees was Engaeus australis and is only known to occur at Wilsons Prom. A few other Engaeus species also live at the Prom, but they also occur elsewhere in Victoria. Engaeus crayfish are related to yabbies (genus Cherax) and the larger Murray River and Spiny crayfishes (genus Euastacus). There are 22 Engaeus species that occur in several parts of Victoria, and about 10 other species of crayfish, together making Victoria one of the world's most diverse areas for freshwater crayfish.

Links:

Infosheet: Land crayfish

Engaeus australis on the IUCN Redlist

Australian Museum: Drop Bear

Comments (5)

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Jemma 26 February, 2013 17:24
My sister and I nearly stepped on one while climbing Mt Oberon this morning. We thought we were perhaps going crazy...
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Blair 24 November, 2011 11:25
Yeh it's pretty funny. I also had visions of them swinging through the trees on vines like Tarzan - I doubt that they are though. Some good theories too guys on why they might be moving off the ground. Let's see if we get other ideas...
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Rowena 24 November, 2011 08:14
Thats funny. Maybe they are planning their assault on the world. Very slowly.
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Sir 23 November, 2011 18:22
Maybe tree dwellers because of fairly recent floods?Adaptive behaviours ?
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Johnny 23 November, 2011 14:07
Interesting blog Blair! I'm wondering if this crayfish is mainly a burrow-dwelling species, could they be utilising the tree hollows as an alternative means to evade predation?
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