Central Highlands Burrowing Cray Engaeus affinis (Smith & Schuster 1913)

Engaeus affinis from a communal burrow, Healesville, Vic
Engaeus affinis from a communal burrow, Healesville, Vic

This species is endemic to Victoria with a relatively small distribution known at this time (estimated extent of occurrence of approximately 200 km2). Found in the upper Yarra, Acheron, Yea and Big Rivers. An area roughly from Kinglake to Eildon to Jamieson to Noojee to Hoddles Creek. Central Highlands Burrowing Cray Engaeus affinis has been assessed on the IUCN Red List as Data Deficient. 

Engaeus affinis, Healesville, Vic
Engaeus affinis, Healesville, Vic

It’s a robust species and at many sites relatively abundant. Typically, it’s a communal burrower, both type 2 & 3 burrows with multiple surface entrances (20 or so) over a square metre. Both fans shaped entrances and chimneys. Surface openings descend into large central burrows. Central burrows are relatively large in diameter (150 to 200 mm), typically water filled and tending horizontal and descending and converging into a larger chamber.

Engaeus affinis, Badger Creek, Vic
Engaeus affinis, Badger Creek, Vic

Typically, the easiest way to capture is to excavate down to the water level, usually from 200 to 600 mm deep. Once water is found, wait, (patience required), larger males will come to investigate the disturbance and you can grab them, otherwise, every 5 minutes or so, shove your hand down the burrow and feel around in the water. If you are lucky and have good feeling in your fingers you should be able to grab one every 5-10 minutes. That’s the way we collected the specimens for this article.

Burrow entrance, Badger Creek, Vic
Burrow entrance, Badger Creek, Vic

Those from Healesville were in a yellow clay on the slope beside a creek approximately 1.2 metres above the creek water height (7 metres from creek bank) but had water at 650 mm in the burrow system. Those from Badger Creek were in a fine silty material in a seepage area in the tree fern forest with water only 100 mm below ground level and over 100 m from Badger Creek.

Engaeus affinis, Badger Creek, Vic
Engaeus affinis, Badger Creek, Vic

Happy Yabbying

Cheers

Rob

Lowland Burrowing Crayfish Engaeus quadrimanus

Also known as “The Mernda Land Yabby” Engaeus quadrimanus (Clark 1936) is a relatively widespread and locally abundant species. It’s a lowland species generally found under 250 m a.s.l. from just north of Melbourne, east along the Victorian coast to just before the NSW border. Engaeus quadrimanus has been assessed as Least Concern on the IUCN Red List.

Engaeus quadrimanus - note the burrow entrance behind
Engaeus quadrimanus – note the burrow entrance behind

This specimen is from the west of the range. Collected from the bank of Fish Creek a tributary of the Tarwin River crossing Meeniyan-Promontory Rd, Fish Creek, Victoria.

A very robust and adaptable species that usually has large colonies with the area being riddled with burrows. Typically, burrows are round to oval in shape and open with excavated material at the entrance (see photo). In some areas they can create a pelleted chimney but for many areas it’s just an open hole in the ground as the excavated material has been washed away with flood waters. Burrows are type 2 and relatively basic with only 2-3 surface entrances descending to a horizontal corridor then a deeper burrow to water table. Typically most of the burrow system is flooded and typically they are individual burrows with both males and females having their own burrows. One of the keys to the species is that they are intersexed so hard to determine which are males and which females. Breeding season is autumn and they can be found sharing burrows together then. The species is extremely active during flood events and uses the creeks to migrate and find mates, etc.

Fish Creek
Fish Creek

For a similar article on this species and images from populations further east, go to: http://www.austcray.com/2015/09/engaeus-quadrimanus-from-cann-river-victoria/

Cheers
Rob