Residents of south-eastern Australia, especially of the Dandenong Ranges near Melbourne, may find round holes appearing on their lawns. Sometimes if left alone high chimneys of soil grow up from the holes. These structures are the work of land crayfish.
Land crayfish (sometimes called “land crabs” although they are not crabs) are relatives of yabbies, Murray crayfish and, more distantly, marine scampi. This group of Crustacea, the Astacidea, is recognised by the possession of a pair of equal large claws and two other pairs of smaller nippers. That is, three of the five pairs of legs are chelate.
A land crayfishPhotographer: Beverley Van Praagh. Source: Museum Victoria
The family Parastacidae, to which yabbies and land crayfish belong, is found only on southern continents but is most diverse in Australia. Land crayfish are one of 34 species in the genus Engaeus. Many of these species have a quite limited geographic range and some confined only to a single catchment.
Species of Engaeus are smaller than the more familiar and edible yabbies (Cherax destructor) and only grow to a maximum length of 120 mm. The carapace is more flattened from side to side than in a yabby and the abdomen (tail) is smaller and often bristly. So small in fact that they are inedible.
Land crayfish live only in damp environments which is why the hilly regions of eastern Victoria and Tasmania are home to most species. Here, they are found in swamps, near streams, eucalypt forests or rainforests. Their subterranean homes vary according to species and depend on their habitat.
Some species, such as Engaeus urostrictus, live close to streams. Here they build burrows down to 25 cm deep at the level of the water table. Water fills a small chamber at the bottom of the branching burrowing system covering half a square metre. As the crayfish excavates the burrow it brings soil to the surface and places the pellets around the entrance until a chimney grows up to 13 cm high.
A burrowing crayfish burrowPhotographer: Beverley Van Praagh. Source: Museum Victoria.
Other species, Engaeus tuberculatus for example, live on slopes away from streams. Their burrows do not reach the water table and the subterranean chambers rely on rain or seepage to fill with water. Exit burrows diverge near the surface where there are several openings. Waste from the excavations is brought to the surface where pellets of soil are deposited and run down the slope to form a fan of dirt.
The crayfish spends most of its time in the chamber at the bottom of its burrow so is rarely seen. Only at night does it become active bringing soil to the surface. It feeds mostly on decaying roots and buried plant matter, but sometimes eats worms or insects. Some species live alone but others are more communal.
Male and females usually come together to mate in spring and eggs are incubated attached to the tail of the female. Juveniles hatch in mid–late summer. After hatching they may remain in their parents’ burrow or migrate to start a life of their own.
Besides the crayfish is a very specialised fauna of aquatic crustaceans and insects, some not found in other watery habitats.
Because the burrowing crayfish’s habitat is threatened by land clearing and drainage, the species themselves are thought to be threatened.
Horwitz, P. H. J., Richardson, A. M. M. and Boulton, A., 1985. The burrow habit of two sympatric species of land crayfish, Engaeus urostrictus and E. tuberculatus (Decapoda: Parastacidae). Victorian Naturalist 102: 188–197.
Land crayfish are rarely seen during the day due to the fact that they spend most daylight hours in their chambers at the bottom of their burrows. They only become active at night bringing soil to the surface, which probably explains why you never see them!
Regarding the claws you have found crayfish are capable of deliberately discarding a claw for protection which will then gradually be regrown. This could be as a result of an attack from a predator or the fact that, during the breeding season, males have been known to fight for the right to breed. However the more likely explanation for the claws you have found is that crayfish, like all arthropods, shed or moult their outer skin every three to four weeks in order to grow. It is common for the crayfish to lose a claw during this shedding process which will then be regrown.
The holes are most likely from land crayfish, in this case probably Engaeus victoriensis. They don't always build chimneys, particularly when the soil and subsoil are very wet. They look like smaller versions of the common yabby and are generally harmless, so they are unlikely to cause any problems to your dogs, even if swallowed. Land crayfish are rarely seen on the surface so your dogs will not generally come in contact with them unless they are dug up. Although it's good to take measures to protect native wildlife from domestic pets, this species is common and their presence in your yard may be only transient until the soil begins to dry.
Hi Alicia - we referred this to our Live Exhibits Department, who have provided the following response for you:
The crayfish known as a 'yabby' lives in open freshwater bodies (Cherax destructor). What you have in your garden sounds like 'burrowing crayfish', probably in the genus Engaeus.
As their name suggests, they burrow into soil and live in tunnel systems where they feed on organic matter from the soil. They require water to breathe but will also leave the tunnel at night or in damp and heavily overcast weather.
Given their combined aquatic/terrestrial lifestyle and their specialised feeding techniques, it's best not to attempt to keep them in captivity.
Several species of burrowing crayfish are also threatened and are protected by law, so cannot be collected.
Hi June, The Victorian Department of Primary Industries Fisheries page on Freshwater Fish of Victoria: Yabbies at provides information on burrowing freshwater yabbies. Freshwater yabbies (Engaeus species) excavate extensive burrows in damp and wet soils and these are connected to the water table. This can cause water-logging of tree roots and undermine building foundations. This water-logging will be causing your trees to die. Part of their diet is rotting wood, detritus and root material which will further damage your trees.
Hi Julia, There are a number of animals that create holes in the ground. Museum Victoria has a free Identification Service. If you would like to send us a photo of the holes, we'd be very happy to identify them for you.
Hi Stuart, Land Yabbies are a good challenge to try to keep as pets. Some species are threatened in Victoria so they would be better left in their natural environment. Other species are not protected and can be collected from your own backyard, make sure you check with the government before you collect. There are a few main factors that will make keeping these animals a challenge. Firstly – they live in a well formed burrow in muddy substrates – you would very rarely see them as it will be important to leave their burrow intact. You need to keep that moisture level quite well balanced between wet and saturated so they don’t drown or dry out. Second problem is the food that you feed them, in the wild they like to feed on rotting decaying matter that may be hard to offer – I would give vegies and the occasional worm a go as an alternative food source. Lastly and what I think may be very important is they live in quite cool climates and keeping them in a house that heats up over summer may be a bit too warm for them. Here at the museum we have some species of spiders that get too warm in the ambient temperatures so we solve the problem by housing them in a constant temperature cabinet maintained at around 16C. Best of luck with these land yabbies. What may be best is to enjoy this group of animals in their natural environment – head out at night time and see if you can spot them tending their burrows and feeding. By watching them in the wild it will give you good ideas on how you can go about keeping them as pets.
We love receiving comments, but can’t always respond.
Hi Emily, these small invertebrates usually remain deep in their burrows coming close to the surface at night to deposit soil from their diggings. You may be able to go out at night and see if you can collect a specimen. I would imagine that they will probably move back down their burrows quite quickly if disturbed so catching one may be difficult. Be warned that while they are relatively small their pincers are powerful and capable of delivering a painful pinch. We don't know whether food tied to a piece of string may coax them to the surface where you can see them but you may want to try it depending on how keen you are and how much patience you have.
Hi Paul - Whilst we can perform identifications, Museum Victoria does not specialise in invertebrate control. Our entomologist suggests you might wish to investigate any environmental conditions that would be encouraging the crayfish, such as overly damp ground, but other than that, we suggest you speak with your local council for suggestions. All the best!
Department of Sustainability and Environment, Victoria Mallacoota Burrowing Crayfish Action Statement (PDF)
Department of Sustainability and Environment, Victoria Warragul Burrowing Crayfish Action Statement (PDF)
Department of Primary Industries, Parks, Water and Environment, Tasmania Tasmania's Freshwater Burrowing Crayfish webpage
Parks and Wildlife Service, Tasmania Freshwater Burrowing Crayfish Fact Sheet
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