Shining a spotlight on.. Wombats

18/08/2024

Wombats, in general, are not just stout, sturdy marsupials with muscular legs and sharp claws but they have a personality to match being strong and determined animals. They often come in conflict with humans when they build their burrows under houses, driveways or domestic stock routes out in the country. These problems can be solved by studying wombat behaviour and understanding their needs.

Wombat Habitat

Like most living things chasing self preservation, wombats build their burrows to escape heat and to hide from predators. As with any other thinking creature, they will pick a spot where it is easy to dig. Burrows can be upto 30 m long and several meters deep. The burrows diameter is the same size as the wombat itself, but they are agile and can turn around in them quite easily. Wombats dig with their front claws. They then push the loose soil backward with their hind feet and their rump as they back out of their burrow. A wombat can excavate several feet of a tunnel in a single night. One report says that a wombat dug through 6 feet of hard soil in an hour.

In another study it was also found that a wombat would dig with a single front paw for about 5 minutes, and then switch to the other paw. A wombat will use its incisors to cut through underground obstructions like roots.

Burrows that are being actively used can be identified by the cube shaped droppings of this unusual marsupial. Examination of the wombat's digestive tract shows that the elastic properties of the ends of their large intestines are capable of turning liquid excrement into cubical scat.

Photos courtesy NSW Dept of Planning and Environment

Wombat Burrows

Young wombats learn to tunnel by digging while in their mother's burrow. For instance, they may dig a small side tunnel on their own. Full sized burrows will feature multiple sleeping chambers, side tunnels, and more entrances.

Wombat burrows are well designed and well ventilated. Since temperatures underground are more moderate (less variable), the burrows help keep the wombat cooler in the warm months, and warmer in the cooler months. The burrow's design provides a "stable micro-environment" for the wombat by controlling the temperature, oxygen, and carbon dioxide levels.

In the winter, the burrow usually stays above 4 C ( 40 F). During this time the wombat will spend time outside in the daytime to graze or sun themselves.

Near the burrow's entrance, the wombat will often dig a shallow depression which is usually beside a tree or log. This area is used for resting or basking in the sun.

A wombat's burrow is sufficiently deep that it's fireproof. After a fire, a wombat can subsist on roots and bark until the grass regrows.

Underground, burrows will often branch and interconnect. They contain many entrances, side tunnels, and resting chambers. It is thought that a single wombat lives in a burrow; but, burrows could shelter pairs of wombats or family groups.

Wombat burrows are also used by rabbits (introduced to Australia and considered a pest), wallabies (small kangaroos), foxes, and lizards.

Interestingly, the complexity of burrows often depends on the species of wombats. The Bare-nosed wombat's burrows are branched, but appear to be less complex than those of the Hairy-nosed wombat that live in colonies that consist of a large, complex system of interconnected burrows. Many separate burrows often join together to form a central warren or crater. Smaller warrens may surround the main warren.

The best investigation of Bare-nosed wombat burrows was done in the early 1960's by a 16 year old schoolboy, Peter Nicholson. He would sneak out at night to explore the burrows, and crawled through many of them. He found that there was usually only one wombat in a burrow, but sometimes there'd be two. The burrows were often a network of tunnels, and one burrow was about 60 feet long. The wombats were often digging, altering or extending their burrows. They were also sociable and would visit each other's burrows.

Remaining populations are under continued pressure from land clearing, road mortality, disease and illegal shooting. These pressures may be acute for some local populations.

The burrows of the Northern hairy-nosed wombats occur in groups of up to 20 over an area of a few hectares (about 5 acres). Each burrow will have up to 7 entrances, with most having 2 to 3. The group of burrows is usually occupied by 4 to 5 wombats, with 10 being the most. For Northern hairy-nosed wombats, it's estimated that an average of 8 animals live in each warren. Even though they live in these interconnected burrows, they seem to spend most of their time alone.

Courtesy Wombania.com

Wombat characteristics

Wombats are mostly solitary animals, but overlapping home ranges can occasionally result in some wombats using the same burrow. Wombats are possessive about their particular feeding grounds and they will mark out these areas by leaving scent trails and droppings. These markings are prominently placed on rocks and logs around the boundaries. If an intruding wombat encroaches on another’s territory it will be discouraged through a series of snorts and screeches and at times physical aggression.

Breeding occurs year-round with each female typically producing one young. Wombats are seasonal breeders and may have dependent young in burrows from April to June. Juveniles stay in their mothers' pouches for 8 to 9 months, and are weaned at 12 months of age. Young wombats take up to 21 months to reach full independence and 2 years to become sexually mature.

Courtesy NSW Dept of Planning and Environment

Threats to Wombats

Both species of wombats, the Southern hairy-nosed and the Northern hairy-nosed wombats have experienced a population decline between 1870 and 1920, with the main influences being culling by agriculturalists, competition for food with introduced and feral species and predation. Threats to the northern hairy-nosed wombat include small population size, predation, competition for food, disease, floods, droughts, wildfires, and habitat loss. Its small, highly localised population makes the species especially vulnerable to natural disasters. Wild dogs are the wombat's primary predator, but the spread of rabbits and the actions of landowners have also contributed to their decline.

There have been two reports of male northern hairy-nosed wombats contracting a fungal infection caused by Emmonsia parva, a soil saprophytic fungus. It is likely that the northern hairy-nosed wombats are inhaling the infection from the soil.

Courtesy Atlas of Living Australia

Living with Wombats

It is possible to exclude wombats from continuing to use a burrow that is under a building by erecting a one-way sturdy door that allows the animal to leave, but not to return. Steel mesh may need to be buried around the entrance of the burrow to prevent the wombat from digging under the door. Steel mesh can also be used to cover an empty wombat hole on a dam wall to reduce further burrowing at the site.

Another effective measure is to use two electric wires at 15 and 30 centimetres above ground level to prevent access to an area.

Only inactive burrows may be bulldozed. Bulldozing an active burrow can lead to wombats being buried alive and suffering a slow and painful death.

Even if you have found an apparently vacant burrow, you must not fill it in without confirming that it is inactive. Burrow activity can be confirmed by placing sticks across each entrance and checking (every day for at least a week) if these are disturbed.

Remember that if you bulldoze an inactive burrow, the next wombat to enter your property may burrow in a more inconvenient place.

The trapping and relocation of wombats is not permitted. This is because wombats are territorial animals and if relocated, they are likely to be harassed or even killed by resident wombats.

Wombats may avoid the scent of predators. Placing a bag of organic fertiliser like blood or dog urine near the entrance to a burrow may temporarily cause the wombat to vacate the burrow. Also, these materials can be used to stop ‘scrapes’ and ‘test digs’ from becoming a new burrow.

Keep in mind, though, that a displaced wombat may subsequently burrow in a more undesirable location.

Wombats prefer to burrow in areas of vegetation and rocky debris. Land clearing has forced wombats to build burrows along creeks and drainage lines where vegetation still exists. Wombats are also often incorrectly blamed for causing erosion, which is more likely due to poor land management practices.

Planting trees and revegetating areas away from creeks can play a vital role in reducing wombat burrowing activity along creek beds. Retaining existing trees, logs and rocks, and establishing new areas of native vegetation encourages wombats to construct burrows in less fragile areas and reduces the risk of erosion.

What better way to end this than with a children's poem. Thank you for visiting.