Wombat rewilding project lifts numbers but hotter weather, traffic has them staying put
The wombat rewilding program began in early 2015. (Supplied: Greater Sydney Local Land Services)
A wombat rewilding program is showing an increase in population numbers, but weather trends, weeds and road dangers are hindering their movement.
What began in 2015 with 13 orphaned wombats placed back into the wild at a biobank site at Mulgoa in western Sydney, has grown to an estimated 19 animals.
“To have a nice little population established and doing well and settled is quite exciting really,” said Peter Ridgeway, a biodiversity land officer with the Greater Sydney Local Land Services.
The adult marsupials were initially homed at artificial burrows, but since the project’s inception they have dug around 30 wild burrows of their own.
Wildlife cameras have recorded their movements and volunteers have been sorting through the images and data.
“We’ve had 106,000 photos taken on site, so it’s a huge amount of information that we’ve collected,” Mr Ridgeway said.
Wombats feed at night but tend to stay inside burrows if evening temperatures stay above 30C. (Supplied: Greater Sydney Local Land Services)
Animals feeling the heat
But the cameras’ temperature sensors have also recorded a worrying trend.
“Over 30 degrees Celsius the wombats here at Mulgoa simply don’t leave the burrow at all,” Mr Ridgeway said.
“We’ve had quite long periods where the nights didn’t drop under 30 degrees and so the wombats simply don’t come out to feed.”
Mr Ridgeway referred to Bureau of Meteorology records that showed since 1970 the number of days above 35C in western Sydney have more than doubled.
“So we are quite concerned that the wombats are suffering with urban heat island effect in western Sydney.”
Wallaroos have used vacant wombat burrows to train joeys to take their first hops. (Supplied: Greater Sydney Local Land Services)
Weeding out problems
Ecologist Linda Brown is part of the Cumberland Land Conservancy, which manages two properties close to the biobank site where the wombats were rewilded.
She said wombats from the Blue Mountains National Park had started to appear at one site and the wombats from the biobank had been seen entering the other.
Now she’s witnessing the benefits they’re having on the surrounding environment.
There has been an 80 per cent increase of other wildlife around wombat burrow sites. (Supplied: Greater Sydney Local Land Services)
“Wombats are herbivores, they like to eat grass and bark, and what they do, they keep the area quite open, also from weedy species,” she said.
“They create an area which is called a green pick, which has really good nutritious grass and other herbivore species profit from that.”
Mulgoa Valley Landcare volunteers have been removing weeds including lantana, privet and African olive, which then restores the ground feed and accessibility for the animals.
But Ms Brown said more needed to be done to preserve what’s left of the natural landscape from farming and urban development to improve the natural habitat.
“Sadly there is only 5 per cent left of the Cumberland Plain Woodland and a lot of those areas don’t have wombats in them because there’s no connectivity.”
One of the wombats has discovered a drainage culvert to safely travel beneath a major road. (Supplied: Greater Sydney Local Land Services)
Bypassing road dangers
One of the hazards inhibiting the wombats’ migration is the traffic along a major nearby road.
Ms Brown said the current dry conditions were forcing many animals to the roadside to find feed.
Three dead wombats were recently recorded along the route, but there are signs others had found a way beneath it.
One wombat has discovered a drainage culvert and is using it to access greener pastures on the other side of the road, Mr Ridgeway explained.
“It’s quite exciting and it shows what we can do to try and reduce roadkill.
“We’ve started to map all the roadkill across a few sites across western Sydney and then having a look at what solutions we might be able to retrofit onto these roads to reduce that risk.”