The first dead wallabies were found with whitened eyes and foaming mouths in Trinity Beach, in Australia's Queensland state, by conservation group The Agile Project. The non-profit organization was notified of the deaths on August 21, when a football club found a handful of wallaby bodies on a sports field.
Since then, new bodies have been found every day. Several joeys -- baby wallabies -- have also been found inside their mothers' pouches, including one who tried to jump back into its dead mother's pouch.
One joey has died, with six still alive and in the organization's care.
"I've been a rescuer for 9 years and I've never seen anything natural like this," said Shai Ager, the founder of The Agile Project.
The rescuers are awaiting toxicology results, which should be delivered in the next few days, to determine the cause of death.
Potential causes include an attack by dogs, Ager said -- but many of the bodies didn't have wounds, making this unlikely. Or the wallabies could have been chased by dogs, and under stress, accidentally injured themselves.
Another possibility is that the wallabies were targeted or poisoned.
"They died a really sudden death, and it was horrible, painful," said Ager, who had been with several wallabies as they died.
Wallabies are commonly found in open woodland, grassland, and dense vegetation -- but in recent years, they have been pushed out of their habitat by housing developments and forced to take refuge in suburban backyards and next to highways. Ager said that some in the area "despise" wallabies, and see them as pests -- a common controversy across Australia.
Many in the local community, however, have been horrified by the deaths, with commenters on The Agile Project's Facebook page volunteering to do night watches.
One place they could look out would be the local sports fields.
Ager said a one-way gate, designed to keep wallabies out of the fields, had been tampered with every night this week allowing wallabies to enter the fields. The fields aren't dangerous for the wallabies but Ager said the disruption pointed to human interference as more dead wallabies showed up in the fields overnight.
Whatever the cause, the deaths are taking a toll on those who find the animals.
"It's highly disturbing as well, our rescuers are struggling to see so much death every day," said Ager. "We put so much work to save these animals, so mass deaths like this shatter us. It's heartbreaking."