Chris Dickman, an ecologist at the University of Sydney, said that his original figure of 480 million animals was conservative - and only included those in the state of New South Wales (NSW).
Speaking to Huffington Post, he said: "The original figure - the 480m - was based on mammals, birds and reptiles for which we do have densities, and that figure now is a little bit out of date. It's over 800m given the extent of the fires now - in New South Wales alone.
"If 800m sounds a lot, it's not all the animals in the firing line."
According to the news outlet, the original figure was around half a billion, but that only referred to the area of NSW and did not include bats, frogs or invertebrates. With those numbers included, Dickman said that the amount of dead animals exceeds one billion 'without any doubt at all'.
Although the bushfires continue to ravage huge swathes of the region, there are thankfully still a rare few positives to take from the situation, with volunteers coming together to try to do their bit to help.
A video that was posted on Reddit shows two cousins travelling around one of the areas worst hit by the bushfires, as they collected koalas and took the animals to safety.
The short video shows a car filled with koalas that have been rescued. It was filmed on Kangaroo Island, known as Australia's answer to the Galapagos Islands because of the rich biodiversity present there.
Around half of Kangaroo Island is thought to have been destroyed by the fires. It's estimated that more than 20,000 koalas have died, over half of the island's 50,000-strong population, but the two men made sure it didn't spell the end for at least some of them.
The two cousins in question are 19-year-old Micah and 18-year-old Caleb. While there's no exact figure on how many koalas they managed to rescue, they reckon that it's around 20.
Of that number, six of the marsupials were orphaned and two of them were mothers with children.
As well as rescuing them, Micah and Caleb are going to look after the koalas until they can return to the wild, and refuse to take them off the island because it would further hurt an already decimated local population.Featured Image Credit: PA