 Hundreds of thousands of native Australian animals such as koalas and kangaroos have been killed in bushfires that have burnt across southeast Australia in the past two weeks, wildlife officials said on Monday. The bushfires, which are still burning in three eastern states, have been so big and intense that wildlife officials fear some species may become extinct as the fires destroy large swathes of animal habitats. "The fires are so devastating and moving so quickly that animals just don't have a chance to get out of the way," said Pat O'Brien, president of the Wildlife Protection Association. "Because of the heat and the fireballs that are happening the animals are just bursting into flames and just being killed even before the fire gets to them because its so hot," O'Brien told Reuters on Monday. Koalas and possums, which instinctively climb to the treetops for safety, would have had no chance of escaping the blazes, and kangaroos and bush birds would have been unable to outrun the fast-burning fires, he said. This meant a very real threat of seeing species unique to the burnt-out areas, such as frogs and birds, becoming extinct, O'Brien said. "These fires will directly contribute to the extinction of a number of species and we won't know the full effects for another 10 years," he said. "It takes 100 years for some animals to move back in an area, if there's any available to move back in. In the case of gliders, which are rare and endangered anyway, they may never come back ... they'll just go into extinction." Fires in Victoria, Tasmania and New South Wales states have burnt more than 847,000 hectares (2 million acres). The worst fires are in Victoria where more than 4,000 firefighters are battling four large blazes which have blackened 750,000 hectares. Police say more than 30 homes have so far been razed. Firefighters said on Monday cooler conditions had eased the bushfire threat in the three eastern states but fires were still burning out of control. In Western Australia, a fire which has already destroyed 12,000 hectares is blazing unchecked.  Wildlife officials said a major factor in the high animal death toll was the predominance of eucalyptus trees in burning bushland. The oil in the trees explodes into flames. "As soon as they get hot the eucalypt oil catches on fire and then it just goes like a steam train," said Hugh Wirth, president of Victoria's Royal Society for the Prevention of Cruelty to Animals (RSPCA). "If you've got a crown fire, in other words the fire is going through the treetops ... those fires move extremely rapidly and the animals just can't outrun them, not even kangaroos." Wirth said he believed close to 100 percent of the animals in the path of the Victorian blazes had been destroyed, with wildlife rescuers reporting no survivors. "Surviving wildlife usually comes out of hiding within three to four days of a fire going through the area and unfortunately we're not getting any reports of any survivors so far," he said. Wildlife officials fear the animal death toll will rise even further as those animals which survive the fires may now starve to death in the charred landscape. "Even if they do survive the fires there's starvation issues beyond that. It's just another nail in the coffin of the species which may have survived otherwise," said O'Brien. Australia faces extreme fire danger this summer due to a drought. Bushfires are a regular feature of the summer and, over the past 40 years, they have killed more than 250 people. Scientists fear climate change will bring more frequent higher temperatures and less rainfall.