The state government is investigating after a jarrah tree estimated to be about 300-400 years old was felled just south of Bunbury in an apparent act of environmental vandalism.

In Western Australia, clearing native vegetation without permits is illegal and both Main Roads WA and the local shire have confirmed they did not chop the tree down nor authorise anyone else to.

The Gelorup jarrah was felled by an unknown party without warning or explanation.

The Department of Water and Environmental Regulation is now looking into the felling of the tree, which contained several large hollows of the type that only form in trees more than 150 years old.

These hollows are habitat for threatened black cockatoos and also for the western ring-tail possum, the conservation status of which was in May lifted from vulnerable to critically endangered — the penultimate step before extinction.