A ''rat tsunami'' is infesting homes and threatening wildlife across Northland as a booming rodent population munches its way through anything in its path.

While there's nothing unusual about rats seeking warmth in people's homes during winter, pest control firms say this year's rodent invasion started earlier and in numbers far higher than normal.

The population explosion is irritating, and frightening, for home owners and is a cost and hassle for hospitality businesses. For native wildlife, it can be disastrous, as the rat plagues are linked to local extinctions of birds, bats and insects.

The cause is thought to be