Officials in Australia's capital Canberra are expected to shoot dead more than 1,600 kangaroos in this year's annual cull - a big increase from 2013.
But according the Sydney Morning Herald around 500 of the marsupials will escape death because of an experiment to given them the contraceptive pill in a bid to control their numbers.
The move is designed to soften the blow for protesters angry at the increased numbers of kangaroos expected to be killed this year.
The government is working with local animal rights group Alphadog and is planning to tranquilize the kangaroos before giving them a fertility drug called Deslorelin.
Eight nature reserves around the capital were closed from Wednesday night and two shooters have been contracted out by the gunmen to carry out the cull.