More than 50 guinea pigs were dumped in bushland in Furnissdale near Mandurah on Tuesday.
Volunteers spent the afternoon scouring bushland for the dumped pets.
They recovered more than 40 of them.
Shocked witnesses said a car dumped the guinea pigs near a boat ramp.
A post on Facebook group Perth Have a Whinge brought the plight of the guinea pigs to the public’s attention.
One group member wrote that RSPCA WA officers told her they were happy for members of the group to rehome the pigs.
RSPCA WA has been contacted for comment.