The discovery of four headless deer carcasses has prompted Wollongong police to urge residents to dob in anyone illegally hunting the animals.
The bodies have been found in recent weeks on Sutherland Shire Sports Flying Association grounds near Helensburgh.
In a separate incident, police charged an 18-year-old Berkeley man with a string of offences after he allegedly shot two deer in suburban Figtree, near Road, using a .223 rifle.
Police will allege the man, due to appear in court on September 10, gained permission from a property owner under the premise he would be using a bow and arrow.
It will also be alleged the man was operating without a deer shooting licence, and had trespassed into a neighbouring property when he killed the animals.
Rusa deer in the Illawarra traditionally become more noticeable during winter as they enter their rut, or breeding season, and Wollongong City Council estimates there are about 4000 of them living within its local government borders.
However, the council noted in its latest Deer Pest Management Plan that "no accurate estimate of deer abundance currently exists for the Wollongong LGA".
Wollongong police licensing officer Senior Constable Wayne Hadfield said illegal deer poaching was common, but it was difficult to catch offenders.
"It's difficult to aid the public to identify the vehicles because they just see it and don't realise ... [they] need to get the registration," he said.
"I really don't have a problem with guys shooting deer as long as they've got the appropriate licence and the appropriate authorisation," Snr Const Hadfield said.
In July, the NSW Department of Primary Industries disbanded the Game Council and temporarily suspended licensed hunting in State Forests after a review found the council was conflicted in its position as hunting regulator.
There are few private properties within Wollongong City Council boundaries where hunters can legally shoot deer with permission of the landholder.