"Crocs have been moving further south over the years."
Yes NJ and they will continue to do so. The male rules his own territory and the younger males move on or get killed by the larger one...usually daddy.
Whilst they have many eggs croc survival rate is small and maybe only one or two per year survive.
But one or two x one or two soon multiplies to be very significant and crocs will need to be culled with in the next 10 years although currently protected I believe in FNQ.
So what would happen to our eco system if Great whites no longer existed?
