Have you ever witnessed a possum talking? I have a pair that have visited my yard this year and while I was standing near my pond, feeding my koi just after dusk, I happened on to the pair who were foraging in my garden. I think they were hunting for slugs and other jucie delights and they didn't know I was nearby. They were wandering around about 5 ft. from each other and one was giving a repeated and constant "click, click, click", very subtle but enough to be heard 10 feet away.
I don't know if this was a mating call or idle chat, but until they spotted me, they were calmly foraging and walking around. After my presence was known, the talking stopped and they proceeded to find cover and an exit. I had expected a growl or warning call, but there were no other verbal sounds as they retreated.