[boomboomsubban]

Having lived near mountain lions, it was hard to believe any could be hidden given how loud they are. Looking it up, their roars seem associated with mating or territory battles, so if there were only one it's possible it'd be quiet.

[giantg2]

Some of the reports I know of were around a captive lion. They said they could hear other lions calling (or responding) to the captive one.

[boomboomsubban]

That seems like a scenario where it'd be very easy to collect evidence, though looking it up there are numerous confirmed sightings in Eastern states so they probably did set up a recorder.

[giantg2]

The one about the calling was a long time ago, before cheap digital recording would allow. Most of the sightings these days are people misidentifying other animals (bobcats, house cats, etc). A few turnbout to be real but are escaped or migrated from the western states or Canada. I think the last true eastern lion was in the 1930s in Maine or something.