Even having plenty of good water to drink the gnats will still hit every mud puddle, some even breed in moving water so that's not a block, Chuck Swann is a peninsula surrounded by Norris lake, in 2007 they lost a pile of deer, you couldn't drive any road there and not smell deer every 100y or less. I would bet we lost 50+% or more that year, a couple of years ago I killed a deer that was shedding his hoof's. Not all deer die from it and the ones who live get some immunity from it, not sure if it dissipates and the cycle starts again or what. It's tough to be a wild animal more so every year.