....my take is somehow they were poisoned.

I was thinking it could be the water, as you said, I always look for ducks. Have not seen any in a while there. Something is up though. I don't think they died by natural causes.

That picture has EHD written all over it. It is all to common of a sight here in West Central Indiana in recent years. EHD is transmitted from the midge fly. Areas with high deer densities get hit the hardest.Typically the worst outbreaks occur after flooding as the Midge fly lays it larvae in the mud flats that the receding waters leave behind. This will also occur in severe drought conditions as the water evaporates and leaves mud flats behind.What have your weather conditions been in recent weeks? While scouting this past summer my son and I found a total of 12 dead deer at various ponds on this particular farm. Several weeks back I watched a show that Micheal Wadell was hosting and it was about the massive EHD kill on the Milk River in Montanna.It was very sad to say the least. They found deer after after deer lying dead upon the banks and in the water. While filming a buck came to the river and waded in and started swimming in circles until he became to exhausted to carry on and drowned. The worst about this disease is that there is nothing they can do about it.

the water was full of big tadpoles. If there is poison in the water then it would have to affect deer but not frogs. If there is any substance that could do that. I doubt the ponds are poisoned.

Frogs are one of the 1st species to show signs from polluted water.
Be careful poking around there you don't fall in yourself Catman. Seems drowning is the most likely cause. Someone should notify county officials of the danger.

Im betting some type poison somewhere as well, may not be the pond water, may just be where they ended up dieing!