Many times folks accidentally poison wild animals, and it slowly builds up, along with the symptoms! My dad was very big into feeding wild birds all winter long, so much so, he bought seed in 100 lb bags! One morning he found a dead bird in the yard, couple days later he found 2 more. He blamed it on a new stray cat they started taking care of! Couple days later, he walked out into a nightmare of dead, dying, crippled birds all over the yard! Cause? He, without thinking was storing the seed in an empty chlorine barrel! As the levels built up, it became deadly for the poor birds! This took a couple months to build up to this level! Further down into the barrel, higher the concentration! To say the least, he was devastated!