It's definitely antifreeze. In Quebec, we use "prestone" in cars like in many other places in the world. Sadly, those are not only super toxic for animals, but also very tempting for them (it tastes sweet).
I am having mixed feeling now. I can't help but wonder if I could have done something more. But I've never seen any of that in the yard. I keep my eye open.
Though, now I know that non toxic prestone can be used. I also learned that in BC it's even illegal to use something else than non toxic one.
You would have never seen a girl becoming part of a cause faster than this. I will fight 'til my last breath to make sure that toxic prestone becomes history.