>Dogs will also drink radiator antifreeze.
They do. So do young children. Do you find antifreeze (a sweet, purified
single substance without any hint of toxicity in it's flavor) in the natural
environment? I don't know of any antifreeze trees. It would be easy to name
quite a few isolated substances that taste and smell good but are also
toxic.
There is the thought that animals are programmed to go after what tastes
good. Rabbits seem to most enjoy sweet and bitter flavors, for example. It
would stand to reason that dogs (and wolves, and people) also consume what
tastes good. This behavior, in general, works in the natural environment. It
falls apart when purified substances are introduced. Glycerin is also sweet
and non-nutritive, though not as toxic.

>Dogs are clearly domesticated enough to have "unnatural" behavior.
We are clearly "domesticated" enough to eat refined foods, minimally tested
pharmaceuticals, food additives, and too much food in general, though they
produce undesireable effects. I wouldn't necessarily call it unnatural. It's
perfectly natural behavior. It's the substances and the environment that are
off.

>Do wolves eat berries?
Yes they do. They also eat leafy greens. This information is easy to find by
watching wolf documentaries, or reading a book on them. There are even a few
species that produce berries that are named "wolfberry" or something
similar, depending on species, because wolves prefer them.