Women mostly, I expect. Bored housewives with big dogs.
If you've seen the behaviour of a excited labrador or retriever dog, it doesn't take much of a leap of imagination to realise it wouldn't be difficult to get their consent!
In fact, I remember someone posting a link on here a year or so back of the attempted "rape" of an innocent granny by a randy golden retriever. The skill with which he manipulated her into the required position made me think that this wasn't his first two-legged partner! (Maybe his owner was a bored housewife!?). The only thing he didn't do was lift her skirt! Had he done so, or had the woman been a willing partner in this act, the outcome would have been just what he was after.
If this took place somewhere other than Germany, I wonder who would be prosecuted, the woman or the dog?