i had a show bred whippet, 191/2 ats 26 pound, that took foxes single handed, always had them in a throat hold by the time I got there, only time he was bitten was when another dog was present and stopped him getting his usual hold, most modern working whippets are bigger and heavier now days, 30 pound plus and should be well able of taking the occasional fox.i don't think a whippet taking a fox is that usual.