pretty uncommon, and has a pretty reasonable explanation.
What is surplus killing? Why do wolves do it? Do wolves kill for sport? This post aims to answer those common wolf questions.
wolf.org
In the book, Dr. Mech wrote that “it is rare for wolves to kill wild prey in surplus. All cases of surplus killing of wild prey reported for wolves have occurred during a few weeks in late winter or spring when snow was unusually deep. In 30 years of wolf-deer study, Mech observed this phenomenon only twice, and in forty winters of wolf-moose studies, it was seen in only three winters (Peterson and Allen, 1974; R.O. Peterson, unpublished data).”
“Presumably what happens when wolves kill more than they can immediately eat is that they respond normally to a situation that is drastically different than usual – prey are highly vulnerable, rather than being especially hard to catch. Programmed to kill whenever possible because it is rarely possible to kill, wolves automatically take advantage of an unusual opportunity.”
I remember reading about wolves a while back and their hunting success rate is incredibly low. So kind of makes sense they go full retard when there's a buffet in front of them.