Well, the paternity tests are in and the results are not looking very good. It turns out that arctic foxes are not monogamous after all. When resources are abundant, populations of breeding pairs expand and the female arctic foxes mate with other males, cheating on their partner. In fact, researchers have found that with abundant food (in this case geese) up to 31% of the pups in a population were the result of extra-pair relations. They hypothesize this genetic flow is important for maintaining genetic diversity.
C Camerona, D Berteauxa, F Dufresneb. Spatial variation in food availability predicts extrapair paternity in the arctic fox. Behavioral Ecology. 22 (6): 1364-1373, 2011.