Further explanation of my belief;
Iowa has had & still does have, plenty of feral dogs. A female coyote in heat. I believe would be "more" approachable from a male feral dog suiter. As compared to a prospective male coyote suiter, approaching a female dog in heat.
Dogs don't typically dig a den ie;[hole in the ground]. Although, I know of one litter. That has used a field drive culvert, to raise her pups.
Feral dogs are typically detested as much or more than even coyote. As they are well versed in being overly aggressive[especially in a pack or pr] to livestock & people. Farmers & everyone & their brother, [hunters]included. Shoot them often, when they are seen. The ole, [SSS]method.
A female coyote, with dog sired pups. Are IMO, more likely to get some, if not most of her pups, past the weened stage. While tending to her pup's alone.