Brad, I wouldn't bother looking for dens right now. The pups are big enough to move on their own and the adults will have moved them to what are called rendevous sites. These are usually the areas of heaviest cover in the vicinity. Intra-seasonal variation in response rates to coyote vocalization is well documented and it is a given that during pup-rearing season the residents tolerate boundary intrusions and may only defend the core area of their territory. There are two types of response that you can expect to your howls ,depending on type of howl and location of howl, and they are movement and vocal.There are two types of movement response, approach and retreat, again determined by howl type and location. Research with radio-collared coyotes has shown that coyotes move and vocalize less in response to howls during this period, but when they are inclined to do so they vocalize more to group yip-howls than to group howls and they approach more to lone howls than to group vocalizations. Finally, they found that coyotes vocalized more and moved SIGNIFICANTLY more to howls produced within core territories, than to those produced along boundaries or outside territories. Any light bulbs flicker, Brad? You did real well on a similar post on Huntmasters, I'll bet you can pick this one up and really run with it. Ideas?