Not sure what your exact set up is, but they're very likely checking out the fence while also simultaneously being curious about your dogs. There have been cases of coyotes playing with or attempting to play with dogs. If your dogs are small and free-roaming the yard, the coyotes could also (I'm sorry to say) be interested in whether they could be snacks. But if they're bigger dogs, it's more likely to be simple curiosity. Also, if your fence is new, the yotes might be scoping it out to see what exactly it is.