"The Ridgeback is a breed of extremes," explains one owner, and the same could be said of the cast of Ridgeback aficionados Walden spent two years following. There are the breeders, determined to create the ultimate balance of "fronts," "ridges," and "top lines" that make for a perfect dog. There is the animal communicator, who says she can hear dog's voices, uncovering one Ridgeback's tragic hidden past.

There is Diane, the breeder cum Ridgeback sage, who warns that the dogs will "take over your world," "kick you off the couch," and "call for pizza." She dispenses blunt judgments on the show dog world -- "campaigning a bitch," she informs us, matter-of-factly, "is beating your head against the wall" -- but declines to evaluate her dogs on camera because their structure might be perceived as flawed. Agreement among breeders on the finer points of Ridgeback assembly, it seems, is quite rare.

Alongside Diane are the spirited owners who train their dogs for "lure coursing," in which they exercise their "prey drive" by chasing machine-pulled plastic bags around a field. "You get kind of wound up in that competition deal, it almost becomes a burden," says one lure coursing enthusiast, in a moment of self-reflection. "'Oh my god she's won 20 times in a row, if she doesn't win today I'm gonna be so depressed.' And then you think, 'Get out! Who cares? She doesn't.'"

Then there is the Ridgeback savior, a woman so devoted to rescuing unwanted dogs that it costs her a marriage. Although most of her rescues can be rehabilitated and placed in loving homes, a rare few are so traumatized that they must be euthanized. Walden's camera captures one such Ridgeback's heartbreaking fate.

Through all their owner's sweet obsessions, the film's dogs patiently endure, from the whelping box to their last breaths on the vet room floor. At turns hilarious and moving, Den Mothers is an intimate glimpse not just of a dog-loving subculture, but of how our passions can come to define our lives. "We're sort of like our dogs," as one owner observes. "I can't think of any wimpy people, truly wimpy, that could have a whole bunch of Ridgebacks."