Zoo

"One day we did a turkey and a ham." So says the man known only as 'H' (and played by an actor) in Robin Devor's Zoo. He is describing the elaborate dinner parties that he would hold for weekend guests at his farmhouse in Enumclaw, Washington State – but given that this is a film about bestiality, it is difficult to miss the double-entendre, intended or unconscious, in his words.

In fact, this mildly comic moment turns out to be a rare exception, in a film that otherwise treats its subjects with utter seriousness. The trigger for Zoo, outlined bluntly in rolling text at its beginning, was the death, in 2005, of a Seattle man whose colon had been accidentally perforated during anal intercourse with a stallion.

A police investigation uncovered an internet community of male zoophiles who would regularly meet at an Enumclaw farm, and make video recordings of their barnyard activities. As bestiality was not illegal in Washington, no one was ever charged with a crime, but nonetheless the case quickly attracted national and international attention, along with the sort of knee-jerk judgements or sniggering commentary that Zoo itself steadfastly eschews. For Devor is not interested either in condemning or condoning bestiality, but rather in trying to understand the strange workings of the human animal.

What emerges from Devor's extensive audio interviews with three members of the Enumclaw zoophile community (H, Coyote and Happy Horseman), as well as with the woman (Jenny Edwards) who subsequently rescued a horse owned by the victim, is an introspective, contemplative look at some very grey moral boundaries and some understated parallels, where categories blur and contradictions cannot easily be resolved.

The zoophiles (two of whom refuse to appear on camera, and all of whom use internet pseudonyms) are at pains to stress, on the one hand, the relative normality of their lives and backgrounds, and on the other hand, the total willingness of the animals to participate in sex with them.

Their love of animals, Coyote claims, is "the same thing" as a husband's love for his wife and children. Although it may express the strength and range of the zoophile's feelings, this analogy is not without its problems – for the love that a husband feels for his wife ought, in fact, to be of a different order from the love that he feels for his children (let alone for the family pet).

Then again, Coyote's heartfelt (yet familiar sounding) struggle to "balance religion and being zoo" recalls the problematic status of gays within the Church, raising the possibility – who knows? - that one day zoophilia might become as normalised and acceptable (outside of religion) as homosexuality has in the last half a century. Far from being fixed, mainstream morality has a tendency to shift with the times – and the men who speak out so frankly in this film may one day be regarded as pioneers in a sexual revolution – or may become even more reviled than they already are.

Jenny Edwards gives full voice to a sense of disgust at zoophilia that no doubt many viewers will share – yet as a person who has devoted her life to rescuing horses, she too is an animal-lover (of a strictly platonic sort, naturally) – much like the teenaged girl we see near the end stroking and riding a horse. At one point, Edwards describes how spending the whole night alone with one of her horses helped her cope with cancer: "I could just cry and talk and hang out – it was exactly what I needed at the time." Of course, no bodily fluids were exchanged, but this anecdote has evidently been included because of its similarity to the zoophiles' own accounts of their close relationships with animals, which, though certainly of a sexual nature, clearly have an emotional and psychological dimension to them as well. Treating an animal as friend, confidante or emotional crutch is one thing, and getting your rocks off with an animal is another – but perhaps the distance between these two is just a few small steps rather than the gaping gulf it first seems.

It is also Edwards who insists that animals are "innocent" and can no more give consent than children, as though zoophiles are little different from pædophiles – but that, too, is a difficult equation, coming from someone willing to have a horse surgically neutered in what she considers its own interests, but who, it can safely be assumed, would be far less willing to do the same to a (human) child, with or without consent. Unless you are a strict vegan – and that is not even true of the turkey-and-ham-eating zoophiles – it hardly seems possible to regard animals and humans as having the same moral value. And in any case, as conservative commentator Rush Limbaugh (of all people) is quoted saying in an audio clip near the film's end: "If the horse didn't consent, then none of this would have happened."

Focusing on an activity that all decorum prevents from being shown explicitly in a respectable documentary, and on interviewees who are unwilling to show their faces or use their real names, Zoo ought to present insurmountable problems to any artist working in a visual medium – but Devor turns every obstacle into a virtue. The real 'Coyote' (whatever his real name may be) and the actors playing his fellow animal enthusiasts are all shot in deep shadow, so that their secretive society is given a suitably noirish texture. Meanwhile, DP Sean Kirby offers a stunning array of 16mm Hopperesque vistas - hyper-ordinary smalltown/rural settings made sinister merely by their association with the film's subject matter. It is an effect that serves to reinforce the notion that the most commonplace surfaces can conceal the darkest desires.

Best of all, instead of being embarrassed by his need to use actors in his (ever abstract) dramatisations, Devor embraces the opportunities that this affords, at one point even interviewing Michael J Minard about his thoughts on being cast as 'cop #1'. And so it is that Minard, an otherwise unnoticed background extra, gets to deliver an all too easily forgotten corrective to all the sensationalist shock and scandal that first surrounded the case. "When someone dies," he says, "there's nothing trivial about it – there's people that loved that individual and they'll never see them again, and that's a tragedy." It is a moment at the film's centre that encapsulates Devor's bold attempt to bring this whole story back from the bestial to the human.

The fact is, if you want to see graphic images of zoophilia, these are only a few clicks away on the internet. Zoo, however, offers something new: a strangely beautiful film on this most taboo of subjects, designed to stimulate the mind rather than stir the loins.