Audra Houghton, left, and Andy Thomas get the attention of three of their four dogs in their west Dallas home. The couple says merging their households has required them to establish themselves as pack leaders.

MCT / Ron T. Ennis

They didn’t realize how bad things were until Christi McDowell found herself in the emergency room with a bloody hand.

Before they were married, Christi and Michael McDowell of Fort Worth each had a rescue dog: Christi, a hospital chaplain, had Sierra; Michael, a controller at an oil company, had Mildred. The dogs were both roughly 2 when Michael and Christi started dating. They shuttled back and forth to each other’s houses, dogs in tow, and all was harmonious.

Then Christi and Sierra moved into Michael’s house, launching a soap opera peppered with canines, humans, overprotective snarling and isolation.

When couples or roommates move in together, and both people bring pets into the household, the transition can be bumpy. When trying to get everyone to co-exist, remember that some animals react strongly to major changes in their lives, says Audra Houghton, a professional dog trainer. “Some dogs who were housetrained may begin to have accidents,” Houghton says. “Some may chew things, and some may become aggressive.”

Be prepared to deal with the friction, says Stacy Hiebert, a canine behavior therapist with Adventures in Canine Training, a chain in Texas.

“I’ve heard old-school trainers or vets say that the theory that (dogs) will ‘work it out,’” Hiebert says. “Never, ever do that. (Meeting and introductions) should always be slow, and if you don’t feel comfortable doing it, you need to call a professional. Don’t just let dogs duke it out.”

But what “should” you do when your new husband’s Rottweiler wants to have your bichon frise for an hors d’oeuvre? Or when your girlfriend’s terrier starts eating the door frame in the bedroom? Here’s how two families have gingerly managed to bring together their animals.

The overprotective aggressor

Michael and Christi McDowell

Pets: Mildred (black Lab mix) and Sierra (golden retriever-Lab mix).

The problems: One night last year, Michael and Christi were watching TV, with the dogs lying on the floor. Mildred — previously known as Michael’s dog — got up and started making her way over to Christi. Sierra jumped up suddenly, bared her teeth and went berserk on Mildred, prompting a full-on dogfight. The couple thought it was a fluke. But it happened again. The dogs were both happy in the backyard, until Christi walked out. Sierra became territorial over Christi, and the fight was on again. Christi went to break it up, but got her hand in the middle of gnashing teeth.

Curiously, the dogs never had a problem when the two of them were alone together; they frolic like best friends. And they never have a problem when they’re with just Michael. The common denominator is Christi: Sierra casts herself as Christi’s protector and treats Mildred as a menace.

What they’ve tried: Three different dog behaviorists, including one who charged $250 for an hour. “But we’re still not where we need to be, as far as having both of them totally relaxed,” Michael says. “(The behaviorist’s) solution was instead of trying to make them become best friends, try to teach them to ignore each other.” Meanwhile, Christi is working on trying to assert herself as more of a pack leader, to plug them back into their basic instinct of the pack mentality.

How they live now: Christi can’t be alone with both dogs in the same room. When she’s home, the dogs are rotated in and out of their crates.

Outlook: “I think eventually we’ll get past it,” Michael says. Meanwhile, they’re looking into a fourth behaviorist, one who works with you for the lifetime of your dog. Christi worries: “The real fear is what would happen if we have kids. I couldn’t deal with the way things are now, with kids.”

Angus the angry joins the family circus

Audra Houghton and Andy Thomas

Pets: Angus (English bulldog), Marlo (Great Dane), Tyson (boxer), Wee Dog (Chihuahua mix) and Bill the lovebird.

The problems: Dog lover Andy Thomas had good fortune; he fell in love with a professional dog trainer. His girlfriend, Audra Houghton, has been training dogs professionally for six years, after completing a 120-hour course through PetSmart; she’s also earned certifications as a K9 handler from the National Narcotics Detector Dog Association.

When Andy moved into Audra’s house in Dallas a few months ago, he brought Angus, who is a sweetheart with humans but slightly aggressive toward other dogs. And Audra has a bird and three dogs of her own, plus a few she fosters.

In their living room on a recent afternoon, there were just four, plus the lovebird in his cage. Angus snorted his way around the room, overturning a coffee table. And as Tyson stood on his hind legs and pawed visitors, Wee Dog tore around like a tiny dervish. All the while, Marlo happily wagged her mile-long tail.

When Andy and Angus moved in, the couple wanted to make sure they could trust Angus with the other dogs — notably tiny Wee Dog. But Angus has also been known to snap at Marlo, who, despite being as big as a pony, is still all gangly puppy, at a year and a half. Marlo wants to play; Angus does not.

One other issue needed work: the relationship between Marlo and Bill the lovebird. “She’s so big she could easily knock that cage over,” Audra says.

What they’ve tried: With Audra’s training, the couple say it really didn’t take Angus long to calm down considerably. The humans had to assert themselves as the pack leaders. As for what happens with the rest of the pack status, Audra says it’s best to let the dogs establish their own pecking order. It’s tempting, she says, to label a dog “dominant,” “submissive“ or “alpha,” but she says those aren’t really labels so much as descriptions of behavior that’s occurring at a specific point in time. Another important element was making sure each dog had its own space. Angus usually stays in the kitchen with the baby gates up, or in the living room. Marlo sleeps in her crate, and Wee Dog and Tyson stay loose in the house.

Audra has also used a technique respected among trainers that’s called the “Nothing in Life for Free” method. How it works: Whenever you’re rewarding your dog with anything — a treat, a scratch behind the ears, a walk, affection in general — make the dog work for it by giving him or her a command, such as “Sit.“

“Your dog needs to have a job,” Audra says. “Setting guidelines and rules can really help to mentally stimulate them. It causes them to need to think instead of just reacting.”

How they live now: There’s relative harmony now, with pets mostly knowing their place in the pack. There are a few issues to work out with Angus, who can still tense up around other dogs. Meanwhile, Marlo and Bill have established a bit of a Tracy-Hepburn-like rapport. When Marlo presses her face up against Bill’s birdcage, Bill occasionally bites her on the nose.

Audra notes that the dogs weren’t the only ones who had to adjust to the move: Andy has had to learn to sleep with the noise of so many animals in one house. The solution: sleeping with fans on to drown out the noises.

Outlook: The couple are betting that one big life change will help everyone: They’re moving to San Antonio, into a place that’ll be new to everyone. That means all the dogs will be on neutral territory, which is generally easier on blended-pet families, Audra says.