Does Sex Matter When Getting a Second Pet?

If you’re thinking about bringing a second pet into your home, chances are you’re chewing on several questions at once. Among them: Are you really up to the task of feeding, caring for, and cleaning up after two pets instead of one? Does your first pet even want a “sibling?” And where should the second food bowl go? 

But once you’ve answered those and begun looking for your next BFF, another quandary might emerge. Will your new dog or cat get along better with your current baby based on their sex? In other words: Does the ancient proverb men are from Mars, women are from Venus hold true when it comes to animals? 

If you’re dead set on a particular combo, rest assured that hormones should not interfere. According to the two experts we spoke with, bringing a second pet into your home will not launch a Battle of the Sexes if both animals are spayed or neutered. That said, there are a few nuances to consider.

Is the boy-girl combo really the best one?

Despite the conventional wisdom that male-female dog pairings are the safest bet, the truth comes down to the individual. 

Lisa M. Gunter, behaviorist and assistant professor of animal behavior and welfare at Virginia Tech, usually tells pet parents considering a second dog to think about their pup’s past experiences and social habits. “Maybe their dog has developed a preference because of another dog they lived with, or other dogs they like to hang out with on walks or playdates,” Gunter says. Use that information and let your dog’s personal tastes take the lead.  

Some questions to consider: Does your dog like getting really physical during play? Do they prefer running side by side? Do they like sharing their toys? 

A quick aside for the cat-dog hybrid households. In case you’re worried they will be mortal enemies, it actually turns out cats and dogs can make wonderful playmates for each other. “Great combinations tend to enjoy doing similar things,” Gunter says. Some like rough housing, some like chasing one another, and some relish the relaxation of a communal nap. Funnily enough, Gunter notes that of all the critters in her home, her female dog and female cat play the most together.

How about cats?

Dr. Julie Hunt, veterinary consultant for Embrace Pet Insurance, says that sex won’t matter when bringing a second cat into the home. That is, assuming both of them have been spayed or neutered. And regardless of sex, Dr. Hunt insists that any pet cat definitely should be. 

“The reason I say that cats should be spayed or neutered to be good pets is because an intact female cat will continue to come into heat until she is bred,” Dr. Hunt says. “Look up videos — it’s bad!” Meanwhile, she adds, “An intact male cat has very stinky urine and will spray urine in the house to mark its territory.” Yuck!

Does it matter if the pets are “fixed”?

Oh, yes — and not just for cats.

According to Gunter, “a female dog’s estrous cycle can certainly influence her behavior and that of other individuals around her.” And if you have two male dogs, Dr. Hunt adds, you should “definitely neuter them” to ensure their testosterone doesn’t put them in competition for territory, female dogs, and more. 

If you’re considering combining a male and female dog, the reason for spaying and neutering should be obvious, unless you’re ready to welcome a litter of puppies into your home. But if you are considering breeding your pets, Dr. Hunt recommends making sure that their genetics are ideal to pass on. To do this, you can ask your veterinarian what tests would be appropriate or look up your dog’s breed on the AKC website.

Although it’s technically safe to pair female dogs and cats whether or not they’re intact, Dr. Hunt still recommends spaying them both to prevent accidental breeding and, in the cats’ case, incessant yowling.

How can I tell if my animals are not getting along because of their sex?

OK, so you’ve brought home your second pet, and there seems to be some tension. How can you tell if it’s because of their sex and not something else?

If you suspect your pets are locked in some kind of hormonal feud and happen to be unaltered male dogs, Dr. Hunt recommends watching for testosterone-based aggression or territorial behavior. You can also watch for “sex-based interactions” among male-female pairs. 

All of that said, Gunter would not consider sex the most likely reason for two pets not getting along — “especially if they have lived together successfully.” More likely, she says, the animosity could come down to the two animals’ social habits, which might or might not be compatible. “Preferences for certain toys, food, places to rest, or even people in the household can also cause conflict,” she says. And if one dog or cat is slowing down from old age, there’s a chance that a younger sibling's desire for physical play could become irritating due to discomfort, pain, or medical conditions.

Whatever pairing you choose, Dr. Hunt has just one request: Seriously, please spay and neuter your cats and dogs.

“It solves so many of these problems and really does create better pets,” Dr. Hunt says. “It also helps to alleviate the pet overpopulation problem. Animal shelters are euthanizing healthy dogs and cats every day simply because of overpopulation.”

Until we can all fulfill our dreams of creating animal sanctuaries out in the countryside (seriously — if you want to be my rich benefactor, please reach out via email so we can discuss) it’s our job as pet parents to do our part.