A Question With More Nuance Than Most Guides Suggest
Ask a dog owner whether you should get a male or female, and you will get a confident answer. Ask ten owners and you will get ten different confident answers. The reality is that the research on sex-based differences in dogs is more nuanced than popular opinion suggests, and many of the most strongly held beliefs about male versus female behaviour are based on anecdote rather than evidence. Here is what the science actually shows.
Behavioural Differences: Real but Often Overstated
There are documented average differences in behaviour between male and female dogs, but they are smaller than most people assume and are substantially influenced by factors such as breed, individual temperament, socialisation history, and crucially, neuter status. A study published in the journal Frontiers in Ecology and Evolution found that sex differences in dog behaviour were present but modest, and that breed accounted for far more behavioural variation than sex did.
The commonly cited claim that male dogs are more aggressive is not well supported by the literature when neutered status is controlled for. Intact (unneutered) male dogs do show higher rates of inter-male aggression and roaming behaviour driven by testosterone, but neutered males are broadly comparable to females in most behavioural measures. Similarly, the idea that female dogs are automatically calmer or easier to train has limited scientific backing — individual variation within each sex is enormous.
What About Intact Dogs?
The behavioural and management differences between intact males and intact females are more substantial than those between neutered dogs of either sex.
Intact male dogs are driven by testosterone to roam in search of females in season, mark territory with urine more frequently and in more locations, and may show increased arousal and frustration. These tendencies are manageable with training and appropriate exercise, but they are real considerations.
Intact female dogs come into season (oestrus) approximately twice a year, with each cycle lasting around three weeks. During this period they attract male dogs from a considerable distance, require supervision to prevent unwanted mating, and may display behavioural changes including restlessness or increased affection. Some female dogs experience false pregnancy (pseudopregnancy) after a season, which can cause significant behavioural and physical changes including nest-building, mammary gland development, and in some cases, considerable emotional distress.
Health Considerations by Sex
Both sexes carry sex-specific health considerations that are worth factoring into your decision.
Females
Intact female dogs face a risk of pyometra — a serious and potentially life-threatening infection of the uterus — that increases with age. By the age of ten, studies estimate that approximately one in four intact bitches will develop pyometra. Mammary tumours are also more common in intact females, with evidence suggesting that neutering before the second season substantially reduces this risk. On the other side of the ledger, some evidence indicates that spaying, particularly early spaying, may increase the risk of certain orthopaedic conditions and specific cancers in some breeds, making the neutering decision more complex than it once appeared.
Males
Intact male dogs face a risk of testicular tumours and benign prostatic hyperplasia (prostate enlargement), both of which are addressed by castration. The relationship between castration timing and health outcomes in males has also become more nuanced — research in breeds such as Golden Retrievers and German Shepherds has found associations between early neutering and increased rates of certain joint disorders and cancers, suggesting that breed-specific timing advice from your vet is more appropriate than a blanket early neuter recommendation.
Interaction With Other Pets in the Household
If you already have a dog at home, sex can be a relevant factor in compatibility — but again, the research suggests this is frequently overstated. The common advice that opposite-sex pairings work better than same-sex pairings has some basis, particularly when it comes to same-sex aggression in intact males. However, individual temperament, proper introduction protocols, and the existing dog's tolerance for sharing their space matter considerably more than whether the dogs are the same sex.
A 2022 study examining inter-dog household dynamics found that while mixed-sex pairings showed marginally fewer conflict incidents on average, the overlap between groups was so large that sex alone was a poor predictor of household harmony. Resource guarding, space competition, and mismatched energy levels were stronger predictors of conflict than sex.
Physical Differences
In most breeds, males are noticeably larger than females — heavier, taller, and often more powerfully built. In some breeds the difference is subtle; in others it is significant. A male Rottweiler can weigh fifteen to twenty kilograms more than a female of the same breed. If physical management is a concern — whether due to your own size, mobility, or living situation — this is worth considering practically rather than dismissing.
What Actually Predicts a Good Match?
When you strip away the myths, the most reliable predictors of whether a dog will suit your household have very little to do with sex. Breed (or breed mix) accounts for the largest share of temperamental and energy-level variation. Early socialisation quality shapes how a dog relates to people, other animals, and novel environments. Individual temperament within a litter can be assessed to some degree through structured puppy aptitude testing. And your own lifestyle — exercise habits, home environment, experience with dogs, and what you want from the relationship — matters more than any biological variable.
If you have a strong preference for one sex, follow it — owner confidence and comfort have real effects on how a dog is trained and managed. If you have no preference, let temperament, the specific puppy or dog in front of you, and breed characteristics guide the decision instead. The sex of your dog is unlikely to be the thing that defines your experience of living with them.