Mating season mode activated

It’s not rebelliousness, it’s biology

When a female dog or cat goes into heat, her behaviour can change dramatically, even if she had previously been calm, predictable or very well-balanced. This baffles many owners, even the most attentive and experienced ones. Suddenly, your pet starts vocalising insistently, urinating more frequently, and acting restless, clingy or aggressive for no apparent reason.

These behaviours should not be interpreted as “bad temper” or a phase of rebellion: they are natural expressions of an intense physiological process, governed by reproductive hormones that affect both the animal’s body and emotional state. The oestrous cycle, in addition to preparing the body for possible pregnancy, also modifies the perception of the environment, energy levels and social behaviours.

Understanding this aspect of heat allows us to handle the situation with more empathy, adjust domestic routines and prevent unnecessary conflicts. The key is to anticipate: the more we know about what happens at this stage, the better we can care for our furry companions and make responsible decisions such as sterilisation.

The hormonal orchestra of heat: who’s in charge and why behaviour changes

Heat is part of the oestrous cycle, which is the reproductive cycle of female dogs and cats. This cycle is not ‘decided’ by the uterus: it is directed by the hypothalamic-pituitary-ovarian axis, which is a chain of command in which the brain activates hormonal signals and the ovary responds by producing sex hormones.

When we talk about hormones, it is important to remember that they do not just ‘prepare the reproductive system’. They also act as messengers on the nervous system and modify perception of the environment, motivation and reactivity. This is why, during oestrus, patience, sleep, tolerance to contact and the tendency to seek social stimuli can change.

In female dogs, the cycle is usually divided into fairly distinct phases. First comes proestrus, then oestrus (the receptive phase), then diestrus (the luteal phase, with high progesterone), and finally anaestrus (the resting period). In general terms, many bitches come into heat approximately twice a year, although there are notable variations depending on breed, size, and environmental conditions. A very important detail to understand what happens after heat is that, after ovulation, progesterone can remain high for weeks even if there is no pregnancy. This “hormonal signal of pregnancy” is part of the reason why some bitches develop signs of pseudopregnancy later on.

In cats, the story is different. Cats are seasonal polyestrous, which means that during times of the year with longer daylight hours, they can repeat cycles quite frequently if there is no pregnancy. In addition, cats are classically described as induced ovulators, meaning that ovulation is usually triggered after mating stimuli through a neurohormonal cascade. Simply put, heat in female cats can recur and become very noticeable at home, especially due to vocalisation, because the body is ‘trying’ to complete the reproductive process.

Did you know: female cats do not always need a male to ovulate?

Although it is described as induced ovulation, there is evidence that spontaneous ovulation can occur under certain conditions.

Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC11292940/

Typical behaviours during heat: it’s not a ‘fad’, it’s applied neuroendocrinology

During heat, the animal does not become ‘bad’ or ‘capricious’. What happens is that the brain receives a hormonal rush that prioritises search behaviour, sexual communication and receptivity. It is exactly the opposite of a malfunction: it is a biological system functioning as designed, even if it is uncomfortable in a flat with neighbours and human schedules.

In female dogs, one of the most typical signs is urine marking or increased urination. It is not “done on purpose”: it is chemical communication, because the urine releases scent signals that attract males and announce reproductive status. It is also common to see more restlessness, more “nervous” walks, greater distractibility and an insistent need to go out or explore. Some female dogs also become more sensitive to contact or handling, and this can translate into irritability if they are invaded when they do not feel like it. Others, on the other hand, seek more attention and contact. Appetite can vary in both directions, because the balance between stress, activity, and hormones is not identical in all individuals.

In cats, the hallmark of domestic heat is usually intense vocalisation, often at night, accompanied by rubbing, rolling on the floor and a typical posture of receptivity (the famous lordosis, with the hindquarters raised and the tail tilted). This vocalisation does not imply pain by default; it is a calling behaviour to attract males. Even so, it is important to remember that not everything that looks like heat is heat. Pain, infections, urinary problems or stress can also change behaviour and vocalisation. Therefore, if the symptoms are unusual or accompanied by systemic signs, it is worth having them checked out.

As for aggression, it can occur, but it usually has fairly “mundane” explanations. Sometimes it is frustration, because the animal wants to access a stimulus (go out, search, interact) and cannot. Sometimes it is hypersensitivity, because they are less tolerant of contact or restrictions. And sometimes it is a different problem that coincides with the heat cycle, which can confuse us if we assume that “everything is hormonal”.

Warning signs that warrant a visit to the vet as soon as possible:

• Marked lethargy, fever, vomiting, or abdominal pain.
• Purulent or foul-smelling vaginal discharge, especially weeks after heat.
• A very noticeable increase in thirst and urination without explanation.
• Persistent panting, collapse or rapid deterioration of general condition.

Living with your pet in ‘heat mode’: practical management and responsible decisions

The first common mistake is to try to “correct” heat as if it were a behavioural challenge. Punishing, scolding or forcing only adds stress. And when stress rises, so does reactivity and behavioural disorganisation. Instead, what does help is managing the environment and channelling energy intelligently.

A simple approach is to think of three objectives: reduce opportunities for escape or mounting, decrease general arousal, and provide safe outlets for exploratory impulses. At home, this is achieved through a stable routine, environmental control, and enrichment.

Practical protocol for those days:

1. Maintain predictable schedules for walks, meals, and rest to lower baseline arousal.
2. Increase mental exertion with scent and search games, as these tire dogs without overexciting them.
3. Reinforce calm behaviours (lying down, looking at you, waiting) with small, repeated rewards.
4. Control doors, windows and encounters with males; in female cats, be extremely vigilant about balconies and escapes.
5. If the heat is particularly intense or there are strong emotional changes, consult your vet to assess whether veterinary support is needed and to rule out any associated problems.

In female dogs, a phenomenon that deserves its own chapter, although it is not always well explained to owners, is pseudopregnancy. After heat, some female dogs develop nesting behaviour, protect toys or objects, experience mammary changes and even lactate. This is not “acting”: it has an endocrine basis related to the luteal phase and the balance of progesterone and prolactin. On a practical level, pseudopregnancy can amplify problems of irritability, anxiety or possessive behaviour, and management must be delicate: avoid stimulating maternal behaviours, control excessive licking and, if necessary, treat under veterinary supervision.

As for sterilisation, the most important thing is to explain it clearly and without marketing hype. Sterilisation eliminates the main source of ovarian hormones and therefore usually eliminates heat and associated behavioural peaks. It also reduces significant medical risks, such as pyometra, which is a potentially serious uterine infection. There are also nuances: the ideal time depends on the animal, its breed, size, lifestyle and the guardian’s objectives. The decision should not be ‘automatic’, but informed.

Finally, regarding hormonal treatments to “cut” or space out heat, there are pharmacological options, but they are not candy. Progestogens, for example, are associated with significant risks in certain cases. Therefore, if they are considered, it should always be done with an individual assessment, explanation of risks, and a follow-up plan.

Your vet advises: be careful with hormone-based methods of suppressing heat

Megestrol acetate and other progestogens are associated with significant risks (e.g., pyometra, diabetes, mammary changes), so they should not be used “lightly”.

Source: https://www.merckvetmanual.com/reproductive-system/reproductive-diseases-of-the-female-small-animal/reproductive-management-of-the-female-small-animal 

“How Long Are Dogs in Heat? What to Know About Heat Cycles.” American Kennel Club (AKC). AKC website, n.d. Explains the stages of heat, typical signs, and practical advice for owners. https://www.akc.org/expert-advice/health/how-long-dogs-in-heat/

Dog estrous cycles. Cornell University College of Veterinary Medicine (Riney Canine Health Centre). Cornell CVM website, n.d. Clinical summary of the oestrus cycle and its phases with a physiological focus. https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/dog-estrous-cycles

“Estrus Cycles in Cats.” VCA Animal Hospitals. VCA website, n.d. Describes behavioural signs of feline oestrus and its seasonal pattern. https://vcahospitals.com/know-your-pet/estrus-cycles-in-cats

“Breed risk of pyometra in insured dogs in Sweden.” Egenvall, A.; Hagman, R.; Bonnett, B. N.; Hedhammar, Å.; Olson, P.; Lagerstedt, A.-S. Journal of Veterinary Internal Medicine, 2001. Large epidemiological study estimating incidence and risk by breed/age. https://pubmed.ncbi.nlm.nih.gov/11817057/

“The effect of neutering on the risk of mammary tumours in dogs— a systematic review“. Beauvais, W.; Cardwell, J. M.; Brodbelt, D. C. Journal of Small Animal Practice, 2012. Reviews the evidence and highlights limitations/biases in classic studies. https://pubmed.ncbi.nlm.nih.gov/22647210/

“Systematic Review: Does Pre-Pubertal Spaying Reduce the Risk of Canine Mammary Tumours?” Guirguis, P.; Beggs, D. S. Animals (MDPI), 2025. Modern review synthesising results and heterogeneity of recent evidence. https://www.mdpi.com/2076-2615/15/3/436

“Comparison of long-term effects of ovariectomy versus ovariohysterectomy in bitches.” Okkens, A. C.; Kooistra, H. S.; Nickel, R. F. Journal of Reproduction and Fertility Supplement, 1997. Discusses long-term results and the debate between “removing ovaries” versus “removing ovaries and uterus”. https://pubmed.ncbi.nlm.nih.gov/9404289/

Reproductive Management of the Female Small Animal. Merck Veterinary Manual (editorial team). Online veterinary manual, n.d. Clinical chapter on physiology and management/contraception options with risks and benefits. https://www.merckvetmanual.com/reproductive-system/reproductive-diseases-of-the-female-small-animal/reproductive-management-of-the-female-small-animal

“Manipulation of the Estrous Cycle in Bitches and Queens.” MSD Veterinary Manual (editorial team). Online veterinary manual, n.d. Practical review of methods for controlling heat and warnings about adverse effects. https://www.msdvetmanual.com/management-and-nutrition/management-of-reproduction-dogs-and-cats/manipulation-of-the-estrous-cycle-in-bitches-and-queens

“Etymology of ‘oestrus/estrus'” (Estrus — Etymology, Origin & Meaning). Online Etymology Dictionary (Douglas Harper). Online etymological dictionary, n.d. Useful linguistic curiosity for a cultural box in the article. https://www.etymonline.com/word/estrus