Love is definitely in the air in the dog world at the moment.

Twice a year, roughly around February and October, all the intact female dogs on the island come into heat. There is a lot of variability in the timing with different breeds and sizes of dog but the heat cycle happens around every six months in most cases. It can start in dogs as early as five months old or much later, well into their first year.

The first sign of oestrus is a swollen vulva and a bloody vaginal discharge. This is often the first the owner knows that their dog is in heat and steps need to be taken immediately to prevent an unwanted pregnancy.

The first week or so of the heat cycle is a non-breeding phase. She will urinate more frequently and the urine contains pheromones and hormones, which signal to other dogs her reproductive state. Male dogs can pick up on the scent of the female heat cycle from a great distance, over a mile in some cases, and they will begin to make their way towards the female. It’s why we see an increase in dogs roaming about and being more aggressive and territorial during these seasons.

The second week of oestrus is the breeding week, where the female dogs will be receptive to their male suitors. This phase can continue into the third week but usually is over by the end of week two. The semen from the male can last in the reproductive tract for up to a week so if two dogs mate, she is very likely to become pregnant.

The male dogs can be pretty determined when it comes to breeding. I have seen two dogs mate through a chain-link fence; males jump into windows, mate, and jump out again; big dogs mating with tiny dogs and vice versa with dogs using steps or holes in the ground to even up the size difference.

When I say the urge to breed is strong, I mean really very strong. I always smile when an owner is adamant that their darling princess pooch definitely didn’t breed but the pups come out looking surprisingly like the neighbour’s scruffy mutt. (You’ve seen Lady and the Tramp, right?) These dogs can be very crafty when they want to be.

Dogs breed seasonally as a survival tactic so that, in the wild, all the female dogs can be on hand to help with the litters. It’s really a very good evolutionary trait. It is also why some dogs have false pregnancies. The hormone changes in non-pregnant intact females are almost identical to pregnant females, causing them to feel like they are pregnant and even to begin to produce milk. They can then act as wet nurses, supplying more milk for the puppies and giving them a better chance of survival.

If you do not intend to breed your dog, the best solution is to have them spayed or neutered. This removes all the urges to breed as well as reducing their risk of certain types of cancer associated with the reproductive tract. It also reduces your annual dog licence fee significantly, saving you money in the long run. If you do not spay your female dog, the risk of mismating is high. If this happens, contact your vet as soon as possible and discuss the options with them. Believe me, the cost of spaying your dog is nothing compared to the cost of rearing eight unwanted puppies, but more about that in my next column.

• Lucy Richardson graduated from Edinburgh University in 2005. She started CedarTree Vets in August 2012 with her husband, Mark. They live at the practice with their two children, Ray and Stella, and their dog, two cats and two guinea pigs. Dr Lucy is also the FEI national head veterinarian for Bermuda