Although the ages varies, female Leonbergers often come into their first season (or heat) when they are between nine and twelve months old. Like other big dogs, however, they may experience their first season when they are a bit older. They are in heat for around three weeks and come into heat approximately every six months.
When she is in heat, the female releases a bloody discharge. The discharge contains pheromones, which are chemicals that attract males. A female in heat should never be left alone out of doors, including in her own backyard. A male dog attracted by the pheromones may jump a fence or even dig under it to get to the female and impregnate her. Nevertheless, the female still needs exercise. She could chase balls or toys in the home or play in a securely fenced backyard with careful supervision.
In some dogs the bloody discharge is more problematic than in others. Owners may decide to limit their dog’s access to certain parts of the home. While it’s understandable that the owner wouldn’t want blood on their upholstery, carpets, or bedding, it’s important that the dog doesn’t feel isolated from the family or feel like she’s being punished for being in heat. Gates, crates, and special pants sold for dogs in heat can all be useful, as long as they are used wisely and with kindness.
I’ve only given a summary of how to care for a Leonberger in heat. If an owner hasn’t spayed the female and the dog is approaching the age when coming into season is possible, the owner should do some research about how best to care for their dog.