Scotch Collies generally reach sexual maturity between the ages of 6 and 12 months. This period can vary slightly among individual dogs, as factors such as genetics, health, and overall development can influence the timing of sexual maturity.

Sexual maturity in dogs is characterised by the onset of reproductive capability. In female Scotch Collies, this is marked by the first heat cycle, also known as estrus. The first heat cycle typically occurs around 6 to 12 months of age but can vary. It is important to note that early spaying or neutering can affect the timing of sexual maturity.

Male Scotch Collies, on the other hand, may begin exhibiting signs of sexual maturity around the same age range. They may display increased interest in female dogs, mark their territory more frequently, or show signs of mounting behaviour.

It is essential for responsible dog owners to be prepared for the potential changes associated with sexual maturity. This includes understanding the signs of heat in females and monitoring male dogs' behaviour and interactions with intact females to prevent unwanted breeding.