when is a beagle considered senior
9 Years and on: Senior; there is no official age that a Beagle becomes a senior dog. Veterinarians will make this declaration based on a dog's health, mobility and other factors. Therefore, a Beagle will be pronounced a senior sometime between 9 and 10 years old. Facts About Growth & Maturity 1) Final Beagle size is usually reached by the 18-month mark.