Why TNR Is So Important TNR is essential for maintaining the health and managing the population of feral cat colonies. A female cat can become pregnant as young as 3–4 months of age, giving birth to a litter at just 5–6 months old. Each litter can contain anywhere from 3 to 6 kittens. Although many kittens will not survive their first year of life due to disease, weather conditions, and other challenges, the numbers remain staggering. It is easy to see how the population continues to grow without intervention