Mammal reproduction primarily occurs through internal fertilization, where the male's sperm fertilizes the female's egg inside her body. Most mammals give birth to live young, although some, like the platypus and echidna, lay eggs. The gestation period varies widely among species, ranging from a few weeks to several months. After birth, mammal mothers typically nurse their young with milk produced by mammary glands. This nurturing process is crucial for the young's growth and development. Mammals exhibit various reproductive strategies, including monogamy, polygamy, and seasonal breeding, depending on their environment and species-specific behaviors.