The Javan rusa breeds around July and August. When stags contest by calling in a loud, shrill bark and duelling with the antlers. The doe gives birth to one or two calves after a gestation of 8 months, at the beginning of spring. The young ones stop taking milk and start eating solid food at 6–8 months. They reach sexual maturity at 3–5 years, depending on the type of habitat. Javan rusas live 15–20 years both in the wild and in captivity.