Harvest mice are busy breeding from May to October, often producing 3 litters a year. A courting male chases a female who is often very aggressive and turns round to bite him! Eventually she usually relents, and when they have mated she chases him away.
The female now sets about preparing a nest ready for her babies which will be born after a gestation period (time between mating and birth) of 17-19 days. To make the intricate, tennis ball size nest, she balances 30-60cm up a stem and bends and weaves living, green leaves to form a framework. She splits lengthways more leaves, sometimes splitting one leaf as many as 15 times, and weaves these into the framework to form a spherical shape. She then lines the nest with chewed-up dead leaves. It takes her about 48 hours to complete the nest. After her 3-8 babies are born, she closes the entrance to the nest over with grasses.
The young are blind, naked and helpless to begin with - looking rather like little pink raisins! They grow very quickly, and by the eighth day they have grown grey-brown fur and opened their eyes. When they are 10 days old, the mother reduces their milk feed and supplements their diet with regurgitated seeds which she has chewed and swallowed. On the eleventh day they leave the nest and begin to explore, practising the skill of climbing grass stems. By 16 days of age they are completely independent. Their mother, who is usually pregnant again, abandons them, and looks for a new nesting site.
The young remain near the nest for a couple of days and then go off to search for territories of their own. Most baby harvest mice do not live for more than six weeks - eaten by one of their many predators.Read More: Threats to the Harvest Mouse