The European badger has been used for many years as a model for the study of delayed implantation. Extensive experimental work has shown that implantation, which occurs around the winter solstice, is triggered by photoperiod. This paper presents data on estimated implantation dates in a wild population of badgers, measured by ultrasound scanning. It shows that females' nutritional state prior to implantation also influences implantation date, with females in good condition implanting relatively early. Photoperiod is known to influence implantation on a timescale of months, but body condition acted on a timescale of days; thus while photoperiod may be used to set the time of breeding to correspond approximately with seasonal variation in good availability, females may use body condition to calibrate their reproduction in response to their own local conditions. Giving birth early in the year provides cubs with the maximum period of growth prior to the summer, when food availability is very low. Since females feed little during gestation and the early phases of lactation, females in good condition will be able to afford to implant earlier than those with smaller fat reserves.