Many wildlife species experience seasonal birth pulses and density fluctuations, and while it has been established that birth pulses can have strong effects on disease transmission , we now see that the shape of the transmission–density function can have further significant effects on disease invasion and persistence. The implementation of the transmission–density function should therefore be done with care, and as informed as possible. Although currently few studies have quantified the relationship between contacts and density, other relevant knowledge about host biology and behaviour can potentially be used for deciding on the best possible shape of the transmission–density function.