Modeling annual energy metabolism rhythms in mammals

The energy cost of living of free-ranging animals, or ecological metabolism, can be estimated over the annual cycle with a coefficient that is multiplied by a mass-specific common denominator. The common denominator is called base-line metabolism per day (BLMD) and the coefficient is called the multiple of base-line metabolism (MBLM). This coefficient shows a sinusoidal pattern over the annual cycle, reaching its highest value at peak lactation and its lowest value when maintenance, activity and production costs are at a minimum. The multiple is strikingly similar among species with similar reproductive costs and off-season activities, such as hibernation, denning or idling, even when body mass varies widely. Daily energy requirements generated as a continuous function over the annual cycle with a tandem cosine algorithm provide time-specific estimates that are more biologically realistic than average values applied throughout the year, or discontinuous estimates for specific time periods within a year. This approach is particularly useful in ecological modeling applications that extend over the annual cycle.