Alarm calling in yellow-bellied marmots: II. The importance of direct fitness

Abstract

Alarm calling in sciurid rodents is often explained by inclusive fitness benefits that callers accrue. Inclusive fitness arguments imply that indirect fitness plays an important role in the evolution and maintenance of alarm calling. A more parsimonious hypothesis is that animals alarm call to increase their direct fitness by warning their offspring. Group-living animals are related to each other social group member by a coefficient of relatedness,rthat theoretically ranges from 0–1.0. The sum of these pair-wise coefficients, ‘totalr’, reflects the magnitude of possible inclusive fitness benefits. The amount of variation in the rate of yellow-bellied marmot,Marmota flaviventrisalarm calling that was explained by direct parental care was compared with that variation explained by totalr. After pups emerged, adult females with pups called more than other age/sex classes. Additionally, 42% of the variation in the rate of calling over the entire study was a function of whether the caller was a female who had pups emerge above ground that year. Totalrexplained no significant variation in the rate of alarm calling. Alarm calling in group-living yellow-bellied marmots is a form of direct parental care and inclusive fitness, broadly defined, is of little importance for the maintenance of alarm calling.