The burden of size and growth for the juveniles of large mammalian herbivores: structural and functional constraints in the feeding biology of juveniles relative to adults in red kangaroos, Osphranter rufus

Juvenile mammals in their post weaning developmental stages face many challenges in transitioning to adulthood. Among large grazing species such as ruminant bovids and cervids an overarching challenge is acquiring and processing sufficient nutrients to survive and grow, with a gut that may not yet be fully developed. Marsupial kangaroos of Australia face similar challenges; they also digest vegetation by fermentation in a large foregut. In red kangaroos, Osphranter rufus (= Macropus rufus), the dominant species of Australia’s arid interior, females may breed continuously; however, juvenile recruitment to the adult population is irregular and coincident with sporadic rainfall. As compared with adult females the nutritional requirements of juvenile O. rufus are high in relation to their body mass (BM), largely due to the cost of their rapid growth. We examined processes that juveniles have in their morphology, physiology and behaviours to meet their elevated nutritional needs, by comparin...