Researchers from Monash University reveal that baby weight relative to adult body mass best explains why mammals exist in such diverse sizes.
The diversity in mammal sizes, from the Etruscan shrew which weighs around two grams to the blue whale which weighs almost 200 tonnes, has always perplexed scientists. However, after conducting a new study, a group of international scientists including those from Monash University found that baby weight relative to adult body mass best explains why mammals exist in such diverse sizes.
Size has a major influence on all aspects of an animal's physiology and anatomy, and the roles it can play in ecosystems, reveals Dr Alistair Evans, of the Monash School of Biological Sciences in a press release. It governs how fast the heart beats, how one moves and how much food one eats.
Mammals were able to flourish and increase in size after the extinction of the dinosaur. This study looked into larger sized mammals like elephants, whales, primates and rodents and examined the constraints they face because of their size. Through the study, researchers found that species that matured more quickly and produced a larger mass of young each year relative to body weight were able to evolve to a larger maximum size and also attained this large size in fewer generations. It doesn't matter whether many small young or just one large offspring are born in a year. However, an overall high rate of production is necessary to attain larger sizes.
Citing the blue whale to be a perfect example, Dr Evans said "The blue whale is the largest animal to have evolved, even larger than dinosaurs, and it reached this size at the fastest rates we recorded. Key to this success is that they produce large young that mature quickly, reaching around 30 metrers in eight to 10 years."
The study also provided clues that suggested a link between maximum size and mortality rate.
"This is a really surprising finding," said Dr Evans. "It points to why many of the large animals went extinct after the last Ice Age, as changing climates probably increase mortality rates. Large animals are also at high risk of extinction in modern environments because it takes a long time for their population to rebound from disasters."
