Mammals can have a wide range of different dimensions from the weight of a coin to the multiple of a bus’ weight. Elephants and whales for instance have become really big over the time, while primates have always been extremely small. Scientists seem to have found the reason of difference in mammal size.
Studies on mammal size
A theory made by an interdisciplinary group lead by Jordan Okie from University of Arizona has recently found some answers. They have studies the reason why certain organisms end up gigantic and others don’t. An international research group of paleontologists, biologists and ecologists have studied how fast different species grow. Based on these information they could predict how big they were going to grow over the time.
Some species have a shorter life and others live longer before they reach maturity. On the one hand, mice live a number of stages in a short period of time. On the other hand, for people it takes quite long before they have their first child.
Studies show that species living a faster life are more likely to grow bigger in shorter time, so these mammals’ maximum size is going to be a lot bigger. The group has studied 70 million-year-old fossils of whales, elephants, seals and primates. They concluded their theory was right.
The theory also predicts the chance of extinction of certain species. Mammal size does affect the reproduction rate of the species. Small animals reproduce more frequently than bigger ones. If the mortality rate of big mammals double, they will probably become 16 times smaller.
The research points out differences between the main groups of mammals. Moreover, it makes predictions on the way changes in mammal size are going to affect evolution. This information can be used to reduce extinction even if their natural habitat suffers modifications.