Why are lions not as big as elephants?
Carnivores are some of the widest ranging terrestrial mammals for their
size, and this affects their energy intake and needs. This difference
is also played out in the different hunting strategies of small and
large carnivores. Smaller species less than 15-20 kg in weight
specialize on very small vertebrates and invertebrates, which weigh a
small fraction of their own weight, whereas larger species (>15-20
kg) specialize on large vertebrate prey near their own mass. While
carnivores around the size of a lynx or larger can obtain higher net
energy intake by switching to relatively large prey, the difficulty of
catching and subduing these animals means that a large-prey specialist
would expend twice as much energy as a small-prey specialist of
equivalent body size. In a new article published by PLoS Biology, Dr.
Chris Carbone and colleagues from the Institute of Zoology, Zoolog ical
Society of London reveal how this relationship might have led to the
extinction of large carnivores in the past and why our largest modern
mammalian carnivores are so threatened.
We know that the largest carnivores that exist today are particularly vulnerable to threats imposed by humans and have been shown to have higher rates of extinction in the fossil record than smaller species even prior to the evolution of man. Carnivores at the upper limits of body mass would have been heavily reliant on abundant large prey to both minimize energy expenditure and maintain high rates of energy intake. Slight environmental perturbations, anthropogenic or otherwise, leading to lower prey availability, could readily upset this energy balance. It may have also contributed to the extinction of the largest carnivores and explain why the largest modern mammalian carnivores are so rare and vulnerable today.
Public Library of Science. January 2007.
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