John muir commented that every time he saw a grizzly bear the wilderness got bigger. Others faced with such an encounter might readily agree with the Scottish-born American naturalist who explored large parts of the western United States. Yet today's predators are smaller than those of the past, and the reason seems to have something to do with the speed of their prey.rnLarge predators gain tremendous benefits from being big. Killing other animals and protecting or stealing a carcass from others tend to be easier since their teeth and claws are larger. Handling struggling prey is safer as the larger predator has less trouble holding the prey firmly and preventing it from striking out at the hunter's vital organs. These attributes were even more important in the past since life was tougher for predators then (see box).rnA new study, however, reveals that excessive size can interfere with predators' hunting. Daniel MacNulty of the University of Minnesota and his colleagues have found that for predators which need to run after their prey, being big can be more of a hindrance than a help.
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