The research, described in the journal Soft Matter (SRSLY?, http://pubs.rsc.org/en/content/articlelanding/2017/sm/c6sm02795d/unauth#!divAbstract
) (...), examined mammals as small as cats and as large as elephants, finding that they all took around 12 seconds to defecate.
Through their observations and theoretical calculations on the fluid mechanics of defecation, the researchers found that all animals exert the same amount of pressure while pooping.
Previous work (...) found that all mammals pee for about the same amount of time (21 seconds). It’s evolutionarily plausible, too. Pooping makes it hard to run away from predators.