We tend to look at islands like Hawai’i or New Zealand or Madagascar for extreme examples of adaptive radiation. But of course, they are not the only places to see this. Take, for example, this picture I took at the Lincoln Park Zoo in Chicago. What may look like some strange cross between a deer and a rabbit is actually a type of rodent.
Patagonian Mara (Dolichotis patagonum) are part of the cavimorph radiation of rodents mainly centering in South America. One of the most familiar to the general public is the Guinea Pig (Cavia porcellus). Perhaps colonizing South America sometime in the late Eocene/ early Oligocene, cavimorphs evolved into many spectacular forms. Unlike many rodents, Mara are monogamous, active during the day, and eat grasses out on the open plain. Hawai’i has lobelias that turn into trees, Patagonia has rodents that turned into antelope. Touche.
These guys were fairly large too! By my reckoning 20-30 lbs. And just a few million years back, mara had much larger cousins. Josephoartigasia monesi may have weighed 2 tons! Imagine that, a rodent larger than a bull. Not your average mouse by any means.