Figure 8.15

GEO-GRAPHIC: Prairie dogs and their partners. Prairie dogs are keystone species in North American temperate grasslands. They are mutualistic partners of many grassland organisms, including bison and pronghorn. In addition, prairie dog burrowing improves plant growth in grasslands by aerating the soil and allowing water to better infiltrate the ground. The animals also add nitrogen to the soil with their fecal pellets.

(Left, © Merilee Phillips/Flickr Open/Getty Images; center, © Werner & Kerstin Layer Naturfoto/Picture Press/ Getty Images; right, © Danita Delimont/Gallo Images/Getty Images)