Largest colony of mammals

The black-tailed prairie dog (Cynomys ludovicianus) is a rodent in the family Sciuridae found in the western USA and northern Mexico. It forms large colonies or “towns” – an extensive system of burrows and mounds. In 1901, the zoologist and ecologist C H Merriam found a prairie dog town that spanned an area of 6.5 million hectares (16 million acres; 65,000 km2; 25,100 sq mi) - almost the size of the Republic of Ireland - in West Texas, USA. It was estimated that the colony supported more than 400 million prairie dogs.

Their eco-engineering enhances vegetation, invertebrate and vertebrate diversity, but their abundance has drastically declined since 1901 due to land use change (conversion to farming, pasture), extermination because they were considered pests, and disease.