The demise of the American bison, Bison bison (L.), following European settlement has given rise to two hypotheses regarding the fate of their dung-associated insects. The “extant” hypothesis proposes that all of these taxa now persist in the dung of cattle, Bos taurus L. The “extinction” hypothesis proposes that a subset of these taxa were unable to make this transition and have gone extinct. We examined these hypotheses by comparing the response of coprophilous insects to dung of bison versus cattle on similar diets and versus dung of cattle on different diets. Results showed insects to be more responsive to changes in diet than to changes in host species and, therefore, were supportive of the extant hypothesis. To our knowledge, these data provide the first experimental comparisons of bison dung versus cattle dung as habitat for coprophilous insects.