Prairie dog engineering indirectly affects beetle movement behavior

Abstract

Previous studies have shown that landscape structure influences animal movement and population structure. In this study, we show an indirect interaction between beetles and prairie dogs due to prairie dog ecosystem engineering. Gunnison's prairie dog (Cynomys gunnisoni Hollister) towns have more bare ground and are structurally less complex than adjacent unmodified grasslands. This results in bare ground facilitating beetle movement. Differences in landscape structure between prairie dog towns and unmodified grasslands had a significant effect on the movement of the darkling beetle, Eleodes hispilabris Say. Beetle movement tended to be more linear (pathway fractal dimension approached 1) on prairie dog habitats and more sinuous on adjacent grasslands. Beetle velocity was 44% greater and net displacement 63% farther on the prairie dog habitat. These differences were also evident at fine scales when beetles moved between grass and bare ground patches regardless of habitat. Beetles moved 2.3 times faster and displaced 3.0 times farther after making this microhabitat transition. Beetles avoided grass and selected bare ground for movement 12–22% more than the percent of bare ground on the landscape. Since beetles exhibited directed movements and grasslands inhibit movement, it might be expected that beetles would accumulate in this habitat upon encounter. However, beetles were approximately twice as abundant on prairie dog towns as on adjacent grasslands. A difference in beetle movement behavior, between prairie dog towns and grasslands, suggests that prairie dog towns are an important component of this desert grassland landscape for these beetles.