| Populations in this area have been kept low because of repeated outbreaks of campestral plague. |
|
| The geophilous species of eastern North America are with one partial exception campestral in distribution, as would naturally be expected. |
|
| Sylvatic plague, sometimes also called campestral plague, is ever-present in endemic areas, circulating among rock and ground squirrels, deer mice, voles, chipmunks, and others. |
|
| The other woodland types are apparently better able to adapt themselves to certain features of a campestral environment, such as the thicket and scrub formations which tend to overrun waste lands. |
|
| The dimorphic species are restricted in the south to thicket habitats, but in the north, where they are more generally distributed, they occur also on campestral stations. |
|
