Iowa’s beaver records number 351, the eighth-densest tally among the state’s mapped mammals, and they trace flowing water into nearly every corner of the state.
An engineer along Iowa’s spring-fed bluffs
Beavers need permanent water and woody plants close to the bank, and the Driftless Area’s spring-fed streams around Decorah supply both: cold, steady flow cut into timbered limestone bluffs, lined with willow and cottonwood for gnawing and lodge-building. That’s a sharper match for the species than the shallow, seasonal wetlands of the Des Moines Lobe’s prairie-pothole country farther west, where potholes can dry down enough by late summer to leave a colony without the deep water it needs to hide a lodge entrance.
Two seasonal surges in the records
Records climb sharply from March through April, when two-year-old beavers disperse from their birth colony to establish new ones and the fresh work of a newly settled site, cut stems, packed mud, gnawed stumps, is easiest to spot. They rise again in October and November as colonies haul branches into an underwater food cache ahead of freeze-up. Both spikes show up clearly in Iowa’s record count, with the quieter mid-summer months in between reflecting a colony that’s already settled in and harder to notice, not one that’s disappeared.
Status in Iowa
NatureServe ranks the beaver S5, secure, and native to Iowa. Once trapped heavily across Iowa during the 19th-century fur trade, beavers have since recovered enough to occupy nearly every stream system in the state capable of supporting a dam or a bank den.
Full species profile
