Hispid cotton rat ( Sigmodon hispidus ) in Nebraska: distribution, reproduction, and seasonal activity

The hispid cotton rat ( Sigmodon hispidus ) has occurred in Nebraska for about 50 years and entered the state from the south via northward movements through Kansas. However, little is known about its status or distribution in the state in recent decades. We conducted surveys for S. hispidus in southern Nebraska at historical sites and sites without previous records to determine its current status. From 2004 to 2008, we documented cotton rats at 9 of 12 historical sites in south-central and extreme southeastern parts of the state, and we captured this species at 13 new sites in southwestern and south-central Nebraska. In the past 3 decades, the distribution of S. hispidus has expanded westward but not northward in the state. An explanation for such a shift is unclear. At this northern edge of its geographical range, pregnant females were captured from early April to early October, and nonreproductive females were captured from November to January. Males with enlarged testes occurred from late March to September. Aspects of its natural history in Nebraska are similar to those reported in Kansas.