Midwest Mustelid Trends


Principal Investigator:

Robert W. Klaver

Michael Rentz

Student Investigator:





April 15, 2015  to March 31, 2016

Funding Source(s):

Iowa Department of Natural Resources (IDNR), Wildlife Diversity Small Grant

Goals and Objectives:

The core objective of the project was to determine the presence/absence of 3 weasel species in Iowa. We hoped to have high enough detection probabilities to determine coarse distribution. I also planned to use the results of this study to select locations for more intensive research in subsequent seasons, including snow tracking, mark-recapture, and possibly radio/gps collaring.


All 48 sites had a single hair tube for at least 10 days, most the full 2 weeks. Nearly every tube showed visitation by mammals, in many cases mice (assume Peromyscus spp) and northern short-tailed shrew (Blarina brevicauda) based on tracks and scat. Thirty one sites had collectable hair on the brushes, 14 had no collectable hair, 1 trap is still in transit from a colleague who collected it in December, and 2 traps could not be found.

For the 31 traps with hair, we were able to rule out weasels in 14 cases (the hairs keyed out as belonging to rodents or shrews). A small number of samples consisted of only underhair, which could not be keyed out (5) or had hair that was damaged and could not be identified (2). In a further 2 cases hair was collected from the brush, but was lost during the transfer to the slides. In each case there was only a 1-2 hairs, likely of underhair.  We identified 8 samples as containing hair from weasels.


Conclusions and Recommendations:

We were successful in designing and deploying 48 hair snares across the state of Iowa, and were able to recover 46 snares. All but the single tube collected by a colleague have been analyzed using the techniques outlined in the proposal. Although not part of the original objective, the grant allowed 6 ISU students to become involved in faculty research. The opportunity to be a valued team member in this way is invaluable to students.

We would like to submit the 8 weasel samples for DNA testing to determine if we can positively identify the species, as was the goal of this project. Identification to species using only the hair would require a destructive technique to create a reverse image cast of the cuticle. We will investigate this route if DNA sampling is not feasible due to low follicle numbers or if the samples have degraded.

We also plan to re-visit these sites during the next year to look for weasel sign, and begin to get an understanding of how the weasels are using the sites, and how many individuals may reside in the area. This will likely involve snow tracking to begin with, but may include more intensive efforts at non-invasive techniques such as track plates, more snares, or cameras. The extensive nature of the completed project will be helpful in identifying sites on which we can focus these efforts.

I have a new group of students who will be revisiting 2 of the sites (one with a weasel find and one without) and adding an additional 2 sites that were not surveyed. On these sites they will survey intensively, with a grid of 32 snare tubes, rather than a single tube. They hope to determine if the increased effort increases the likelihood of identifying a weasel, and if they can determine space use across the grid.

04/15/2015 to 03/31/2016
Award Number: