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An inexpensive method to avoid tail damage to kangaroo rats (Dipodomys spp.) when using Sherman traps.

The tails of long-tailed rodents occasionally are injured or severed when a sprung trap door comes into contact with them. This injury, which commonly occurs to long-tailed rodents (e.g., Dipodomys spp.) when caught in box live traps, is a methodological problem. Tail injury may cause trap-shy behavioral changes in capture probabilities (White et al. 1982) which could influence the results of mark-recapture studies. Additionally, a severed appendage may shorten the life span of some small mammals (Pavone & Boonstra 1985). Further, morphologically damaged specimens are less desirable for museum collections. Finally, concerns for humane treatment of animals warrant that the least harmful sampling technique be chosen (Schmidt 1990).

A simple solution to avoid tail injuries is to use larger traps when sampling for long-tailed rodents. However, this may not always be a feasible alternative. With this in mind, an inexpensive method which significantly reduces the frequency of tail injuries (without disfiguring traps) when using large Sherman folding, aluminum live traps (8 by 9 by 23 cm) was developed.

The device was made from a modified standard small binder clip. This study utilized binder clips from Charles Leonard, Inc. (#BC-02), but binder clips of the same size from any company could potentially be used. The binder clips were modified by bending one of the arms of the clip to a 70[degrees] angle inwards (towards the other arm when both arms are folded back) 1.3 cm from the end of the arm. The device is attached to the trap by clamping it (similar to how one would clamp papers together with a standard binder clip) to the top left corner of the front trap door. The modified arm is positioned towards the outside of the door and folded back. The unmodified arm lies along the backside of the door, folded forward (towards the base of the door) and lies flush against the inside of the door. When the trap is opened, the modified arm rests on top of the interior plate (inside of the trap) which is located directly in front of the treadle. With proper modification and application of the binder clips, traps can be set as they would normally be without the device in place. When the trap is sprung, a one to one and one-half cm space remains open at the top of the trap door. The device can be attached through the back door when the trap is fully assembled or directly when the trap is apart.

Traps can still be folded with the tail-saver device in place. They cannot, however, be folded as flat as traps that do not have the device attached. Therefore, standard Sherman trap boxes can still be used, but placement of only seven traps into a standard 10-trap slot is recommended.

To test the device, 20 study plots were sampled in a saltbush (Atriplex canescens) community on Holloman Air Force Base in the Tularosa Basin of south-central New Mexico during July 1996. Ten study plots had the tail-saver device employed on all traps and 10 study plots did not have the tail-saver device employed. Within each study plot 50 traps spaced at 10 m intervals were placed within two, 250 m trap lines spaced 25 m apart. Traps were baited with quick oats and set for a single night. Traps were checked the next morning and tail status (injured with visible bleeding, severed or undamaged) was recorded for each kangaroo rat. Blood or tail pieces were observed for every animal that was classified as injured or severed, respectively. Additionally, captures of other species were recorded to determine if smaller rodent species were able to escape the traps when the tail-saver device was employed.

Thirty-five kangaroo rats (Dipodomys merriami and Dipodomys ordii) were captured in traps which had the tail-saver device. None of these subjects had severed or injured tails. Twenty-seven kangaroo rats were captured in traps which did not have the tail-saver device. Twelve of these individuals (44.4%) had either severed (nine) or injured (three) tails caused by trapping efforts from the previous evening. Because injured or severed tails both indicate damage, these data were pooled for statistical analysis.

Data were converted to the percent of tails damaged and analyzed with Wilcoxon Signed Rank Test. Results showed that fewer tails were damaged on study plots which had traps with the tail-saver device (P = 0.015, one-tailed test, 9 df). Hence, the tail-saver device significantly reduced the frequency of tail damage to kangaroo rats when applied to large Sherman live traps.

Chaetodipus penicillatus (n = 14, n = 6) and Perognathus flavus (n = 1, n = 1) were also captured in traps with the tail-saver device and in traps without the tail-saver device, respectively. These data provide limited support that small pocket mice cannot easily escape traps which have the tail-saver device attached. However, the space at the top of the trap left by the device is dependent on the angle that the arm of the binder clip is bent. Thus, workers should endeavor to bend their clips consistently.

The tail-saver device is an inexpensive means to help prevent damage to kangaroo rat tails. If bought in bulk, binder clips can be modified into tail-saver devices for a few cents each. This device could have applications for both mark recapture studies and museum collections. Workers should be cautious, however, if using traps that have doors that have been chewed when using this device. Once traps are serrated, small mice could wound themselves trying to escape.


We thank Environmental Flight, Holloman Air Force Base, particularly H. Reiser for logistical support. Comments from J. Anderson and two anonymous reviewers helped to improve earlier drafts of this paper. Funding was provided by USA-CERL and Texas Tech University. This is Texas Tech University College of Agricultural Sciences and Natural Resources technical publication T-9-787.


Pavone, L. V. & R. B. Boonstra. 1985. The effects of toe clipping on the survival of the meadow vole (Microtus pennsylvanicus). Can. J. Zool., 63(3):599-601.

Schmidt, R. H. 1990. Why do we debate animal rights? Wildl. Soc. Bull., 18(4):459-461.

White, G. L., D. R. Anderson, K. P. Burnham & D. L. Otis. 1982. Capture-recapture and removal methods for sampling closed populations. Los Alamos National Laboratory, LA-8787-NERP, Los Alamos, New Mexico, xvi + 235 pp.

J. Jeffrey Root*, Nicole L. Marlenee, Eric E. Jorgensen and Stephen Demarais**

Department of Range, Wildlife and Fisheries Management

Texas Tech University, Lubbock, Texas 79409

Current addresses:

*Department of Microbiology, Colorado State University

Fort Collins, Colorado 80523 and

**Department of Wildlife and Fisheries, Mississippi State University

Mississippi State, Mississippi 39762

JJR at:
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Title Annotation:GENERAL NOTES
Author:Root, J. Jeffrey; Marlenee, Nicole L.; Jorgensen, Eric E.; Demarais, Stephen
Publication:The Texas Journal of Science
Geographic Code:1USA
Date:Feb 1, 2000
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