TY - JOUR
AU1 - Brand, Raymond, H.
AB - In recent years a great deal of attention has been given to the design of trapping procedures that conform to some of the assumptions of the statistical techniques often applied to small mammal populations (Stickel, 1946, 1948, 1954; Hayne, 1949; Morris, 1955). Basic to a number of the mathematical models used in the analysis of population data is the assumption of equal probability of capture. Tanaka (1951) and Edwards (1952) have demonstrated that this assumption is violated on both the individual and species level. An additional source of error, although obvious, has received little consideration in many population analyses. This is the practical problem of the disturbance of traps which reduces to zero the probability of a capture occurring for any disturbed trap. Admittedly, this probability is of a different nature from those referred to above, since it is independent of the individual or species, but it is of no less importance in studies concerned with the ascertainment of the number of effective traps available on any given trapping night. That disturbance of traps does occur (in addition to the evidence presented in this paper) and with sufficient frequency to prevent further trapping, has been reported by Brown (1954). He states that while trapping at Silwood Park Field Centre, Berkshire, England, “Squirrels disturbed traps and pulled them apart until trapping of small mammals had to be abandoned.” In connection with a study of the habitat relations of the wood mouse (Peromyscus leucopus noveboracensis) on the E. S. George Reserve, Livingston Co., Michigan (Brand, 1955), I was confronted with a similar problem of excessive trap disturbance. It was essential in this study that all trapping stations provide equal opportunities for capturing small mammals. The consistent disturbance of many stations during preliminary trapping led to the development of a device to protect the traps from further disturbance. I wish to acknowledge F. C. Evans, L. R. Dice, and I. J. Cantrall for their encouragement and helpful suggestions in the development of this protective device. The funds for the aluminum tubes were supplied by the Institute of Human Biology of the University of Michigan. After experimenting with several materials and construction plans, it was found that light weight sheet aluminum (#26 gauge) could be folded into rectangular tubes into which traps could easily be placed (Fig. 1). The folding process may be carried out by bending the aluminum around a four foot length of 4 × 4 lumber, creasing the bends with a wood mallet. If a number of tubes are required (more than 100), it is more economical to have them shaped by a precision machine brake available at most sheet metal shops. A one-half inch overlap should be left on one side so that sheet metal screws can be used to fasten the tube securely together. The position and number of holes at the ends of the tube (cf. D of Fig. 1) should be determined by the size of the largest mammal that one wishes to capture. Various combinations of the position and number of these holes will permit the selective trapping of certain species without varying the size of the trap. Galvanized iron wire in the form of croquet wickets provides an easily inserted and durable block to the entrance of unwanted species. The tubes may be staked to the ground in the manner illustrated in Fig. 1. The wood (or metal) stakes serve as a permanent foundation to which the tubes may be fastened by means of flexible iron wire. The wire is easily loosened to permit the removal of tubes to another trapping station. After a tube has been secured to the ground, set traps may be placed inside by removing the wires from one or both ends and sliding the traps into position. Care must be exercised in placing traps in the center of the tube so that animals cannot reach them through the wires at the end. In this study, small, fiber-board traps were used (Blair, 1941), but many types of standard traps, either live or snap traps, could readily be used in this protective device. Fig. 1 Open in new tabDownload slide Construction diagram of aluminum tubes Fig. 1 Open in new tabDownload slide Construction diagram of aluminum tubes Table 1 presents the amount of trap disturbance that occurred using several different trapping procedures. The first part of the table indicates the excessive amount of disturbance prior to the use of any protective device (trapping periods in the summer and fall of 1952 and the spring of 1953), whereas the second part illustrates the effectiveness of the aluminum tubes in eliminating disturbance. The tubes were put into use in June, 1953, and were used continuously for trapping periods in the summer and fall of 1953 and 1954. For each trapping procedure used (lines, grids, and isolated points), one night has been selected to illustrate the maximum amount of disturbance that occurred. A summary is also given of the amount of disturbance for total trapping for each trapping procedure. The percentage of disturbance is calculated on the basis of the number of trapping stations disturbed rather than on the number of traps disturbed, since the number of traps at each station varied from one to eight for the different procedures used. Stations were considered disturbed if one or more traps were turned over or pulled out of position, or were otherwise incapable of capturing a small mammal when they were checked on the next morning (treadle mechanism jammed, etc.). Table 1. Effectiveness of aluminum tubes in eliminating trap disturbance Date . Trapping procedure . Trapping nights* . Minimum dist. (ft.) between stations . No. of trap stations set . No. of trap stations disturbed . Percentage of disturbance . Before using tubes 1952 Summer Trap lines 1 45 32 32 100 16 45 315 159 50 Fall Trap grids 1 60 100 87 87 8 60 800 390 49 1953 Spring Isolated points 1 240 32 22 69 12 240 385 109 28 Using tubes 1953 Summer, fall, &954 spring Fall Isolated points 1 240 30 2 07 76 240 2040 25 01 Trap grids 1 120 41 2 05 4 120 164 5 03 Date . Trapping procedure . Trapping nights* . Minimum dist. (ft.) between stations . No. of trap stations set . No. of trap stations disturbed . Percentage of disturbance . Before using tubes 1952 Summer Trap lines 1 45 32 32 100 16 45 315 159 50 Fall Trap grids 1 60 100 87 87 8 60 800 390 49 1953 Spring Isolated points 1 240 32 22 69 12 240 385 109 28 Using tubes 1953 Summer, fall, &954 spring Fall Isolated points 1 240 30 2 07 76 240 2040 25 01 Trap grids 1 120 41 2 05 4 120 164 5 03 * The first line of numerals after each trapping procedure indicates the maximum disturbance on one night; the second line represents the total disturbance for all trapping by that procedure. 439 Open in new tab Table 1. Effectiveness of aluminum tubes in eliminating trap disturbance Date . Trapping procedure . Trapping nights* . Minimum dist. (ft.) between stations . No. of trap stations set . No. of trap stations disturbed . Percentage of disturbance . Before using tubes 1952 Summer Trap lines 1 45 32 32 100 16 45 315 159 50 Fall Trap grids 1 60 100 87 87 8 60 800 390 49 1953 Spring Isolated points 1 240 32 22 69 12 240 385 109 28 Using tubes 1953 Summer, fall, &954 spring Fall Isolated points 1 240 30 2 07 76 240 2040 25 01 Trap grids 1 120 41 2 05 4 120 164 5 03 Date . Trapping procedure . Trapping nights* . Minimum dist. (ft.) between stations . No. of trap stations set . No. of trap stations disturbed . Percentage of disturbance . Before using tubes 1952 Summer Trap lines 1 45 32 32 100 16 45 315 159 50 Fall Trap grids 1 60 100 87 87 8 60 800 390 49 1953 Spring Isolated points 1 240 32 22 69 12 240 385 109 28 Using tubes 1953 Summer, fall, &954 spring Fall Isolated points 1 240 30 2 07 76 240 2040 25 01 Trap grids 1 120 41 2 05 4 120 164 5 03 * The first line of numerals after each trapping procedure indicates the maximum disturbance on one night; the second line represents the total disturbance for all trapping by that procedure. 439 Open in new tab In this study the primary source of disturbance seems to have been the larger mammals of the area (raccoons, foxes, and opossums). The aluminum tubes were exceedingly efficient in eliminating this source of disturbance. The neglible amount of disturbance that occurred when the tubes were in use was probably the result of squirrel and chipmunk activity, since the wires at the end of the tubes were not spaced to prevent animals of this size from entering. In addition to their utility in preventing animal disturbance, the tubes also proved valuable in providing insulation and waterproof covering for the traps. Literature Cited Blair W. F. 1941 . A simple and effective live trap for small mammals . Jour. Wildlife Mgt. , 5 : 191 – 193 . Google Scholar Crossref Search ADS WorldCat Brand R. H. 1955 . Abundance and activity of the wood mouse (Peromyscus leucopus noveboracensis) in relation to the character of its habitat . Univ. Michigan Ph.D. Thesis , University Microfilms , Ann Arbor, Michigan . Brown L. E. 1954 . Small mammal populations at Silwood Park Field Centre, Berkshire, England . Jour. Mamm. , 35 : 161 – 177 . Google Scholar Crossref Search ADS WorldCat Edwards R. Y. 1952 . How efficient are snap-traps in taking small mammals? Jour. Mamm. , 33 : 497 – 498 . Google Scholar Crossref Search ADS WorldCat Hayne D. W. 1949 . Two methods for estimating population from trapping records . Jour. Mamm. , 30 : 399 – 411 . Google Scholar Crossref Search ADS WorldCat Morris R. F. 1955 . Population studies on some small forest mammals in Eastern Canada . Jour. Mamm. , 36 : 21 – 35 . Google Scholar Crossref Search ADS WorldCat Stickel L. F. 1946 . Experimental analysis of methods for measuring small mammal populations . Jour. Wildlife Mgt. , 10 : 150 – 159 . Google Scholar Crossref Search ADS WorldCat Stickel L. F. 1948 . The trap line as a measure of small mammal populations . Jour Wildlife Mgt. , 12 : 153 – 161 . Google Scholar Crossref Search ADS WorldCat Stickel L. F. 1954 . A comparison of certain methods of measuring ranges of small mammals . Jour. Mamm. , 35 : 1 – 15 . Google Scholar Crossref Search ADS WorldCat Tanaka R. 1951 . Estimation of vole and mouse populations on Mt. Ishizuchi and on the uplands of Southern Shikoku . Jour. Mamm. , 32 : 450 – 458 . Google Scholar Crossref Search ADS WorldCat 1956 American Society of Mammalogists
TI - A Protective Device for Reducing Trap Disturbance
JF - Journal of Mammalogy
DO - 10.2307/1376746
DA - 1956-08-01
UR - https://www.deepdyve.com/lp/oxford-university-press/a-protective-device-for-reducing-trap-disturbance-N8DdyraDbT
SP - 428
EP - 431
VL - 37
IS - 3
DP - DeepDyve
ER -