An Improved TRAP FOR BATS

May 1974 GE:\ERAL :\OTES 475 Al'i I~IPROVED TRAP FOR BATS Numerous methods of collecting bats have been den "loped, the most important of which are summarized by Constantine (1958: 17) and by Greenhall and Paradiso 1908:8-19), Most of these an; useful only under relatively restricted conditions. Even the widely-used "mist net" requires constant attention, soon becomes d.uuuged, and entangles bats to such an extent that Lipid handling of large numbers is impossible. Constantine (19.58) first described an "automatic bat-collecting device" capable of taking large samples. l~nlike "mist nets" Constantine's trap did not require excessive labor for the removal of captured bats. His original trap, which caught more than -~5,OOOfree-tailed bats. \,';;1.5 too bulky for general use, but modifications (Constantine, 1\:lS8; 1962; 1969) produc--c! smaller, folding traps which were easily transported by two men. Each of Constanu.«:", traps consisted of a single rectangular frame, supporting fine vertical wires spaced ut one inch intervals and kept taut. These traps proved satisfactory for vanrpi res and for fast fl~'ing free-tailed hats, but were not generally useful in capturing other species. In order to trap efficiently the highly maneuverable vespr-rtilionid and emballouueid bats, I have developed a trap which employs a double frame and other modifications. This trap is easily portable by one man and can be assembled or broken dov II in -t.Sminutes. It can be used under a wide range of conditions and has proven successful in --c.rpt uring many temperate and tropical species. The trap consists of two rectangular frames held two inches apart by four I} inch (.6i centimeters. cm) threaded steel rods (Fig. Ia }. The sides of the frames consist of aluminum tubes (inside diameter, 29 millimeters, nun: outside di.uneter, 32 111m) 72 inches (182.9 em) long. A hole is drilled 1~-i inches (3.2 em) from, each end of each tube for boltn.c the frame together (Fig. l.b). and two more located 31,~ und ·nl inches (h.3 and 10.8 em up from the base on each side are for attachment of the bag support plates \ Fig. Le}. TL,' extra set of holes allows for vertical adjustrue-nt of the bag. Additional holes aredrtll-d 22:;.! and 27::'_1inches (57.8 and 70.5 em) from the base to allow for attachment of legs (Fig.ld). The upper and 10\\"(>rends of eadl are identical, consisting of tvvo ();2-inch 157.,3 em) lengths of ahuuinum tubing (iHSH1c diameter. 2.5 c-ru ; outvidc di.un.ter. 2.8 em Theends of each tube ure cut at~·S d--m-cc-s. .uu] a fi-inclt \ 15.:2 c-ru 'I lengt! of the same --ib' of tubing is welded at that an aleFig. 11, The end pieces are' drilled til match the hob--. previously drilled in the sides into which tLL>~- telescope and are bolted. Holes are drillt'cI 5 1 /-! and :!l~S inches (13.3 and 5 tfi cm t [rom each l'nd\ Fig. IlJ) for sl.\ppurt of tl» aluminum angle to which the wires are att.rclu-d. For attachment of wire strands a section (It angled aluminum .59 inches i I-19.Y em) jUli'.c: is drilled to match the holes already present in the frame (Fig. lb . One section is bolted to the base whereas the other is attached to the top h~' means of four c-mch (IL7 ern I threaded steel rods (Fig. Ib) which allow for udjustment of wire tension. Prior to installation on the frame the angled sections are drilled at l-inch (2.5 em) intervals to allow for attachment of wires (Fig. Ib ): Receptacles for the legs arc formed by \\Tlding 1uti and -l t i-fuch 20.7 and 10.8 crn' pieces of aluminum tubing (inside diameter. 2.9 Oil; outside diameter :3,2 ctu ) together at an angle of 80 degrct's ~Fig. l d \. Each 10 1 ~-inch 2G.7 em 'j section is drilled 3~~~and 8 1 i inches (8.3 and 21.0 cm ) from its upper e-nd, ~t11o\\'ing for attachment to the frame ( Fig'. .ld ): A hole is drilled on the inner side of tiH:l' ~~inch \ 11.--1crn ) section Poi inches (3.2 em) from the lower end, and a l_~-inch (.6--t cm : nut is welded OH'r the hole (Fi~. Ic ). Each leg consists of two :3o-indl (91.-4 em) sections of tl'lc<'-()r~n~ aluminum tubing (inside diameter, 2.5 cm; outside. diameter. 2.8 em fitting over inslue diameter, :2.0 em; outside diameter, 2.2 ern}. The outer section is drilled 2 1 1inches (5.7 l'm) from one end, and a %-inch (.G--1 cm) nut is welded over the hole (fig. Lc ). TIll.' L'~s are attached to the kg receptacles and adjusted for length by use of thumb bolts (Fig. L'!. 476 JOURNAL OF MAM~IALOGY Vol. 55, No.2 The canvas bag is 25 inches (6.3.5 cm) deep by 60 inches (152.4 cm) long and 14 inches (.35.6 cm) wide at the top. The original material is 60 inches (152.4 cm) long and 5~ inches (1.37.2 em) wide, allowing 2 inches (5.1 em) extra per side which is folded outward and sewed down along the entire length. This leaves space for the supporting rods (Fig. l.e) from which the hag is suspended. Both ends are completely lined with plastic on the inside, and a strip of plastic 5 inches (12.7 em) wide and 15 inches (.38.1 em) long is sewed vertically to the bag adjacent to the ends beginning at the top of the bag. It is important that all seams be turned to the outside so that bats cannot climb out. An additional plastic flap 18 inches (45.7 cm I oide and 60 inches (152.4 cm) long is sewed along the edge, to the outside of the hag, 2 inches (5.1 em) below the top on both sides of the bag. Then each flap is sewed anam along the le-ngth of the inside of the hag 6 inches from the top, allowing a Iu-inch \ '::':.5.-4 em) flap to hang free On each side. Bats are unable to climb the plastic and take shelter beneath the flaps. Metal grommets should be attached along the bottom of the bag, -in the middle, and at both ends to act as drains in case of rain. A bal! support plate (Fig. Le) is bolted to each end of the trap -Pi? inches (11.4 em) above the base. Each plate consists of a single piece of aluminum I-t inches (35.6 em) long, l~ inch (.32 em) thick, and 11/2 inches (3.8 em) wide. Five vertical slots arc cut % inch (1.59 crn ] deep by '4 inch (.6~ cm) wide, at lf2-inch (1.27 cm) intervals .. beginning '/2 inch (1.27 crn ) from the end of each plate (Fig. Ie ): Horizontal slots 2 inches (5.1 cm) long by '.~ iw')' (.64 cm ) wide begin 4 inches (10.2 cm ) from each end (Fig. Ie ): The latter allow for adjustment of distance between the frames. The bag is hung from the support plates by means of two 72-inch (182.9 em) aluminum rods, %: inch (1.27 crn ) wide by '4 inch (.64 cm) thick. The following nuts, bolts, and washers are required in order to assemble the trap (all are 1'4, inch (.64 em) in diarnct--r 0): 36 wing nuts, -14 regular nuts, 28 washers (to support attachments to angled aluminum), 14 3-ino:::h (7.6 cm ) bolts, 10 llf2-inch (3.8 cm) bolts, four 2-inch (5.1 cm) bolts, and eiuht thumb nuts. At least 12 of the nuts must be aluminum in order to permit heliarc welding for attachment to legs. In order to string the trap with wire, the wing nuts on the four 5-inch (12.7 cm ) threaded rods at the top of the trap (Fig. Ib) are loosened until each rod projects 3 inches helow the frame. Springs are attached at j-tnch intervals along the top (Fig. lh ), and the trap is strung with .OOS-inch (.20 mm ) diameter stainless spring steel wire. Each strand is tied May 1974 GENERAL NOTES 477 individually starting at one side and working to the other. Strand') should be pulled until barely tight in order to insure uniformity of tension. When the trap is strung the wing nuts at the top can be tightened slightly in order to adjust for any bow in the middle of the frame. Capture success for batsencountering such a trap is largely dependent upon two ad- [ustrnents. Of greatest importance IS the tension of the ve-rtical wires. Generally, the wires should be tightened until no slack remains, but little or no more. Special conditions, however, necessitate occasional adjustment, depending on the speed and angle of approach of the bats. The tautness of the wires should he directly proportional to the speed of the bat. When bats escape by bouncing off, the wires should be loosened, and when they pass completely through both frames, tightened. The spacing of \dres between the tvvo frames is normally 3 inches. When the distance between the frames is either increased or decreased the number of bats capable of passing through both seems to increase. It is possible, however, that slight adjustment in width between the Frames would increase the trap's effectiveness for a particular species or body size of hat. Like "mist nets," traps arc set wherever bats are likely to pass; traps are effective in cave entrances, over trails and streams, under small bridges, under treesin open fields, and at water holes and feeding sites. Because one trap covers an area of only 6 by 5 feet. naturally "closed-in" sites along a suspected flyway are usually selected, or else brush or netting is used to reduce the area through which buts may flv. I thank ~Ir. Arthur ~1. Oreenhall for his initial suggestion;, Dr. Charles O. Handlev, [r.. for use of facilities at the United States Xational Museum, Dr. Thomas H. Kunz for his extensive testing of early trap designs, and Dr. Robert S. Hoffmann for critically reading the manuscript. This work was supported by grants from the u.s. Army Medical Research and Development Command (Contract D..\-~9-193-~[D-l788), The University of Kansas Biomedical Sciences Support, the Theodore Roosevelt Memorial Committee of the American Museum of Xntural History, and the Elizabeth .\1. Watkins Fur.d of the University of Kansas 'Museum of Xatural History. LITERATCRE CITED CO~STANTI:'\E. D. C. 1958. An automatic bat-collecting device. .r. Wildlife \1g-Il1t.. 17-22. 1962. Methodes de luchn control Ins vampiros transmisores de la rabin. BoL Ofic. Sanitaria Panarnericana . .33:7-12. 1969. Tr.unpa portatil para vampiros usad., en prograiuas de carnpanu nntirrabicn. Bol. Oftc. Sanitaria Panamericana, 67: 39-!2. CHEE ...•.iULL. :\. \1.. A:'\D J. L PARADISO. 1968. Bats and bat banding. Resource Publ. Bur. Sport Fisheries and Wildlife, 7l:iv + 1-18. \(EHU D. TCTTLE •. \[wellTn of Natural History, Unit.ersitu of KaTl.'lQs. LatL'rcncc Kan'.>as 6604.5. Submitted. 8 'tay 1.97.3. Accepted 6 Xocemher 1.97.3.