Modern Snares for Capturing Mammals: - Association of Fish and ...

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We do not believe, for a static load test, that the length of the snare will have any appreciableinfluence on breakaway ratings. While snare cable can stretch when tension is applied, thepotential is quite low that any stretching will occur for the typical snare lengths used andloads applied, and any stretching that may occur is not likely to be a noteworthy componentof breakaway variability. We acknowledge, however, that after a breakaway device israted, subsequent field testing to evaluate efficiency and selectivity for a specificapplication (e.g., capture wolves but release moose) should always report the length ofsnare tested, as snare length will have an impact on efficiency and selectivity.Although we only recommend one component of the static load test (i.e., cinch the looparound a 2-inch steel pipe), we do discuss 2 possible testing methods as a way to illustratepossible approaches.1) Use of weights – the snare is suspended from a rigid anchoring point, with the snare loopcinched around a 2” steel pipe. Attached to and hanging below the steel pipe is a ‘loadtray’ upon which weights of the desired increment are sequentially placed until thebreakaway device releases. The breakaway poundage rating is the sum of the load trayweights, the weight of the tray, and the weight of the steel pipe. In such a design, it isimportant to ensure that weights are gently placed, not dropped, on the load tray. Uponrelease, the weight tray will drop, requiring careful safety considerations.2) Use of slow-pull devices and load scales – in this type of design, the testing apparatuscould be positioned vertically or horizontally. On 1 end is a stationary device used togenerate tension on the snare. Examples include a hydraulic cylinder, an electric winch,or a ratcheting pulley. Attached to this force-generating mechanism is a device toquantify the amount of force being exerted. Examples include a heavy-duty spring scaleor more sophisticated digital strain gauge or load cell. The anchor end of the snare isthen attached to the measuring scale, while the snare loop is cinched around a 2” steelpipe (with pipe attached to a fixed point). As tension is slowly increased, the measuringscale should preferably record the maximum force upon breaking, rather than requiring aperson to read it during the test. Because there will be tension on the snare upon release,appropriate safety is warranted.We note that there will be some amount of breakaway variability attributable to quality controlduring breakaway manufacturing. Manufacturers or researchers involved in determining a ratingfor a particular breakaway device should consider an appropriate sample size for quantifyingvariability, and if applicable, those involved with determining compliance with breakawayrecommendations or laws must consider how much variation is acceptable.12Ver. 1.0
Loop StopsA loop stop is a device that is attached to the snare cable to prevent the loop from either openingor closing beyond a specified point. They can be placed either inside or outside the loop, therebydetermining either a minimum or maximum loop circumference. Loop stops are consideredoptional snare components, and while used most commonly to influence selectivity, they canalso influence snare lethality and efficiency (see pp. 17, 20, 21, and 22).Minimum Loop Stop – a device incorporated inside the snare loop that prevents the loop fromclosing beyond a specified circumference.The term “deer stop”, commonly used by many, should be considered a specific application fora minimum loop stop (i.e., a stop that prevents loop closure smaller than the diameter of a deer’sleg).Maximum Loop Stop - a device incorporated outside the snare loop that prevents the loop fromopening beyond a specified circumference.SwivelsSwivels are often incorporated into a snare to prevent the wires or strands in a cable fromkinking or separating, and ultimately breaking, if an animal twists or rolls. While they areprimarily intended to improve capture efficiency of snares (see p. 22), they may play a role inother snare performance measures (see p. 18).In-line swivels may be used instead of, or in conjunction with, end swivels, and may beparticularly useful in situations where there is concern that the anchoring system, or vegetationbetween the anchor and the animal, could cause the end swivel to become effectively inoperable.The closer the in-line swivel is to the animal, the more likely it will retain its intendedeffectiveness.End Swivel - a device incorporated at the point where the snare is attached to a stake, tree, orother anchoring point that allows the snare to freely rotate if the animal twists or rolls.In-line Swivel – a device incorporated between the anchoring point and the opened snare loopthat allows the snare to freely rotate if the animal twists or rolls.Many swivel designs are currently available, and a few examples are shown below.Snare ActivationEnd swivel In-line swivel In-line swivel End and In-line swivel13Ver. 1.0
Page 2 and 3: ACKNOWLEDGMENTSThis document was pr
Page 4 and 5: FORWARD“Modern Snares for Capturi
Page 6 and 7: facilitate over-harvest of furbeare
Page 8 and 9: In either single-strand designs wit
Page 10 and 11: Most snare locks currently availabl
Page 14 and 15: SNARING SYSTEM COMPONENTSIn additio
Page 16 and 17: snaring system can be characterized
Page 18 and 19: the animal is able wrap the snare c
Page 20 and 21: caught, but a deer may simply walk
Page 22 and 23: animals may be more apt to see larg
Page 24: There will always be a need to desc

Modern Snares for Capturing Mammals: - Association of Fish and ...

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