DOC traps are a family of spring traps designed for the Department of Conservation (DOC) in New Zealand. The intention was to replace older spring traps (Fenn traps) with a new generation that would meet humaneness standards based on emerging international agreements.
Three models of DOC trap (the DOC 150, 200, 250) have been approved for use in England to catch grey squirrels, rats, stoats and weasels (see Spring Traps Approval Order 2007).
The Order stipulates that the traps must “be set in the tunnel provided by the manufacturer of the trap for use in the UK”. This is because tunnel design contributes significantly to its humaneness, selectivity and safety.
Weasels and stoats were imported to New Zealand during the 1880s, and began to have a very serious impact on New Zealand's native bird fauna. To combat this, the Department of Conservation adopted the tunnel trapping methods developed during the 1950s for game management in the UK.
However, the recent international debate on humaneness in animal trapping, particularly in the context of fur trapping, had considerable influence on the New Zealand authorities. Field experience and unpublished tests by Landcare in New Zealand (Poutu & Warburton, 2005) indicated that Fenn Mk IV traps did not kill stoats within the sort of time-frame discussed at international levels. This led to the development of alternative trap designs which would meet such targets. These were designated DOC traps and made in three sizes to match different overlapping ranges of target species.
It was apparent from laboratory tests and early field trials with DOC traps that positioning of the animal when it depressed the treadle plate contributed significantly to the humaneness of the outcome. To ensure this in use, tunnels were equipped with double entry baffles at each open end. These consisted of two mesh screens, with apertures cut to allow entry by target animals. The size and position of the apertures ensured a slow approach and positioned the animal optimally. Together the combination of trap and tunnel have been shown to pass international humaneness standards agreed between the EU and fur-trading countries.
The three trap models differ only in size and power, the DOC 150 being the smallest and the DOC 250 the largest. All three models are currently approved for the same list of species. However, the very large DOC 250 would be an overkill for anything smaller than a mink. It is hoped that in due course it will be tested and approved by Defra for that species. The DOC 150 has the same dimensions as a Fenn Mk IV, but similar power to the DOC 200. Because of its larger dimensions, the DOC 200 is actually the easier to set, but obviously appreciably bulkier. On the basis of preliminary trials we would recommend it over the DOC 150 where grey squirrels are the chief target (you might also consider the Kania traps and live-capture cage traps).
The fundamental design is the same in all three DOC trap models. A single grid-shaped moving jaw is powered by springs from a vertical stand-by position to the horizontal. The trigger is a large treadle plate.
A small secondary spring underneath the treadle plate guards against false trips caused by the repeated passage of small non-target mammals such as mice, progressively lowering the treadle until it finally trips. This has been a common problem with Fenn-type traps. The secondary spring in DOC traps is designed to restore treadle height after each disturbance by a small non-target.
All three models are very powerful and could cause serious human injury. Nevertheless, because they are fixed into their tunnels, they are also easy to set, and there is no reason to place your fingers at risk!
A generic limitation with Fenn traps and other body-grip traps, including rotating-jaw traps such as the Conibear and Magnum, is that they kill by striking and crushing the body of the animal. The most humane death would result from a strike to the head sufficient to fracture the skull, causing instant irreversible loss of consciousness. This rarely happens in body-grip traps, in which the best outcome is that the body is gripped in the chest or neck, with brain death following as a consequence.
In other trap types, like the Kania and the DOC series, a head-strike is the intended norm. In 2008 we conducted field trials to compare the DOC 200 with its designated single-entry tunnel against Nº 4 Springer traps (Fenn copies) in customary run-through tunnels to represent current practice. DOC 200 traps almost always struck squirrels across the head, or head and neck, while Springer traps almost never struck the head.