When traps are set near carcasses additional care should be undertaken to
underpin the trap pan so that it will not spring under the weight of a
magpie, buzzard, or other carnivorous bird that may be attracted to the
carcass.
In forested areas a mountain-lion hunter may find his traps sprung by
small animals, for squirrels and other rodents (and sometimes small
birds) may dig or scratch around and between the jaws of the trap. Unless
the trap pan is properly supported, these animals are unnecessarily
endangered, and in addition the trap is frequently sprung. This may be
prevented by setting the trap pan so that it will carry a weight of
several pounds.
One simple way of underpinning the trap is to place a small twig
perpendicularly from the base snugly up to the middle point of the pan.
Instead of the small twig, some hunters use a fine coiled-steel spring.
Such contrivances will permit the trap pan to carry the weight of the
smaller mammals or birds without endangering them or releasing the trap
jaws and thus spoiling a set well placed for a mountain-lion. Devices
adjusted to mountain-lion traps to prevent their being sprung by small
mammals and birds are illustrated in Figure 4. The Biological Survey pan
spring (fig. 4, D), recently developed in this bureau can be readily
attached to the No. 14 steel trap used for mountain-lions. A slightly
larger spring is required for the No. 4½ trap. A patent on this device
has been applied for, to be dedicated to public use.