structural:scholar_edition, structural:summarization, linguistic:paraphrasing
Predators

Small mammals ingest conifer seeds, and also consume seedlings. Cage feeding of deer mice (Peromyscus maniculatus) and red-backed vole (Myodes gapperi) showed a daily maximum seed consumption of 2000 white spruce seeds and of 1000 seeds of lodgepole pine, with the two species of mice consuming equal amounts of seed, but showing a preference for the pine over the spruce (Wagg 1963). The short-tailed meadow vole (Microtus pennsylvanicus Ord) voraciously ate all available white spruce and lodgepole pine seedlings, pulling them out of the ground and holding them between their front feet until the whole seedling had been consumed. Wagg (1963) attributed damage observed to the bark and cambium at ground level of small white spruce seedlings over several seasons to meadow voles.

Once shed, seeds contribute to the diet of small mammals, e.g., deer mice, red-backed voles, mountain voles (Microtus montanus), and chipmunks (Eutamias minimus). The magnitude of the loss is difficult to determine, and studies with and without seed protection have yielded conflicting results. In western Montana, for example, spruce seedling success was little better on protected than on unprotected seed spots (Schopmeyer and Helmers 1947), but in British Columbia spruce regeneration depended on protection from rodents (Smith 1955).

An important albeit indirect biotic constraint on spruce establishment is the depredation of seed by squirrels. As much as 90% of a cone crop has been harvested by red squirrels (Zasada et al. 1978). Deer mice, voles, chipmunks, and shrews can consume large quantities of seed; one mouse can eat 2000 seeds per night. Repeated applications of half a million seeds/ha failed to produce the 750 trees/ha sought by Northwest Pulp and Power, Ltd., near Hinton, Alberta (Radvanyi 1972), but no doubt left a lot of well-fed small mammals. Foraging by squirrels for winter buds (Rowe 1952) has not been reported in relation to young plantations, but Wagg (1963) noted that at Hinton AB, red squirrels were observed cutting the lateral and terminal twigs and feeding on the vegetative and flower buds of white spruce.

Red squirrels in Alaska have harvested as much as 90% of a cone crop (Zasada et al. 1978); their modus operandi is to cut off great numbers of cones with great expedition early in the fall, and then "spend the rest of the fall shelling out the seeds". In Manitoba, Rowe (1952) ascribed widespread severing of branch tips 5 cm to 10 cm long on white spruce ranging "from sapling to veteran size" to squirrels foraging for winter buds, cone failure having excluded the more usual food source. The damage has not been reported in relation to small trees, outplants or otherwise.

Porcupines (Erethizon dorsatum L.) may damage spruce (Nienstaedt 1957), but prefer red pine. Bark-stripping of white spruce by black bear (Euarctos americanus perniger) is locally important in Alaska (Lutz 1951), but the bark of white spruce is not attacked by field mice (Microtus pennsylvanicus Ord), even in years of heavy infestation.