The efficacy of conifer seeds as major food resources to deer mice (Peromyscus maniculatus) and southern red-backed voles (Myodes gapperi)

Abstract

a b s t r a c tConifer seeds are a component of the diet of many rodents, but it is not known whether these seeds can be used as a major food source by rodents. Investigating this is critical to understanding how individual rodents utilize conifer seeds, and how their populations interact with seed production by coniferous trees. We examined the effects of conifer seed-diets on survival, body condition, food consumption, and gut morphology of deer mice (Peromyscus maniculatus) and southern red-backed voles (Myodes gapperi) in the laboratory. Experiments were conducted for 14 days using control food (laboratory rodent chow) and lodgepole pine (Pinus contorta), white spruce (Picea glauca), and subalpine fir (Abies lasiocarpa) seeds. The nutritional compositions of these seeds were also analyzed. Subalpine fir seeds contained the lowest crude protein content and highest fibre content relative to the other seeds. 60% of voles fed subalpine fir seeds were euthanized prior to the end of the experiment after losing greater than 25% of their initial body mass, whereas all mice survived to the end of the experiment in each group. Body masses of mice fed subalpine fir seeds were lower than those fed control food early in the experiment, but they compensated for this by increasing seed intake over the remainder of the experiment. They also retained more digesta in the caecum, which could increase digestion efficiency of the low-quality seeds. On the other hand, voles did not compensate for the low quality of subalpine fir seeds behaviourally (food intake) or morphologically (gut dimensions), and decreased in body mass dramatically. They also decreased in body mass in the longterm on white spruce seed-diets. It is likely that plant secondary metabolites played a major role in the deterioration of body condition of voles fed subalpine fir and white spruce seeds. These results indicate that conifer seeds are a sufficient food resource for mice, but cannot be used by primarily herbivorous voles as a major/sole food source.

Indirect and mitigated effects of pulsed resources on the population dynamics of a northern rodent

“…Deer mouse demography was not positively affected by white spruce mast seeding, despite all contrary indications from individual‐level experiments (Lobo, Duong & Millar ; Lobo & Millar ; Lobo ) and our simulated spruce masting event. Conversely, we observed an unexpected delayed effect of subalpine fir mast seeding, where increased fall fir seed production did not influence overwinter or spring mouse demography, but instead enhanced summer survival, body masses and pregnancy rates of OW adults.…”

“…However, this is unlikely, given that PSCs in seeds are resistant to degradation over time (e.g. Shimada ), and the low nutritional value of fir seeds (Lobo & Millar ) is probably insufficient to enhance survival and breeding in rodents. It is more likely that the delayed effect of subalpine fir masting on deer mouse populations was mediated by population responses of invertebrate seed predators.…”

Food choice of Eurasian red squirrels and concentrations of anti-predatory secondary compounds

“…Several studies on food selection of small rodents showed that seeds of the genus Picea are preferred over Abies seeds (Schreiner et al 2000;Lobo et al 2009;Lobo and Millar 2011).…”

“…Conifer tree seeds are an important component of the diet of many rodents and the major food resource for arboreal species, such as tree squirrels, in boreal and alpine conifer forests, manmade conifer stands and mixed broadleaf-conifer woods (Abbott and Quink 1970;Wauters and Dhondt 1987;Lurz et al 2000;Boutin et al 2006;Wauters et al 2008;Lobo and Millar 2011). Often, these rodents are not only seed predators, potentially reducing the tree's reproductive output, but also act as seed dispersers, potentially enhancing seedling establishment (reviewed in Theimer 2005;Steele et al 2005).…”

A generalist rodent benefits from logging regardless of deer density

“…Deer mice may also be positively influenced by deer density because of the natural disturbance induced by browsing, which may maintain attributes of early succession in forests (Potvin, Boots & Dempster, 2003;Tremblay, Huot & Potvin, 2006). Given that the diversity and abundance of major food resources like seedlings and insects (Desrosiers, Morin & Jutras, 2002;Lobo & Millar, 2011) appear highest at deer densities (Tremblay, Huot & Potvin, 2006;Brousseau et al, 2013), deer mice should mostly be favoured at these deer densities.…”