Cone consumption by southeastern fox squirrels: a potential basis for clonal preferences in a loblolly and slash pine seed orchard

Abstract

Southeastern fox squirrels were observed feeding preferentially on seeds of certain clones of loblolly pine in a central Georgia seed orchard in the early 1990s and, similarly, on slash pine seed in an orchard in central Florida in the late 1990s. In each orchard, the degree of feeding preference and avoidance among selected clones was documented and quantified. We tested three hypotheses to explain this phenomenon: (1) seeds of preferred clones have greater nutritional quality or energy content; (2) cone armature differed between preferred and avoided clones; or (3) preferred clones have lower quantities of deterrent compounds present in cone tissue. Hypothesis 1 was tested using cones collected from three preferred and two avoided clones within a loblolly pine seed orchard. We found no consistent differences in total number of seeds per cone, viable seeds per cone, seed weight per cone, average weight per seed, energy content per seed, and energy content per cone between preferred and avoided cones. Hypotheses 2 and 3 were tested using cones collected from four preferred and four avoided clones within a slash pine seed orchard. We found a strong positive association between spine length and cone avoidance. Avoided cones had significantly higher concentrations of myrcene, α-phellandrene, β-phellandrene, β-caryophyllene, and α-humulene but lower concentrations of α-pinene. These physical and chemical cone defenses may increase handling time or reduce seed palatability and therefore act as significant deterrents to seed predation by fox squirrels when preferred feeding options are readily available, such as in a seed orchard.