Costs of Franklin’s ground squirrel (Poliocitellus franklinii) ectoparasitism reveal adaptive sex allocation

Parasite infestation may impose direct costs of blood, nutrient, and energy depletion, along with indirect costs of increased immune response upon hosts. We investigated how ectoparasitism influences body mass and reproduction in a free-living population of Franklin’s ground squirrels (Poliocitellus franklinii (Sabine, 1822)) located near Delta Marsh, Manitoba, Canada. We experimentally reduced ectoparasite burden by treating seven reproductive females with an insecticide following breeding and contrasted body mass and reproductive performance of those individuals to seven sham-treated control females. Insecticide-treated dams did not differ from sham-treated dams in body mass, litter size, or juvenile mass, and thus, dam growth and reproduction were not compromised by ectoparasite defense at the infestation levels experienced in this study. However, litter sex ratio differed significantly between insecticide-treated and control females, with a higher proportion of male offspring produced among females with reduced ectoparasite load. Our findings are thus consistent with the Trivers–Willard model for adaptive sex allocation, yet they provide novel comparative insight into how sociality may modulate the expression of adaptive sex allocation among small mammals given the differential payoff associated with the production of high-quality female versus male offspring in more social versus less social species.

Distribution, Abundance, and Habitat Associations of Franklin’s Ground Squirrel (Spermophilus franklinii Sabine 1822)

To better inform conservation and management strategies directed at Franklin’s ground squirrel, Spermophilus franklinii, I reviewed published and unpublished accounts of the squirrel’s distribution, abundance, and principally, habitat associations. I present the body of literature on S. franklinii and include portions of original accounts to avoid potential bias from paraphrasing. A consensus of the literature indicates that S. franklinii is most frequently associated with habitat characterized by a mixture of grassy and woody vegetation, referred to as savanna-like or parkland habitat. Moreover, S. franklinii has had an affinity for this type of habitat throughout its geographic range in recent, historic, and even prehistoric times. This is in contrast to a view of the species as primarily associated with tallgrass prairie habitat. As indicated in the literature, populations of S. franklinii are subject to marked fluctuations, which probably are influenced by local disturbances in addition to regular dispersal events. In the southern part of its geographic range, S. franklinii is currently limited in its occurrence principally to roadside and railroad right-of-ways. In these southern regions S. franklinii is justifiably of conservation concern. I suggest that more detailed surveys for the species (such as those that have recently occurred in Illinois and Missouri) take place in Iowa and Kansas.

Importance of individual species of predators on nesting success of ducks in the Canadian Prairie Pothole Region

We followed 3094 upland nests of several species of ducks. Clutches in most nests were lost to predation. We related daily nest predation rates to indices of activity of eight egg-eating predators, precipitation during the nesting season, and measures of wetland conditions. Activity indices of red fox (Vulpes vulpes), striped skunk (Mephitis mephitis), and raccoon (Procyon lotor) activity were positively correlated, as were activity indices of coyote (Canis latrans), Franklin's ground squirrel (Spermophilus franklinii), and black-billed magpie (Pica pica). Indices of fox and coyote activity were strongly negatively correlated (r = −0.51), as were those of badger (Taxidea taxus) and skunk (r = −0.46). Nest predation rates in the early part of the breeding season were positively related to indices of fox, American crow (Corvus brachyrhynchos), and badger activity. Predation rates in the latter part of the season were positively related to indices of fox and skunk activity. Predation rates on early-season nests were lower in areas and years in which larger fractions of seasonal wetlands contained water. For late-season nests, a similar relationship held involving semipermanent wetlands. We suspect that the wetland measures, which reflect precipitation during some previous period, also indicate vegetation growth and the abundance of buffer prey, factors that may influence nest predation rates.