Energy Requirements for Lactation and Postnatal Growth in Captive Golden-Mantled Ground Squirrels

Abstract

Pregnant female golden-mantled ground squirrels (Spermophilus saturatus) were captured in the field and maintained in the laboratory at 22° C on a diet of Purina Rodent Chow. ® Three to five young were born (mode 4) in each litter. Growth of young was linear (2.13 g • d⁻¹) for the first 30-35 d, by the end of which the young reached thermal and nutritional independence. From the time of this transition until adult body mass was reached at day 60, the linear growth rate increased more than 2.5-fold (5.67 g • d⁻¹). Pup body mass at birth was independent of litter size (mean 5.97g), but the average mass of young in the smallest litters was significantly greater than that in the largest litters by day 35. Over the course of lactation mothers showed an average 2.1-fold increase in food consumption, with an increase of about 10% in body mass and about 20% in rate of both whole-animal and mass-specific oxygen consumption. Estimated milk production per pup was 115 kJ • d⁻¹ milk energy for litters of three versus ...