Meeting Abstract
P1.189 Friday, Jan. 4 High cost of paternal care in the kit fox, Vulpes macrotis. GIRARD, I; University of Wisconsin-Madison girard@rarc.wisc.edu
Cost of reproduction in mammals is usually estimated in females, with less attention to paternal investment in young. In many species of canids, males participate in rearing young by providing food to lactating females and older pups. The paternal cost of reproduction in the kit fox, Vulpes macrotis, was estimated from the cost of the increased daily movement distance of males provisioning lactating females and pups (4 – 6 weeks of age). Paired (n = 24) and unpaired (n = 7) foxes were radio-tracked and monitored in spring, summer, and winter over a 28-month period in the southern Mojave Desert of California. Most pairs were socially monogamous, with duration of mate relationship ranging from 1 – 28 months. Females serially associated with 0 to 3 males during the study: two of three solitary females did not produce pups. Two males each provisioned two dens simultaneously. The effect of provisioning mates and pups on male daily movement distance (DMD) was calculated from a repeated-measures model using monogamously paired animals: prey abundance, mean nighttime temperature, and reproductive status had significant effects on DMD, but body mass did not. When provisioning the lactating females, male DMD averaged 29.3 ± 1.1 km (LSMean ± SE), as compared with an average DMD of 17.5 ± 0.7 km during non-reproductive seasons. With an estimated field cost of locomotion of 15.6 kJ km-1 (Girard 2001), male cost of provisioning was 183 kJ d-1 or about 11% of total male field metabolic rate. In contrast, lactating females traveled only short distances away from the den. Maternal energetic investment in milk averaged 454 kJ d-1, or about 37% of a female’s metabolizable energy intake. Thus, paternal effort is impressive (40% of maternal investment in milk) and plays an important role in providing food, reducing maternal activity costs, and allowing increased maternal vigilance.
