Energy cost of parental care in free-ranging Arctic foxes (Vulpes lagopus)
In Canidae, monogamy is the most prevalent rearing system. It has been suggested that this obligatory monogamy may be a consequence of the levels of post-partum care. Estimated postnatal growth rates from captive canids are higher than in any other carnivore and milk energy output estimated during peak lactation is surpassed only by hyenas. High energy demands, and the widespread phenomena of biparental care within Canidae support the premise that monogamy may be a consequence of high reproductive costs. Studies examining reproductive costs in canids have focused mainly on the energy costs of captive pregnant and lactating females, and have neglected to evaluate male parental investment. Previous field studies suggest that significant male parental care (e.g., food provision to the female and pups) occurs within Arctic foxes (Alopex lagopus). The goal of our proposed study is to determine field metabolic rate (FMR) in free-ranging male and female Arctic foxes during the post-lactation period. We assume that an increase in parental care is associated with an increase in FMR. We predict that males with pups will invest considerably more energy than males without pups. This prediction will be tested within sex comparisons of FMR and activity patterns in reproductively successful pairs during the breeding period (spring). We intend to use double-labelled water to determine FMR, fully automated radio-telemetry to estimate daily activity budget, video cameras to evaluate rate of food provisioning, a series of field manipulations, and microsatellite analysis (single locus DNA fingerprinting) to confirm parentage and monogamy.