Meeting Abstract
Ecoimmunologists model bacterial infection in free-living animals using lipopolysaccharide (LPS), a macromolecule found in bacterial membranes, but the concentration of LPS varies among these studies. It is unclear what dose triggers a response that is most reflective of the natural avian response to pathogens. Additionally, little is known about how immune challenges may alter parental feeding behavior. To test how the dose of LPS administered to nestlings influences parental provisioning, we injected house sparrow nestlings with either 0, 0.01, 0.1, or 1.0 mg LPS per kg body mass prior to fledging. We conducted behavioral observations three times per nest: 18 h pre-injection, 6 h post-injection, and 30 h post-injection. We observed each nest for one hour and recorded the number and duration of parental visits and sex of the parent during each visit. Preliminary analyses suggest that there were no differences in feeding rate 6 h post-injection in response to LPS doses. However, parental feeding rate after 30 h was higher for nestlings injected with 0 or 1.0 mg LPS per kg body mass than it was for nestlings injected with 0.1 and 0.01 mg LPS per kg body mass. These findings suggest that house sparrow parents alter their feeding rate based on the degree of immune challenge experienced by their nestlings. It is possible that the highest dose initiates a more rapid immune response, which is thus completed more quickly, whereas the lower doses incite a less intense but longer immune response, so nestlings reflect longer-lasting sickness behavior, such as decreased begging. The variability of parental behavior in response to LPS dose in nestlings stresses the importance of using various LPS concentrations in ecoimmunology studies.
