Nicarbazin for contraception of Canada geese: Laboratory and field studies

Contraception may provide a nonlethal management too! to reduce wild bird populations. We conducted studies to develop NCZ as a contraceptive for Canada geese. The results of these studies can be used to formulate conclusions about the effect of nicarbazin on reproduction at the molecular level and on the level of the whole animal.;At the molecular level, nicarbazin increases the activity of lipoprotein lipase, which causes premature degradation of VLDL in the blood stream, preventing deposition of lipids in the egg yolk. In addition, nicarbazin acts as a calcium ionophore, inserting itself into the vitelline membrane, and causing yolk mottling. Nicarbazin may also affect the outer vitelline membrane proteins VMOI and VMOII. The degradation of the vitelline membrane creates an inhospitable environment for the embryo, ultimately resulting in reduced egg hatchability.;At the level of the whole animal, mallards fed nicarbazin coated cracked corn achieved higher plasma DNC levels than mallards fed nicarbazin treated pellets. If pelleted bait is to be used in the field, it must be manufactured with a higher level of nicarbazin than cracked corn to achieve comparable plasma DNC levels. Measurements of fecal fluorescein were correlated with plasma DNC levels. Fecal fluorescein measurements provide a non-invasive technique to measure nicarbazin bait consumption in the field.;Finally, when Canada geese were baited with cracked corn coated with 1,320 mg nicarbazin/kg corn, egg hatchability was reduced by 53%. Nests located ≤ 70 m from bait sites had ≤ 45% hatchability, whereas nests located farther from bait sites had higher hatchability. Egg DNC levels were negatively correlated with hatchability, fertility, clutch sizes, and stage of embryonic development, and were positively correlated with eggshell thickness. Baiting Canada geese with nicarbazin treated bait is effective in reducing reproductive rates, but cannot reduce the population size overall at the level of contraception achieved in this study. Population modeling indicates that treating geese every year with nicarbazin bait in addition to culling 50% of the population every 4 years (e.g. through round up and removal) is sufficient to maintain a population within 80 geese of the starting population for ≤ 20 years.