Provisioning Strategies of Antarctic Fur Seals and Chinstrap Penguins Produce Different Responses to Distribution of Common Prey and Habitat

Central-place foragers that must return to a breeding site to deliver food to offspring are faced with trade-offs between prey patch quality and distance from the colony. Among colonial animals, pinnipeds and seabirds may have different provisioning strategies, due to differences in their ability to travel and store energy. We compared the foraging areas of lactating Antarctic fur seals and chinstrap penguins breeding at Seal Island, Antarctica, to investigate whether they responded differently to the distribution of their prey (Antarctic krill and myctophid fish) and spatial heterogeneity in their habitat. Dense krill concentrations occurred in the shelf region near the colony. However, only brooding penguins, which are expected to be time-minimizers because they must return frequently with whole food for their chicks, foraged mainly in this proximal shelf region. Lactating fur seals and incubating penguins, which can make longer trips to increase energy gain per trip, and so are expected to be energy-maximizers, foraged in the more distant (>20 km from the island) slope and oceanic regions. The shelf region was characterized by more abundant, but lower-energy-content immature krill, whereas the slope and oceanic regions had less abundant but higher-energy-content gravid krill, as well as high-energy-content myctophids. Furthermore, krill in the shelf region undertook diurnal vertical migration, whereas those in the slope and oceanic regions stayed near the surface throughout the day, which may enhance the capture rate for visual predators. Therefore, we sug- gest that the energy-maximizers foraged in distant, but potentially more profitable feeding regions, while the time-minimizers foraged in closer, but potentially less profitable regions. Thus, time and energy constraints derived from different provisioning strategies may result in sympatric colonial predator species using different foraging areas, and as a result, some central-place foragers use sub- optimal foraging habitats, in terms of the quality or quantity of available prey.

Reducing the Public Health Impact of Bovine Tuberculosis by Controlling Disease Transmission Between Cattle and White-Tailed Deer in Northwestern Minnesota

Bovine tuberculosis, caused by infection with Mycobacterium bovis, is a re-emerging zoonotic disease. It has staged a comeback by establishing infections in wildlife and cattle, creating the potential for human disease in locations where it was thought to be under control. In northwestern Minnesota, infected cattle and white-tailed deer were first discovered in 2005. A major bovine tuberculosis eradication campaign is underway in the state, with multiple efforts employed to control M. bovis infection in both cattle and deer populations. In order to effectively eradicate bovine tuberculosis in Minnesota, there is a need for better understanding of the factors that increase the risk of deer and cattle interacting in a way that facilitates tuberculosis transmission. By reducing the risk of disease transmission within the animal populations, we will also reduce the risk that bovine tuberculosis will again become a common disease in human populations. The purpose of this study is to characterize the risk of interactions between cattle and white-tailed deer in northern Minnesota in order to prevent M. bovis transmission. A survey originally developed to assess deer-cattle interactions in Michigan was modified for use in Minnesota, introducing a scoring method to evaluate the areas of highest priority at risk of potential deer-cattle interaction. The resulting semi-quantitative deer-cattle interaction risk assessment was used at 53 cattle herds located in the region adjacent to the bovine tuberculosis “Core Area”. Two evaluators each scored the farm separately, and then created a management plan for the farm that prioritized the areas of greatest risk for deer-cattle interactions. Herds located within the “Management Zone” were evaluated by Minnesota Board of Animal Health staff, and results from these surveys were used as a point of comparison.