Browsing by Subject "sea otter"
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Item Activity Budget, Field Metabolic Rate, and Foraging Ecology of Female Sea Otters (Enhydra lutris kenyoni) with Dependent Pups in Alaska(2014-04-30) Wolt, Ryan C.Sea otter (Enhydra lutris kenyoni) foraging behavior and prey preference (2001- 2004) and the behavior and activity budgets of females with dependent pups (2005- 2010) were studied during the summer (June-August) in Simpson Bay, Prince William Sound, Alaska. Unlike most previous studies of sea otters which were conducted in coastal areas with a rocky benthos and kelp canopy, the benthic habitat in this study was primarily soft sediment (mud or mixed mud and gravel) with no canopy-forming kelps. Foraging behavior and prey preference. A total of 1,816 foraging dives from 211 bouts were recorded. 87% of foraging dives were successful, and 44% of the prey was identified: 75% clams, 9% Pacific blue mussels, 6% crabs, 2% scallops and a variety of other invertebrates. Significantly more prey items/area were brought up from mixed mud/gravel than mud (p-value <0.0001). Sea otters in Simpson Bay have relied heavily on bivalves for the past 20 years, and the summer population has been constant for at least the past twelve years. It appears that bivalves are the predominant and stable component of the diet, and their productivity is sufficient to sustain a stable population of sea otters with a peak summer density of 4.3 adult otters km^(-2) for the past twelve years and probably longer. Behavior and activity budgets of females with dependent pups. Females with dependent pups spent the greatest percentage of the day resting (42%), about equal percentages foraging (18%), grooming (15%) and swimming (15%), and the remainder swimming slowly (8%) and interacting (2%). The estimated FMR was 12.69 MJ day^(-1). Sea otters reoccupied the study area in the early 1980s, and the population has been stable for over a decade. However, the time spent foraging is more similar to areas that have been recently occupied. The relatively small amount of time spent foraging may indicate that geographic differences (structure of the near-shore community: substrate, water depth, kelp canopy, prey assemblage, and competitors) may play a greater role in determining the amount of time spent foraging than population status.Item Photo Identification, Summer Activity Pattern, Estimated Field Metabolic Rate and Territory Quality of Adult Male Sea Otters (Enhydra lutris) in Simpson Bay, Prince William Sound, Alaska(2010-07-14) Finerty, Shannon E.This project describes a portion of a long-term study of the behavioral ecology of sea otters. Sub-studies of this project include the development of an individual recognition program for sea otters, the construction of male sea otter activity and energy budgets, and the assessment of male sea otter territory quality. The Sea Otter Nose Matching Program, or "SONMaP", was developed to identify individual sea otters in Simpson Bay, Prince William Sound, Alaska, using a blotch-pattern recognition algorithm based on the shape and location of nose scars. The performance of the SONMaP program was tested using images of otters collected during the 2002-03 field seasons, and previously matched by visually comparing every image in a catalog of 1,638 animals. In 48.9% of the visually matched images, the program accurately selected the correct image in the first 10% of the catalog. Individual follows and instantaneous sampling were used during the summers of 2004-06, to observe male sea otter behavior. Six behaviors (foraging, grooming, interacting with other otters, patrolling, resting, and surface swimming) were observed during four time periods (dawn, day, dusk, night) to create 24-hr activity budgets. Male sea otters spent 27% of their time resting, 26% swimming, 19% grooming, 14% foraging, 9% patrolling and 5% interacting with other otters. Field Metabolic Rate (FMR) was estimated by combining the energetic costs for foraging, grooming, resting, and swimming behaviors of captive otters from Yeates et al. (2007) with these activity budgets. "Swimming" accounted for the greatest percentage (43%) of energy expended each day followed by grooming (23%), resting (15%), feeding (13%) and other (5%). With a peak summer sea otter density of 5.6 otters km-2, the low percentage of time spent foraging indicates that Simpson Bay is below equilibrium density. Territory quality was assessed for male sea otters using four attributes: territory size, shoreline enclosure, accessibility, and number of females observed feeding in each territory. Each attribute was coded with a score of 0-2, and total quality scores ranged from 0.14-1.96 (0.9 + 0.61 SD). High quality territories had large areas, moderate shoreline enclosure, high accessibility, and many foraging females.