Kenneth S. Norris Rancho Marino Reserve

01 Jan, 12 AM - 30 Dec, 09 PM

Our first objective is to better understand the reason for the current population decline. The recent decline in the California sea otter population is almost certainly a consequence of increased mortality, and not redistribution or reduced fertility, however, we do not know the cause of this increased mortality or what age/sex classes are affected. Contrasts in diet and activity-time budgets will help ascertain whether the increased mortality is food-related. Additionally, blood and tissue samples collected during the captures will be incorporated into ongoing studies of sea otter disease, parasite and contaminant levels, thus providing important biomedical data for sea otters at the southern end of their range. Contrasts with existing biomedical data (CDFG, unpublished data) will help define geographical patterns of disease and contaminant levels. Our second objective is to examine the link between the physiological capabilities and habitat requirements of the California sea otter. To accomplish this, the relationships between the thermal biology, time-activity patterns, and nutritional requirements of sea otters will be studied in both the southern extreme and the center of the range. Sea otters, because of their small body size, their unique method of thermal insulation (exclusively fur), and the cold environment in which they live, may be continually challenged by a high capacity for heat loss. Previous work by members of our group has shown that sea otters have little or no energetic safety margin, with the result that an added stressor such as reduced prey availability or oil contamination may result in energetic demands beyond the daily foraging capabilities of the animal. We can begin to evaluate this possibility based on core temperature profiles obtained from telemeteric temperature measurements. The study will be conducted over a 3 year period: this is the minimum amount of time required to gain an accurate understanding of sea otter demographics and movement patterns, and also corresponds to the expected functional life-span of the telemetric instrumentation. Range-wide surveys of the entire California sea otter population will continue to be conducted twice annually, and the collection and analysis of beach cast carcasses will also continue following current protocols. Sixty sea otters will be captured and instrumented during the first 2 years of the study?30 from the area south of Pt. Conception and 30 from Pt. Piedras Blancas, near the center of the range. All study animals will be instrumented with VHF radio transmitters, and 15 of the study animals at each location will also be instrumented with time-depth recorders (TDRs). The VHF radios will be used to track individuals, while the TDRs will simultaneously obtain and store a continuous time record of dive profiles. In combination, these data will allow us to determine, for each individual, location and movements, reproduction, mortality, diet, feeding behavior and activity-time budget. Patterns of seasonal movement and habitat use, together with any associated changes in behavior and demography, will be determined by follow-up study of the animals marked near Pt. Conception. The sample of 30 animals marked near Pt. Piedras Blancas will serve as a source population for understanding patterns of seasonal southward movement by sea otters from within their established range. From the VHF radio signals, we will be able to track the movements of each individual over a period of several years. Many of these study animals are expected to utilize the kelp beds off Rancho Marina as part of their home range; consequently, this reserve represents an ideal location for tracking sea otters in this region. Reasons for the recent decline in the California sea otter population will be evaluated by contrasting the detailed demographic, behavioral, biomedical and physiological data collected from instrumented otters in this study with those obtained by Siniff and Ralls in the 1980s, when the population was increasing, and by comparing data collected at the southern edge of the range (where otter numbers are still increasing) and at the center of the range (where numbers are now decreasing).

Visit #2125 @Kenneth S. Norris Rancho Marino Reserve

Approved

Under Project # 1701 | Research

Population Dynamics and Biology of the California Sea Otter at the Southern End of its Range

research_scientist - University of California, Santa Cruz

Reservation Members(s)

Group of 5 Graduate Student Jan 1, 2002 - Dec 30, 2004 (1095 days)
Group of 6 Research Assistant (non-student/faculty/postdoc) Jan 1, 2002 - Dec 30, 2004 (1095 days)
Tim Tinker Jan 1, 2002 - Dec 30, 2004 (1095 days)
Group of 5 Research Scientist/Post Doc Jan 1, 2002 - Dec 30, 2004 (1095 days)
Group of 2 Volunteer Jan 1, 2002 - Dec 30, 2004 (1095 days)

Reserve Resources(s) | Create Invoice

Day Use Only 19 Jan 1, 2002 - Dec 30, 2004