Публикации

Movements and Foraging Behavior of Northern Fur Seal Pups (Callorhinus Ursinus) From the Commander Islands during Their First Winter at Sea

Olivia Lee, Russel D. Andrews, Vladimir Burkanov, Randall Davis

High mortality rates of pups during their first winter at sea may be contributing to the decline of northern fur seals on the Pribilof Islands, but due to their highly dispersed migratory nature, little is known about individuals during this life stage. In contrast, the northern fur seal population on the Commander Islands has been stable over the last decade. Dive behavior and movements were hypothesized to be similar for pups from both populations, but differences could explain whether Commander Island pups increase their survival by using different foraging tactics or exhibiting different habitat preferences. Satellite-linked stomach temperature telemetry was used to track 35 pups from Bering Island, Russia beginning 30 October 2007. A total of 17 males and 18 females were instrumented with Mk10-AL satellite tags and stomach temperature pills to determine movements, and diving and foraging behavior. Habitat associations were determined using GIS data of bathymetry, geostrophic currents, sea surface temperature and sea surface height anomalies, and chlorophyll a concentrations. Individuals began to leave Bering Island by 2 November, and by 22 November only one pup remained on the island. Most individuals traveled south, although one traveled north, five traveled east, and six traveled west towards the Kamchatka Peninsula before heading south, where they encountered a cyclonic, cold-core eddy along the coast. The mean dive depth and dive duration was 3.4 m and 20 seconds, respectively, with the deepest and longest dives occurring between 16:00 - 10:00 local time, suggesting that most searching behavior occurred during the dark hours. Ingestion events also occurred most frequently during the night at a mean depth of 4 m. The dive behavior and wide ranging movements were similar to pups from the Pribilof Islands during the first three weeks at sea, but differences may occur as winter progresses and pups increase their foraging skills. Behavioral differences may subsequently affect pup survival rates and partially explain the divergent population trends.
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Steller Sea Lion Brand Resight Database Using MS Access

Alexey V. Altukhov, Vladimir N. Burkanov

Permanent marking of Steller sea lions for long-term research and monitoring of individuals was started in the Russian Far East in 1989. Over 6,800 new born pups have been marked since that time using the hot branding technique. Resighting data has been collected using different printed forms and protocols using Excel spreadsheet for data storage. Preliminary data analysis revealed several problems related to accuracy of identification of branded animals in the field (different errors in 22% of sightings), visual confirmation of sighted individuals and data retrieving for analysis. This problem increased dramatically with the start of a long-term brand resight project in 2002 when 8 field teams began collecting data on different islands spread across the Russian Far East. Using digital photography for sighting confirmation and a custom MS Access application for brand identification based on pictures of branded animals collected in previous years, we significantly increased our accuracy in data collection. Positive results using the MS Access application encouraged us to develop the data base as a primer tool for identification of brands, recording data, storage, and retrieving information on Steller sea lion brand resight data in Russian Far East. The current version of the database includes several modules which help observers reliably identify marked animals, properly record information of each sighting, store collected information in proper format, and check accuracy of data before offloading information into the archive data base after field season. Separate modules for animal counts, mortality events, marked female attendance patterns, birth and copulation events and locations on the rookery were added to the data base to improve completeness and standardize data collection by different field teams on different remote rookeries. Currently, the database contains information about all pups branded in Russian Far East since 1989 and repeated observations on over 3,000 branded Steller sea lions with total over 65,000 records of resighting events.
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Olfaction of Abiotic Objects and the Social Environment in Steller Sea Lion's (Eumetopias jubatus) Rookery Life

Olga A. Belonovich, Evgeniy G. Mamaev, Viacheslav V. Rozhnov

Olfaction is one of the most important senses for the sustentation of social structure in populations of Steller sea lions (SSL). Olfaction serves as one of the main ways of receiving information regarding the surrounding social environment as well as to detect attributes about the surrounding abiotic objects. To understand the development of olfaction and its role in the social life of different sexes and age classes of SSL in connection with their harem was the aim of our research. The observations were conducted on Medny Island (Commander Islands) during the summers of 2005/06. During the two seasons of study 2564 olfactory contacts were registered (652-muzzle of understratum of rookery, 15- olfactory contacts with Northern fur seals and 1872-olfactory contacts with the conspecifics). Besides these mentioned olfactory contacts, SSL often were also observed smelling the air of the rookery. Unfortunately, we were unable to estimate the quantity of this behavior, but it seems likely that general olfaction of wind contents influences SSL behavior very much. During the reproductive period the smell duration of abiotic objects averaged 1.5s (n=338; min=1; max=10), while the average duration of interspecific olfactory contact was 2.8s (n=913, min=1, max=45). Our observations demonstrate that SSL spend more time on olfactory contacts with conspecifics than with abiotic things. At the time immediately after leaving the water SSL devote most of their olfactory energies toward the understratum of rookery, and only then continue to move onto the rookery. Olfaction of abiotic objects borrows approximate 1/4 of all SSL's muzzle. Adult females smell the rookery's understratum more often than males and other age classes of both sexes of SSL, however this does not appear to depend on whether the female gave birth that season or not. Various rookery smells are very informative for SSL, but in a reproductive gathering, intimate contact with conspecifics seems the most important.
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Philopatry and Dispersion in Steller Sea Lion

Vladimir N. Burkanov, Don G. Calkins

Philopatry and dispersion are two natural phenomena that play an important role in occupation of new areas and species survival. Studying these phenomena in Steller sea lions (SSL) is difficult due their nomadic marine life style and our limited ability to identify individual SSLs. There are 10 major breeding sites of SSL located in Russian Far East. Permanent marking of new born pups has been conducted on nine of them since 1989. As of 2006, 6,312 pups have been marked there with hot brands. Visual observations were conducted on 8 rookeries in 2007 during the breeding season (May-August). Average length of field observation on each rookery was 51 days (range 32 - 88). Observers resighted 1,027 branded Steller sea lions (16.3% of total branded), of which 92 animals were repeatedly sighted on several different rookeries during the season. All marked SSLs resighted on other rookeries than they were born were classified as “non-resident”. We analyzed 988 sightings of 905 marked animals resighted on 7 breeding sights located a distance of 45 to 2,000 km apart. Non-resident SSL appeared on 6 of 7 analyzed rookeries. On average 21% (0 – 33%) of the marked population on rookeries were non-resident animals (all ages and sexes). Among mature females (age 4+) non-residents were 24% (0-44%), while among females that gave birth, only 9% (0-19%) were non-residents. More non-resident individuals of all ages and sexes were recorded on rookeries located less than 100 km apart (Lovushki and Raykoke Islands) or located at specific geographic areas close to natural migrating borders (Antsiferov and Tuleny Islands, and Kozlova Cape). Minimum distance between natal and breeding rookery among non-resident marked females given birth was 45 km and maximum over 1,400 km. A high level of isolation was recorded for Medny Island (Commander Islands) where no non-resident SSL were seen in 2007. Our data show a relatively higher level of mixing of SSL among rookeries than previously believed. In SSL, the degree of philopatry and dispersion highly depends on the location of natal rookery and distance to other rookeries, as seen in other Otariidae species such as northern fur seals.
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Killer Whale Predation on Northern Fur Seals – Activity is Increasing?

Evgeniy G. Mamaev, Vladimir N. Burkanov

In recent years, mammal-eating killer whales have attracted a particular interest. It is supposed that killer whales, as an apex predator of the marine trophic pyramid, may significantly influence the numbers of marine mammals. Observations on mammal-eating killer whales were held on the southern end of Medniy Island, Commander I. during the summer periods of 2000-2007 where are located the northern fur seals and Steller sea lions rookery. For the years 2000 and 2003-2006, first encounters took place from June 14 until July 12. In 2007 the first encounters took place May 30. The last time in the season the whales were encountered was from July 15 until August 7. Killer whales were observed hunting on northern fur seals 1 day in 2000, 1 day in 2003, 3 days in 2004, 9 days in 2005, and 10 days in 2006. In 2007 we was observed 4 hunting days, but approximately all summer was stormy and foggy with poor observed conditions. Only one attack of killer whales on fur seals was recorded in 2000, but in 2006, 16 attacks were observed. 8 predation cases were observed in 2007. The number of attacks varied by day and on average 2.0 attacks on adults and subadults males fur seals were observed per day. The majority of the attacks on fur seals were observed near Yuzhny Cape on the border of the kelp. In 2000, two adult males killer whales were observed hunting and between 4-7 individuals in 2003-07. In 2003-2007 was registered one group which includes same individuals. One more group of mammal-eating killer whales was observed in 2006. The number of attacks near the southern end of Medniy Island has noticeably increased over the last 6 years. Before 2000 no observed attacks killer whales on fur seals throughout all historical period of observations on Medniy I. It is interesting to note that with the exception of only one short attack on Dall’s porpoises (Phocoenoides dalli) killer whales paid absolutely no attention to other species of pinnipeds or sea otters, which are also abundant. It is possible that the observed group killer whales acute specialize in preying on northern fur seals.
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Foraging Behavior of Lactating Northern Fur Seal (Callorhinus ursinus) Females near the Lovushki Island Complex of the Kuril Islands, Russia

John P. Skinner, Vladimir N. Burkanov, Russel D. Andrews

In the last half of the century, the northern fur seal (Callorhinus ursinus) eastern Pacific stock declined significantly, leading to its listing as “depleted” in 1988 under the Marine Mammal Protection Act. While this population continues to decline at 6% per year, fur seal numbers along the Kuril Islands, Russia are near their historical high. One hypothesis for the decline of Pribilof fur seals is reduced prey availability – a factor which could be examined in terms of diving effort. By studying the dive behavior of seals from an increasing population and contrasting that with published information on seals from the declining Pribilof population, we hope to gain insight into whether prey limitation may explain the different population demographics between these populations. In the first phase of this project our objectives were to: (1) characterize diving behavior of females in the vicinity of Lovushki Island, Kuril Islands, Russia; (2) investigate the potential effects of tag size on diving behavior and; (3) examine the potential for using stomach temperature data to characterize dives associated with foraging. Five lactating females in 2005 and an additional eight in 2006 were captured on the rookery, measured, and equipped with data logging telemetry. Blood and milk samples were also collected to evaluate the health status of each female. Data loggers provided depth and stomach temperature profiles’ over the entire period of deployment. A separate group of five lactating female seals were instrumented only with very small, low-profile time depth recorders (TDRs) in 2006. Preliminary analyses revealed that Lovushki Island fur seals typically exhibited nocturnal, pelagic foraging patterns, although in a few cases seals engaged in benthic foraging, making flat-bottom dives during the day, close to the rookery. For the seals with small TDRs, maximum dive durations (= 2.6 min) and dive depths (= 72 m) were limited compared to previously reported values for seals from the Pribilof Islands. The presentation of final results will provide the basis for a more thorough discussion about the influence of prey availability on population dynamics for northern fur seals throughout the Pacific.
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