PUPPING IN THE MOST NORTHERLY HARBOR SEAL (PHOCA VITULINA)

The Norwegian high arctic archipelago Svalbard is the home of the world's northernmost population of harbor seals. Due to their limited distribution in isolated areas of the archipelago, little is known about their biology. Until now no information has been published on their pupping or whether it differs from that of harbor seals in other regions. This paper shows that the peak pupping period for harbor seals in Svalbard coincides with that in Europe, i.e., the second half of June. The pups are born with an adult-like pelt and not with a white coat.     

THE DISTRIBUTION, ABUNDANCE AND SELECTED PREY OF THE HARBOR SEAL, PHOCA VITULINA CONCOLOR, IN SOUTHERN NEW ENGLAND

The seasonal distribution and abundance of harbor seals occurring south of Maine were documented by counting the number of seals at traditional haulout locations. The average number of seals counted during each survey in Massachusetts and New Hampshire was 3,560 ± 255 (95% CI), 1983–1987. The maximum number of seals counted on any individual survey was 4,736 individuals. Fifty percent of all the surveys since January 1985 have resulted in counts greater than 4,000 seals reflecting a 27% increase in the abundance of seals in our study area since that date. Seventy-five percent of the seals in southern New England are located at haulout sites on Cape Cod and Nantucket Island. The largest aggregation of seals in the eastern United States occurs mid-winter at Monomoy Island and adjacent shoals. A single high count of 1,672 seals occurred at this site during the study period. An additional 271–374 seals were also counted in Rhode Island, Connecticut and eastern Long Island Sound during surveys conducted in March 1986 and 1987. The American sandlance Ammodytes americanus was the single dominant prey item of harbor seals in waters adjacent to Cape Cod based on the modified frequency of occurrence of each prey species in scat samples collected from three haulout sites on Cape Cod between 1984–1987. During January and February sandlance was the near exclusive prey item at Monomoy (99%, n= 80). During March and April, the frequency of Atlantic herring Clupea harengus increased in the scat samples at this site. Regional differences in the diet of seals reflect distinct prey communities throughout the study area. Since 1986, the percent occurrence and importance of sandlance in the diet of seals has decreased, reflecting an overall decrease in abundance of this prey species in waters adjacent to Cape Cod. In spite of fluctuations in abundance, and regional differences in the diet of seals throughout the study area, sandlance still comprised a minimum 55% of the total prey species of harbor seals throughout the study area.     

THE MOST NORTHERLY HARBOR SEAL, PHOCA VITULINA, AT PRINS KARLS FORLAND, SVALBARD

The harbor seal ( Phoca vitulina ) has its northernmost distribution at the Norwegian arctic archipelago of Svalbard. Little information exists on this particular harbor seal population. The present paper summarizes this information, and gives the result of surveys of harbor seals conducted in Svalbard in 1984, 1985 and 1987. These surveys show that harbor seals in Svalbard are limited to the area around Prins Karls Forland, the westernmost island in the archipelago. The harbor seal population at Prins Karls Forland numbers at least five to six hundred animals.     

DO PHOTOPERIOD AND TEMPERATURE INFLUENCE THE MOLT CYCLE OF PHOCA VITULINA IN CAPTIVITY?

Photoperiod variations are the principal environmental signals entraining circannual activity in mammals, which is also believed to be influenced by changes in temperature and nutrition. Control of the molt in phocids has not been extensively studied with experimental manipulations of environmental factors, but substantial work indicates that photoperiod has a primary influence on mammalian breeding and furring mechanisms. Studies were under taken to reestablish the molt cycle in five harbor seals ( Phoca vitulina ) previously kept in an enclosed facility with a limited air/water temperature gradient and artificial photoperiod. The seals were exposed to an extended temperature gradient during the first period of study, and no molting was observed. The second period of study was characterized by a natural occurring photoperiod of 8 h 53 min light (L)/15 h 07 min dark (D) and a maximal 15 h 31 min L/8h 29 min D duration, and molting occurred in all individuals. These results suggest a prevalent influence of photoperiod variation on the harbor seal molt.     

INVESTIGATING TROPHIC RELATIONSHIPS OF PINNIPEDS IN ALASKA AND WASHINGTON USING STABLE ISOTOPE RATIOS OF NITROGEN AND CARBON

We measured stable-nitrogen (δ¹⁵N) and stable-carbon (δ¹³C) isotope ratios in muscle and hair from 7 northern fur seals (Callorhinus ursinus) from the Pribilof Islands, Alaska, and 27 Steller sea lions (Eumetopias jubatus), and 14 harbor seals (Phoca vitulina) from the Gulf of Alaska and coast of Washington State, in order to contrast dietary information derived from isotopic vs. available conventional dietary studies. Stable-nitrogen-isotope analysis of muscle revealed that harbor seals were enriched over sea lions (mean δ¹⁵N = 18.6‰vs. 17.5‰) which were in turn enriched over northern fur seals (mean δ¹⁵N = 16.6‰). Trophic segregation among these species likely results primarily from differential reliance on herring (Clupea harengus), Atka mackerel (Pleurogrammus monopterygius), and large vs. small walleye pollock (Theregra chalcogramma). According to their δ¹⁵N values, adult male Steller sea lions showed a higher trophic position than adult females (mean δ¹⁵N: 18.0‰vs. 17.2‰), whereas adult female northern fur seals were trophically higher than juvenile male fur seals (mean δ¹⁵N: 16.5‰vs. 15.0‰). Each of these observed differences likely resulted from differential reliance on squid or differences in the size range of pollock consumed. Three northern fur seal pups showed higher δ¹⁵N enrichment over adults (mean 17.7‰vs. 15.8‰) due to their reliance on their mother's milk. Stable-carbon isotope measurements of hair revealed a cline toward more negative values with latitude. Segregation in hair δ¹³C between Steller sea lions and harbor seals off the coast of Washington (mean δ¹³C: ?13.6‰vs.?15.0‰) reflected the greater association of harbor seals with freshwater input from the Columbia River. Our study demonstrates the utility of the stable isotope approach to augment conventional dietary analyses of pinnipeds and other marine mammals.     

HARBOR SEAL TRACKING AND TELEMETRY BY SATELLITE

We tested a satellite Platform Transmitter Terminal (PTT) in the laboratory (on a float and on captive seals) and on a free-ranging harbor seal in the Southern California Bight to investigate the utility of satellite telemetry in documenting seals'at-sea behavior and movements. We used records from a microprocessor-based time-depth recorder (TDR) to interpret location and diving records from the PTT. For the free-ranging harbor seal, we obtained at least one uplink during 70% (while the seal was at sea) to 82% (while she was ashore) of satellite passes and at least one location each day. Of 62 locations determined by Service Argos for the free-ranging seal, 20 were verified from TDR records to have been at sea; these indicated that the seal may have ranged up to 48 km from the haul-out site, although most locations were within 5 km. The accuracies of locations calculated when the seal was at sea (±15 km) were substantially less than when it was ashore (±1.5 km), thus limiting at-sea tracking of seals by satellite to rather gross movements. Fewer transmissions were detected and locations calculated when the seal was actively diving than when it was swimming near the surface as it departed from or returned to the haul-out site. Consequently, average dive durations indicated by the PTT were substantially shorter than those calculated from TDR records. Documentation of foraging areas and detailed at-sea movements using satellite technology may not be possible for pinnipeds unless PTT-transmission rates are increased substantially from the 1 per 45 set maximum rate now permitted by Service Argos.     

REBUILDING SEAL STOCKS IN THE KATTEGAT-SKAGERRAK

The harbor seal ( Phoca vitulina ) population in the Kattegat-Skagerrak area has been dwindling for several centuries due to excessive hunting pressure. Corrected hunting statistics during 1890–1976 are used to estimate changes in population size over the past century. After protection was introduced in the 1960s and 1970s the harbor seal population in the area increased at an exponential rate of 0.12 and exceeded 5,000 animals in 1986. The present rate of population growth is used for modelling the influence of fertility and age-specific mortality. It is found that the observed high rate of increase is only realistic if female fertility rate is very high, the range of juvenile mortality rate is 0.33–0.52 and adult mortality is less than 0.15. Commonly cited higher mortality rates are not realistic in the Kattegat-Skagerrak area.     

PLASMA PROGESTERONE CONCENTRATIONS MEASURED USING AN ENZYME-LINKED IMMUNOSORBENT ASSAY USEFUL FOR DIAGNOSING PREGNANCY IN HARBOR SEALS (PHOCA VITULINA)

Wild-caught female harbor seals ( Phoca vitulina ) were classified as sexually mature or immature on the basis of standard body length (< 125 cm immature, > 125 cm mature) and plasma progesterone concentrations measured using an enzyme-linked immunosorbent assay (ELISA), a technique usable in the field. Sexually mature females were classified as pregnant or non-pregnant on the basis of their plasma progesterone concentrations. Of 28 wild mature female harbor seals caught in the Moray Firth, N.E. Scotland, between the end of February and the end of May, 79% had plasma progesterone concentrations greater than 60 nmol liter⁻¹, the lowest plasma progesterone concentration measured in one of eight females later observed with a pup, and were diagnosed as pregnant. A linear discriminant function, calculated to provide a method of distinguishing pregnant and non-pregnant females, predicted 100% of non-pregnant females and 95.8% of pregnant females using plasma progesterone concentration, standard length, and month of capture as parameters. Plasma progesterone concentrations were less than 30 nmol liter⁻¹ in all mature and immature males and immature females. In mature females plasma progesterone concentrations ranged from 0-318 nmol liter⁻¹.     

THE SOUTHERN SEA LION,OTARIA BYRONIA OR OTARIA FLAVESCENS?

Abstract: The status of the specific name of the Southern sea lion is controversial; currently two names are in use: Otaria flavescens (Shaw, 1800) and Otaria byronia (de Blainville, 1820). The former was based on a two-foot-long yellowish otariid collected in the Strait of Magellan and the latter on a skull stated to have been collected on the Tinian Island (Marianas Archipelago); unfortunately both holotypes are lost. Otaria flavescens has date priority over Otaria byronia , but its identification was uncertain. This paper focuses on analyzing the main features of Shaw's holotype (body length, ear size, and hair color), which fit with the features of a Southern sea lion pup. As this was a tangible specimen from a valid locality and has priority over other available epithets, the specific name of the Southern sea lion should be Otaria flavescens (Shaw, 1800).