Individual variation in predation on fur seals by southern sea lions (Otaria byronia) in Peru

1993 ◽  
Vol 71 (9) ◽  
pp. 1908-1911 ◽  
Author(s):  
Robert Harcourt
Keyword(s):  
Adult Female ◽  
Individual Variation ◽  
Small Proportion ◽  
South American ◽  
Adult Males ◽  
Sea Lion ◽  
Subadult Male ◽  
Sea Lions ◽  
Hunting Success ◽  
Fur Seals

Southern sea lions (Otaria byronia) were observed to prey on juvenile and adult female South American fur seals (Arctocephalus australis) at Punta San Juan, Peru (15°22′S, 75°12′W) between October 1987 and December 1988. Over the course of the study there were 165 attacks on fur seals with 33 seals killed. While both adult male and subadult male sea lions captured and killed fur seals, adult female and juvenile sea lions never acted aggressively towards fur seals. Adult males attacked fur seals on 82.4% of the occasions when they were present at the rookery, subadults on 52% of occasions. Distinctive pelage characteristics allowed some of the male sea lions to be individually identified, and differences in hunting success were observed between adults and subadults, and between five identifiable adults who hunted on at least five occasions. Motivation for attacks differed for subadults and adults, with subadult males using captured fur seals as female sea lion substitutes, guarding them from others and copulating with them, whilst adult sea lions hunted fur seals as food. However, only a small proportion of adult sea lions hunted fur seals, and with differing rates of success.

VOCAL COMMUNICATION AND INDIVIDUAL VARIATION IN BREEDING SOUTH AMERICAN SEA LIONS

Behaviour ◽  
1999 ◽  
Vol 136 (4) ◽  
pp. 495-517 ◽  
Author(s):  
Esteban Fern Ndez-Juricic ◽  
Victor Enriquez ◽  
Claudio Campagna ◽  
Charles Leo Ortiz
Keyword(s):  
Individual Variation ◽  
Vocal Communication ◽  
Social Contexts ◽  
Relative Advantage ◽  
South American ◽  
Adult Males ◽  
Aggressive Interactions ◽  
Sea Lions ◽  
Acoustic Environments ◽  
Pup Development

AbstractThe purpose of this study was to analyse the structure, social contexts, and individual variation of South American sea lion (Otaria flavescens) airborne vocal communication during the breeding season. This is the first comprehensive analysis of the vocal repertoire of this species. Since breeding colonies are complex acoustic environments, we expect that male, female, and pup vocalizations would show individuality, and that individual variation would rely on several acoustic traits. We identified four calls for adult males: high pitched call or HPC (aggressive interactions, such as attack and retreat displays, and fights), bark (aggressive interactions, territory establishment, and usually combined with growls), growl (male-female interactions), and exhalation (after agonistic encounters); and two for adult females: mother primary call or MPC (female-pup interactions, such as after birth, during pup separation, and pup development), and grunt (agonistic interactions between females). Juveniles vocalized yearling primary calls or YPC (searching for their mothers or after being threatened by females), pups gave pup primary calls or PPC (in response to MPCs, when hungry, searching for their mothers, if nursing was interrupted, or when trying to nurse). Our results suggest that male's HPC and bark, female's MPC, and pup's PPC have acoustic features that support individuality. These calls are associated with contexts in which recognition of neighbours (HPC and bark) or relatives (MPC and PPC) may confer a relative advantage in reproductive performance. Individual variation depended on frequency, temporal, and intensity traits; such multi-trait individuality could be regarded as an adaptation to colonial life to overcome the high noise levels within pinniped breeding colonies.

First observations of operational interactions between bottom-trawling fisheries and South American sea lion, Otaria flavescens in south-central Chile

2012 ◽  
Vol 93 (2) ◽  
pp. 489-494 ◽  
Author(s):  
Pablo Reyes ◽  
Rodrigo Hucke-Gaete ◽  
Juan Pablo Torres-Florez
Keyword(s):  
South American ◽  
The South ◽  
Sea Lion ◽  
Central Chile ◽  
Otaria Flavescens ◽  
Sea Lions ◽  
South American Sea Lion ◽  
South Central ◽  
By Catch ◽  
Working Day

This paper presents results of a study conducted on the trawling industrial fishery fleet of Merluccius gayi in south-central Chile, and the resulting interactions with the South American sea lion (Otaria flavescens). This study is based on observations made during September 2004, when incidental sea lion catch in the trawls was 6.3 sea lions/working day (1.2 sea lions/trawl−1). A total of 82 animals were incidentally caught, of which 12 were found dead, and the 70 remaining suffered from internal bleeding and/or fractures as a result of their capture. 83.3% of the fatalities occurred during nocturnal trawls, which comprise 30% of all observed trawls. Possible mechanisms of sea lion take are discussed. This note presents the first records of sea lions incidental by-catch by the trawler fleet along the south-east Pacific coast of Chile.

scholarly journals Interactions between the South American sea lion (Otaria flavescens) and the artisanal fishery off Coquimbo, northern Chile

2008 ◽  
Vol 65 (9) ◽  
pp. 1739-1746 ◽  
Author(s):  
Sabine Goetz ◽  
Matthias Wolff ◽  
Wolfgang Stotz ◽  
Mario J. Villegas
Keyword(s):  
South American ◽  
Northern Chile ◽  
Artisanal Fishery ◽  
The South ◽  
Sea Lion ◽  
Management Options ◽  
Otaria Flavescens ◽  
Sea Lions ◽  
South American Sea Lion ◽  
Fishing Vessels

Abstract Goetz, S., Wolff, M., Stotz, W., and Villegas, M. J. 2008. Interactions between the South American sea lion (Otaria flavescens) and the artisanal fishery off Coquimbo, northern Chile. – ICES Journal of Marine Science, 65: 1739–1746. The South American sea lion (Otaria flavescens) forages in coastal waters, where it interacts with fisheries and causes considerable economic loss by removing some catch and damaging gear. This study describes for the fishery region of Coquimbo (Chile) where, when, and with what type of gear interactions occur, characterizes the animals involved (group size, sex, and age), and derives some management recommendations. The study was based on 55 interviews with fishers and observations aboard fishing vessels in the main fishing sectors between October 2003 and March 2004. Interactions were primarily at night (88% of interviewees fished at night), in the bay (“Bahía”) of Coquimbo (81% of interviewees fished in this sector), where shoaling fish were abundant, and with purse-seines (100% of interviewees used this gear). Although some large groups of sea lions were seen, most comprised 1–10 animals. Most animals that interacted with the fishing gear were males (67%), probably because of the different feeding strategies of the two sexes. Management options discussed include the adjustment of fisheries to foraging behaviour of sea lions, and the controlled elimination of conflicting animals.

scholarly journals South American sea lions (Otaria flavescens) and killer whales (Orcinus orca) attending chub mackerel (Scomber japonicus) commercial trawl fisheries over the Patagonian Shelf: a first report

2015 ◽  
Vol 10 (1) ◽  
pp. 48-51
Author(s):  
Juan Pablo Seco Pon ◽  
Marco Favero
Keyword(s):  
Antipredator Behaviour ◽  
Commercial Fishing ◽  
South American ◽  
Killer Whales ◽  
Sea Lion ◽  
Otaria Flavescens ◽  
Sea Lions ◽  
Trawl Fishery ◽  
Fishing Vessels ◽  
Almost All

Killer whale-seal interactions have been reported for almost all pinniped species globally. However the literature on offshore interactions between killer whales and sea lions is rare for the South Atlantic, particularly in Argentine waters. Here we report for the first time the harassment of a South American sea lion (Otaria flavescens) by killer whales (Ornicus orca) while attending commercial fishing vessels in offshore national waters and describe a novel sea lion antipredator behaviour. These observations were made during an ongoing survey to assess seabird-fisheries interactions in the commercial trawl fishery off Argentina.

Survival of Steller sea lions in Alaska: a comparison of increasing and decreasing populations

2006 ◽  
Vol 84 (8) ◽  
pp. 1163-1172 ◽  
Author(s):  
Grey W. Pendleton ◽  
Kenneth W. Pitcher ◽  
Lowell W. Fritz ◽  
Anne E. York ◽  
Kimberly L. Raum-Suryan ◽  
...  
Keyword(s):  
Adult Female ◽  
Past Research ◽  
Steller Sea Lion ◽  
Juvenile Survival ◽  
Sea Lion ◽  
Eastern Population ◽  
Western Population ◽  
Survival Probabilities ◽  
Sea Lions ◽  
Female Survival

Steller sea lion ( Eumetopias jubatus (Schreber, 1776)) populations have had differing dynamics in different regions of Alaska over the past 30 years. The western population (west of 144°W, near Cape Suckling) declined by approximately 85% between the 1970s and 2000, while the eastern population has increased at a rate of over 3%/year. Past research has indicated that the decline in the western population likely resulted from decreased juvenile survival and smaller declines in adult female survival and reproduction. Based on repeated observations (1987–2003) of sea lions branded as pups at Marmot Island (58.216°N, 151.840°W; western population; branded in 1987–1988) and at the Forrester Island rookery complex (54.859°N, 133.539°W; eastern population; branded in 1994–1995), we used mark–resight analyses to estimate age-specific survival probabilities. Juvenile sea lion survival probability at Marmot Island from 1988 to 1991 was lower than survival estimates at that location in the 1970s (assumed stable population) and lower than juvenile survival at Forrester Island from 1995 to 1998 (increasing population). Adult female survival at Marmot Island from 1992 to 2003 was only slightly reduced compared with that in the 1970s but was substantially lower than that at Forrester Island (1999–2003). In addition, and contrary to the typical pattern (e.g., Forrester Island), adult female survival probabilities at Marmot Island were indistinguishable from adult male survival probabilities. This suggests that regardless of which factors altered the dynamics of the western Steller sea lion population, they differentially affected females.

Status of Australian sea lions, Neophoca cinerea, and New Zealand fur seals, Arctocephalus forsteri, on Eyre Peninsula and the far west coast of South Australia

2005 ◽  
Vol 32 (1) ◽  
pp. 85 ◽  
Author(s):  
P. D. Shaughnessy ◽  
T. E. Dennis ◽  
P. G. Seager
Keyword(s):  
New Zealand ◽  
West Coast ◽  
South Australia ◽  
Sea Lion ◽  
The West ◽  
Sea Lions ◽  
Neophoca Cinerea ◽  
Fur Seals ◽  
Fur Seal ◽  
New Zealand Fur Seal

Two seal species breed on the west coast of South Australia, the Australian sea lion, Neophoca cinerea, and the New Zealand fur seal, Arctocephalus forsteri. Aerial surveys were conducted at intervals of ~3 months between April 1995 and June 1997 to determine the breeding status of sea lions and timing of pupping seasons. Ground surveys between October 1994 and April 2004 aimed at counting sea lions and fur seals, particularly pups. In all, 27 sites were examined. Six new sea lion breeding colonies were documented, at Four Hummocks, Price, North Rocky, Dorothee, West Waldegrave and Nicolas Baudin Islands. All were found or confirmed by ground survey. Pup numbers were equivalent to 12% of the total number of pups estimated in surveys conducted from 1987 to 1992, but primarily in 1990. The sighting of brown pups on aerial surveys of Ward Island, Middle and Western Nuyts Reef supports earlier indications, based on dead pups, that they are breeding colonies. The timing of pupping seasons is not synchronous; estimates are presented for colonies between 1995 and early in 2004, with predictions to the end of 2005. The abundance estimates of sea lion pups highlight the importance of visiting a colony early in the pupping season to determine when pupping begins and ~5 months later when the maximum number of pups is expected. For the New Zealand fur seal, small numbers of pups were recorded at Dorothee, West Waldegrave and Nicolas Baudin Islands, and at Nuyts Reef. These and the previously unknown sea lion breeding colonies on the west coast of South Australia suggest that further colonies may remain to be documented. Because planning for aquaculture ventures is active in South Australia, it is important that the localities and status of sea lion and fur seal colonies be established unequivocally to ensure that the need for Prohibited Area status for islands with breeding colonies and for Marine Protected Areas around them is noted.

Remarks on display functions of the snout of the grey seal, Halichoerus grypus (Fab.), with comparative notes

1979 ◽  
Vol 57 (1) ◽  
pp. 140-148 ◽  
Author(s):  
E. H. Miller ◽  
D. J. Boness
Keyword(s):  
Visual Display ◽  
Halichoerus Grypus ◽  
Grey Seal ◽  
Adult Males ◽  
Hooded Seal ◽  
Elephant Seals ◽  
Sea Lions ◽  
Cystophora Cristata ◽  
Fur Seals ◽  
Threat Displays

Adult males of the grey seal, Halichoerus grypus (Fab.) (Phocidae), display the large snout conspicuously in threats. The male's snout has probably evolved through sexual selection as a visual display organ, as in some other extant phocids: the hooded seal, Cystophora cristata (Nilsson) and the two species of elephant seals, Mirounga (Gray). This may also be true of the extinct desmatophocid Allodesmus Kellogg. Cephalic display organs in the form of long tusks have also evolved twice in the Odobenidae (walruses). Comparable display structures do not occur in the Otariidae (fur seals and sea lions). However, the massive neck of adult male otariids is important in undirected static-optical threat displays, especially at long range, and in some kinds of short-range threats. Also, adult otariids show sexual dimorphism in facial appearance, which varies interspecifically.Pinniped species in which large mature males have prominent, constant-growing cephalic display structures show fluid spacing among rutting males, and much agonistic communication at the water surface and on land or ice. This correlation may reflect selective pressures on males to affirm social status repeatedly, through displays which communicate their age (hence strength and experience), and their resource-accruing abilities.

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