Diving behaviour of lactating Antarctic fur seals

1992 ◽  
Vol 70 (5) ◽  
pp. 919-928 ◽  
Author(s):  
I. L. Boyd ◽  
J. P. Croxall
Keyword(s):  
Mixed Layer ◽  
Foraging Strategy ◽  
Dive Depth ◽  
Diving Behaviour ◽  
Cumulative Probability ◽  
Surface Mixed Layer ◽  
Sea Temperature ◽  
Fur Seals ◽  
Fur Seal ◽  
Antarctic Fur Seals

The diving behaviour of 11 lactating female Antarctic fur seals (Arctocephalus gazella) was recorded for a total of 254 animal-days at sea. Median and maximum dive depths for individuals varied from 8 to 19 m and from 82 to 181 m, respectively, and median and maximum dive durations from 0.75 to 1.17 min and from 2.8–10.0 min, respectively. Theoretical aerobic diving limits were exceeded on < 1% of dives. Dives were mainly V-shaped. Sixty percent of dives were to less than 20 m depth, and these dives were distinguished from deep dives (> 20 m) by having slower rates of descent and ascent and by being confined to the mixed layer at the ocean surface, as judged by records of sea temperature obtained concurrently with records of depth. Dives were grouped into bouts, defined by inflexion points observed in the cumulative probability distribution of surface interval after probit transformation. Bouts (defined by preceding and succeeding surface intervals lasting 13–24 min) occurred within a diel pattern of diving activity, with 74–85% of dives occurring at night. The pattern of diving, in terms of division into bouts, showed greater differences between individual seals than did dive depth and duration. Dives tended to be shorter and shallower later in lactation. Most variation in diving behaviour between individuals was in terms of the proportion of available time spent foraging, bout frequency, and bout duration. The foraging strategy in the Antarctic fur seal is geared to exploiting prey within the surface mixed layer.

Ontogeny of Diving Behaviour in the Galápagos Fur Seal

Behaviour ◽  
1997 ◽  
Vol 134 (15-16) ◽  
pp. 1211-1257 ◽  
Author(s):  
Markus Horning ◽  
Fritz Trillmich
Keyword(s):  
Dive Depth ◽  
Observation Time ◽  
Diving Behaviour ◽  
Age Group ◽  
Maternal Milk ◽  
Adult Females ◽  
Fur Seals ◽  
Fur Seal ◽  
One Year ◽  
Travel Distances

AbstractWe studied the ontogeny of diving behaviour in the Galápagos fur seal (Arctocephalus galapagoensis, Heller 1904). Six-month-old seals spent less than 12% of observation time at sea and were entirely dependent on maternal milk for nutrition. Maximum dive depths for this age group averaged 5.6 m, maximum durations 50 s (N = 12). Modal swim speeds averaged 0.55 m/s; maximum observed swim speeds ranged from 0.9-2 m/s (N = 5). Six-month-old seals swam distances of 2.9 km/24 hrs on average (N = 5). No diel patterns were apparent in their diving behaviour. One-year-old fur seals were the youngest age group to show substantial diving activity, reaching maximum depths of 47.5 m and durations of 2.4 min on average (N = 21). Modal swim speeds averaged 0.9 m/s, maximum speeds ranged from 1.4-2.3 m/s (N = 6). Total distances traveled averaged 15.4 km/trip to sea. Yearlings spent 23.9% of observation time at sea, the majority (> 95%) of that at night. This corresponds to the activity pattern of adult females who dive exclusively at night. Yearlings were the youngest age group to contribute to their own nutrition through independent foraging, but were still dependent on their mothers: no yearlings were successfully weaned in this study. 18-month-old seals were better divers, spending 27.6% of observation time at sea, mostly during the night. Maximum dive depths for this age group averaged 61.1 m; durations 3.1 min (N = 11). Modal swim speeds averaged 1.4 m/s (N = 4), and were comparable to modal speeds of two adult females of 1.2 and 1.6 m/s. Maximum speeds for these juveniles ranged from 2.2-2.7 m/s (N = 4); the two adult females reached 2.8 and 4 m/s respectively. Total travel distances averaged 42 km/trip to sea (N = 4 juveniles). These distances corresponded to those covered by two adult females, 43 and 45 km/trip. Two-year-old fur seals included the youngest that were successfully weaned in this study. They spent 35% of observation time at sea, primarily at night. Maximum dive depths averaged 69.7 m, durations 3.4 min (N = 20). Adult females were the best divers in this study, spending 49.5% of observation time at sea, almost exclusively at night. Maximum dive depths averaged 106.5 m, durations 4.5 min (N = 32). During ontogeny, age was the best predictor of time spent at sea. For animals older than six months, body mass was the best predictor for maximum dive depth as well as maximum and median durations. The physiological maturation process precludes weaning before the age of one year. After that, the diving capacity of young fur seals takes a central role in the weaning process, in conjunction with the temporal patterns of relative prey accessibility.

Seasonal dive behaviour of lactating New Zealand fur seals (Arctocephalus forsteri)

1998 ◽  
Vol 76 (2) ◽  
pp. 350-360 ◽  
Author(s):  
R H Mattlin ◽  
N J Gales ◽  
D P Costa
Keyword(s):  
New Zealand ◽  
Dive Depth ◽  
Dive Duration ◽  
Early Summer ◽  
Late Winter ◽  
Individual Values ◽  
Dive Behaviour ◽  
Fur Seals ◽  
Fur Seal ◽  
Bay Islands

The dive behaviour of 18 female New Zealand fur seals (Arctocephalus forsteri) from Taumaka, Open Bay Islands, New Zealand (43°52'S, 168°53'E), was recorded during early (summer; December-February), mid (autumn; March-May), and late (winter; June-August) lactation. Mean dive depth, dive duration, and bottom time for dives >=6 m in depth increased from summer through winter. Variation in individual seal dive behaviour within a season accounted for approximately 11, 9, and 11% of the observed difference between seasons in dive depth, dive duration, and bottom time, respectively. Seasonal dive data (mean ± 1 SD) were as follows: summer: dive depth 30 ± 37 m, dive duration 1.4 ± 1.1 min, and bottom time 0.5 ± 0.6 min; autumn: dive depth 54 ± 47 m, dive duration 2.4 ± 1.3 min, and bottom time 1.0 ± 0.8 min; winter: dive depth 74 ± 64 m, dive duration 2.9 ± 1.5 min, and bottom time 1.2 ± 1.1 min. Maximum recorded dive depth was 274 m for a 5.67-min dive in autumn. Maximum duration was 11.17 min for a dive to 237+ m in winter. New Zealand fur seals are the deepest diving fur seal species reported thus far. The estimated theoretical aerobic dive limit was exceeded on 18.4% of dives (range of individual values 0.2-57.8%). Females (n = 12) were ashore about 1.8 days at a time during February through November, and this increased to about 4.3 days during December and January. Average time spent away from the rookery ranged from 3 to 15 days.

Attendance behaviour of Antarctic and subantarctic fur seal females at Marion Island

1990 ◽  
Vol 2 (4) ◽  
pp. 309-312 ◽  
Author(s):  
Marthán N. Bester ◽  
Peter A. Bartlett
Keyword(s):  
Arctocephalus Gazella ◽  
Marion Island ◽  
Fur Seals ◽  
Fur Seal ◽  
Lactating Females ◽  
The Mean ◽  
Temperate Environment ◽  
The Difference ◽  
Antarctic Fur Seals ◽  
Subantarctic Fur Seals

The female attendance behaviour of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (A.tropicalis), which breed sympatrically on subantarctic Marion Island, was investigated. Over the same period after the breeding season, the mean duration of feeding trips to sea, and percentage of time spent at sea, did not differ significantly between lactating females of the two species. The difference in mean duration of shore visits was significant and the longer onshore attendance of A. tropicalis probably related to the lower demand by their pups which grow at a slower rate. The subpolar maternal adaptations of A. gazella were unchanged under the more temperate environment at Marion Island, and it remains to be established unequivocally whether conditions there are limiting to the species.

scholarly journals Wintertime overlaps between female Antarctic fur seals (Arctocephalus gazella) and the krill fishery at South Georgia, South Atlantic

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0248071
Author(s):  
Connor C. G. Bamford ◽  
Victoria Warwick-Evans ◽  
Iain J. Staniland ◽  
Jennifer A. Jackson ◽  
Philip N. Trathan
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Arctocephalus Gazella ◽  
Habitat Models ◽  
South Georgia ◽  
Fur Seals ◽  
Fur Seal ◽  
Ice Edge ◽  
Future Work ◽  
Antarctic Fur Seals

The diet of Antarctic fur seals (Arctocephalus gazella) at South Georgia is dominated by Antarctic krill (Euphausia superba). During the breeding season, foraging trips by lactating female fur seals are constrained by their need to return to land to provision their pups. Post-breeding, seals disperse in order to feed and recover condition; estimates indicate c.70% of females remain near to South Georgia, whilst others head west towards the Patagonian Shelf or south to the ice-edge. The krill fishery at South Georgia operates only during the winter, providing the potential for fur seal: fishery interaction during these months. Here we use available winter (May to September) tracking data from Platform Terminal Transmitter (PTT) tags deployed on female fur seals at Bird Island, South Georgia. We develop habitat models describing their distribution during the winters of 1999 and 2003 with the aim of visualising and quantifying the degree of spatial overlap between female fur seals and krill harvesting in South Georgia waters. We show that spatial distribution of fur seals around South Georgia is extensive, and that the krill fishery overlaps with small, highly localised areas of available fur seal habitat. From these findings we discuss the implications for management, and future work.

scholarly journals The influence of preceding dive cycles on the foraging decisions of Antarctic fur seals

2015 ◽  
Vol 11 (7) ◽  
pp. 20150227 ◽  
Author(s):  
T. Iwata ◽  
K. Q. Sakamoto ◽  
E. W. J. Edwards ◽  
I. J. Staniland ◽  
P. N. Trathan ◽  
...  
Keyword(s):  
Empirical Studies ◽  
Three Dimensional ◽  
Mouth Opening ◽  
Foraging Strategy ◽  
Horizontal Distance ◽  
Fur Seals ◽  
Linear Distance ◽  
Foraging Experience ◽  
Past Experiences ◽  
Antarctic Fur Seals

The foraging strategy of many animals is thought to be determined by their past experiences. However, few empirical studies have investigated whether this is true in diving animals. We recorded three-dimensional movements and mouth-opening events from three Antarctic fur seals during their foraging trips to examine how they adapt their behaviour based on past experience—continuing to search for prey in the same area or moving to search in a different place. Each dive cycle was divided into a transit phase and a feeding phase. The linear horizontal distance travelled after feeding phases in each dive was affected by the mouth-opening rate during the previous 244 s, which typically covered two to three dive cycles. The linear distance travelled tended to be shorter when the mouth-opening rate in the previous 244 s was higher, i.e. seals tended to stay in the same areas with high prey-encounter rates. These results indicate that Antarctic fur seals follow decision-making strategies based on the past foraging experience over time periods longer than the immediately preceding dive.

scholarly journals Skin temperatures during free-ranging swimming and diving in antarctic fur seals

2000 ◽  
Vol 203 (12) ◽  
pp. 1907-1914 ◽  
Author(s):  
I.L. Boyd
Keyword(s):  
Heat Flux ◽  
Skin Temperature ◽  
Heat Fluxes ◽  
Arctocephalus Gazella ◽  
Fur Seals ◽  
Fur Seal ◽  
The Individual ◽  
Free Ranging ◽  
Skin Temperatures ◽  
Antarctic Fur Seals

This study tests the hypothesis that an endothermic homeotherm should minimise heat flux in cold polar waters by minimising skin temperature. Temperature variability was measured at the surface of the skin of three Antarctic fur seals (Arctocephalus gazella) at intervals of 2 s over a total of 9.7 days while they were swimming and diving freely in polar waters at temperatures of 1.5-4 degrees C. The temperature difference (capdelta T) between skin on the dorsal thorax and the water varied from more than 20 degrees C to close to equality over periods of less than 1 h. Shorter-term variations in capdelta T of up to 5 degrees C occurred in association with diving, although these types of variations also occurred without diving. In general, capdelta T began to decline during the descent phase of a dive and began to increase again during the ascent or at the end of the dive. One of the three individuals examined showed little variation in capdelta T, which remained low (approximately 3 degrees C) throughout the experiment. In the other two fur seals, capdelta T tended to decline during periods of sustained diving and usually increased during periods spent at the surface. Mean calculated heat flux varied from 95 to 236 W m(−)(2) depending on the individual. Metabolic rates based on these calculated heat fluxes were towards the lower end of those measured in previous studies using different methodologies. The study has shown that Antarctic fur seal skin temperature is highly dynamic and suggests that the thoracic surface is an organ used for active thermoregulation.

scholarly journals Fine-scale linkages between the diving behaviour of Antarctic fur seals and oceanographic features in the southern Indian Ocean

2003 ◽  
Vol 60 (5) ◽  
pp. 990-1002 ◽  
Author(s):  
Mary-Anne Lea ◽  
Laurent Dubroca
Keyword(s):  
Multivariate Analysis ◽  
Indian Ocean ◽  
Environmental Parameters ◽  
Mass Gain ◽  
Surface Expression ◽  
Polar Front ◽  
Diving Behaviour ◽  
Southern Indian Ocean ◽  
Fur Seals ◽  
Antarctic Fur Seals

AbstractDiving activity, foraging locations and pup provisioning behaviour of 10 female Antarctic fur seals (Arctocephalus gazella) were examined with respect to a range of oceanographic parameters (sea surface temperature, chlorophyll distribution and bathymetry) at the Kerguelen Archipelago in the southern Indian Ocean in February 2000. A multivariate analysis of the environmental parameters at each of the nightly foraging locations indicated the existence of two ecoregions within the foraging range of the seals. Five seals actively foraged in oceanic waters (1870 m) with relatively warm surface water (5.4°C) to the north and east of the colony (ecoregion 1), while four others travelled to the southeast (ecoregion 2) to waters typical of the surface expression of the Polar Front (3.7°C) located over the continental shelf break (597 m). Only one seal foraged in both regions. Diving behaviour, parameterised on a nightly basis using seven variables, clearly differed between regions, with the diving activity in the warmer ecoregion 1 being characterised by deep dives (55 m), and relatively little time spent diving (47%). Conversely, dives within ecoregion 2 were, on average, to shallower depths (34.5 m), and proportionately more time was spent diving (54%). Despite differences in environmental conditions encountered and associated differences in diving activity, the foraging success of mothers, in terms of daily pup mass gain per foraging cycle, was similar in both ecoregions. The study highlights the use of multivariate analysis in categorising the foraging zones and behaviour of Antarctic fur seals.

Numerical Investigation of the Upper Ocean Response to the Typhoon Winnie (1997) Using an Air-Sea Coupled Model

2013 ◽  
Vol 726-731 ◽  
pp. 3443-3446
Author(s):  
Li Wen Huang ◽  
Yi Jun Ge
Keyword(s):  
Mixed Layer ◽  
Mixed Layer Depth ◽  
Vertical Mixing ◽  
Coupled Model ◽  
Upper Ocean ◽  
Surface Mixed Layer ◽  
Large Area ◽  
Surface Cooling ◽  
Sea Temperature ◽  
The Impact

In order to investigate the impact of air-sea interaction on the ocean surface mixed layer, Typhoon Winnie (1997) was numerical simulated with a two-way air-sea coupled model MCM (Mesoscale Coupled Model). It shows that the Sea Surface Temperature (SST) decreases over a large area with a magnitude up to 4°C. The sea temperature at 30-50 m depth increases about 1°C corresponding to the surface cooling. Moreover, the oceanic mixed layer depth deepens by 20-30 m. It can be included that these variations in the upper ocean are mainly due to vertical mixing induced by the wind stress of the typhoon.

The ontogeny of diving behaviour in New Zealand fur seal pups (Arctocephalus forsteri)

2005 ◽  
Vol 83 (9) ◽  
pp. 1149-1161 ◽  
Author(s):  
A M.M Baylis ◽  
B Page ◽  
K Peters ◽  
R McIntosh ◽  
J Mckenzie ◽  
...  
Keyword(s):  
New Zealand ◽  
Dive Depth ◽  
Dive Duration ◽  
Diving Behaviour ◽  
South American ◽  
Fur Seal ◽  
Time Periods ◽  
Prey Remains ◽  
New Zealand Fur Seal ◽  
Prey Items

This study investigated the development of diving in 21 New Zealand fur seal pups, Arctocephalus forsteri (Lesson, 1828), prior to weaning at Cape Gantheaume, Kangaroo Island. Diving behaviour was examined using time–depth recorders, which were deployed during two time periods, 5 months prior to weaning (n = 6) and 2 months prior to weaning (n = 15). Scats were also examined to assess whether fur seal pups foraged prior to weaning. The maximum dive depth attained was 44 m, while the maximum dive duration was 3.3 min. Immediately prior to weaning, fur seal pups spent a greater proportion of their time diving at night, and concomitantly several measures of diving performance also increased. In general, pups dived successively deeper (6–44 m between June and September), and the average number of dives per day, dive frequency, and vertical distance travelled increased. Prey remains were present in approximately 30% of scats and indicated that some pups were foraging as early as June (5–6 months of age, approximately 4–5 months prior to weaning). Of the scats that contained prey remains, fish (South American pilchard, Sardinops sagax (Jenyns, 1842); Australian anchovy, Engraulis australis (White, 1790); and redbait, Emmelichthys nitidus Richardson, 1845) accounted for 43% of the prey items found, crustaceans accounted for 36%, and cephalopods (Gould's squid, Nototodarus gouldi (McCoy, 1888)) accounted for 20%.

Geographic variation in at-sea movements, habitat use and diving behaviour of female Cape fur seals

2020 ◽  
Vol 649 ◽  
pp. 201-218
Author(s):  
JA Botha ◽  
SP Kirkman ◽  
JPY Arnould ◽  
AT Lombard ◽  
GJG Hofmeyr ◽  
...  
Keyword(s):  
Habitat Use ◽  
Prey Species ◽  
Dive Depth ◽  
Diving Behaviour ◽  
Foraging Strategies ◽  
Suitable Habitat ◽  
Vertical Movements ◽  
Marine Predator ◽  
Fur Seals ◽  
Shelf Slope

Knowledge of animal foraging behaviour has implications for management and conservation. While Cape fur seals Arctocephalus pusillus pusillus comprise a major proportion of the southern African marine predator biomass, little is known about their at-sea movements. We investigated foraging distribution, habitat use and diving behaviour for 35 adult female Cape fur seals from 3 breeding colonies experiencing contrasting oceanographic regimes. Animals from Black Rocks, the smallest and eastern-most colony, undertook shorter foraging trips and utilised shallower waters over the shelf. In comparison, animals from the larger west coast colonies, at Kleinsee and False Bay, travelled further and utilised deeper shelf and shelf-slope waters. However, across colonies, females typically preferred depths of <500 m and slopes of <5°. Kleinsee and False Bay seals selected sea surface temperatures within the range typically preferred by pelagic prey species such as round herring, sardine and anchovy (14-19°C). Black Rocks individuals showed bimodal preferences for colder (16°C) and warmer waters (>22°C). Dive behaviour was similar between Kleinsee and False Bay individuals (unavailable from Black Rocks), with both pelagic and benthic foraging evident. Diel patterns were apparent at both sites, as dive depth and benthic diving increased significantly during daylight hours, likely reflecting vertical movements of prey species. We provide the first assessment of Cape fur seal movement behaviour for the South African component of the population. Observed geographic differences likely reflect the availability of suitable habitat but may also indicate differences in foraging strategies and density-dependent effects throughout the range of this species.

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