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.

Foraging strategies of southern elephant seals (Mirounga leonina) in relation to frontal zones and water masses

2001 ◽  
Vol 13 (4) ◽  
pp. 371-379 ◽  
Author(s):  
Iain Field ◽  
Mark Hindell ◽  
David Slip ◽  
Kelvin Michael
Keyword(s):  
Dive Depth ◽  
Polar Front ◽  
Water Masses ◽  
Diving Behaviour ◽  
Water Bodies ◽  
Foraging Strategies ◽  
Mirounga Leonina ◽  
Mode Water ◽  
Elephant Seals ◽  
Southern Elephant Seals

Geolocating-time-depth-temperature-recorders (GLTDTR) provided a continuous record of diving behaviour in relation to water temperature for ten female southern elephant seals from Macquarie Island during their post-breeding trips to sea. Four water bodies were determined from depth/temperature profiles recorded by the GLTDTRs. These water bodies corresponded to Sub-Antarctic Mode Water (SAMW), Polar Front Zone Water (PFZW), Polar Front Water (PFW) and Antarctic Water Masses (AWM). Thermal structures within these water bodies did not influence seal diving behaviour. Overall mean dive depth, nocturnal dive depths, diurnal dive depths and dive duration were similar in all areas. However, individuals did change behaviour as they moved between different water bodies. Seals also used different water bodies in the two different years of the study. We suggest that variations in foraging behaviour among seals are a result of prey distribution associated with local oceanographic conditions, but also reflect important individual foraging strategies within thermal zones.

Some characteristics of narwhal, Monodon monoceros, diving behaviour in Baffin Bay

1995 ◽  
Vol 73 (11) ◽  
pp. 2120-2132 ◽  
Author(s):  
M. P. Heide-JøRgensen ◽  
R. Dietz
Keyword(s):  
Water Column ◽  
Dive Depth ◽  
Diving Behaviour ◽  
The Other ◽  
Small Male ◽  
Vertical Movements ◽  
Baffin Bay ◽  
Monodon Monoceros ◽  
Aerobic Dive Limit

Dive data were collected from nine narwhals, Monodon monoceros, instrumented with satellite-linked dive recorders in northwest Greenland in August–September 1993 and 1994. Data were collected for periods ranging from a few weeks to 9 months. The narwhals made daily dives to depths of more than 500 m and frequently dived to 1000 m or more. However, most of the time spent below the surface was in the water column at depths of between 8 and 52 m. For two males that were tracked from September through November the maximum dive depth increased steadily through time. There were no consistent differences in the duration of dives or the number of dives to depths > 8 m during four 6-h periods that were monitored. There were significant differences in dive rates (number of dives per hour) between the large males, the small male, and the females. More than half of the dives lasted less than 5 min and few lasted more than 20 min. These relatively short dive times suggest that narwhals do not exceed their aerobic dive limit. The average time spent in the upper 5 m of the water column was 39.3% (SD = 13.5%; n = 632) for seven whales combined. Speed of vertical movements increased significantly from 1 m∙s−1 for 100-m dives to more than 2 m∙s−1 for dives deeper than 900 m. A female accompanied by a calf had dive parameters and surfacing times that were identical with those of the other females.

Habitat use and diving behaviour of male Australian fur seals

2017 ◽  
Vol 566 ◽  
pp. 243-256 ◽  
Author(s):  
TC Knox ◽  
AMM Baylis ◽  
JPY Arnould
Keyword(s):  
Habitat Use ◽  
Diving Behaviour ◽  
Fur Seals

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.

Influence of shelf oceanographic variability on alternate foraging strategies in long-nosed fur seals

2019 ◽  
Vol 615 ◽  
pp. 189-204 ◽  
Author(s):  
D Foo ◽  
C McMahon ◽  
M Hindell ◽  
S Goldsworthy ◽  
F Bailleul
Keyword(s):  
Foraging Strategies ◽  
Fur Seals

scholarly journals North Pacific warming shifts the juvenile range of a marine apex predator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kisei R. Tanaka ◽  
Kyle S. Van Houtan ◽  
Eric Mailander ◽  
Beatriz S. Dias ◽  
Carol Galginaitis ◽  
...  
Keyword(s):  
North Pacific ◽  
Species Conservation ◽  
Total Body Length ◽  
Suitable Habitat ◽  
Climate Data ◽  
Marine Predator ◽  
Spatial Shift ◽  
Marine Megafauna ◽  
Community Science ◽  
Juvenile Sharks

AbstractDuring the 2014–2016 North Pacific marine heatwave, unprecedented sightings of juvenile white sharks (Carcharodon carcharias) emerged in central California. These records contradicted the species established life history, where juveniles remain in warmer waters in the southern California Current. This spatial shift is significant as it creates potential conflicts with commercial fisheries, protected species conservation, and public safety concerns. Here, we integrate community science, photogrammetry, biologging, and mesoscale climate data to describe and explain this phenomenon. We find a dramatic increase in white sharks from 2014 to 2019 in Monterey Bay that was overwhelmingly comprised of juvenile sharks < 2.5 m in total body length. Next, we derived thermal preferences from 22 million tag measurements of 14 juvenile sharks and use this to map the cold limit of their range. Consistent with historical records, the position of this cold edge averaged 34° N from 1982 to 2013 but jumped to 38.5° during the 2014–2016 marine heat wave. In addition to a poleward shift, thermally suitable habitat for juvenile sharks declined 223.2 km2 year−1 from 1982 to 2019 and was lowest in 2015 at the peak of the heatwave. In addition to advancing the adaptive management of this apex marine predator, we discuss this opportunity to engage public on climate change through marine megafauna.

Horizontal and vertical movements of telemetered rainbow trout (Oncorhynchus mykiss) in Lake Washington

1995 ◽  
Vol 73 (1) ◽  
pp. 146-153 ◽  
Author(s):  
Eric J. Warner ◽  
Thomas P. Quinn
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Average Velocity ◽  
Sockeye Salmon ◽  
Depth Distribution ◽  
Prey Species ◽  
Nearshore Zone ◽  
Vertical Movements ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Lake Washington

In summer and fall 1989, six rainbow trout (Oncorhynchus mykiss) were tracked in Lake Washington with ultrasonic transmitters for a total of 349 h to determine their movements in relation to the distribution of possible prey species. The trout moved primarily in the nearshore area at an average velocity of 12.4 cm/s (~ 0.25–0.3 body lengths/s). Five of the six fish made one more rapid (>1 body lengths/s) excursion across the lake, then continued moving in the nearshore zone. The trout were generally inactive, staying close (<50 m) to shore at night, and became more active near dawn; however, the highest average velocities were at dusk. They spent over 90% of their time in the top 3 m of the water column and 10% in brief (2 min), shallow (mean 6.6 m) dives. Dives occurred most frequently at dawn and during the day (0.8/h), less often near dusk (0.5/h), and seldom at night (0.1/h). The depth distribution and movement patterns suggest that the trout were feeding on Daphnia pulicaria during the day, in both nearshore and offshore areas, supplementing this diet with nearshore fishes such as prickly sculpins (Cottus asper). Predation on pelagic planktivores (longfin smelt, Spirinchus thaleichthyes, and juvenile sockeye salmon, Oncorhynchus nerka) was unlikely because the trout were primarily found nearshore and near the surface, whereas the planktivores are primarily offshore and closer to the bottom.

Assisted colonisation trial of the eastern barred bandicoot (Perameles gunnii) to a fox-free island

2017 ◽  
Vol 44 (7) ◽  
pp. 484 ◽  
Author(s):  
Rebecca Groenewegen ◽  
Dan Harley ◽  
Richard Hill ◽  
Graeme Coulson
Keyword(s):  
Habitat Use ◽  
Body Condition ◽  
Red Fox ◽  
Suitable Habitat ◽  
Viable Option ◽  
Predator Exclusion ◽  
In The Wild ◽  
Radio Transmitters ◽  
Release Group ◽  
Small Sites

Context Assisted colonisation has the potential to protect species from intractable threats within their historical ranges. The Australian mainland subspecies of the eastern barred bandicoot (Perameles gunnii) is extinct in the wild, with surviving populations restricted to small sites protected by predator–barrier fences. PVA modelling shows that a self-sustaining bandicoot population would require an area free of the introduced red fox (Vulpes vulpes) of at least 2500ha. French Island is outside the historic range of the species, but is fox-free and contains around 9000ha of potentially suitable habitat. Aims This study will assess the suitability of French Island as a potential site for a self-sustaining eastern barred bandicoot population by conducting a 1-year assisted colonisation trial to assess habitat use, body condition and survival. Methods Between July and September 2012, 18 adult bandicoots were released. We radio-tracked bandicoots using intraperitoneal radio-transmitters for up to 122 days and trapped fortnightly. Key results The release group met the three measures of success: (1) appropriate habitat use; (2) recovery of post-release bodyweight; and (3) founder survival exceeding 100 days. Habitat use and body condition throughout the trial reflected that of mainland populations, and seven bandicoots survived longer than 100 days. Mortality was greatest in the first month, with veterinary investigations confirming two deaths due to cat predation, two deaths from toxoplasmosis and one unknown cause of death. Bandicoots that survived longer than 100 days occupied higher, drier ground than those that did not. Toxoplasmosis cases were associated with lower topographic position on the site. Conclusions Our results suggest that French Island provides suitable habitat for the establishment of a population of eastern barred bandicoots. On French Island, toxoplasmosis was identified as an important source of mortality in addition to cat predation, and warrants further investigation. Implications Given the costs and challenges of predator control and the maintenance of predator exclusion fences, assisted colonisation to one or more fox-free islands remains the most viable option to establish self-sustaining bandicoot populations. Our results highlight the value in conducting trial releases ahead of major translocations.

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