Diverse foraging strategies in lactating New Zealand sea lions

Recognizing the individual variability of foraging behaviour of marine predators is important for understanding their role in the marine ecosystem and identifying how species may respond to environmental variability or human impacts. This research examines stable isotope signatures (δ13C and δ15N) of blood serum and whiskers from 22 female New Zealand sea lions (Phocarctos hookeri (Gray, 1844)) to determine if the isotopic composition of serum reflects foraging strategy, and whether serum and proximal whisker growth have similar signatures, therefore indicating the isotopic composition of whiskers also reflects the foraging strategy diet at the time of their growth. Female New Zealand sea lions are known to have two distinct foraging strategies (mesopelagic or benthic ecotypes), shown to be habitual within and between years. Females who are known to be mesopelagic foragers have higher overlap and are at greater risk of harmful interactions with fisheries. This research found that the two foraging strategies identified from telemetry are also associated with different δ13C and δ15N isotopic values from blood serum and whiskers. Therefore, stable isotope analysis could be used to determine the proportion of the female population that are likely to be exposed to the detrimental direct and indirect interactions with fisheries.

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Swimming speed and foraging strategies of New Zealand sea lions (Phocarctos hookeri)

Journal of Zoology ◽

10.1017/s0952836901000784 ◽

2001 ◽

Vol 254 (2) ◽

pp. 267-277 ◽

Cited By ~ 34

Author(s):

D. E. Crocker ◽

N. J. Gales ◽

D. P. Costa

Keyword(s):

New Zealand ◽

Swimming Speed ◽

Foraging Strategies ◽

Sea Lions ◽

Phocarctos Hookeri

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Whisker stable isotope values indicate long-term foraging strategies for female New Zealand sea lions

Endangered Species Research ◽

10.3354/esr00934 ◽

2019 ◽

Vol 38 ◽

pp. 55-66 ◽

Cited By ~ 4

Author(s):

BL Chilvers

Keyword(s):

New Zealand ◽

Stable Isotope ◽

Foraging Strategies ◽

Sea Lions

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NEONATAL MORTALITY IN NEW ZEALAND SEA LIONS (PHOCARCTOS HOOKERI ) AT SANDY BAY, ENDERBY ISLAND, AUCKLAND ISLANDS FROM 1998 TO 2005

Journal of Wildlife Diseases ◽

10.7589/0090-3558-43.3.461 ◽

2007 ◽

Vol 43 (3) ◽

pp. 461-474 ◽

Cited By ~ 43

Author(s):

A. Castinel ◽

P. J. Duignan ◽

W. E. Pomroy ◽

N. López-Villalobos ◽

N. J. Gibbs ◽

...

Keyword(s):

New Zealand ◽

Neonatal Mortality ◽

Sea Lions ◽

Phocarctos Hookeri

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Diving deep into trouble: the role of foraging strategy and morphology in adapting to a changing environment

Conservation Physiology ◽

10.1093/conphys/coaa111 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Monique Ladds ◽

David Rosen ◽

Carling Gerlinsky ◽

David Slip ◽

Robert Harcourt

Keyword(s):

Foraging Strategy ◽

Central Place ◽

Dive Duration ◽

Foraging Strategies ◽

Body Morphology ◽

Sea Lions ◽

Fur Seals ◽

Adequate Food ◽

Physiological Capacity ◽

Total Body Oxygen

Abstract Physiology places constraints on an animal’s ability to forage and those unable to adapt to changing conditions may face increased challenges to reproduce and survive. As the global marine environment continues to change, small, air-breathing, endothermic marine predators such as otariids (fur seals and sea lions) and particularly females, who are constrained by central place foraging during breeding, may experience increased difficulties in successfully obtaining adequate food resources. We explored whether physiological limits of female otariids may be innately related to body morphology (fur seals vs sea lions) and/or dictate foraging strategies (epipelagic vs mesopelagic or benthic). We conducted a systematic review of the increased body of literature since the original reviews of Costa et al. (When does physiology limit the foraging behaviour of freely diving mammals? Int Congr Ser 2004;1275:359–366) and Arnould and Costa (Sea lions in drag, fur seals incognito: insights from the otariid deviants. In Sea Lions of the World Fairbanks. Alaska Sea Grant College Program, Alaska, USA, pp. 309–324, 2006) on behavioural (dive duration and depth) and physiological (total body oxygen stores and diving metabolic rates) parameters. We estimated calculated aerobic dive limit (cADL—estimated duration of aerobic dives) for species and used simulations to predict the proportion of dives that exceeded the cADL. We tested whether body morphology or foraging strategy was the primary predictor of these behavioural and physiological characteristics. We found that the foraging strategy compared to morphology was a better predictor of most parameters, including whether a species was more likely to exceed their cADL during a dive and the ratio of dive time to cADL. This suggests that benthic and mesopelagic divers are more likely to be foraging at their physiological capacity. For species operating near their physiological capacity (regularly exceeding their cADL), the ability to switch strategies is limited as the cost of foraging deeper and longer is disproportionally high, unless it is accompanied by physiological adaptations. It is proposed that some otariids may not have the ability to switch foraging strategies and so be unable adapt to a changing oceanic ecosystem.

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Pathology and Epidemiology of Stillbirth in New Zealand Sea Lions (Phocarctos hookeri) From Enderby Island, Auckland Islands, 1998–2012

Veterinary Pathology ◽

10.1177/0300985816638723 ◽

2016 ◽

Vol 53 (6) ◽

pp. 1241-1247 ◽

Cited By ~ 1

Author(s):

S. A. Michael ◽

B. L. Chilvers ◽

S. A. Hunter ◽

P. Duignan ◽

W. Roe

Keyword(s):

New Zealand ◽

Sea Lions ◽

Phocarctos Hookeri

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Foraging energetics and diving behavior of lactating New Zealand sea lions, Phocarctos hookeri

Journal of Experimental Biology ◽

10.1242/jeb.203.23.3655 ◽

2000 ◽

Vol 203 (23) ◽

pp. 3655-3665 ◽

Cited By ~ 6

Author(s):

D.P. Costa ◽

N.J. Gales

Keyword(s):

New Zealand ◽

Metabolic Rate ◽

Dive Depth ◽

Diving Behavior ◽

Metabolic Rates ◽

Sea Lion ◽

Water Turnover ◽

Sea Lions ◽

The Mean ◽

Phocarctos Hookeri

The New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50 degrees 30′S, 166 degrees 17′E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO(2) production) and water turnover were measured using the (18)O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0+/−1.1 % (mean +/− s.d.) and mean rate of CO(2) production was 0. 835+/−0.114 ml g(−)(1)h(−)(1), which provides an estimated mass-specific field metabolic rate (FMR) of 5.47+/−0.75 W kg(−)(1). After correction for time on shore, the at-sea FMR was estimated to be 6.65+/−1.09 W kg(−)(1), a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size. The mean maximum dive depth was 353+/−164 m, with a mean diving depth of 124+/−36 m. The mean maximum dive duration was 8.3+/−1.7 min, with an average duration of 3.4+/−0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg). Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O(2) storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.

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First Complete Wing of a Stem Group Sphenisciform from the Paleocene of New Zealand Sheds Light on the Evolution of the Penguin Flipper

Diversity ◽

10.3390/d12020046 ◽

2020 ◽

Vol 12 (2) ◽

pp. 46 ◽

Cited By ~ 1

Author(s):

Gerald Mayr ◽

Vanesa L. De Pietri ◽

Leigh Love ◽

Al A. Mannering ◽

Joseph J. Bevitt ◽

...

Keyword(s):

New Zealand ◽

Marine Mammals ◽

Early Stage ◽

Foraging Strategies ◽

Cold Climates ◽

Functional Categories ◽

Stem Group ◽

Partial Skeleton

We describe a partial skeleton of a stem group penguin from the Waipara Greensand in New Zealand, which is tentatively assigned to Muriwaimanu tuatahi. The fossil includes the first complete wing of a Paleocene penguin and informs on previously unknown features of the mandible and tibiotarsus of small-sized Sphenisciformes from the Waipara Greensand. The wing is distinguished by important features from that of all geologically younger Sphenisciformes and documents an early stage in the evolution of wing-propelled diving in penguins. In particular, the wing of the new fossil exhibits a well-developed alular phalanx and the distal phalanges are not flattened. Because the wing phalanges resemble those of volant birds, we consider it likely that the wing feathers remained differentiated into functional categories and were not short and scale-like as they are in extant penguins. Even though the flippers of geologically younger penguins may favor survival in extremely cold climates, they are likely to have been shaped by hydrodynamic demands. Possible selective drivers include a diminished importance of the hindlimbs in subaquatic propulsion, new foraging strategies (the caudal end of the mandible of the new fossil distinctly differs from that of extant penguins), or increased predation by marine mammals.

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