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

2001 ◽  
Vol 254 (2) ◽  
pp. 267-277 ◽  
Author(s):  
D. E. Crocker ◽  
N. J. Gales ◽  
D. P. Costa
Keyword(s):  
New Zealand ◽  
Swimming Speed ◽  
Foraging Strategies ◽  
Sea Lions ◽  
Phocarctos Hookeri

Stable isotope signatures of whisker and blood serum confirm foraging strategies for female New Zealand sea lions (Phocarctos hookeri) derived from telemetry

2017 ◽  
Vol 95 (12) ◽  
pp. 955-963 ◽  
Author(s):  
B.L. Chilvers
Keyword(s):  
New Zealand ◽  
Stable Isotope ◽  
Isotopic Composition ◽  
Blood Serum ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Female Population ◽  
Sea Lions ◽  
Stable Isotope Signatures ◽  
Phocarctos Hookeri

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.

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

2007 ◽  
Vol 43 (3) ◽  
pp. 461-474 ◽  
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

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

2016 ◽  
Vol 53 (6) ◽  
pp. 1241-1247 ◽  
Author(s):  
S. A. Michael ◽  
B. L. Chilvers ◽  
S. A. Hunter ◽  
P. Duignan ◽  
W. Roe
Keyword(s):  
New Zealand ◽  
Sea Lions ◽  
Phocarctos Hookeri

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

2000 ◽  
Vol 203 (23) ◽  
pp. 3655-3665 ◽  
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.

Philopatry and site fidelity of New Zealand sea lions (Phocarctos hookeri)

2008 ◽  
Vol 35 (5) ◽  
pp. 463 ◽  
Author(s):  
B. Louise Chilvers ◽  
Ian S. Wilkinson
Keyword(s):  
New Zealand ◽  
Site Fidelity ◽  
Breeding Area ◽  
Quantitative Investigation ◽  
Sea Lion ◽  
Breeding Sites ◽  
Auckland Island ◽  
Sea Lions ◽  
Breeding Habitats ◽  
Phocarctos Hookeri

The New Zealand sea lion (NZ sea lion), Phocarctos hookeri, is New Zealand’s only endemic pinniped, and one of the worlds rarest otariids. It is classified as ‘Threatened’ based primarily on the low number of breeding sites and restricted distribution. In New Zealand, a species listed as ‘threatened’ is required to be managed to allow its recovery and removal from the list within 20 years. For NZ sea lions this is dependant on the establishment of new breeding areas. However, understanding the recolonisation processes for pinnipeds is still in its infancy with factors such as philopatry needing more research to understand individual dispersal and the recolonisation process. This paper presents the first quantitative investigation into the level of site fidelity and philopatry to breeding beaches in NZ sea lions. Data from resights of NZ sea lions marked as pups from the northern Auckland Island breeding area suggest that both site fidelity and philopatry are important characteristics of this species. Our results show that overall: (1) females have a higher resighting rate than males, particularly at natal sites; (2) female non-natal resightings are predominantly restricted to locations within the northern Auckland Island breeding area (an area of ~10 km2), whereas male resightings are more widely dispersed (up to 700 km to NZ mainland); and (3) philopatry occurs for both sexes, but is more predominant in females than males, with males displaying delay related to sexual and social maturity. The colonisation of new breeding habitats rarely occurs when philopatry is strong and population density is low, stable or declining such as seen for NZ sea lions. Therefore, this research indicates that management of NZ sea lions needs to minimise anthropogenic mortality and encourage population growth to maximise density at breeding sites and encourage females to disperse to establish new breeding areas.

scholarly journals Pup mortality in New Zealand sea lions (Phocarctos hookeri) at Enderby Island, Auckland Islands, 2013-18

PLoS ONE ◽  
2019 ◽  
Vol 14 (11) ◽  
pp. e0225461
Author(s):  
Sarah A. Michael ◽  
David T. S. Hayman ◽  
Rachael Gray ◽  
Ji Zhang ◽  
Lynn Rogers ◽  
...  
Keyword(s):  
New Zealand ◽  
Sea Lions ◽  
Pup Mortality ◽  
Phocarctos Hookeri

scholarly journals Interannual and individual variation in milk composition of New Zealand sea lions (Phocarctos hookeri)

2012 ◽  
Vol 93 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
Federico G. Riet-Sapriza ◽  
PÁdraig J. Duignan ◽  
B. Louise Chilvers ◽  
Ian S. Wilkinson ◽  
Nicolás Lopez-Villalobos ◽  
...  
Keyword(s):  
New Zealand ◽  
Individual Variation ◽  
Milk Composition ◽  
Sea Lions ◽  
Phocarctos Hookeri

scholarly journals Historical population size of the threatened New Zealand sea lion Phocarctos hookeri

2015 ◽  
Vol 97 (2) ◽  
pp. 436-443 ◽  
Author(s):  
Catherine J. Collins ◽  
B. Louise Chilvers ◽  
Matthew Taylor ◽  
Bruce C. Robertson
Keyword(s):  
New Zealand ◽  
Population Size ◽  
Effective Population Size ◽  
Carrying Capacity ◽  
Effective Population ◽  
Sea Lion ◽  
Sea Lions ◽  
Target Values ◽  
Phocarctos Hookeri

Abstract Marine mammal species were exploited worldwide during periods of commercial sealing in the 18th and 19th centuries. For many of these species, an estimate of the pre-exploitation abundance of the species is lacking, as historical catch records are generally scarce and inaccurate. Genetic estimates of long-term effective population size provide a means to estimate the pre-exploitation abundance. Here, we apply genetic methods to estimate the long-term effective population size of the subantarctic lineage of the New Zealand sea lion (NZ sea lion), Phocarctos hookeri . This species is predominantly restricted to the subantarctic islands, south of mainland New Zealand, following commercial sealing in the 19th century. Today, the population consists of ~9,880 animals and population growth is slow. Auckland Island breeding colonies of NZ sea lion are currently impacted by commercial trawl fisheries via regular sea lion deaths as bycatch. In order to estimate sustainable levels of bycatch, an estimate of the population’s carrying capacity ( K ) is required. We apply the genetically estimated long-term effective population size of NZ sea lions as a proxy for the estimated historical carrying capacity of the subantarctic population. The historical abundance of subantarctic NZ sea lions was significantly higher than the target values of K employed by the contemporary management. The current management strategy may allow unsustainable bycatch levels, thereby limiting the recovery of the NZ sea lion population toward historical carrying capacity.

Male harassment of female New Zealand sea lions, Phocarctos hookeri: mortality, injury, and harassment avoidance

2005 ◽  
Vol 83 (5) ◽  
pp. 642-648 ◽  
Author(s):  
B Louise Chilvers ◽  
Bruce C Robertson ◽  
Ian S Wilkinson ◽  
Padraig J Duignan ◽  
Neil J Gemmell
Keyword(s):  
New Zealand ◽  
Injury Rate ◽  
Long Term Effects ◽  
Visible Injury ◽  
Male Harassment ◽  
Sea Lions ◽  
Indirect Impacts ◽  
The Cost ◽  
Time And Energy ◽  
Phocarctos Hookeri

Sexual aggression by male pinnipeds during breeding can lead to female injury and death, affecting reproductive success, fecundity, and increasing the cost of mating for females. Thus, females that employ strategies to minimize the probability of being injured will be at an advantage. Here we investigate the extent of injuries and the number of deaths attributed to male harassment, and test the hypothesis of whether the arrival and departure behaviour of female New Zealand sea lions (Phocarctos hookeri (Gray, 1844); NZSL) at Sandy Bay, Enderby Island, the Auckland Islands, is adapted to reduce the chance of injury or death from encounters with male NZSLs. During the breeding season, harassment by non-territorial male NZSLs causes mortality in adult female NZSLs, approximately 5 in every 1000 females breeding each year. Permanent scars from male bites are observed on 84% of adult females. This mortality and visible injury rate only represents the direct impacts on female NZSL from male harassment. Indirect impacts, such as the time and energy cost of avoidance behaviour, pup separation, and pup injury and death, can have as significant long-term effects on individuals and the population. We find that male harassment can influence the behaviour of individuals in NZSL breeding harems.

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