Winter foraging behaviour of lactating New Zealand sea lions (<i>Phocarctos hookeri</i>)

Chilvers, B. Louise; Childerhouse, SJ; Gales, Nicholas J.

doi:10.1080/00288330.2012.752755

Cited by 11 publications

(25 citation statements)

References 23 publications

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“…These individual foraging traits are believed to persist through the year and across years (Chilvers et al 2005(Chilvers et al , 2013Chilvers 2008). Benthic females also have a lower body condition (BCI of −2 versus 9 kg).…”

Section: Foraging Strategy and Energy Intakementioning

confidence: 98%

Foraging diversity in lactating New Zealand sea lions: insights from qualitative and quantitative fatty acid analysis

MeynierLaureline

MorelPatrick

Chilvers

et al. 2014

Can. J. Fish. Aquat. Sci.

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Lactating New Zealand (NZ) sea lions (Phocarctos hookeri) exhibit different foraging patterns during their foraging trips, with benthic divers spending more energy at sea than mesopelagic conspecifics. We compared blubber fatty acids (FAs) of 14 benthic and 12 mesopelagic females captured at the Auckland Islands, NZ subantarctic, in late January 2000 using an analysis of similarities (ANOSIM). FA profiles between foraging types were significantly different (global R = 0.30, p = 0.001), suggesting a different use in prey resources. We then compared the diet predictions by quantitative FA signature analysis (QFASA) by using a prey FA library available in the region. Overall, diet predictions were significantly distinct between benthic and mesopelagic females (global R = 0.17, p = 0.022), although the diets consisted of the same prey but in different contributions. The results suggest benthic females do not compensate their higher foraging costs by feeding on prey with higher energy densities. Foraging areas of benthic females are not exploited by the trawling fishery; therefore, the benthic tactic might be a trade-off between a higher foraging cost and less resource competition.Résumé : Les lionnes de mer de Nouvelle Zélande (NZ) lactantes utilisent des tactiques de chasse en mer différentes : les individus chassant sur le benthos dépensant plus d'énergie que les individus mesopélagiques. Nous avons comparé avec une ANOSIM les acides gras (AG) du lard de 14 lionnes de mer benthiques et 12 mesopélagiques capturées aux Iles Auckland (région subantarctique de la NZ) fin janvier 2000. Les profiles d'AG entre les comportements de chasse présentent des différences significatives (global R = 0.30, p = 0.001), probablement dues à une utilisation différente des ressources entre ces deux groupes. La composition du régime alimentaire a été estimée par l'analyse quantitative des profiles d'AG (QFASA), en utilisant un catalogue d'AG de proies venant de la même région. Les régimes alimentaires des deux types de chasse comprennent les mêmes espèces de proies mais avec des proportions significativement différentes (global R = 0.17, p = 0.022). Il semble donc que les femelles chassant sur le benthos ne compensent pas leurs dépenses énergétiques plus élevées en mer par des proies de qualité supérieure. Les zones de chasse des femelles benthiques ne sont pas exploitées par les pêcheries; ces individus pourraient chercher un compromis entre une dépense énergétique élevée et une compétition faible pour la ressource.

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Section: Foraging Strategy and Energy Intakementioning

confidence: 98%

Foraging diversity in lactating New Zealand sea lions: insights from qualitative and quantitative fatty acid analysis

MeynierLaureline

MorelPatrick

Chilvers

et al. 2014

Can. J. Fish. Aquat. Sci.

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“…The Auckland Islands population (which represents 73% of the total population) has shown a >50% decline in pup production over 17 years (1998 to 2015) and exhibited extreme diving and foraging behaviour as well as long-term individual foraging specialisation during this same period (Gales & Mattlin 1997;Costa & Gales 2000;Chilvers et al 2006;Chilvers 2008Chilvers & Wilkinson 2009;Chilvers & Meyer 2017). Animals that operate at or near their maximum physiological limits and those that show highly specialised foraging behaviours tend to be less able to adapt to changing environments, which can result in decreasing survival, reproduction and eventually population size and higher risk of extinction (Gallagher et al 2015).…”

Section: Discussionmentioning

confidence: 99%

Preliminary assessment of the foraging behaviour and population dynamics of a cryptic population of the endangered New Zealand sea lion

Chilvers¹

2018

NZ J Ecol

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Abstract:The endangered New Zealand sea lion (Phocarctos hookeri) has recently been confirmed as breeding on Stewart Island/Rakiura, southern New Zealand. This area is thought to have the largest number of sea lion pups born outside of the New Zealand subantarctics. However, the sparse distribution and cryptic behaviour of this population means known human threats and their effects on the population will be difficult to determine, limiting conservation priority setting and management. This research aimed to investigate the foraging behaviour of adult females from the population and examine what information is available to help determine current population parameters including undertaking pup surveys in the area. Foraging behaviour research was undertaken in the Austral autumn 2012 and 2013, while pup production surveys were undertaken in March each year between 2011 and 2016. Pup production surveys show up to 36 pups are born in the Stewart Island area annually. The foraging behaviour of 14 adult female New Zealand sea lions was characterised by short foraging trips (c. 12 hrs), close to shore or in areas of known upwellings, undertaking short, shallow dives (average 2.5 mins, 60 m). This diving behaviour is intermediate between the foraging behaviours of females from Enderby Island (Auckland Islands), the largest but severely declining population of New Zealand sea lions, and Otago (mainland New Zealand), a smaller, increasing recolonising population. Based on the foraging behaviour and limited population dynamic information collected from the Stewart Island population, it is likely the Stewart Island population has survival and reproductive parameters more like the recolonising Otago population than the declining Auckland Islands population. Such information is critical for determining the impacts of the known direct and indirect human impacts on this small isolated population, which is likely to be important for the survival of the endangered New Zealand sea lion species as a whole.

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“…Research on foraging by adult males (Geschke & Chilvers 2009) and adult females (Gales & Mattlin 1997, Chilvers et al. 2005, 2006, Chilvers 2008a, b, 2009, Chilvers & Wilkinson 2009) has been undertaken at the Auckland Islands. Here, the research focus is on female foraging behaviour, as females are the most comprehensively studied of the sexes and have the most restricted foraging areas.…”

Section: Possible Reasons For the Nz Sea Lion Declinementioning

confidence: 99%

“…Female NZ sea lions forage over the entire Auckland Island shelf (Chilvers 2008a, b, 2009). They are restricted in their area and duration of foraging by their need to return to dependent pups ashore.…”

Section: Possible Reasons For the Nz Sea Lion Declinementioning

confidence: 99%

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The population decline of the New Zealand sea lion Phocarctos hookeri: a review of possible causes

Robertson¹,

Chilvers²

2011

Mammal Review

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1. The New Zealand (NZ) sea lion Phocarctos hookeri is NZ's only endemic pinniped and is listed as 'nationally critical'. The species breeds in the NZ sub-Antarctic: 71% of the population at the Auckland Islands (2010 pup production: 1814 Ϯ 39) and the remaining 29% on Campbell Island (726 pups in 2010). 2.Pup production at the Auckland Islands has declined by 40% since 1998 (1998: 3021 pups produced): only 1501 pups were born in 2009. This decline is directly linked to philopatric females not returning to breeding areas. While the Auckland Island population has declined, the Campbell Island population appears to be increasing slowly. 3. Potential reasons for the decline in the Auckland Island population, but not in the Campbell Island population, include non-anthropogenic factors: (i) disease epizootics, (ii) predation, (iii) permanent dispersal or migration, (iv) environmental change; and anthropogenic impacts: (v) population 'overshoot', (vi) genetic effects, (vii) effects of contaminants, (viii) indirect effects of fisheries (i.e. resource competition) and (ix) direct effects of fisheries (i.e. by-catch deaths). Of the nine potential reasons examined here, six can be discounted (ii-vii). Bacterial epizootics (i) occur in the NZ sea lion population, but their impact has predominantly increased pup mortality, which is unlikely to cause the severe decline observed, as pup mortality throughout the species is naturally high and variable. 4. The most plausible hypotheses, based on available evidence, are that the observed decline, in particular, the decreasing number of breeding females in the Auckland Island population, is caused by (viii) fisheries-induced resource competition and (ix) fisheries-related by-catch. By-catch is the main known anthropogenic cause of mortality in the species. Competition with fisheries resulting in resource competition, nutrient stress and decreased reproductive ability in NZ sea lions should be a priority area for future research.

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Winter foraging behaviour of lactating New Zealand sea lions (Phocarctos hookeri)

Cited by 11 publications

References 23 publications

Foraging diversity in lactating New Zealand sea lions: insights from qualitative and quantitative fatty acid analysis

Foraging diversity in lactating New Zealand sea lions: insights from qualitative and quantitative fatty acid analysis

Preliminary assessment of the foraging behaviour and population dynamics of a cryptic population of the endangered New Zealand sea lion

The population decline of the New Zealand sea lion Phocarctos hookeri: a review of possible causes

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