Phocarctos Research Articles

In the shallow end: diving behaviour of recolonising female New Zealand sea lions (Phocarctos hookeri) around the Otago Peninsula

Female New Zealand sea lions ( Phocarctos hookeri (Gray, 1844)) at the Auckland Islands (remnant populations) are the deepest and longest diving otariids. These remnant populations are found at the margin of the historical range of the species. We hypothesized that diving behaviours of animals in the core of their historical range is less extreme owing to a better marine habitat. All female New Zealand sea lions (n = 13, aged 2–14 years) born on the Otago Peninsula (initial recolonising population) were equipped with time–depth recorders during April and May 2008, 2009, and 2010. The mean dive depth was 20.2 ± 24.5 m and mean dive duration was 1.8 ± 1.1 min, some of the lowest values reported for otariids. Otago female New Zealand sea lions did not exhibit two distinct diving specialisations as reported at the Auckland Islands. Otago adult females exceeded calculated aerobic dive limits in 7.1% of dives compared with 68.7% at the Auckland Islands. The contrasting differences in diving behaviour between Otago and the Auckland Islands suggest that Otago represents a better marine habitat for New Zealand sea lions, with food easily accessible to animals of all ages.

On‐land habitat preferences of female New Zealand sea lions at Sandy Bay, Auckland Islands

AbstractTerrestrial habitat is important for breeding in most pinnipeds. On land, most species remain near the shore, but New Zealand (NZ) sea lions, Phocarctos hookeri, often rest inland up to 1.5 km from the sea. Only three breeding areas of NZ sea lions exist today after the species was extirpated from its historical range (NZ mainland). The study was conducted at the Sandy Bay breeding colony, Auckland Islands, between December 2002 and March 2003. We used daily Global Positioning System locations of breeding females with pups and mapping in a Geographic Information System to determine terrestrial habitat use and preferences. Slopes less than 20° were preferred throughout the study. Females chose nursing sites with a seasonal change, preferentially based on the distance from the sea and habitat type. Comparisons with the other breeding colonies of NZ sea lions are presented and data are discussed in the context of the recolonization of the NZ mainland. Overall, the most suitable terrestrial habitat configuration for a breeding aggregation of NZ sea lions appears to be a sandy beach, with a wide area above high tide and moderate intertidal zone (for breeding), backed with vegetated sand dunes and forest on primarily flat terrain (for later dispersion).

Foraging behaviour indicates marginal marine habitat for New Zealand sea lions: remnant versus recolonising populations

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 432:247-256 (2011) - DOI: https://doi.org/10.3354/meps09176 Foraging behaviour indicates marginal marine habitat for New Zealand sea lions: remnant versus recolonising populations A. A. Augé1,*, B. L. Chilvers2, A. B. Moore3, L. S. Davis1 1Zoology Department, and 3School of Surveying, University of Otago, Dunedin 9016, New Zealand 2Aquatic and Threats Unit, Department of Conservation, Wellington 6011, New Zealand *Email: amelie.auge@gmail.com ABSTRACT: The New Zealand sea lion Phocarctos hookeri historically bred on the New Zealand mainland (South and North Islands). Subsistence hunting and later commercial sealing reduced its distribution to 3 breeding areas at the spatial edges of its historical distribution range, in the Auckland Islands (AI) and on Campbell Island. Here, we present foraging areas and foraging trips of female New Zealand sea lions from the Otago Peninsula, where a recolonising population has been found in the core of the historical range of the species. We compare the results with data from the AI in order to assess the theory that the spatial margin of a species’ distribution represents the lower end of habitat suitability. Female New Zealand sea lions at Otago had significantly smaller foraging ranges than females at the AI (mean 65% Kernel ranges: 47 ± 25 km2 versus 687 ± 109 km2), made shorter foraging trips (mean 11.8 ± 2.3 h versus 66.2 ± 4.2 h), and spent 40% less time at sea overall. Juvenile females at Otago from age 2 onwards could access foraging grounds used by adult females nursing pups; this is unlikely to be the case at the AI due to the large distances and associated depths of foraging grounds. Our study illustrates the theory that spatial marginality is related to habitat marginality. Existing management measures to mitigate the impact of bycatch in fisheries on declining remnant colonies around the AI were modelled based on populations exploiting optimal habitat. They should now integrate this new information. KEY WORDS: Phocarctos hookeri · Pinnipeds · Spatial · Marginal · Satellite tracking · Marine ­conservation Full text in pdf format PreviousNextCite this article as: Augé AA, Chilvers BL, Moore AB, Davis LS (2011) Foraging behaviour indicates marginal marine habitat for New Zealand sea lions: remnant versus recolonising populations. Mar Ecol Prog Ser 432:247-256. https://doi.org/10.3354/meps09176 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 432. Online publication date: June 27, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

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

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 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 epizoot- ics, (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 compe- tition, nutrient stress and decreased reproductive ability in NZ sea lions should be a priority area for future research.

An evaluation of hot-iron branding as a permanent marking method for adult New Zealand sea lions, Phocarctos hookeri

Context Studies of the population and behavioural ecology of pinnipeds require the ability to identify individuals over periods ranging from a single season to an entire lifetime. Aims The aims of this research were to examine the efficacy of hot-iron branding as a permanent marking technique including the legibility of marks over time and comparing estimates of survival for animals marked with brands versus flipper tags. Methods Adult female New Zealand sea lions (n = 135) aged between 4 and 24 years of age were hot-iron branded with four-digit numbers during the austral summer of 2000. Key results Ten years on, 100% of animals still alive could be identified from these brands. Over the 10-year research period, it was observed that the skin of fully healed individual brands could, on occasion, become lacerated due to injuries received from shark bites and/or bites from other sea lions, removing or temporarily reducing the legibility of single characters of some brands. However, these animals were still identifiable when all digits were considered – and scars could become an identifying mark in their own right. Key conclusions Survival estimates derived from branded versus tagged-only individuals were similar, although the variance associated with tagged-only survival estimates was higher, giving less robust estimates. This is likely a result of higher resight probabilities observed for branded individuals. Resighting of tags requires a close approach with a high associated level of disturbance to both the marked animal and those associated with it, especially when considered over the lifetime of the animal, while brands can be read from a considerable distance with little or no disturbance. Implications Thus, hot-iron branding can be an effective method for permanently identifying sea lions that provides robust parameter estimates, causes low disturbance in the resighting process, and does not compromise survival.

Quantitative fatty acid signature analysis on New Zealand sea lions: model sensitivity and diet estimates

We used quantitative fatty acid signature analysis (QFASA) to predict the long-term diet of New Zealand (NZ) sea lions (Phocarctos hookeri) incidentally caught in the NZ arrow squid (Nototodarus spp.) fishery. The QFASA model used fatty acid (FA) profiles based on 82 blubber samples of NZ sea lions bycaught between 2000 and 2006. First, the model was optimized by a series of simulations for which 1 model parameter—6 different sets of calibration coefficients (CCs) from different pinniped species and feeding regime, 2 sets of FAs, and the consideration of individual prey values, or mean prey values—varied each time. The best-fit parameters were those giving the lowest Kullback–Liebler distance values. Second, these parameters were used in a model to estimate the diet of NZ sea lions. QFASA was highly sensitive to the set of CCs applied. Across years the most important prey estimated with the best-fit CCs were southern arrow squid (Nototodarus sloani, 18–28% mass), hoki (Macruronus novaezelandiae, 10–27% mass), rattails (Macrouridae, 7–27% mass), and possibly scampi (Metanephrops challengeri, 1–19% mass). Despite the uncertainty on the accuracy of the match between the best-fit CCs used and the true FA metabolism of NZ sea lions, the variation of prey estimated among years was highly consistent with the trends of commercial catches during the same period, providing some confidence in the present QFASA predictions. The most important estimated prey were demersal species living mainly at depths .200 m that NZ sea lions encounter on the slopes of the Auckland Islands shelf. Our study emphasized the importance of these areas for bycaught NZ sea lions over the 1st half of the lactation period. DOI: 10.1644/09-MAMM-A-299.1.

Investigating foraging utilization distribution of female New Zealand sea lions, Auckland Islands

Detrimental interactions between marine mammals and fisheries are increasing worldwide. The ability to manage these interactions requires the knowledge of where and how interactions occur and the effects they have on species. Many pinnipeds are central place foraging colonial breeders who are restricted in foraging range during breeding. Here, we use a utilization distribution approach to examine the foraging habitats of lactating New Zealand (NZ) sea lions (Phocarctos hookeri) from Dundas and Enderby Islands, Auckland Islands. Annually, the NZ sea lions which breed on these two islands produce 83% of this Nationally Critical species’ pups. Satellite transmitters were attached to 55 females during 2001–2007. Data showed that NZ sea lions utilize the entire Auckland Island shelf with partial habitat partitioning between females from the two breeding islands. This habitat partitioning results in differing degrees of overlap with fisheries and therefore possible differing fishery-related impacts on breeding areas.

Serologic Evaluation of New Zealand Sea Lions for Exposure to Brucella and Leptospira spp.

A serologic survey of anti-Brucella and antileptospiral antibodies was conducted on 147 adult, female New Zealand sea lions (Phocarctos hookeri). Most sea lions (n=138) were sampled at Sandy Bay, Enderby Island, Auckland Islands (50°30'S, 166°17'E), January 2000-March 2005. Nine were sampled at Otago, New Zealand (46°0'S, 170°40'E); four in April 2008 and five in March 2009. Serum from one of the Enderby Island females was weakly positive for antibodies to Brucella abortus using the competitive enzyme-linked immunosorbent assay, and one female had a low titer for Leptospira interrogans serovar pomona using the microscope agglutination test. All serum samples from Otago animals were negative. Brucellosis and leptospirosis are therefore considered unlikely to play a major role in population dynamics of these populations, and the low antibody prevalence of these agents suggests that they are an unlikely source of infection for humans, wildlife, or domestic species on mainland New Zealand.

Age- and sex-specific survival estimates incorporating tag loss for New Zealand sea lions,Phocarctos hookeri

The estimation of life-history parameters for a threatened species is important for understanding its biology and helping to determine management options. This research investigates age- and sex-related survival estimates incorporating tag loss for New Zealand (NZ) sea lions (Phocarctos hookeri) from Sandy Bay, Enderby Island, Auckland Islands, New Zealand, using multistate mark-recapture data from known-age individuals over 8 years (1997–1998 to 2005–2006). Survival estimates and tag loss rates differed significantly by sex and age class, with adult males having the lowest tag retention of any age or sex class and females ≥ 3 years old having lower survival estimates than their male counterparts. The variability and lower female survival relative to males is a critical problem for NZ sea lions, because even small changes in adult female survival significantly affect population trends for such large, long-lived mammals.

Behavioural responses and attraction of New Zealand sea lions to on-land female decoys

Using decoys to attract gregarious animals is a common management practice, but rarely used for pinnipeds. We investigated the behavioural responses of New Zealand (NZ) sea lions, Phocarctos hookeri, at Sandy Bay, Enderby Island, to determine whether decoys can attract female sea lions and so could be useful for the establishment of new colonies. We deployed decoys near existing breeding aggregations for 4 hours at a time. One or a group of three artificial decoys, made of white fabric, attracted up to 54% of females coming ashore, of which 73% came close enough to sniff the decoys. Up to 62% of males coming ashore within 15 m either side of these decoys moved towards them. A single taxidermied female NZ sea lion did not attract females significantly more often than a single fabric one, but was investigated as if alive by males. It appears that female NZ sea lions are attracted to decoys by their colour, at least when located close to an existing group of females. A technique using decoys could be trialled to direct recolonising females to suitable pupping sites.

Conservation status of New Zealand marine mammals (suborders Cetacea and Pinnipedia), 2009

The conservation status of New Zealand (NZ) marine mammals (suborders Cetacea and Pinnipedia) is reappraised using the 2008 version of the NZ Threat Classification System. The list comprises 56 taxa (named species or subspecies, and as yet unnamed forms or types) in the following categories: Threatened—eight taxa (five Nationally Critical and three Nationally Endangered); Vagrant—six taxa; Migrant—20 taxa; and Data Deficient—13 taxa. A further nine taxa are listed as Not Threatened. Relative to the previous listing, the threat status of two species worsened: the NZ sea lion (Phocarctos hookeri) was uplisted to Nationally Critical and the bottlenose dolphin (Tursiops truncatus) was uplisted to Nationally Endangered. No species was considered to have an improved status. With the uplisting of the NZ sea lion and the continued listing of the Hector's dolphin (Cephalorhynchus hectori hectori) as Endangered and Maui's dolphin (C. hectori maui) as Nationally Critical, all three endemic NZ marine mammals are now considered threatened with extinction. We considered future research or management actions that would allow the downlisting of the eight taxa currently listed as Threatened.

Growth and reproduction of female New Zealand sea lions

Abstract A sample of 834 female New Zealand sea lions (Phocarctos hookeri), which were aged and measured, was obtained between 1998 and 2001. In addition, the reproductive histories of 505 marked females from the Auckland Islands were recorded from 1998 to 2005. These data sets were used to investigate growth and reproductive rates. Length and weight ranged from 134 to 197 cm and 49 to 156 kg, respectively. A Gompertz growth model best described growth and predicted that females attained 90% of asymptotic length (161.7 cm) and weight (112.0) at ages 4 and 11 years, respectively. No significant differences were found in growth rates among years, nor between the 2 major breeding colonies in the Auckland Islands. Females reproduced between the ages of 3 and 26 years, with evidence of reproductive senescence starting at age 23 years. Although females up to age 28 years were observed, no females over 26 years were recorded as reproductive. Age-specific reproductive rate p(x) increased rapidly between ages 3 an...

Predicting Life-History Traits for Female New Zealand Sea Lions, Phocarctos hookeri: Integrating Short-Term Mark-Recapture Data and Population Modeling

The trade-off between survival and reproduction by individuals is central to understanding life-history parameters of a species. Few mammal species have life-history information from long-term research. Instead, demographic models are commonly utilized to investigate an individual’s life-history strategy, species dynamics, and population trends. This research investigates age-related survival and reproductive performance of adult female New Zealand (NZ) sea lions (Phocarctos hookeri), using multi-state mark-recapture data from known-age branded individuals over five years. The mark-recapture analysis was integrated with a population model to predict the lifetime reproductive output of female NZ sea lions. The integration of an analysis of short-term datasets with population modeling allows for the prediction of life-history parameters of long lived animals when long-term information is not available. While such approaches involve some caveats, it provides a framework for investigating population dynamics and is preferential to unsubstantiated assumptions. This technique can lead to better design and implementation of conservation management for long lived species.

Age distribution of lactating New Zealand sea lions: Interannual and intersite variation

The age distribution of 865 lactating New Zealand sea lions (NZSLs; Phocarctos hookeri) was investigated over 3 yr (1999–2001) at two breeding colonies, Sandy Bay and Dundas Island, New Zealand. Lactating females were aged between 3 and 26 yr with a maximum observed age of 28 yr. The mean age of lactating females was 11.1 (SE = 0.16) yr. Age distributions peaked at ages 8 and 9 with a strong skew toward younger females, likely indicative of maximum recruitment into the breeding population by this age. There were significant intersite differences in age structure and also significant interannual differences in age distributions at Sandy Bay, but not at Dundas Island. Given that the two colonies are less than 10 km apart, have some interchange, and share foraging areas, these differences are surprising. However, the colony at Dundas Island is almost four times larger than Sandy Bay and may therefore be less sensitive to demographic or environmental stochasticity. That age distributions of NZSLs vary significantly over small temporal and spatial scales has important implications for the extrapolation of data from one site or year to the population level, and hence for their management and conservation.

Comparison of methods for the analysis of New Zealand sea lion, Phocarctos hookeri, milk

The milk composition of New Zealand sea lion, Phocarctos hookeri, was determined using standard analytical methods, a MilkoScan™ FT 120 and an accelerated solvent extractor (ASE) for fat concentration. The results for fat, protein and total solid concentrations between the different analytical methods were assessed using different measures of statistical fitness including coefficient of determination, concordance correlation coefficient, mean prediction error, and intraclass correlation coefficient. The repeatability and reliability of the results obtained with the calibrated MilkoScan™ FT 120 were comparable with those obtained using standard methods, the Roese‐Gottlieb method for fat, Kjeldahl method for protein and gravimetric method for total solids. The MilkoScan™ FT 120s are fast and cost‐effective and are widely used in dairy laboratories around the world, which should make them readily accessible to ecologists/biologists studying the milk composition of non‐domestic animals.

Redescription of Antarctophthirus microchir (Anoplura: Echinophthiriidae) from the South American Sea Lion, Otaria flavescens, from Patagonia, Argentina

Antarctophthirus microchir was originally described from Phocarctos hookeri on the basis of 1 female and 1 male only. We redescribe adults and describe, for the first time, the 3 nymphal stages from specimens collected from Otaria flavescens from Patagonia, using light and scanning electron microscopy. The present material can be distinguished from other Antarctophthirus species by the presence of a fringe of setae on the back of the head, only present in Antarctophthirus trichechi and Antarctophthirus callorhini. However, A. trichechi also possess a prominent proboscis with large hooks, and A. callorhini presents less abundant and nonuniform abdominal scales in shape and size. Other differential features of A. microchir are the pattern of ovoid and uniform scales and longitudinal grooves in the surface of spines. Nymphal stage 1 differs from 2 and 3 mainly by the absence of scales and thorax without ventral spines or hairs. Nymphal stages 2 and 3 may be distinguished by the disposition of the occipital apophyses. Antarctophthirus microchir has been reported from 5 sea lion species from both hemispheres. Considering the conservative morphology, and ecological and evolutionary features of sucking lice, we raise the question of whether A. microchir from different sea lion hosts may represent a complex of cryptic species.

Diverse foraging strategies in lactating New Zealand sea lions

Diving and foraging behaviours of marine predators are thought to be coupled with species demographics, with benthic foraging species found to have small population sizes and low growth rates. This was thought to be the case for New Zealand (NZ) sea lions Phocarctos hookeri, previously identified as solely benthic foragers with a small declining population. Female NZ sea lions dive deeper and for longer than any other otariids (eared seals). They exceed their calculated aerobic dive limits (cADL) during 68% of all dives, indicating that they are operating near their max- imum physiological capacity. Recently, however, individual NZ sea lions have been found to have 2 distinct dive profile types or foraging patterns: a benthic diving profile and a deeper, more varied meso-pelagic diving profile. The ecological significance and implications of individual foraging specialisation in otariids have had limited attention in the past. Here, we compared the foraging behaviour of female NZ sea lions that use these 2 distinct dive profiles and discuss how the 2 forag- ing patterns may indicate differing prey choice, as well as their possible implications for individual reproductive ability and interactions with fisheries and, therefore, species demographics. Our ulti- mate goal is to understand the causes of this individual foraging specialisation and to incorporate such variation when determining management options for this threatened, declining species.

Managing big boys: a case study on remote anaesthesia and satellite tracking of adult male New Zealand sea lions (Phocarctos hookeri)

Context. Handling animals is essential for many applications in wildlife management. However, currently there are limited techniques to safely handle and move large mobile pinnipeds, particularly when they cannot be physically restrained first. Such animals can be the cause of many land-based wildlife–human conflicts. The New Zealand (NZ) sea lion (Phocarctos hookeri) is the world’s rarest and second largest otariid, and is in severe decline. Although most NZ sea lions live on uninhabited NZ subantarctic islands, a small population is recolonising the coastline of Otago, NZ and this close proximity with humans can cause conflict. Aims. The aim of this research was to assess a method of remote chemical anaesthesia for its ability to safely and practically immobilise large pinnipeds to allow attachment of satellite tracking equipment and to handle and potentially move animals if in situations of conflict. Methods. The chemical anaesthetic Zoletil® was remotely applied to immobilise adult male NZ sea lions at Enderby Island, Auckland Islands, to allow handling and the application of satellite tracking equipment. Key results. Six adult males weighing up to 330 kg were successfully anaesthetised, weighed and measured. Two of these had satellite location tags attached, which showed two very different post-breeding movement patterns by adult males and indicated minimum overlap with local fisheries activities. Conclusions. This remote anaesthesia technique was successful for adult male NZ sea lions and could be used for the immobilisation and management of other large mobile pinnipeds. Implications. The ability to anaesthetise and safely handle large adult male pinnipeds will provide better management in areas where animals come in close contact with human populations with possible lethal interactions or where attachment of monitoring equipment is required to investigate population parameters or possible lethal interactions.

Aggregation and dispersion of female New Zealand sea lions at the Sandy Bay breeding colony, Auckland Islands: How unusual is their spatial behaviour?

We investigated the spatial behaviour adopted by female New Zealand sea lions, Phocarctos hookeri, at the Sandy Bay breeding colony in 2002 and 2003. Each breeding female exhibited a spatio-temporal behaviour based on two phases: breeding and dispersion. The breeding phase, typical of all otariids, led to the formation of the breeding aggregation where all pupping took place. Each female later moved outside the breeding area and entered a dispersion phase. The female population spread inland, and progressively decreased as females took their pups away from Sandy Bay. Pup survival was not affected by this spatial behaviour though the year had an effect. A larger population size during one year may have created a dilution of male aggressiveness and resulted in fewer movements of females. Females that had to move more during the pupping day were found to be more likely to lose their pups. Although a few studies have shown that mother and pup pairs of other species may exhibit dispersal after breeding, the observed terrestrial dispersion phase of the female New Zealand sea lions has never been reported for any other pinniped species and is likely unusual.

Effects of hookworms (Uncinaria sp.) on the early growth and survival of New Zealand sea lion (Phocarctos hookeri) pups

Parasites can have both direct and indirect impacts on organisms through changes in health, growth, reproductive success, behaviour and survival. This research investigates the effects of hookworms (Uncinaria sp.) on the growth and mortality of New Zealand sea lion (NZ sea lion, Phocarctos hookeri) pups between birth and 3 months of age. NZ sea lion pups that received ivermectin treatment to reduce their hookworm burden had higher growth rates. Hookworm infection had no significant effect on mortality rate except when overall mortality was high during epidemics caused by other pathogens. Understanding the impacts of parasites on wild populations of pinnipeds is important for the management of the species, particularly when the species is threatened, as is the case for the NZ sea lion. There are at least two reasons for this: first, to quantify the impact of the parasite on parameters of population dynamics such as offspring survival and, as a consequence, female reproductive output; and second, to gain sufficient knowledge of the host/parasite dynamics to allow the balance to be manipulated in favour of the host should this be required for conservation management.