Zealand Fur Seals Research Articles

Mitochondrial DNA structure and colony expansion dynamics of New Zealand fur seals (Arctocephalus forsteri) around Banks Peninsula

ABSTRACTNew Zealand fur seals are one of many pinniped species that survived the commercial sealing of the eighteenth and nineteenth centuries in dangerously low numbers. After the enforcement of a series of protection measures in the early twentieth century, New Zealand fur seals began to recover from the brink of extinction. We examined the New Zealand fur seal populations of Banks Peninsula, South Island, New Zealand using the mitochondrial DNA control region. We identified a panmictic population structure around Banks Peninsula. The most abundant haplotype in the area showed a slight significant aggregated structure. The Horseshoe Bay colony showed the least number of shared haplotypes with other colonies, suggesting a different origin of re-colonisation of this specific colony. The effective population size of the New Zealand fur seal population at Banks Peninsula was estimated at approximately 2500 individuals. The exponential population growth rate parameter for the area was 35, which corresponds to an expanding population. In general, samples from adjacent colonies shared 4.4 haplotypes while samples collected from colonies separated by between five and eight bays shared 1.9 haplotypes. The genetic data support the spill-over dynamics of colony expansion already suggested for this species. Approximate Bayesian computations analysis suggests re-colonisation of the area from two main clades identified across New Zealand with a most likely admixture coefficient of 0.41 to form the Banks Peninsula population. Approximate Bayesian computations analysis estimated a founder population size of approximately 372 breeding individuals for the area, which then rapidly increased in size with successive waves of external recruitment. The population of fur seals in the area is probably in the late phase of maturity in the colony expansion dynamic.

Identifying prey items from New Zealand fur seal (Arctocephalus forsteri) faeces using massive parallel sequencing

Identifying prey items from New Zealand fur seal (Arctocephalus forsteri) faeces using massive parallel sequencing

Complete mitochondrial genome of the stoat (Mustela erminea) and New Zealand fur seal (Arctocephalus forsteri) and their significance for mammalian phylogeny

The complete mitochondrial genome of three mustelid species, stoats (Mustela erminea), weasels (Mustela nivalis) and ferrets (Mustela furo), and the New Zealand fur seal (Arctocephalus forsteri) were sequenced using direct mitochondrial DNA extraction and overlapping long PCRs. The usual 37 mammalian mitochondrial genes (13 protein coding genes, 22 t-RNA and 2 r-RNA) were identified in all four mitogenomes. The divergence of stoats from other members of the sub-family Mustelinae was dated 4.5 million years ago. The mitogenomic data were consistent with a bear-like origin of seals.

Enamel ultrastructure of fossil and modern pinnipeds: evaluating hypotheses of feeding adaptations in the extinct walrus Pelagiarctos.

This study aimed to assess the enamel ultrastructure in modern otariid pinnipeds and in the extinct walrus Pelagiarctos. Teeth of the New Zealand fur seal (Arctocephalus forsteri), sea lion (Phocarctos hookeri), and fossil walrus Pelagiarctos thomasi were embedded, sectioned, etched, and analyzed via scanning electron microscopy. The enamel of NZ otariids and Pelagiarctos was prismatic and moderately thick, measuring 150-450μm on average. It consisted of transversely oriented Hunter-Schreger bands (HSBs) from the enamel-dentine junction (EDJ) to near the outer surface, where it faded into prismless enamel less than 10μm thick. The width of HSB was variable and averaged between 6 and 10 prisms, and they presented an undulating course both in longitudinal and cross sections. The overall organization of the enamel was similar in all teeth sampled; however, the enamel was thicker in canines and postcanines than in incisors. The crowns of all teeth sampled were uniformly covered by enamel; however, the grooved incisors lacked an enamel cover on the posterior side of the buccal face. Large tubules and tuft-like structures were seen at the EDJ. HSB enamel as well as tubules and tufts at the EDJ suggest increased occlusal loads during feeding, a biomechanical adaptation to avoid enamel cracking and failure. Despite overall simplification in tooth morphology and reduced mastication, the fossil and modern pinnipeds analyzed here retained the complex undulating HSB structure of other fossils and living Carnivora, while other marine mammals such as cetaceans developed simplified radial enamel.

Reconstructing climate–growth relations from the teeth of a marine mammal

Sclerochronological analysis of growth increment patterns (growth layer groups; GLG) in marine mammal teeth offers a unique opportunity to reconstruct climate–growth relations of marine mammal populations over long time series. We developed sclerochronologies from GLG width measures in the cementum of male and female New Zealand fur seal (Arctocephalus forsteri) post-canine teeth collected from southern Australia. Tooth growth chronologies spanned 15 years and encompassed the period from 1987 to 2001. We also developed a rigorous analytical framework for assessing species suitability for sclerochronological analyses. Suitability assessments indicated that GLG clarity and relative width measures were variable among regions within individual teeth, and therefore, measurements were standardised to a consistent tissue type. Deposition of cementum in post-canine teeth was also correlated with body size, suggesting tooth growth measures were a suitable proxy of somatic growth. Inter-annual patterns of tooth growth were negatively correlated with mean annual sea surface temperature and the Southern Oscillation Index (both lagged by 1 year), but the strength of the relationships differed between the sexes. These results suggest both local- and regional-scale physical processes influence variations in growth and provide the first evidence of an environmental effect on cementum growth in a marine mammal. This study demonstrates the underutilised potential of marine mammal teeth to provide extended time series of growth, critical information which facilitates predictions of future ecological response to environmental change.

Effects of seismic surveys on New Zealand fur seals during daylight hours: Do fur seals respond to obstacles rather than airgun noise?

The responses of New Zealand fur seals (Arctocephalus forsteri) during a three-dimensional marine seismic survey were recorded in the first quantified investigation of the effects of seismic exploration operations on otariid seals. The survey was over the continental slope off southern New Zealand, where fur seals dive to forage at night and rest on the surface during daylight hours. Data were restricted to daylight sightings from the source vessel while towed seismic gear was fully deployed, with comparisons made between fur seal responses when airguns were off and when airguns were operating at full power. Results were inconclusive. Comparisons were confounded because both sighting rate and distance first seen decreased with deteriorating sea state. The key finding of this study was that the source vessel and towed gear created physical obstacles that often generated responses from fur seals. A more thorough investigation is recommended in order to differentiate between responses to airgun noise and responses to physical obstacles, and improvements are suggested to rectify shortfalls in data collection that should generate conclusive outcomes.

Seals (Pinnipedia) at Norfolk Island, south-west Pacific

Five seals were observed at Norfolk Island (29°S, 168°E) between 2000 and 2013. Two have been identified as Arctocephalus forsteri on the basis of photographs, a juvenile or weaned pup that weighed 9.5 kg and a subadult male. The nearest known aggregation of these fur seals is at Three Kings Islands (34°S, 172°E), 700 km to the south-east. Because New Zealand fur seals are increasing in abundance in New Zealand and Australia, sightings of vagrant fur seals at Norfolk Island are likely to increase.

The long-nosed fur seal (Arctocephalus forsteri) in South Australia in 2013–14: abundance, status and trends

The long-nosed (or New Zealand) fur seal (Arctocephalus forsteri) breeds in southern Australia and New Zealand. Most of the Australian population is in South Australia, between Kangaroo Island and Eyre Peninsula. Fur seal populations in southern Australia were heavily exploited by colonial sealers between 1801 and 1830, resulting in major reductions. Numbers remained low for 150 years, then slowly built up and new colonies established across their presumed former range. Here we present estimates of pup abundance at South Australia colonies, mostly during the 2013–14 breeding season. Long-nosed fur seals bred from Baudin Rocks in the south-east to Fenelon Island in the north-west. In total, 29 breeding colonies produced 20 431 pups, 3.6 times greater than the 1989–90 estimate; the increase is attributed to recovery from 19th century overharvesting. The 2013–14 pup estimate leads to an estimate of abundance of long-nosed fur seals in South Australia of 97 200. Most pups were on Kangaroo Island (49.6%) and the Neptune Islands (38.6%). New breeding colonies were identified on Williams Island and at two small sites on Kangaroo Island. The increasing trend in South Australia is likely to continue over the coming decade, primarily by expansion in colonies on Kangaroo Island and by establishment of new colonies.

Population trends of New Zealand fur seals in the Rakiura region based on long-term population surveys and traditional ecological knowledge

We estimated population abundance of New Zealand fur seal (Arctocephalus forsteri) pups on Bench Island off Stewart Island, New Zealand seven times between 1996 and 2012. Overall, there was a 29% increase in pup abundance from 1996 to 2012 at the Main Beach colony, corresponding to a mean annual growth rate of 1.6% and a doubling time of approximately 40 years. At the Sprat Point colony, there was an overall increase of 29% between 2003 and 2012 corresponding to a mean annual growth rate of 2.9% and a doubling time of approximately 25 years. The area occupied by both colonies has also increased. In 2006, we surveyed East Beach and counted a total of 201 pups. We obtained traditional ecological knowledge of fur seal distribution and breeding status from local Māori for 46 locations around Stewart Island, 36 of which have not been surveyed since Wilson in 1971–1974; this supports an expansion of fur seal presence and breeding areas in the region in the last 41 years.

The effects of vessel approaches on the New Zealand fur seal (Arctocephalus forsteri) in the Bay of Plenty, New Zealand

AbstractAnimals that establish new sites near the edge of the species' range may be vulnerable to disturbance as they are low in numbers and are not tied to the sites. Pinniped distributions world‐wide are changing as many species are recolonizing areas of their former ranges and establishing new colonies. Little research is available on the impact that vessel presence may pose on pinnipeds at such sites. This study documents responses of New Zealand fur seals to vessels in the Bay of Plenty, New Zealand, at a recently established breeding colony. Fur seal behavior at the breeding location was recorded in the presence of vessels. GLMM and GAM analyses revealed that fur seal responses varied with month, time of day, duration of vessel exposure, and the distance to the vessel. Age and sex of the seals, and the number of seals present also influenced fur seal response. Fur seals at this site became disturbed when vessels approached to the 10–20 m distance category, and a precautionary minimum approach distance of 50 m has been suggested. This research provides direction for monitoring and minimizing impacts of vessels on fur seals, especially where new sites are being colonized.

Armed Escorts: Dusky Dolphin (Lagenorhynchus obscurus) Interactions with Octopuses (Pinnoctopus cordiformis) in New Zealand

Between October 2011 and December 2013, three interactions between dusky dolphins (Lagenorhynchus obscurus) and common New Zealand octopuses (Pinnoctopus cordiformis) were witnessed and photographed off Kaikoura, New Zealand. In two interactions, an octopus was attached to a dusky dolphin; and in a third interaction, dusky dolphins appeared to be playing with an octopus. The attachment might have been an escape tactic for the octopuses. This is the first published record of interactions between dusky dolphins and octopuses in New Zealand. The few anecdotal reports of octopuses attached to dolphins are limited to species that commonly prey on octopuses. The evidence for dusky dolphins foraging on octopuses off Kaikoura is weak. The two species have different habitats but could come into initial contact through shallow nearshore dives performed by the dusky dolphins or by other species observed in the area, including New Zealand fur seals (Arctocephalus forsteri), humpback whales (Megaptera novaeangliae), or fishermen retrieving craypots. When the dusky dolphins encountered this unusual object in their environment, they may have initiated exploratory or playful behavior, which changed to distressed or defensive behavior upon the attachment of the octopuses. The erratic behaviors of the dolphins, including tail thrashes, rolling over, and rapid changes in swimming speed and direction, indicate they were disturbed by the presence of the affixed octopus. The dolphins did not perform acrobatic leaps, which are predicted to remove or reposition large “hitchhikers.”

Multisystemic toxoplasmosis associated with a type II-like Toxoplasma gondii strain in a New Zealand fur seal (Arctocephalus forsteri) from New South Wales, Australia

We report the first confirmed case of toxoplasmosis in an Australian pinniped. Presence of Toxoplasma gondii DNA was detected in the brain of a free-ranging subadult New Zealand fur seal (Arctocephalus forsteri) with nonsuppurative meningoencephalitis, hypophysitis, posterior uveitis, retrobulbar cellulitis, and myocarditis associated with protozoan cysts and tachyzoites. The emaciated seal stranded moribund on a beach in northern Sydney in New South Wales. Histopathology coupled with specific immunohistochemistry and PCR assays confirmed the presence of T. gondii. The T. gondii sample (NZfs8825) identified in this study has an identical genotype as the type II (ToxoDB PCR-RFLP genotype #1) based on the direct sequencing and virtual RFLP of multilocus DNA markers including SAG1, 5′- and 3′-SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico. Direct sequencing of T. gondii B1 DNA marker from the T. gondii sample (NZfs8825) identified a type II-like strain, based on presence of non-archetypal B1 gene polymorphisms previously reported as unique to Australia. This study suggests that T. gondii oocysts originating from mainland Australia, which has a large population of feral cats, may act as a disease threat to native marine fauna. Therefore, emerging toxoplasmosis in the Arctic has a relevant parallel in the Southern Ocean within Australian waters with yet unknown relevance to Antarctica.

Changes in the abundance and distribution of the New Zealand fur seal (Arctocephalus forsteri) in Western Australia: are they approaching carrying capacity?

New Zealand fur seals have been increasing in abundance across Australia over the past 20 years, with annual population growth rates of 10–15%. Recent changes in distribution in Western Australia suggested that the population was increasing and expanding in range beyond the known historical distribution. We aimed to determine the growth rate of individual colonies and the overall population across Western Australia and identify new breeding and haulout sites. We used the direct count technique to estimate New Zealand fur seal pup production at 17 breeding sites. We estimated pup production to be 3518 in the 2010/11 austral summer, producing a resultant population estimate of ~17 200 New Zealand fur seals in Western Australia. This represented an exponential growth rate over the past 12 years of ~1% per annum, a significant reduction from the estimated rate of 10% per annum between 1989 and 1999. There were clusters of colonies that showed large annual declines of 6–7% in pup production over the past 12 years and at other colonies maximal rates of increase of pup production were 6–9% per annum. Three new breeding colonies were discovered. It appears that the New Zealand fur seal population is nearing its carrying capacity in Western Australia.

Records of vagrant fur seals (family Otariidae) in South Australia

Two fur seal species breed on the southern coast of Australia: the Australian fur seal (Arctocephalus pusillus doriferus) and the New Zealand fur seal (A. forsteri). Two other species are vagrants: the subantarctic fur seal (A. tropicalis) and the Antarctic fur seal (A. gazella). We document records of vagrant fur seals in South Australia from 1982 to 2012 based primarily on records from the South Australian Museum. There were 86 subantarctic fur seals: 49 specimens and 37 sightings. Most (77%) were recorded from July to October and 83% of all records were juveniles. All but two specimens were collected between July and November. Sightings were prevalent during the same period, but there were also nine sightings during summer (December–February), several of healthy-looking adults. Notable concentrations were near Victor Harbor, on Kangaroo Island and Eyre Peninsula. Likely sources of subantarctic fur seals seen in South Australia are Macquarie and Amsterdam Islands in the South Indian Ocean, ~2700 km south-east and 5200 km west of SA, respectively. There were two sightings of Antarctic fur seals, both of adults, on Kangaroo Island at New Zealand fur seal breeding colonies. Records of this species for continental Australia and nearby islands are infrequent.

Contrast in the importance of arrow squid as prey of male New Zealand sea lions and New Zealand fur seals at The Snares, subantarctic New Zealand

New Zealand sea lions (Phocarctos hookeri) are threatened by incidental bycatch in the trawl fishery for southern arrow squid (Nototodarus sloanii). An overlap between the fishery and foraging sea lions has previously been interpreted as one piece of evidence supporting resource competition for squid. However, there is currently no consensus about the importance of squid in the diet of New Zealand sea lions. Therefore, we investigated this importance independently of spatial and temporal differences in squid availability through a simultaneous study with sympatric New Zealand fur seals (Arctocephalus forsteri), a species known to target arrow squid. Diet sampling at The Snares (48°01′S 166°32′E), subantarctic New Zealand, in February 2012 coincided with peak annual catch in the nearby squid fishery. Diets were deduced by analyses of diagnostic prey remains from scats (faeces) and casts (regurgitations). The contribution of each prey species to the diet was quantified using the per cent index of relative importance (% IRI) that combined frequency of occurrence, mass and number of prey items. Arrow squid was a minor component in sea lion scats (2 % IRI), and none was found in their casts. In contrast, arrow squid was the major component in fur seal scats and casts (93 and 99 % IRI, respectively). This study found that New Zealand sea lions ate minimal squid at a time when squid was clearly available as evidenced by the diet of New Zealand fur seals; hence, there was no indication of resource competition between sea lions and the squid fishery.

The effects of seal-swim activities on the New Zealand fur seal (Arctophoca australis forsteri) in the Bay of Plenty, New Zealand, and recommendations for a sustainable tourism industry

Wildlife tourism (including pinniped tourism) offers people the opportunity to see wildlife in their natural environment. It can provide positive outcomes for the animals, through improved resources for conservation, or negative outcomes, such as inducing the animals to move away. This study assessed the impacts and sustainability of a novel but growing tourism industry, swimming with seals, based on interactions with New Zealand fur seals (Arctophoca australis forsteri) in the Bay of Plenty, New Zealand, between December 2011 and March 2012. The behaviour of all seals in the water (interaction, neutral, and avoidance) was monitored at 1min intervals, during 16 seal-swim events. Seals mostly ignored the swimmers (54% of records), some interacted with swimmers (41%); seals rarely avoided the swimmers (5%). Interactions peaked in frequency at 6min into the swims, then declined. They occurred most frequently during December, corresponding with the pupping period when juvenile seals—the age class most likely to interact—are excluded from breeding areas and so spend much of their time in the water. Compliance of tour operators to regulations was also monitored during seal-swim activities and the industry was found to be highly compliant. The results suggest the activities monitored had minimal impact on seals in the water, and are likely to be sustainable in relation to seal conservation. Tourism can be site and time specific, and it is recommended that approaches such as those trialled here be adopted to monitor other wildlife tourism activities to ensure their sustainability. Further research needs to examine potential impacts of the tours on seals ashore.

Identification of a Novel Circular DNA Virus in New Zealand Fur Seal (Arctocephalus forsteri) Fecal Matter.

Fur seal feces-associated circular DNA virus (FSfaCV) is a novel virus isolated from the fecal matter of New Zealand fur seals. FSfaCV has two main open reading frames in its 2,925-nucleotide (nt) genome. The replication-associated protein (Rep) of FSfaCV has similarity to Rep-like sequences in the Giardia intestinalis genome.

Morphometric and molecular characterization of the species of Uncinaria Frölich, 1789 (Nematoda) parasitic in the Australian fur seal Arctocephalus pusillus doriferus (Schreber), with notes on hookworms in three other pinniped hosts

This study presents morphological and molecular data on hookworms from the Australian fur seal Arctocephalus pusillus doriferus (Schreber) currently identified in Australian waters as Uncinaria hamiltoni Baylis, 1933. Additional specimens from the Australian sea lion Neophoca cinerea (Péron) and the New Zealand fur seal Arctocephalus forsteri (Lesson) from Australia, and the Southern elephant seal Mirounga leonina (Linnaeus) from Antarctica, were included. Using the internal transcribed spacer (ITS), hookworms from A. p. doriferus, N. cinerea and A. forsteri were found to be genetically similar but distinct from Uncinaria spp. found in M. leonina from Antarctica, as well as from Zalophus californianus (Lesson) and Callorhinus ursinus (Linnaeus) from California. Few morphological differences were detected between these taxa.

Freezing and thawing of pinniped carcasses results in artefacts that resemble traumatic lesions

The objective of this study was to assess whether the freezing and thawing of pinniped carcasses prior to post-mortem examination could create artefacts that resembled lesions caused by trauma. Necropsy findings in New Zealand fur seals (Arctocephalus forsteri), captured incidental to commercial fishing, and either chilled (n=5) or frozen (n=5), were compared. Changes in frozen, but not in chilled, carcasses included: pseudo-bruising of subcutis; the accumulation of thick dark red fluid (resembling haemorrhage) in the thoracic cavity, pericardial sac and abdominal cavity; apparent subcapsular renal haemorrhage; pseudo-contusions of the brain; apparent haemorrhage from the nares; and blood-staining of the anterior ocular chamber. The processes of freezing and thawing were strongly associated with subcutaneous pseudo-bruises, the presence of thick, dark red abdominal fluid and renal subcapsular 'haemorrhage' (P=0.004). These artefacts probably develop due to a combination of autolysis and 'freeze-thaw' effects including lysis of cell membranes, fluid shifts into the extracellular space, and disruption of blood vessel walls. The results of the study demonstrate that artefacts resembling traumatic lesions are created during freezing and thawing of pinniped bodies. Such changes must be taken into consideration at post-mortem examination of previously frozen carcasses.

Population recovery of the New Zealand fur seal in southern Australia: a molecular DNA analysis

Commercial harvest severely reduced the abundance of New Zealand fur seals (NZFSs; Arctocephalus australis forsteri), and the subspecies may have become regionally extinct in Western Australia (WA). NZFS populations are now expanding in WA and this study aimed to determine the origin of these populations and distinguish local recruitment from external recolonization. Mitochondrial cytochrome-b gene sequences were obtained from 137 NZFSs from breeding colonies in WA and South Australia (SA), and analyzed with sequences from Tasmania and New Zealand. Genetic differentiation among WA and SA populations was low, indicating extensive genetic exchange throughout this large region. Three unique haplotypes, however, were recorded from WA, supporting the local recruitment hypothesis. Moreover, a test for asymmetrical gene flow identified a predominance of migration from WA to SA, suggesting a role of WA NZFSs in the recovery of more heavily exploited SA NZFS populations. Significant genetic differentiation was evident between SA and Tasmania, indicating limited genetic exchange despite the close proximity of these populations. Examination of our data suggests NZFSs were not extirpated from WA, have retained unique genetic variants, and that peripheral, lowdensity populations may have had a role in the recolonization of heavily exploited populations.