Zealand Fur Seals Research Articles

Behavioral responses of New Zealand fur seals (Arctophoca australis forsteri) to darting and the effectiveness of midazolam and tiletamine‐zolazepam for remote chemical immobilization

AbstractWe evaluated the behavioral response of 125 free‐ranging New Zealand fur seals (75 females and 50 males) to darting and the effectiveness and safety of midazolam and tiletamine‐zolazepam for remote chemical immobilization. Behavioral reactions to darting were minor and brief. Overall, severe reactions to darting such as long flight responses (7%) and escape to the sea (7%) were uncommon. Midazolam administered by dart failed to produce a satisfactory level of immobilization. Tiletamine‐zolazepam was administered to 120 animals (35 females and 85 males), 104 of which were successfully immobilized and 16 escaped to the water following darting or attempted net capture. At least 10 of the 16 animals are known to have survived. Tiletamine‐zolazepam caused moderate depression of swimming and diving behavior in the animals that escaped to the water. Data from dive loggers confirmed that seals that escaped remained near the sea surface for extended periods. Tiletamine‐zolazepam administered by dart at a mean dosage of 1.87 ± 0.18 mg/kg for females and 1.49 ± 0.23 mg/kg for males provided effective and safe immobilization, reducing capture stress for both animals and personnel. Although there is still a risk of drugged animals escaping to the water and possibly drowning, this risk is much lower than previously reported for other pinnipeds.

Unusual stability of diet of the New Zealand fur seal (Arctocephalus forsteri) at Banks Peninsula, New Zealand

The diet of the New Zealand fur seal Arctocephalus forsteri was determined from examination of scats and regurgitates collected from two breeding colonies at Banks Peninsula, Canterbury. Identifiable otoliths and squid beaks were obtained from 392 scats and 16 regurgitations collected over four seasons in 2008. Nine species were identified in scats and three species were identified in regurgitates. Arrow squid (Nototodarus sloanii) accounted for the greatest proportion of biomass taken (>90%), followed by lanternfish (Lampanyctodes hectoris and Symbolophorus sp.; 4%) and barracouta (Thyrsites atun; 2.6%). Although slight differences in diet were detected spatially and temporally, both colonies had a squid-dominated diet year round. This differs from the seasonal dietary variation shown in other areas around mainland New Zealand.

The assessment of lethal propeller strike injuries in sea mammals

Assessment of injuries in marine mammals may be required to help authorities determine whether human activity was involved. Three cases of marine animal deaths involving propeller blade strikes are reported to demonstrate characteristic features of such cases and diagnostic difficulties that may occur. Case 1: A juvenile New Zealand fur seal (Arctocephalus forsteri) suffered two parallel linear incised wounds of the flank and died following small intestinal herniation. Case 2: An Indo-Pacific bottlenose dolphin neonate (Tursiops aduncus) died from a deeply incised wound of the left side of the head with shattering of the skull and laceration of the underlying brain.Case 3: An adult female Indo-Pacific bottlenose dolphin (T. aduncus) died from two parallel chop wounds to the torso with opening of the thoracic and abdominal cavities with fractures of the ribs and vertebrae. Given that some animals may recover, and that the carcasses of those that are killed may simply not be found or reported, it is impossible to provide an estimate of the incidence of this type of injury amongst wild sea mammals. In cases that do come to forensic attention accurate evaluation of the type of injury may potentially have great medicolegal significance. Post-mortem putrefaction and post-mortem feeding by other sea animals may complicate assessments.

Attack on blue penguin by a New Zealand fur seal

A free-ranging New Zealand fur seal (Actocephalus forsteri), considered a sub-adult male based on size, was observed and photographed on 15 July 2010 in the Hauraki Gulf, New Zealand, attacking a blue penguin (Eudyptula minor), likely an adult. While fur seals of various species are known to feed on penguins, most published data originate from dietary analyses rather than direct observations. New Zealand fur seals are rarely encountered within the Hauraki Gulf and while marine birds are considered to form a minor part of their diet, this record acts as the first documented observation of an attack on a blue penguin within this region and only the second published record within New Zealand waters involving these two species. The carcass of the penguin was not consumed but instead manipulated before being subsequently abandoned. Injuries sustained by the penguin were consistent with those inflicted by terrestrial mammalian carnivores considered important predators of blue penguin.

Individual foraging site fidelity in lactating New Zealand fur seals: Continental shelf vs. oceanic habitats

AbstractWide‐ranging marine central place foragers often exhibit foraging site fidelity to oceanographic features over differing spatial scales (i.e., localized coastal upwellings and oceanic fronts). Few studies have tested how the degree of site fidelity to foraging areas varies in relation to the type of ocean features used. In order to determine how foraging site fidelity varied between continental shelf and oceanic foraging habitats, 31 lactating New Zealand fur seals (Arctocephalus australis forsteri1) were satellite tracked over consecutive foraging trips (14–108 d). Thirty‐seven foraging trips were recorded from 11 females that foraged on the continental shelf, in a region associated with a coastal upwelling, while 65 foraging trips were recorded from 20 females that foraged in oceanic waters. There were no significant differences in the mean bearings (to maximum distance) of individual's consecutive foraging trips, suggesting individual fidelity to foraging areas. However, overlap in area and time spent in area varied considerably between continental shelf and oceanic foragers. Females that foraged on the continental shelf had significantly greater overlap in consecutive foraging trips when compared to females that foraged in oceanic waters (overlap in 5 × 5 km grid cells visited on consecutive trips 55.9%± 20.4% and 13.4%± 7.6%, respectively). Females that foraged on the continental shelf also spent significantly more time within the same grid cell than females that foraged in oceanic waters (maximum time spent in 5 × 5 km grid cells: 14%± 5% and 4%± 2%, respectively). This comparatively high foraging site fidelity may reflect the concentration of productivity associated with a coastal upwelling system, the Bonney Upwelling. Lower foraging site fidelity recorded by seals that foraged in oceanic waters implies a lower density/larger scale habitat, where prey are more dispersed or less predictable at fine scales, when compared to the continental shelf region.

The potential role of forensic pathologists in veterinary forensic medicine

There has been an increasing awareness over recent years of the field of veterinary forensic medicine, with involvement of veterinarians in a wide range of activities extending from the assessment of possible inflicted injuries in domestic animals to wildlife crime concerning the entrapment, transport and killing of protected and endangered species [1, 2]. More publications are occurring in this area, with for example, a special issue of Forensic Science Medicine and Pathology being recently devoted to wildlife crime, and comprehensive textbooks now emerging [2–4]. The opportunity for forensic pathologists to contribute to this area is also being increasingly recognized [5]. The link between human forensic pathology and that involving animals is obvious and the opportunity to foster collaboration between these two areas of practice should be seized upon, as information and techniques utilized by forensic pathologists may be of great use in veterinary practice. As forensic pathologists are exposed on a daily basis to lethal injuries and processes, they also have a wealth of information that can be shared with veterinary colleagues who may not have such intense exposure to this type of material. It is quite obvious that forensic pathologists with training in human disease and injury have a great deal to learn from veterinary colleagues, and that many of the dissections and conditions encountered will be completely outside their experience. However, certain conditions affecting both humans and animals may show common features, and as lethal episodes in humans may have been studied more extensively than in non-humans, cross-species comparison of cases may provide a useful guide for the possible investigation of nonhuman fatalities. A good example of this was a young adult male Indian Ocean Bottlenose dolphin (Tursiops cf aduncus) that was found dead with a small Cobbler Carpetshark (Sutorectus tentaculatus) wedged firmly within its upper aerodigestive tract. Known as cafe coronary syndrome in humans, this type of death raised the possibility of neurological impairment and prompted a search for intrinsic central nervous system disease, or heavy metal poisoning in the affected animal [6]. The use of human imaging modalities, such as CT scanning, in animals with significant injuries may demonstrate more clearly the nature of the injuries than standard dissection or skeletal defleshing. For example, comminuted fracturing of the midfacial skeleton in a juvenile New Zealand fur seal (Arctocephalus forsteri) was far more clearly shown by CT scanning prior to necropsy than afterwards, as the delicate central facial skeleton had collapsed once supporting fascia and soft tissues had been removed [7]. Unfortunately techniques routinely used in humans, such as immunohistochemical staining of tissues for microscopy using anti-human reagents may not always work in animals [8], although on occasion there may be a surprising degree of cross reactivity [9]. Another area that forensic pathologists can contribute to is in lecturing to veterinary science students on basic injury assessment and evaluation. A patterned abrasion, a stab R. W. Byard (&) Discipline of Anatomy and Pathology, Level 3 Medical School North Building, The University of Adelaide, Frome Road, Adelaide 5005, Australia e-mail: roger.byard@sa.gov.au

How Effective are Posted Signs to Regulate Tourism? An Example with New Zealand Fur Seals

Increased tourism has augmented harassment to wildlife and posted signs are commonly used to manage such interactions. This study determined whether signs increased tourist compliance with regulations to remain >10 m from New Zealand fur seals (Arctocephalus forsteri) at Kaikoura Peninsula. We observed 362 tourist groups interacting with seals. The percentage of groups in which all members respected the posted distance was similar whether tourists saw the signs or not [60.6% vs. 65.9%; G(1) = 0.98, p = 0.32]. Results indicate that posted signs were ineffective in increasing compliance to regulations and suggest that alternative approaches must be considered to increase regulation compliance and better manage interactions between tourists and wildlife.

Invasive species in penguin worlds: An ethical taxonomy of killing for conservation

This paper explores various attempts to manage predation threats to an endangered population of little penguins (<i>Eudyptula minor</i>) living in Sydney's North Harbour. Some of these threats have come from species that are generally termed 'exotic' (such as the red fox, <i>Vulpes vulpes</i>), while other threats have potentially come from 'natives' (such as the New Zealand fur seal, <i>Arctocephalus forsteri</i>). This paper explores the problematic notion of 'invasiveness' as it applies to native and introduced predators, and the role that these rhetorical distinctions play in positioning various species as 'threats' to the continuity of this penguin colony. In particular, the paper is concerned with conservation legislation and practice in New South Wales, and the unique kind of 'ethical work' done by these processes of classifying living things. Finally, the paper asks, in the absence of a simplistic-but helpful-correlation between exotic and invasive species, how might we understand and justify the conservation of an isolated colony of little penguins? What kinds of interventions (from humans and nonhumans) are warranted, and which are not? What might it mean to genuinely inhabit these difficulties, making conservation decisions outside of any space of simple and absolute answers?

Effects of the Presence of Official-Looking Volunteers on Harassment of New Zealand Fur Seals

An increased number of tourists viewing animals in the wild have increased stress on these animals (hereafter wildlife). Many wildlife-viewing locations rely on voluntary compliance with posted regulations to protect animals from tourists because of the expense of employing on-site enforcement personnel. Voluntary compliance, however, is ineffective. The presence of official-looking volunteers may decrease the incidence of wildlife harassment by tourists. To test this possibility, we observed tourists interacting with 5- to 12-month-old New Zealand fur seals (Arctocephalus forsteri) at the popular Ohau Stream waterfall while in the absence or presence of a young woman in plain sight wearing a neon vest (i.e., observer) and when an observer was not present. We observed 254 tourist groups at the waterfall when young seals were present. The percentage of groups in which at least one person harassed (approached, touched, or threw objects) a young seal was two-thirds lower when the official-looking observer was present. Frequency of harassment was inversely related to observer presence. Programs in which volunteers work at tourist sites are popular in countries with high tourism rates, such as New Zealand. Our results show that a relatively inexpensive and effective tourism-management strategy may be to post such volunteers as observers at sites where tourists view wildlife.

Mutation scanning-coupled sequencing of nuclear ribosomal DNA spacers as a tool for the specific identification of different Contracaecum (Nematoda: Anisakidae) larval types

In the present study, various morphotypes of Contracaecum (Nematoda) larvae in different developmental stages were described and then genetically characterised using sequence data obtained from the first and second internal transcribed spacers (ITS-1 and ITS-2) of nuclear ribosomal DNA (rDNA). The alignment of ITS-1 and ITS-2 sequence data for larvae investigated with those from well characterised adults in previous studies showed that fourth-stage Contracaecum larvae from the Australian pelican, Pelecanus conspicillatus, had the same sequence as Contracaecum microcephalum reported from the little pied cormorant, Phalacrocorax melanoleucos. In addition, four different morphotypes of third-stage larvae, including types I to IV, were found in various species of fish. Contracaecum type I larvae were composed of two distict genotypes; those collected from mullet, Mugil cephalus, had the same sequence as C. multipapillatum, and those from an unknown species of hardyhead (family Atherinidae) were C. pyripapillatum. Contracaecum type II larvae from mackerel, Scomber australasicus, had the same sequence as adult C. ogmorhini sensu stricto, found in the Australian and New Zealand fur seals ( Arctocephalus spp). Contracaecum type III larvae from flathead, Platycephalus laevigatus, had the same sequence as C. rudolphii D found in the black cormorant, Phalacrocorax carbo. The approach used herein was an effective means of matching incompletely identifiable larval nematodes with reference sequences and provides a basis for exploring the composition of populations of anisakid larvae in fish as well as their ecology, particularly their life cycles and transmission patterns.

Correlation between Male Social Status, Testosterone Levels, and Parasitism in a Dimorphic Polygynous Mammal

Life history trade-offs have often been assumed to be the consequence of restrictions in the availability of critical resources such as energy and nutrients, which necessitate the differential allocation of resources to costly traits. Here, we examined endocrine (testosterone) and health (parasite burdens) parameters in territorial and non-territorial New Zealand fur seal males. We documented intra-sexual differences in sexual behaviours, testosterone levels, and parasitism that suggest a trade-off exists between reproductive success and physical health, particularly susceptibility to helminths and acanthocephalans, in males displaying different mating tactics (i.e., territorial and non-territorial tactics). Levels of testosterone were higher in territorial males and correlated positively with reproductive effort (i.e., intra- and inter-sexual interactions). However, these territorial males also exhibited high levels of parasitic infection, which may impair survival in the long-term. Our study, while limited in sample size, provides preliminary evidence for a link between male mating tactics, testosterone levels and parasite loads, and potential effects on reproductive success and life history that should be explored further.

Fish feed on faeces and vomits of New Zealand fur seals: marine mammals bring nutrients from open to inshore waters

New Zealand fur seals ( Arctocephalus forsteri ) forage mostly in open waters at night and spend parts of the day in coastal sheltered sites, where they may play, rest and eliminate wastes. We recorded the purple wrasse ( Notolabrus fucicola ) feeding on faeces and vomits of these pinnipeds at Fortescue Bay in the Tasman Peninsula, Australia. This behaviour allows the wrasse to get nutrients from open waters that otherwise would not be available. Thus, it is suggested that the fur seals have the role of transferring nutrients from open waters to inshore reefs and provide them as particulate food to fish. This functional role is apparently recorded for only one species of marine mammal so far, the spinner dolphin ( Stenella longirostris ), in tropical oceanic waters.

Mechanisms of deaths in captive juvenile New Zealand fur seals (Arctocephalus forsteri)

Juvenile seals are sometimes encountered in waters around South Australia with injuries and/or diseases that require veterinary treatment. Two cases are reported where apparently stable animals died soon after being rescued due to quite disparate conditions. In Case 1 a juvenile male New Zealand fur seal (Arctocephalus forsteri) was found unexpectedly dead in its enclosure. A necropsy examination revealed an emaciated juvenile male with no injuries. The intestine was filled throughout its length with melena stool that was due to heavy infestation of the stomach with roundworms with adjacent gastritis. Death was due to shock from upper gastrointestinal blood loss secondary to parasitosis. In Case 2 a second juvenile male New Zealand fur seal (Arctocephalus forsteri) also died unexpectedly in its enclosure. It had been listless with loud respirations since capture. At necropsy there was no blood around the head, neck or mouth, and no acute external injuries were identified. An area of induration was, however, present over the snout with fragmentation of underlying bones. The maxilla was freely mobile and CT scanning revealed multiple comminuted fractures of the adjacent facial skeleton. Examination of the defleshed skull showed fragmentation of the facial skeleton with roughening of bones in keeping with osteomyelitis. Death was attributed to sepsis from osteomyelitis of a comminuted midfacial fracture. These cases demonstrate two unusual and occult conditions that may be present in recently retrieved juvenile fur seals. Failure to establish the correct diagnosis rapidly may result in death soon after capture. The usefulness of imaging techniques such as CT scanning in delineating underlying injuries prior to necropsy is clearly demonstrated.

Agonistic Behaviour in Female New Zealand Fur Seals, Arctocephalus forsteri

New Zealand fur seals, Arctocephalus forsteri, breed in densely packed colonies where males hold exclusive territories. Both sexes overheat while on land and use shade and pools of water for cooling. In addition, females are aggressive towards one another and rarely tolerate neighbours closer than 1 m away. At a New Zealand colony of this species, agonistic interactions among females occurred most often in areas used for thermoregulation: shaded rock substrate and pools of water. Fewest interactions occurred in sunny, dry areas. These findings suggest that females are competing for a limited resource, which could limit harem size.

Assessing trauma in frozen carcasses: Freeze artefact in New Zealand fur seals

Assessing trauma in frozen carcasses: Freeze artefact in New Zealand fur seals

Australian fur seals establish haulout sites and a breeding colony in South Australia

Australian fur seals (Arctocephalus pusillus doriferus) breed on Bass Strait islands in Victoria and Tasmania. They have been recorded in South Australia (SA) for many years as non-breeding visitors and on Kangaroo Island frequently since 1988, mostly in breeding colonies of the New Zealand fur seal (A. forsteri) which is the most numerous pinniped in SA. Australian fur seals have displaced New Zealand fur seals from sections of the Cape Gantheaume colony on Kangaroo Island. North Casuarina Island produced 29 Australian fur seal pups in February 2008. Australian fur seal pups were larger than New Zealand fur seal pups in the same colony and have been identified genetically using a 263-bp fragment of the mitochondrial DNA control region. North Casuarina Island has been an important breeding colony of New Zealand fur seals, but pup numbers there decreased since 1992–93 (contrary to trends in SA for New Zealand fur seals), while numbers of Australian fur seals there have increased. This study confirms that Australian fur seals breed in SA. The two fur seal species compete for space onshore at several sites. Australian fur seals may compete for food with endangered Australian sea lions (Neophoca cinerea) because both are bottom feeders.

Observations of mortality of fur seals between 1998 and 2005 in Tasmania, Australia

Because of their often close relationship with the human environment, the deaths of marine mammals are often documented, particularly if there are links to anthropogenic influences. Between 1998 and 2005 a total of 504 dead Australian Fur Seals, Arctocephalus pusillus doriferus, and New Zealand Fur Seals, Arctocephalus forsteri, were reported in Tasmanian waters. Ninety individuals (18%) were dependent unweaned pups that had been displaced from their natal colonies. Of the 209 adult or subadult seals for which the cause of death could be ascertained,anthropogenic activities were identified as being responsible for the deaths of 172 individuals (82%), with 112 (53%) associated with fish farms. Most fish farm-related deaths occurred during the winter when adult and subadult seals were away from breeding colonies and seal numbers are highest around farms. The next most common cause of death was from firearms (41 individuals - 20%). Death of adults and subadults by natural causes accounted for 37 animals, or 18% of all deaths for which the cause was identified. Excluding pups, most seals were identified as Australian (80%) or New Zealand fur seals (3%). The remainder (17%) were identified as fur seals but not to species. Males were most common (58%), with only 6% identified as females; the sex of 36% could not be determined. Of the males, 106 (26%) were adults and 98 (24%) were subadults or juveniles.

Calibrations to estimate absolute numbers of New Zealand fur seal (Arctocephalus forsteri) pups from direct counts

Annual direct counts of seal pups can indicate long‐term trends in population size, but mark‐recapture estimates are needed to deduce absolute numbers. A calibration between results from these two methods would facilitate the use of direct counts to estimate absolute numbers, an outcome that is relatively quick, cheap and minimises disturbance of animals. Mark‐recapture estimates for the numbers of New Zealand fur seal (Arctocephalus forsteri) pups in 2003 at 10 colonies at Otago, southeastern New Zealand, were compared with independent single counts at the same colonies. A single ratio to estimate absolute numbers (y) from direct counts x was not statistically significant. Instead, two ratios were deduced, based on differences in habitat among colonies: y = 1.51x for colonies with hiding places for pups and y = 0.96x for colonies without hiding places. Application of these calibrations and their 95% prediction intervals produce estimates and ranges for the absolute numbers of pups from single annual counts.

Fur seals at Macquarie Island: post-sealing colonisation, trends in abundance and hybridisation of three species

Commercial sealers exterminated the original fur seal population at Macquarie Island in the early 1800s. The first breeding record since the sealing era was not reported until March 1955. Three species of fur seal now occur at Macquarie Island, the Antarctic (Arctocephalus gazella), subantarctic (A. tropicalis) and New Zealand (A. forsteri) fur seal. Census data from 54 breeding seasons in the period 1954–2007 were used to estimate population status and growth for each species. Between the 1950s and 1970s, annual increases in pup production for the species aggregate were low. Between 1986 and 2007, pup production of Antarctic fur seals increased by about 8.8% per year and subantarctic fur seals by 6.8% per year. The New Zealand fur seal, although the most numerous fur seal species on Macquarie Island, has yet to establish a breeding population, due to the absence of reproductively mature females. Hybridisation among species is significant, but appears to be declining. The slow establishment and growth of fur seal populations on Macquarie Island appears to have been affected by its distance from major population centres and hence low immigration rates, asynchronous colonisation times of males and females of each species, and extensive hybridisation.

Milk fatty acids predict the foraging locations of the New Zealand fur seal: continental shelf versus oceanic waters

Lactating New Zealand fur seals Arctocephalus forsteri utilise 2 ecological regions: con- tinental shelf habitats and oceanic habitats associated with the Subtropical Front. Using milk fatty acids (FA) obtained from 29 satellite-tracked fur seals, we characterised the FA composition of seals that foraged on the continental shelf, and those that foraged in oceanic waters. Seals that foraged within oceanic waters were characterised by milk being comparatively high in monounsaturated fatty acids (MUFA; 47.4 ± 4.4%, mean ± SD), and lower in polyunsaturated fatty acids (PUFA; 23.8 ± 4.0%) when compared to seals that foraged in continental shelf waters (MUFA 36.7 ± 5.4 and PUFA 31.4 ± 5.5%). Based on FA compositions, we predicted the likelihood that milk samples collected at random (n = 131) represented individual seals having foraged either on the continental shelf or in dis- tant oceanic waters. Results indicated that 74% (n = 97) of seals were likely to have foraged in oceanic waters, with 26% (n = 34) likely to have foraged within continental shelf waters. These results were supported by the small sub-sample of 29 satellite-tracked seals, which indicated that 62% of seals had foraged in oceanic waters. FA analysis and satellite-tracking results contrasted with scat analyses, from which only 7% of scats contained prey remains from oceanic waters. The results suggest scats were biased toward females foraging on the continental shelf. To further understand the diet of New Zealand fur seals, additional information on potential prey species that inhabit waters associated with the Subtropical Front south of Australia is required, as well as the continued devel- opment and application of alternative dietary techniques.