Rochelle Constantine

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

Abstract 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 Hectors dolphin (Cephalorhynchus hectori hectori) as Endangered and Mauis 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.

The world’s rarest whale

Summary The vast expanses of the South Pacific Ocean have, until recently, concealed the identity of the worlds rarest whale, the spade-toothed beaked whale ( Mesoplodon traversii ). Based on the scarcity of records and the total absence of previous sightings, this species is the least known species of whale and one of the worlds rarest living mammals. Two individuals of this species, previously known from only two skull fragments and a mandible, were recently discovered beach-cast in New Zealand. Although initially misidentified, we have used DNA analysis to reveal their true identity. We provide the first morphological description and images of this enigmatic species. This study highlights the importance of DNA typing and reference collections for the identification of rare species.

First record of True's beaked whale Mesoplodon mirus in New Zealand

On 27 November 2011, a whale resembling a Trues beaked whale, Mesoplodon mirus , was found stranded on the South Island of New Zealand. Sequencing of two mitochondrial regions (cytochrome b and mtDNA control region) confirmed species identification as a Trues beaked whale that was genetically identified as female. Further examination of the carcass found that the whale was pregnant although decomposition excluded determination of the age of the foetus. This specimen is confirmed as the first record of the species in New Zealand further supporting New Zealand as a whale stranding hotspot.

A preliminary photo‐identification study of bottlenose dolphin (Tursiops truncatus) in Hauraki Gulf, New Zealand

Abstract Analysis of photographs of individual bottlenose dolphin (Tursiops truncatus) taken in Hauraki Gulf, New Zealand between 2000 and 2003 resulted in 162 uniquely identifiable individuals being included in the Hauraki Gulf bottlenose dolphin photo‐identification catalogue. Seventy percent of these catalogued animals were sighted more than once, with sighting frequency ranging from one to eleven encounters. Seasonality was apparent inside the gulf with the majority of observations occurring betweenApril and June, inclusively. Comparison of individual photo‐identification catalogues between Bay of Islands and Hauraki Gulf resulted in 59% of the individuals catalogued in Hauraki Gulf being confirmed as occurring in both locations. However, 41% of individuals did not match with animals in the Bay of Islands catalogue, possibly indicating a larger population size than previously suggested for the northeastern region of the North Island, and/or the possibility of individuals overlapping in range between at least two sites along this coastline.

Population structure of humpback whales in the western and central South Pacific Ocean as determined by vocal exchange among populations

For cetaceans, population structure is traditionally determined by molecular genetics or photographically identified individuals. Acoustic data, however, has provided information on movement and population structure with less effort and cost than traditional methods in an array of taxa. Male humpback whales (Megaptera novaeangliae) produce a continually evolving vocal sexual display, or song, that is similar among all males in a population. The rapid cultural transmission (the transfer of information or behavior between conspecifics through social learning) of different versions of this display between distinct but interconnected populations in the western and central South Pacific region presents a unique way to investigate population structure based on the movement dynamics of a song (acoustic) display. Using 11 years of data, we investigated an acoustically based population structure for the region by comparing stereotyped song sequences among populations and years. We used the Levenshtein distance technique to group previously defined populations into (vocally based) clusters based on the overall similarity of their song display in space and time. We identified the following distinct vocal clusters: western cluster, 1 population off eastern Australia; central cluster, populations around New Caledonia, Tonga, and American Samoa; and eastern region, either a single cluster or 2 clusters, one around the Cook Islands and the other off French Polynesia. These results are consistent with the hypothesis that each breeding aggregation represents a distinct population (each occupied a single, terminal node) in a metapopulation, similar to the current understanding of population structure based on genetic and photo-identification studies. However, the central vocal cluster had higher levels of song-sharing among populations than the other clusters, indicating that levels of vocal connectivity varied within the region. Our results demonstrate the utility and value of using culturally transmitted vocal patterns as a way of defining connectivity to infer population structure. We suggest vocal patterns be incorporated by the International Whaling Commission in conjunction with traditional methods in the assessment of structure.

Paternity assignment and demographic closure in the New Zealand southern right whale

The identification and characterization of reproductively isolated subpopulations or ‘stocks’ are essential for effective conservation and management decisions. This can be difficult in vagile marine species like marine mammals. We used paternity assignment and ‘gametic recapture’ to examine the reproductive autonomy of southern right whales (Eubalaena australis) on their New Zealand (NZ) calving grounds. We derived DNA profiles for 34 mother–calf pairs from skin biopsy samples, using sex‐specific markers, 13 microsatellite loci and mtDNA haplotypes. We constructed DNA profiles for 314 adult males, representing 30% of the census male abundance of the NZ stock, previously estimated from genotypic mark‐recapture modelling to be 1085 (95% CL 855, 1416). Under the hypothesis of demographic closure and the assumption of equal reproductive success among males, we predict: (i) the proportion of paternities assigned will reflect the proportion of the male population sampled and (ii) the gametic mark–recapture (GMR) estimate of male abundance will be equivalent to the census male estimate for the NZ stock. Consistent with these predictions, we found that the proportion of assigned paternities equalled the proportion of the census male population size sampled. Using the sample of males as the initial capture, and paternity assignment as the recapture, the GMR estimate of male abundance was 1001 (95% CL 542, 1469), similar to the male census estimate. These findings suggest that right whales returning to the NZ calving ground are reproductively autonomous on a generational timescale, as well as isolated by maternal fidelity on an evolutionary timescale, from others in the Indo‐Pacific region.

Bucking the trend: genetic analysis reveals high diversity, large population size and low differentiation in a deep ocean cetacean

Understanding the genetic structure of a population is essential to its conservation and management. We report the level of genetic diversity and determine the population structure of a cryptic deep ocean cetacean, the Gray’s beaked whale (Mesoplodon grayi). We analysed 530 bp of mitochondrial control region and 12 microsatellite loci from 94 individuals stranded around New Zealand and Australia. The samples cover a large area of the species distribution (~6000 km) and were collected over a 22-year period. We show high genetic diversity (h=0.933–0.987, π=0.763–0.996% and Rs=4.22–4.37, He=0.624–0.675), and, in contrast to other cetaceans, we found a complete lack of genetic structure in both maternally and biparentally inherited markers. The oceanic habitats around New Zealand are diverse with extremely deep waters, seamounts and submarine canyons that are suitable for Gray’s beaked whales and their prey. We propose that the abundance of this rich habitat has promoted genetic homogeneity in this species. Furthermore, it has been suggested that the lack of beaked whale sightings is the result of their low abundance, but this is in contrast to our estimates of female effective population size based on mitochondrial data. In conclusion, the high diversity and lack of genetic structure can be explained by a historically large population size, in combination with no known exploitation, few apparent behavioural barriers and abundant habitat.

High coverage of the complete mitochondrial genome of the rare Gray’s beaked whale (Mesoplodon grayi) using Illumina next generation sequencing

Abstract Using an Illumina platform, we shot-gun sequenced the complete mitochondrial genome of Gray’s beaked whale (Mesoplodon grayi) to an average coverage of 152X. We performed a de novo assembly using SOAPdenovo2 and determined the total mitogenome length to be 16,347 bp. The nucleotide composition was asymmetric (33.3% A, 24.6% C, 12.6% G, 29.5% T) with an overall GC content of 37.2%. The gene organization was similar to that of other cetaceans with 13 protein-coding genes, 2 rRNAs (12S and 16S), 22 predicted tRNAs and 1 control region or D-loop. We found no evidence of heteroplasmy or nuclear copies of mitochondrial DNA in this individual. Beaked whales within the genus Mesoplodon are rarely seen at sea and their basic biology is poorly understood. These data will contribute to resolving the phylogeography and population ecology of this speciose group.

Exploring spatial and temporal trends in the soundscape of an ecologically significant embayment

The Hauraki Gulf, a shallow embayment in north-eastern New Zealand, provides an interesting environment for ecological soundscape research. It is situated on a tectonic plate boundary, contains one of the busiest ports in the southern hemisphere and is home to a diverse range of soniferous animals. The underwater soundscape was monitored for spatial and temporal trends at six different listening stations using passive acoustic recorders. The RMS sound pressure level of ambient sound (50–24,000 Hz) at the six listening stations was similar, ranging from 90–110 dB re 1 μPa throughout the recording period. Biophony had distinct temporal patterns and biological choruses of urchins were significantly correlated to temperature. Geophony and biophony followed the acoustic niche hypothesis, where each sound exhibited both temporal and frequency partitioning. Vessel passage sound were identified in 1.9–35.2% of recordings from the different listening stations. Vessel sound recorded in the Hauraki Gulf has the potential to mask concurrent geophony and biophony, sounds that may be important to marine life. This study provides a baseline of ambient sound, useful for future management strategies in shallow embayments where anthropogenic pressure is likewise increasing.

Night-life of Bryde’s whales: ecological implications of resting in a baleen whale

Many animals require intervals of rest or sleep in which their vigilance level is reduced. For marine fauna, including large baleen whales, resting potentially increases the risk of predation and vessel-strike. However, there is scarce information about how, and how often, whales rest which makes it difficult to assess the severity of this risk. Here we examine resting patterns of Bryde’s whales (Baleaenoptera edeni/brydei), using data collected by sound and movement archival tags (DTAGs) deployed on four whales in the Hauraki Gulf, New Zealand. To identify low activity levels associated with resting, we used RMS jerk and mean flow noise (as proxies for activity and speed, respectively), as well as changes in dive patterns (dive depth and shape), fluking, and respiration rates. The tagged whales showed strong diel differences in behavior with long periods of low activity consistent with resting occurring exclusively during the night. This pattern indicates that either (i) Bryde’s whales rely on senses that are less effective in the dark to locate prey, or (ii) that prey aggregate less densely at night, making foraging less efficient. Thus, Bryde’s whales conserve energy through rest during times when the net benefit of foraging effort is low. However, by reducing their interaction level with their environment, night-time resting also makes Bryde’s whales more vulnerable to vessel strikes, an important source of mortality for cetaceans.Significant statementAll mammals need to rest periodically and whales are no exception. But while resting land mammals can be observed directly, little is known about when and how whales rest; even though lower vigilance levels during resting could make them more vulnerable to threats such as collisions with boat traffic. We used sound and movement logging tags on resident Bryde’s whales in a busy gulf to study their daily activity patterns. We found that, while whales were active during daytime making energetic lunges to capture tonnes of plankton, they dedicated much of the night to rest. This suggests that whales may rely on vision to find prey or that prey are less densely aggregated at night making foraging less efficient. However, this near-surface resting behavior which may also be shared by the other giant baleen whales increases the risk of ship strikes.