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Biodiversity loss is a major global challenge of the 21st century. Ultimately, extinctions of species are determined by birth and death rates; thus, conservation management of at-risk species is dependent on robust demographic data. In this study, data gathered from 381 (227 females, 154 males) long-finned pilot whales (Globicephala melas edwardii) that died in 14 stranding events on the New Zealand coast between 2006 and 2017 were used to construct the first age- and sex-specific life tables for the subspecies. Survivorship curves were fitted to these data using (1) a traditional maximum likelihood approach, and (2) Siler’s competing-risk model. Life table construction and subsequent survival curves revealed distinct differences in the age- and sex-specific survival rates, with females outliving males. Both sexes revealed slightly elevated rates of mortality among the youngest age-classes (

Reproductive biology was assessed in 106 female common dolphins (Delphinus delphis) examined post-mortem from stranding and bycatch events along the New Zealand coastline between 1997 and 2019. The average age (ASM) and length (LSM) at sexual maturity was estimated at 7.5 years and 183.5 cm, respectively. The total number of corpora in mature individuals increased with age and appeared to persist throughout life. Ovarian asymmetry was apparent, with the left ovary displaying higher rates of ovulation, and a maximum of 19 corpora recorded for a 24-year-old female. The estimated ovulation and annual pregnancy rates for mature females were 0.39 year−1 and 30%, respectively. Conception and calving occurred year-round, with a weak seasonal increase observed in late austral spring and early austral summer. As these data did not clearly show whether seasonality was present, the gestation, lactation, and resting periods were calculated as either 12.6 or 12.8 months based on the presence/absence of seasonality, respectively. Similarly, calving interval ranged from 3.15 to 3.2 years, depending upon whether seasonality was considered. The estimated LSM of the New Zealand population aligns with other populations globally, although the estimated ASM is younger by approximately 6 months. Other reproductive parameters align with Northern Hemisphere populations, although demonstrate variation, which may reflect adaptations to local conditions such as water temperature and prey availability. As the species is subject to anthropogenic impacts including pollution and bycatch, we suggest our findings be used as a baseline with which to monitor trends in population parameters.

Dolphins are among the largest and most diverse predators in marine ecosystems, but our understanding of their foraging ecology, which is crucial for ecosystem management, is poor. Delphinus delphis (common dolphins) are found in tropical and temperate waters globally. Stomach content studies indicate they are opportunistic predators that feed locally on abundant small pelagic schooling fish, but information is lacking on how their diet may vary seasonally and with ontogeny. We investigated effects of body length, sex, season, and year on D. delphis diet in the Hauraki Gulf, New Zealand, using carbon (δ13C) and nitrogen (δ15N) stable isotope analysis of 56 skin samples collected during 13 years (2004-2016). Dolphin δ15N values changed with body length, suggesting ontogenetic dietary variation. Nitrogen isotope values were higher in austral autumn/winter compared to spring/summer, whilst δ13C values decreased throughout the study period, suggesting temporal changes in primary productivity likely affecting the dolphins’ diet. Sex had a minor effect on dolphin δ13C values, with male and female isotopic niches overlapping by 62.6% and 45.2% (respectively). Our results provide a baseline for detecting future changes in the trophic ecology of D. delphis in a key habitat in New Zealand and highlight their role as a sentinel species in this coastal ecosystem.

Knowledge of population biological parameters can contribute to assessing the resilience of a population in the face of increasing anthropogenic pressures. Southern Hemisphere long-finned pilot whales (Globicephala melas edwardii) are susceptible to high rates of live stranding-related mortality. However, the biological parameters of this population largely are unknown. In this study, age, growth, allometry, and sexual dimorphism are described using teeth and external body measurements obtained from 515 male, 776 female, and 229 individuals of unknown sex, stranded on the New Zealand coastline between 1948 and 2017. Maximum ages of 31 and 38 years were estimated for males (n = 163) and females (n = 239), respectively. Females ranged in length from 160 to 500 cm (modal size class 400–449 cm) and males from 165 to 622 cm (modal size class 500–549 cm). Length-at-birth for both sexes was estimated at 170 cm using a logistic regression model. Growth models for both sexes indicated a preliminary rapid growth phase followed by a second phase of slower growth. For males, a two-phase growth model also indicated a moderate growth spurt around the average age at attainment of sexual maturity (ca.12–13 years). Asymptotic lengths were estimated at 570 and 438 cm for males and females, respectively. We found strong evidence of sexual size dimorphism, with males significantly larger than females for 13 of 14 external measurements. We also found sexual dimorphism with respect to shape, with males having proportionally longer pectoral fins, wider tail flukes, and taller dorsal fins, than females. Estimates of length-at-birth, maximum ages, and sexual shape dimorphism for G. m. edwardii differed from those previously reported for the North Atlantic subspecies (G. m. melas), which may indicate subspecies or population-level differences in morphology, longevity, and sociality.

Conservation monitoring of highly mobile species in relatively inaccessible habitats presents a considerable challenge to wildlife biologists. Effective conservation strategies require knowledge of cetacean ecology that is often challenging and expensive to obtain. Despite their caveats, stranding data represent an underused resource to study the long-term dynamics of cetacean populations. Using long-finned pilot whale (LFPW; Globicephala melas edwardii) strandings on the New Zealand coast as a case study, we present a novel approach to demonstrate how stranding data can inform conservation management of data-poor species. A total of 8571 LFPWs stranded on the New Zealand coast within a 40-year period between January 1978 and December 2017. Overall, where sex was recorded, mass stranded adults were significantly biased towards females, while a significant male bias was observed in juveniles. Strandings occurred in all months, though significant seasonal variation was evident, with 66% of stranding events reported during austral spring and summer months (October–February). Hot spot analysis (ArcGIS) identified the majority of LFPWs stranded at Golden Bay, Great Barrier Island, Stewart Island and the Chatham Islands, with emerging hot spot analysis (ArcGIS) used to identify spatiotemporal trends. While emerging hot spot analysis revealed no significant temporal trend in the annual frequency of stranding events or numbers of individuals stranded, it did reveal a significant spatiotemporal trend, with the numbers of stranded individuals declining in areas of the Far North, Coromandel, Canterbury, Otago and the Chatham Islands, and increasing in Golden Bay and Stewart Island. When combined with other contextual information, such trends help identify the most significant clusters of LFPW strandings on the New Zealand coast, provide baseline ecological data on a poorly understood subspecies, and can be used to guide conservation management of G. m. edwardii in New Zealand waters.

Investigating past responses to variations in the marine environment can provide insights into how species might respond to future change. Using long-finned pilot whales Globicephala melas stranded in New Zealand (2011) and Australia (2012), we investigated relationships between tooth growth chronologies, as a proxy for energy budgets (which underpin population state), and interannual variations in broad-scale climate indices (Southern Oscillation Index [SOI], Indian Ocean Dipole [IOD]) and spatially explicit, seasonally averaged sea surface temperature (SST). Tooth chronologies from pilot whales that stranded in Australia had a positive relationship with the SOI and a negative relationship with the IOD. Those from New Zealand had a positive relationship with the SOI, but at a 1 yr lag. Positive SOI and negative IOD conditions are associated with increased storm activity across the southern Australian/New Zealand region. The resulting changes in regional SST, currents and frontal activity likely influences the distribution of prey resources and associated high-order predators such as pilot whales. Correlation maps between tooth growth chronologies and SSTs suggest differences in habitat utilisation between the 2 regional groups, with pilot whales stranded in Australia associating with the subtropical and subantarctic fronts south of Tasmania, and those stranded in New Zealand associating with a number of regions of seasonally enhanced productivity close to New Zealand. This study greatly enhances our understanding of the environmental conditions influencing populations of an insufficiently studied species in the region.

Male reproductive biology is described for the Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii), a subspecies that regularly mass strands along the New Zealand coastline. Ten mass stranding events sampled over a 7-year period enabled assessments of key life history parameters. Sexual maturation in immature, maturing, and mature males was assessed using morphological data and histological examination of testicular tissue. Variation was observed in the age (11–15 years) and length (450–490 cm) at which individuals attained sexual maturity. Using Bayesian cumulative logit regression models, we estimated the average age and length at the attainment of sexual maturity to be 13.5 years and 472 cm, respectively. Combined testes weight, combined testes length, an index of testicular development (combined testes weight/combined testes length), and mean seminiferous tubule diameter were all good indicators of sexual maturity status. Combined testes length was the best nonhistological indicator, and all testicular measures were found to be better indicators of sexual maturation for G. m. edwardii than age or total body length. Sexual maturity was attained before physical maturity (> 40 years and 570 cm), and at a younger age and smaller body length than previously reported for Globicephala melas melas in the North Atlantic. Given the ease of collection, minimal processing, and applicability to suboptimal material collected from stranding events, future studies should assess the value of testicular size as an indicator of sexual maturity in pilot whales and other cetacean species. Estimates of the average age and length at sexual maturity for G. m. edwardii provided in this study may be used to inform population models required for conservation management of the subspecies, which is subject to high levels of stranding-related mortality.

Here we provide a first assessment of microplastics (MPs) in stomach contents of 15 common dolphins (Delphinus delphis) from both single and mass stranding events along the New Zealand coast between 2019 and 2020. MPs were observed in all examined individuals, with an average of 7.8 pieces per stomach. Most MPs were fragments (77%, n = 90) as opposed to fibres (23%, n = 27), with translucent/clear (46%) the most prevalent colour. Fourier transform infrared (FTIR) spectroscopy revealed polyethylene terephthalate (65%) as the most predominant polymer in fibres, whereas polypropylene (31%) and acrylonitrile butadiene styrene (20%) were more frequently recorded as fragments. Mean fragment and fibre size was 584 μm and 1567 μm, respectively. No correlation between total number of MPs and biological parameters (total body length, age, sexual maturity, axillary girth, or blubber thickness) was observed, with similar levels of MPs observed between each of the mass stranding events. Considering MPs are being increasingly linked to a wide range of deleterious effects across taxa, these findings in a typically pelagic marine sentinel species warrants further investigation.

Knowledge of population biological parameters can contribute to assessing the resilience of a population in the face of increasing anthropogenic pressures. Southern Hemisphere long-finned pilot whales (

Profiles of 33 PFAS analytes and 12 essential and non-essential trace elements were measured in livers of stranded common dolphins (Delphinus delphis) from New Zealand. PFAS concentrations reported were largely comparable to those measured in other marine mammal species globally and composed mostly of long-chain compounds including perfluorooctanesulfonic acid (PFOS), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA) and perfluorooctanesulfonamide (FOSA). PFAS profiles did not vary significantly by location, body condition, or life history. Notably, significant positive correlations were observed within respective PFAS and trace elements. However, only negative correlations were evident between these two contaminant types, suggesting different exposure and metabolic pathways. Age-associated concentrations were found for PFTrDA and four trace elements, i.e. silver, mercury, cadmium, selenium, indicating differences in the bioaccumulation biomagnification mechanisms. Overall, our results contribute to global understanding of accumulation of PFAS by offering first insights of PFAS exposure in cetaceans living within South Pacific Australasian waters.

The Southern Hemisphere long-finned pilot whale (Globicephala melas edwardii) is a top predator in the New Zealand pelagic food web, feeding predominantly on arrow squids. This study quantified trace element concentrations (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Ni, Mn, Pb, Se, V, Zn) in four tissues (blubber, kidney, liver, muscle) from 21 individuals from stranding sites in New Zealand. Maximum Cd and Hg concentrations were measured in liver and kidney, respectively. Selenium had a positive correlation with Cd and Hg, suggesting the involvement of Se in Cd and Hg detoxification. Arrow squids from the whales' stomach contents were DNA barcoded and identified as Nototodarus sloanii. Trace element concentrations were measured in squid samples from the whale stomach contents. The significant correlation for Hg between the squid tissue and the whale tissue suggests that arrow squids play a major role in trace element uptake by G. m. edwardii.

International audience; New data are reported from analyses of stomach contents from 114 long-finned pilot whalesmass-stranded at four locations around Tasmania, Australia from 1992–2006. Identifiableprey remains were recovered from 84 (74%) individuals, with 30 (26%) individuals (17females and 13 males) having empty stomachs. Prey remains comprised 966 identifiablelower beaks and 1244 upper beaks, belonging to 17 families (26 species) of cephalopods.Ommastrephidae spp. were the most important cephalopod prey accounting for 16.9% bynumber and 45.6% by reconstructed mass. Lycoteuthis lorigera was the next most important,followed by Ancistrocheirus lesueurii. Multivariate statistics identified significant differencesin diet among the four stranding locations. Long-finned pilot whales foraging offSouthern Australia appear to be targeting a diverse assemblage of prey (�10 species dominatedby cephalopods). This is compared to other similar studies from New Zealand andsome locations in the Northern Hemisphere, where the diet has been reported to be primarilyrestricted to �3 species dominated by cephalopods. This study emphasises the importanceof cephalopods as primary prey for Southern long-finned pilot whales and othermarine vertebrates, and has increased our understanding of long-finned pilot whale diet inSouthern Ocean waters.

This study describes the stranding record of the Pygmy Sperm Whale, Kogia breviceps, in Tasmanian waters, and the diet of a single individual. The Pygmy Sperm Whale is one of the most commonly stranded cetaceans in some parts of Australia, although it occurs infrequently in the Tasmanian stranding record, with only seven known stranding events. Dietary items were investigated from a single juvenile male Pygmy Sperm Whale stranded in southeast Tasmania. The recoverable diet consisted of approximately three kilograms of reconstructed cephalopod prey mass from at least 11 cephalopod species within nine families. Using reconstructed biomass, the most important family was Histioteuthidae (Histioteuthis atlantica and H. miranda: 29% of reconstructed biomass), followed by Ommastrephidae (unknown sp.: 27% of reconstructed biomass), Enoploteuthidae (Enoploteuthis sp): 25% of reconstructed biomass), Cranchiidae (Cranchia scabra and Teuthowenia pellucida), Chiroteuthidae (Chiroteuthis veranyi), Brachioteuthidae (Brachioteuthis linkovskyi), Neoteuthidae (Nototeuthis dimegacotyle), Pyroteuthidae (Pyroteuthis margaritifera) and Sepiolidae (Heteroteuthis sp.). Collection and analysis of biological material from Pygmy Sperm Whale strandings around Australia should be a high priority to better understand the ecology of this poorly known species.