Quantifying the abundance and survival rates of island-associated spinner dolphins using a multi-state open robust design model.

Spinner dolphins (Stenella longirostris subsp.) occupy the nearshore waters of several Hawaiian Islands. Due to their constrained behavioral pattern and genetic isolation, they are vulnerable to anthropogenic threats. Their occurrence and behavior are well-described, yet a lack of data on their abundance and survival rates hinders optimal conservation action. Using design-based photo-identification surveys, this study estimated the abundance, apparent survival, and emigration of spinner dolphins off the Wai'anae Coast of O'ahu through multi-state open robust design (MSORD) and POPAN modelling. Eight seasonal field seasons, (two winter, spring, summer, and autumn) each comprised of six surveys of the study area, were completed during two consecutive years. Seasonal abundance estimates derived from the best fitting model ranged from 140 (± 36.8 SE, 95% CI 84-232) to 373 (± 60.0, 95% CI 273-509) individuals and were lowest during winter seasons. The MSORD estimated a survival rate of 0.95 (± 0.02 SE) and a Markovian pattern of temporary emigration. POPAN modelling estimated a super-population size of 633 (± 78 SE, 95% CI 492-798), reflecting the total number of individual dolphins that used the study area during the entire study period. Additional research on circum- and inter-island dolphin movements around and between O'ahu and the Maui Nui region may shed light on both seasonal movement patterns and overall abundance for the O'ahu/4-Islands stock. This work represents the first systematic mark-recapture effort to assess the abundance and survival rates of these highly exposed dolphins, providing valuable insights for conservation and management.

Bellwethers of change: population modelling of North Pacific humpback whales from 2002 through 2021 reveals shift from recovery to climate response.

For the 40 years after the end of commercial whaling in 1976, humpback whale populations in the North Pacific Ocean exhibited a prolonged period of recovery. Using mark-recapture methods on the largest individual photo-identification dataset ever assembled for a cetacean, we estimated annual ocean-basin-wide abundance for the species from 2002 through 2021. Trends in annual estimates describe strong post-whaling era population recovery from 16 875 (± 5955) in 2002 to a peak abundance estimate of 33 488 (± 4455) in 2012. An apparent 20% decline from 2012 to 2021, 33 488 (± 4455) to 26 662 (± 4192), suggests the population abruptly reached carrying capacity due to loss of prey resources. This was particularly evident for humpback whales wintering in Hawai'i, where, by 2021, estimated abundance had declined by 34% from a peak in 2013, down to abundance levels previously seen in 2006, and contrasted to an absence of decline in Mainland Mexico breeding humpbacks. The strongest marine heatwave recorded globally to date during the 2014-2016 period appeared to have altered the course of species recovery, with enduring effects. Extending this time series will allow humpback whales to serve as an indicator species for the ecosystem in the face of a changing climate.

Morphology of nares associated with stereo-olfaction in baleen whales.

The sensory mechanisms used by baleen whales (Mysticeti) for locating ephemeral, dense prey patches in vast marine habitats are poorly understood. Baleen whales have a functional olfactory system with paired rather than single blowholes (nares), potentially enabling stereo-olfaction. Dimethyl sulfide (DMS) is an odorous gas emitted by phytoplankton in response to grazing by zooplankton. Some seabirds use DMS to locate prey, but this ability has not been demonstrated in whales. For 14 extant species of baleen whale, nares morphometrics (imagery from unoccupied aerial systems, UAS) was related to published trophic level indices using Bayesian phylogenetic mixed modelling. A significant negative relationship was found between nares width and whale trophic level (ß = -0.08, lower 95% CI = -0.13, upper 95% CI = -0.03), corresponding with a 39% increase in nares width from highest to lowest trophic level. Thus, species with nasal morphology best suited to stereo-olfaction are more zooplanktivorous. These findings provide evidence that some baleen whale species may be able to localize odorants e.g. DMS. Our results help direct future behavioural trials of olfaction in baleen whales, by highlighting the most appropriate species to study. This is a research priority, given the potential for DMS-mediated plastic ingestion by whales.

Quantifying the age structure of free-ranging delphinid populations: Testing the accuracy of Unoccupied Aerial System photogrammetry.

Understanding the population health status of long-lived and slow-reproducing species is critical for their management. However, it can take decades with traditional monitoring techniques to detect population-level changes in demographic parameters. Early detection of the effects of environmental and anthropogenic stressors on vital rates would aid in forecasting changes in population dynamics and therefore inform management efforts. Changes in vital rates strongly correlate with deviations in population growth, highlighting the need for novel approaches that can provide early warning signs of population decline (e.g., changes in age structure). We tested a novel and frequentist approach, using Unoccupied Aerial System (UAS) photogrammetry, to assess the population age structure of small delphinids. First, we measured the precision and accuracy of UAS photogrammetry in estimating total body length (TL) of trained bottlenose dolphins (Tursiops truncatus). Using a log-transformed linear model, we estimated TL using the blowhole to dorsal fin distance (BHDF) for surfacing animals. To test the performance of UAS photogrammetry to age-classify individuals, we then used length measurements from a 35-year dataset from a free-ranging bottlenose dolphin community to simulate UAS estimates of BHDF and TL. We tested five age classifiers and determined where young individuals (<10 years) were assigned when misclassified. Finally, we tested whether UAS-simulated BHDF only or the associated TL estimates provided better classifications. TL of surfacing dolphins was overestimated by 3.3% ±3.1% based on UAS-estimated BHDF. Our age classifiers performed best in predicting age-class when using broader and fewer (two and three) age-class bins with ~80% and ~72% assignment performance, respectively. Overall, 72.5%-93% of the individuals were correctly classified within 2 years of their actual age-class bin. Similar classification performances were obtained using both proxies. UAS photogrammetry is a non-invasive, inexpensive, and effective method to estimate TL and age-class of free-swimming dolphins. UAS photogrammetry can facilitate the detection of early signs of population changes, which can provide important insights for timely management decisions.

Energy expenditure of southern right whales varies with body size, reproductive state and activity level.

Quantifying the energy expenditure of animals is critical to understanding the cost of anthropogenic disturbance relative to their overall energy requirements. We used novel drone focal follows (776 follows, 185 individuals) and aerial photogrammetry (5372 measurements, 791 individuals) to measure the respiration rate and body condition loss of southern right whales (Eubalaena australis) on a breeding ground in Australia. Respiration rates were converted to oxygen consumption rate and field metabolic rate (FMR) using published bioenergetic models. The intra-seasonal loss in body condition of different reproductive classes (calves, juveniles, adults, pregnant and lactating females) was converted to blubber energy loss and total energy expenditure (TEE). Using these two metrics, we tested the effects of body size, reproductive state and activity level on right whale energy expenditure. Respiration rates and mass-specific FMR decreased exponentially with an increase in body size, as expected based on allometric scaling. FMR increased curvilinearly with an increase in swim speed, probably as a result of increased drag and increased locomotion costs. Respiration rates and FMR were 44% higher for pregnant and lactating females compared with those of adults, suggesting significant costs of fetal maintenance and milk production, respectively. The estimated FMR of adults based on their respiration rates corresponded well with the estimated TEE based on body condition loss. The rate of decline in body condition of pregnant and lactating females was considerably higher than expected based on respiration rates, which probably reflects the milk energy transfer from mothers to calves, which is not reflected in their FMR.

A collaborative and near-comprehensive North Pacific humpback whale photo-ID dataset.

We present an ocean-basin-scale dataset that includes tail fluke photographic identification (photo-ID) and encounter data for most living individual humpback whales (Megaptera novaeangliae) in the North Pacific Ocean. The dataset was built through a broad collaboration combining 39 separate curated photo-ID catalogs, supplemented with community science data. Data from throughout the North Pacific were aggregated into 13 regions, including six breeding regions, six feeding regions, and one migratory corridor. All images were compared with minimal pre-processing using a recently developed image recognition algorithm based on machine learning through artificial intelligence; this system is capable of rapidly detecting matches between individuals with an estimated 97-99% accuracy. For the 2001-2021 study period, a total of 27,956 unique individuals were documented in 157,350 encounters. Each individual was encountered, on average, in 5.6 sampling periods (i.e., breeding and feeding seasons), with an annual average of 87% of whales encountered in more than one season. The combined dataset and image recognition tool represents a living and accessible resource for collaborative, basin-wide studies of a keystone marine mammal in a time of rapid ecological change.

Fast and Furious: Energetic Tradeoffs and Scaling of High-Speed Foraging in Rorqual Whales.

Although gigantic body size and obligate filter feeding mechanisms have evolved in multiple vertebrate lineages (mammals and fishes), intermittent ram (lunge) filter feeding is unique to a specific family of baleen whales: rorquals. Lunge feeding is a high cost, high benefit feeding mechanism that requires the integration of unsteady locomotion (i.e., accelerations and maneuvers); the impact of scale on the biomechanics and energetics of this foraging mode continues to be the subject of intense study. The goal of our investigation was to use a combination of multi-sensor tags paired with UAS footage to determine the impact of morphometrics such as body size on kinematic lunging parameters such as fluking timing, maximum lunging speed, and deceleration during the engulfment period for a range of species from minke to blue whales. Our results show that, in the case of krill-feeding lunges and regardless of size, animals exhibit a skewed gradient between powered and fully unpowered engulfment, with fluking generally ending at the point of both the maximum lunging speed and mouth opening. In all cases, the small amounts of propulsive thrust generated by the tail were unable to overcome the high drag forces experienced during engulfment. Assuming this thrust to be minimal, we predicted the minimum speed of lunging across scale. To minimize the energetic cost of lunge feeding, hydrodynamic theory predicts slower lunge feeding speeds regardless of body size, with a lower boundary set by the ability of the prey to avoid capture. We used empirical data to test this theory and instead found that maximum foraging speeds remain constant and high (∼4 m s-1) across body size, even as higher speeds result in lower foraging efficiency. Regardless, we found an increasing relationship between body size and this foraging efficiency, estimated as the ratio of energetic gain from prey to energetic cost. This trend held across timescales ranging from a single lunge to a single day and suggests that larger whales are capturing more prey-and more energy-at a lower cost.

Residency, movement patterns, behavior and demographics of reef manta rays in Komodo National Park.

Background: The reef manta ray (Mobula alfredi) is a globally threatened species and an iconic tourist attraction for visitors to Indonesia's Komodo National Park (NP). In 2013, manta ray fishing was banned in Komodo NP and its surroundings, preceding the nationwide manta ray protection in 2014. Over a decade ago, a previous acoustic telemetry study demonstrated that reef manta rays had high fidelity to sites within the park, while more recent photo-identification data indicated that some individuals move up to 450 km elsewhere. Characterization of manta ray demographics, behavior, and a focused assessment on site use of popular tourism locations within the park is vital to assist the Komodo NP Management Authority formulate appropriate manta ray conservation and management policies. Methods: This study uses a long-term library (MantaMatcher.org) of photo-identification data collected by researchers and citizen scientists to investigate manta ray demographics and habitat use within the park at four sites frequented by tour operators: Cauldron, Karang Makassar, Mawan, and Manta Alley. Residency and movements of manta rays were investigated with maximum likelihood analyses and Markov movement models. Results: A total of 1,085 individual manta rays were identified from photographs dating from 2013 to 2018. In general, individual manta rays displayed a higher affinity to specific sites than others. The highest re-sighting probabilities came from the remote southern site, Manta Alley. Karang Makassar and Mawan are only ~5 km apart; however, manta rays displayed distinct site affinities. Exchange of individuals between Manta Alley and the two central sites (~35.5 km apart) occurred, particularly seasonally. More manta rays were recorded traveling from the south to the central area than vice versa. Female manta rays were more mobile than males. Similar demographic groups used Karang Makassar, Mawan, and Manta Alley for foraging, cleaning, cruising, or courtship activities. Conversely, a higher proportion of immature manta rays used the northern site, Cauldron, where foraging was commonly observed. Fishing gear-related injuries were noted on 56 individuals (~5%), and predatory injuries were present on 32 individuals (~3%). Tourism within the park increased from 2014 to 2017, with 34% more dive boats per survey at Karang Makassar and Mawan. Discussion: The Komodo NP contains several distinct critical habitats for manta rays that encompass all demographics and accommodate seasonal manta ray movements. While the present study has not examined population trends, it does provide foundational data for such work. Continued research into manta ray abundance, long-range movements, and identifying and protecting other critical aggregation areas within the region is integral to securing the species' recovery. We provide management recommendations to limit undue pressure on manta rays and their critical habitats from tourism.

Fetal growth, birth size and energetic cost of gestation in southern right whales.

The cost of reproduction greatly affects a species' life history strategy. Baleen whales exhibit some of the fastest offspring growth rates in the animal kingdom. We quantified the energetic cost of gestation for southern right whales (Eubalaena australis) by combining whaling catch records of pregnant females with photogrammetry data on southern right whale mothers and calves from two breeding grounds in Argentina and Australia. The relationship between calf birth size and maternal length was determined from repeated measurements of individual females before and after giving birth. Fetal growth was determined from generalized linear models fitted to fetal length data from whaling operations between 1961 and 1967. Fetal length was converted to volume and mass, using the volume-to-length relationship of newborn southern right whales calves, and published tissue composition and energy content estimates. Fetal maintenance costs (heat of gestation) and the energy content of the placenta were predicted from published relationships and added to the fetal growth cost to calculate the total cost of gestation. Our findings showed that fetal growth rates and birth size increased linearly with maternal length, with calves being born at ∼35% maternal length. Fetal length increased curvilinearly through gestation, which resulted in an exponential increase in fetal volume and mass. Consequently, the cost of gestation was very low during the first (0.1% of total cost) and second trimester (4.9%), but increased rapidly during the last trimester (95.0%). The heat of gestation incurred the highest cost for pregnant females (73.8%), followed by fetal growth (21.2%) and the placental energy content (5.0%). KEY POINTS: Baleen whales exhibit some of the fastest fetal growth rates in the animal kingdom. Despite this, the energetic cost of gestation is largely unknown, as well as the influence of maternal body size on fetal growth rates and calf birth sizes. We combined historical whaling records and drone photogrammetry data to determine fetal growth rates and birth sizes in southern right whales (Eubalaena australis), from which we estimated the cost of gestation. Calf birth size, and consequent fetal growth rates, increased positively with maternal body size. The cost of gestation was negligible for southern right whale females during the first two trimesters, but increased rapidly during the last trimester. These results show that late gestation incurs a significant cost for baleen whale females, and needs to be accounted for in bioenergetic models.

Scaling of maneuvering performance in baleen whales: larger whales outperform expectations.

Despite their enormous size, whales make their living as voracious predators. To catch their much smaller, more maneuverable prey, they have developed several unique locomotor strategies that require high energetic input, high mechanical power output and a surprising degree of agility. To better understand how body size affects maneuverability at the largest scale, we used bio-logging data, aerial photogrammetry and a high-throughput approach to quantify the maneuvering performance of seven species of free-swimming baleen whale. We found that as body size increases, absolute maneuvering performance decreases: larger whales use lower accelerations and perform slower pitch-changes, rolls and turns than smaller species. We also found that baleen whales exhibit positive allometry of maneuvering performance: relative to their body size, larger whales use higher accelerations, and perform faster pitch-changes, rolls and certain types of turns than smaller species. However, not all maneuvers were impacted by body size in the same way, and we found that larger whales behaviorally adjust for their decreased agility by using turns that they can perform more effectively. The positive allometry of maneuvering performance suggests that large whales have compensated for their increased body size by evolving more effective control surfaces and by preferentially selecting maneuvers that play to their strengths.

Rapid weight loss in free ranging pygmy killer whales (Feresa attenuata) and the implications for anthropogenic disturbance of odontocetes.

Understanding the impacts of foraging disruptions to odontocete body condition is fundamental to quantifying biological effects of human disturbance and environmental changes on cetacean populations. Here, reductions in body volume of free-ranging pygmy killer whales (Feresa attenuata) were calculated using repeated measurements of the same individuals obtained through Unoccupied Aerial System (UAS)-photogrammetry during a prolonged disruption in foraging activity arising from a 21-day stranding event. Stranded individuals were used to verify UAS-derived volume and length estimates through 3D-imaging, water displacement, and post-mortem measurements. We show that (a) UAS estimates of length were within 1.5% of actual body length and UAS volume estimates were within 10-13% of actual volume, (b) foraging disruption resulted in a daily decrease of 2% of total body mass/day, and (c) pygmy killer whales can lose up to 27% of their total body weight within 17 days. These findings highlight the use of UAS as a promising new method to remotely monitor changes in body condition and animal health, which can be used to determine the potential effects of anthropogenic disturbance and environmental change on free-ranging odontocetes.

Identifying priority habitat for conservation and management of Australian humpback dolphins within a marine protected area.

Increasing human activity along the coast has amplified the extinction risk of inshore delphinids. Informed selection and prioritisation of areas for the conservation of inshore delphinids requires a comprehensive understanding of their distribution and habitat use. In this study, we applied an ensemble species distribution modelling approach, combining results of six modelling algorithms to identify areas of high probability of occurrence of the globally Vulnerable Australian humpback dolphin in northern Ningaloo Marine Park (NMP), north-western Australia. Model outputs were based on sighting data collected during systematic, boat-based surveys between 2013 and 2015, and in relation to various ecogeographic variables. Water depth and distance to coast were identified as the most important variables influencing dolphin presence, with dolphins showing a preference for shallow waters (5-15 m) less than 2 km from the coast. Areas of high probability (> 0.6) of dolphin occurrence were primarily (90%) in multiple use areas where extractive human activities are permitted, and were poorly represented in sanctuary (no-take) zones. This spatial mismatch emphasises the need to reassess for future spatial planning and marine park management plan reviews for NMP. Shallow, coastal waters identified here should be considered priority areas for the conservation of this Vulnerable species.

Anthropogenic Threats to Wild Cetacean Welfare and a Tool to Inform Policy in This Area.

Human activities and anthropogenic environmental changes are having a profound effect on biodiversity and the sustainability and health of many populations and species of wild mammals. There has been less attention devoted to the impact of human activities on the welfare of individual wild mammals, although ethical reasoning suggests that the welfare of an individual is important regardless of species abundance or population health. There is growing interest in developing methodologies and frameworks that could be used to obtain an overview of anthropogenic threats to animal welfare. This paper shows the steps taken to develop a functional welfare assessment tool for wild cetaceans (WATWC) via an iterative process involving input from a wide range of experts and stakeholders. Animal welfare is a multidimensional concept, and the WATWC presented made use of the Five Domains model of animal welfare to ensure that all areas of potential welfare impact were considered. A pilot version of the tool was tested and then refined to improve functionality. We demonstrated that the refined version of the WATWC was useful to assess real-world impacts of human activity on Southern Resident killer whales. There was close within-scenario agreement between assessors as well as between-scenario differentiation of overall welfare impact. The current article discusses the challenges raised by assessing welfare in scenarios where objective data on cetacean behavioral and physiological responses are sparse and proposes that the WATWC approach has value in identifying important information gaps and in contributing to policy decisions relating to human impacts on whales, dolphins, and porpoises.

Morphological differences between coastal bottlenose dolphin (Tursiops aduncus) populations identified using non-invasive stereo-laser photogrammetry.

Obtaining morphometric data on free-ranging marine megafauna is difficult, as traditional methods rely on post-mortem or live-capture techniques. We linked stereo-laser photogrammetry with long-term demographic data to compare length-at-age (LaA) growth curves of two well-studied populations of Indo-Pacific bottlenose dolphins (Tursiops aduncus) in south-western (SW) and Shark Bay (SB), mid-western Australia. First, we determined the relationship between total length (TL) and blowhole-to-dorsal fin (BH-DF) length from post-mortem subjects (R2 = 0.99, n = 12). We then predicted TL from laser-derived BH-DF measurements of 129 and 74 known-age individuals in SW and SB, respectively. Richards growth models best described our LaA data. While birth length (103-110 cm) was similar between study regions, TL estimates at 1, 3, 12, and 25 years differed significantly (p < 0.001). Asymptotic length of adult males (SW = 246 cm, SB = 201 cm) and females (SW = 244 cm, SB = 200 cm) also differed significantly. Morphotypic variations likely reflect regional adaptations to local water temperatures, with the temperate SW having cooler waters than sub-tropical SB. We demonstrate the effectiveness of a non-invasive technique to understand ecological, demographic and life-history characteristics of long-lived marine megafauna, which are critical parameters for informing conservation and management actions.

Is MHC diversity a better marker for conservation than neutral genetic diversity? A case study of two contrasting dolphin populations.

Genetic diversity is essential for populations to adapt to changing environments. Measures of genetic diversity are often based on selectively neutral markers, such as microsatellites. Genetic diversity to guide conservation management, however, is better reflected by adaptive markers, including genes of the major histocompatibility complex (MHC). Our aim was to assess MHC and neutral genetic diversity in two contrasting bottlenose dolphin (Tursiops aduncus) populations in Western Australia-one apparently viable population with high reproductive output (Shark Bay) and one with lower reproductive output that was forecast to decline (Bunbury). We assessed genetic variation in the two populations by sequencing the MHC class II DQB, which encompasses the functionally important peptide binding regions (PBR). Neutral genetic diversity was assessed by genotyping twenty-three microsatellite loci. We confirmed that MHC is an adaptive marker in both populations. Overall, the Shark Bay population exhibited greater MHC diversity than the Bunbury population-for example, it displayed greater MHC nucleotide diversity. In contrast, the difference in microsatellite diversity between the two populations was comparatively low. Our findings are consistent with the hypothesis that viable populations typically display greater genetic diversity than less viable populations. The results also suggest that MHC variation is more closely associated with population viability than neutral genetic variation. Although the inferences from our findings are limited, because we only compared two populations, our results add to a growing number of studies that highlight the usefulness of MHC as a potentially suitable genetic marker for animal conservation. The Shark Bay population, which carries greater adaptive genetic diversity than the Bunbury population, is thus likely more robust to natural or human-induced changes to the coastal ecosystem it inhabits.

Acoustic crypsis in southern right whale mother-calf pairs: infrequent, low-output calls to avoid predation?

Southern right whales (Eubalaena australis) invest substantial amounts of energy in their calves, while facing the risk of having them predated upon by eavesdropping killer whales (Orcinus orca). We tested the hypothesis that southern right whale mother-calf pairs employ acoustic crypsis to reduce acoustic detectability by such predators. Specifically, we deployed multi-sensor DTAGs on nine lactating whales for a total of 62.9 h in a Western Australian breeding ground, and used a SoundTrap to estimate the concomitant acoustic background noise. Vocalisations were recorded at low rates of <10 calls h-1 (1 call per dive) and at low received levels between 123±8 and 134±10 dB re. 1 µPa RMS depending on call type. We conclude that such acoustic crypsis in southern right whales and other baleen whales decreases the risk of alerting potential predators and hence jeopardizing a substantial energetic investment by the mother.

Chronic exposure of Hawaii Island spinner dolphins (Stenella longirostris) to human activities.

Habitat selection is strongly influenced by spatial variations in habitat quality and predation risk. Repeated exposure of wildlife to anthropogenic activities in important habitats may affect habitat selection, leading to negative biological consequences. We quantified the cumulative human exposure of a small, genetically isolated and behaviourally constrained spinner dolphin (Stenella longirostris) population, off Hawaii Island, and exposure effects on their daytime cumulative activity budget. Dolphins were exposed to human activities within 100 m for 82.7% of the daytime, with a median duration of 10 min between exposure events. Individual dolphins spent on average 61.7% (s.d. = 6.5) of their daytime resting. Of their total rest time, greater than 90% occurred inside sheltered bays. Despite high levels of human exposure, we did not observe an effect on dolphin resting behaviour. The short intervals between exposure events probably prevent dolphins from returning to a natural resting state before the next event. Consequently, 'control' observations may represent a resting behaviour of a more vigilant nature. Chronic levels of exposure to human activities could lead to rest deprivation, displacement from preferred resting habitats and ultimately negative population level effects. These results have implications for new proposed legislation aiming to reduce dolphin exposure to human activities.

Implications of survey effort on estimating demographic parameters of a long-lived marine top predator.

Effective management of wildlife populations rely on knowledge of their abundance, survival, and reproductive rates. Maintaining long-term studies capable of estimating demographic parameters for long-lived, slow-reproducing species is challenging. Insights into the effects of research intensity on the statistical power to estimate demographic parameters are limited. Here, we investigate implications of survey effort on estimating abundance, home range sizes, and reproductive output of Indo-Pacific bottlenose dolphins (Tursiops aduncus), using a 3-year subsample of a long-term, capture-recapture study off Bunbury, Western Australia. Photo-identification on individual dolphins was collected following Pollock's Robust Design, where seasons were defined as "primary periods", each consisting of multiple "secondary periods." The full dataset consisted of 12 primary periods and 72 secondary periods, resulting in the study area being surveyed 24 times/year. We simulated reduced survey effort by randomly removing one, two, or three secondary periods per primary period. Capture-recapture models were used to assess the effect of survey intensity on the power to detect trends in population abundance, while individual dolphin sighting histories were used to assess the ability to conduct home range analyses. We used sighting records of adult females and their calving histories to assess survey effort on quantifying reproductive output. A 50% reduction in survey effort resulted in (a) up to a 36% decline in population abundance at the time of detection; (b) a reduced ability to estimate home range sizes, by increasing the time for individuals to be sighted on ≥30 occasions (an often-used metric for home range analyses) from 7.74 to 14.32 years; and (c) 33%, 24%, and 33% of annual calving events across three years going undocumented, respectively. Results clearly illustrate the importance of survey effort on the ability to assess demographic parameters with clear implications for population viability analyses, population forecasting, and conservation efforts to manage human-wildlife interactions.

Microplastics: No Small Problem for Filter-Feeding Megafauna.

Microplastic pollution can impact filter-feeding marine megafauna, namely mobulid rays, filter-feeding sharks, and baleen whales. Emerging research on these flagship species highlights potential exposure to microplastic contamination and plastic-associated toxins. Research and its wide communication are needed to understand the magnitude of the issue and improve marine stewardship.

Demographic collapse and low genetic diversity of the Irrawaddy dolphin population inhabiting the Mekong River.

In threatened wildlife populations, it is important to determine whether observed low genetic diversity may be due to recent anthropogenic pressure or the consequence of historic events. Historical size of the Irrawaddy dolphin (Orcaella brevirostris) population inhabiting the Mekong River is unknown and there is significant concern for long-term survival of the remaining population as a result of low abundance, slow reproduction rate, high neonatal mortality, and continuing anthropogenic threats. We investigated population structure and reconstructed the demographic history based on 60 Irrawaddy dolphins samples collected between 2001 and 2009. The phylogenetic analysis indicated reciprocal monophyly of Mekong River Orcaella haplotypes with respect to haplotypes from other populations, suggesting long-standing isolation of the Mekong dolphin population from other Orcaella populations. We found that at least 85% of all individuals in the two main study areas: Kratie and Stung Treng, bore the same mitochondrial haplotype. Out of the 21 microsatellite loci tested, only ten were polymorphic and exhibited very low levels of genetic diversity. Both individual and frequency-based approaches suggest very low and non-significant genetic differentiation of the Mekong dolphin population. Evidence for recent bottlenecks was equivocal. Some results suggested a recent exponential decline in the Mekong dolphin population, with the current size being only 5.2% of the ancestral population. In order for the Mekong dolphin population to have any potential for long-term survival, it is imperative that management priorities focus on preventing any further population fragmentation or genetic loss, reducing or eliminating anthropogenic threats, and promoting connectivity between all subpopulations.