Lars Bejder

Understanding reproductive performance is essential for assessing the viability of small, threatened marine mammal populations in degraded coastal ecosystems. The bottlenose dolphin Tursiops...

North Pacific humpback whales are a celebrated conservation success, rebounding from extensive commercial whaling. Yet they remain vulnerable to the impacts of climate change, a multifaceted stressor that can exacerbate existing threats. During 2013–2016, a Northeast Pacific marine heatwave severely reduced forage availability in their feeding grounds, concurrent with diminished whale recruitment and increased mortality. We analyzed photo‐identification data of whales that visited the Main Hawaiian Islands from 2002 to 2023 to estimate apparent survival, abundance, and distinct population segment (DPS) growth rates. Survival was high prior to (0.987; SE = 0.003), low during (0.684; SE = 0.022), and higher, but still reduced, after (0.956; SE = 0.006) the heatwave. Annual breeding season abundance estimates averaged 11,617 (SD = 1914) and included a striking 37% decrease from 2014/15 to 2021/22. While the average annual DPS growth rate was stable (1.00) over 20 breeding seasons, shorter periods included high growth (1.09) and steep decline (0.783). Depressed survival and abundance estimates may signal lingering heatwave effects or adjustment to current carrying capacity. Climate change predictions include more frequent, intense, and longer heatwaves; thus, this DPS serves as a crucial ecosystem‐health indicator. Continued research and monitoring are essential to support resiliency against future climate perturbations.

Quantifying energy expenditure of cetacean mother–calf pairs is essential for modelling population-level responses to environmental change and anthropogenic disturbance, especially for capital breeders where mothers face the compounding demands of fasting while lactating. Technological advances in biologging and unoccupied aerial system (UAS; drone) photogrammetry help overcome challenges in translating respirometry methods from animals under human care to the field, creating better energy-use estimates in large cetaceans. We quantified energy expenditure of humpback whale (Megaptera novaeangliae) mothers and calves on their winter breeding ground in Hawaiʻi using 51 biologging suction-cup tag deployments paired with simultaneous UAS-photogrammetric measurements (n = 20 mothers, n = 31 calves) from 2020 to 2025. We used two independent methods, Thrust Power and Breathing Frequency, to calculate per-second energy expenditure, divided deployments into resting dives and other behavioural states and modelled state-specific energy use and daily energy expenditure for mothers and calves. Calves spent more time in resting dives as they aged, and energy expenditure was on average 44% and 35% lower during resting dives for mothers and calves, respectively, compared to other behaviour. Simulated daily energy expenditure for calves ranged from 92 MJ for the smallest and youngest (3.5 m, 1 day) to 452 MJ for the largest and oldest (7.7 m, 110 days), and for mothers from 817 MJ for small females (10 m, 15 000 kg) to 2013 MJ for large females (14 m, 50 000 kg). To illustrate the conservation implications of these energy savings, we simulated the energetic cost of vessel-disturbance-induced reductions in resting behaviour for a representative mother–calf pair. Under a realistic daytime disturbance scenario, daily pair energy expenditure increased by 64 MJ day⁻¹, accumulating to an additional 150 kg of maternal blubber catabolized over 60 days of disturbance. Our findings provide best estimates of humpback whale mother–calf daily and behavioural state-specific energy expenditure, enabling improved quantification of the energetic consequences of disturbance.

Movement is energetically expensive, and locomotor efficiency depends on body size and morphology. Humpback whales Megaptera novaeangliae exhibit a remarkable ontogenetic size range and experience periods of intense fasting coinciding with energetically demanding migration, lactation, and growth. To quantify how propulsive costs scale with body size, we combined accelerometry data and aerial photogrammetry collected from 62 humpback whales ranging from calves to adults (4.4-14.1 m) on their Hawaiian breeding ground. Using a hydrodynamic model incorporating swimming kinematics and morphology, we found that mass-specific propulsive costs declined with increasing body length, representing a 62% reduction between a 4 m calf and a 14 m adult. Elevated activity levels and higher mass-specific propulsive costs in calves energetically burden lactating females, whose energy reserves must support both calf activity and rapid somatic growth. These energetic demands are buffered by the female’s own reduced activity and mass-specific propulsive costs. We estimate that propulsion accounts for approximately 21% of a lactating female’s daily energetic expenditure while on the breeding grounds. Our approach highlights the disproportionately higher cost of displacement in smaller individuals, ranging from approximately 4 kJ m ^-1 in calves to 25 kJ m ^-1 in adults, providing a scalable framework to quantify the energetic consequences of disturbance. These findings underscore the importance of large body size in baleen whales, refine understanding of how activity costs scale across body size in humpback whales on their breeding grounds, and provide an energetic baseline to predict consequences of environmental and anthropogenic disturbance.

Body condition is a critical indicator of health and nutritional status in cetaceans, particularly for small, endangered populations facing ecological stressors. We used aerial photogrammetry to evaluate body size and condition of the endangered false killer whale Pseudorca crassidens population resident in the main Hawaiian Islands. From 2019 to 2025, 68 individuals were assessed across 142 photogrammetric measurements. Relative body width declined with age class, particularly across the mid-body region, indicating early-life lipid accumulation followed by increased energetic demands in adulthood. Photogrammetric volume estimates were validated against 3D-scanned individuals, providing estimates within 3% of scanned volumes. Standardized major axis regression revealed significant differences in the body length-volume relationship across social clusters. Body condition index (BCI) varied across years, with the lowest values in 2020, coinciding with the largest single-year population decline and record sea surface temperatures from a marine heatwave, suggesting that environmental stressors may have contributed to reduced body condition during this period. Individual-level trajectories further highlighted substantial fluctuations in BCI, including one case of 28% estimated body mass loss over a 2.5 mo period, and pronounced variability within one cluster, potentially reflecting higher energetic costs and nutritional stress associated with broader ranging behavior. These findings underscore the influence of spatial ecology and local prey availability on the health of this declining population, while providing a foundation for long-term monitoring of the energetic stressors shaping their viability.

Marine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species’ vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at‐sea threats. The threats we considered included individual fishing gear types, climate‐change‐related subthreats not previously assessed, and threats associated with coastal impacts and maritime disturbances. Our ratings resulted in 70 species having high vulnerability ( v > 0.778 out of 1) to at least 1 threat, primarily drifting longlines, temperature extremes, or fixed gear. These 3 threats were also considered to have the most severe effects (i.e., steepest population declines). Overall, temperature extremes and plastics and other solid waste were rated as affecting the largest proportion of populations. Penguins, pinnipeds, and polar bears had the highest vulnerability to temperature extremes. Bony fishes had the highest vulnerability to drifting longlines and plastics and other solid waste; pelagic cetaceans to 4 maritime disturbance threats; elasmobranchs to 5 fishing threats; and flying birds to drifting longlines and 2 maritime disturbance threats. Sirenians and turtles had the highest vulnerability to at least one threat from all 4 categories. Despite not necessarily having severe effects for most taxonomic groups, temperature extremes were rated among the top threats for all taxa except bony fishes. The vulnerability scores we provide are an important first step in estimating the risk of threats to marine megafauna. Importantly, they help differentiate scope from severity, which is key to identifying threats that should be prioritized for mitigation.

Hawaiian monk seals (HMS; Neomonachus schauinslandi ) are endemic and endangered with a population of approximately 1600 individuals. While research has provided extensive information on HMS biology, movements and population ecology, its underwater vocal behaviour remains largely undocumented, with previous descriptions limited to two individuals in human care. To broaden our understanding of sound production in free-ranging seals, we deployed passive acoustic recorders at five sites across the Hawaiian archipelago. From >4500 h of recordings, we manually detected and classified >23 000 underwater vocalizations. A discriminant function analysis of 10 call types yielded an average correct classification rate of 63%. We identified 25 call types, including five published elemental calls and 20 novel calls. Nineteen of the novel call types were combinational calls—an undocumented communication strategy in pinnipeds. The novel Whine , captured via biologging tag- and citizen-scientist videos, provided a rare example of context-specific call use in pinnipeds. Vocalizations were low frequency (<1 kHz), short–medium duration (<7 s), with 66% occurring in bouts. Calls were detected throughout the day at three of five sites, with peaks at night and late afternoon. These findings establish a baseline for HMS vocal behaviour and emphasize the importance of acoustic communication in future research and conservation efforts.

Diving is one of the most important behaviors undertaken by marine mammals. Pilot whales (Globicephala spp.) are oceanic dolphins that regularly forage at extreme depths (∼600–1000 m) and maintain body sizes similar to beaked whales. They are also listed as data deficient, with little known about their population dynamics. To help fill this knowledge gap, we estimated their energetic demands through a combination of multiple data streams (e.g. unoccupied aerial systems photogrammetry, high-resolution accelerometry tag data, stomach content analysis and long-duration dive data from satellite tags) from short-finned pilot whales (Globicephala macrorhynchus) in Hawaiian waters. We estimated and compared pilot whale field metabolic rates from breathing frequency against a more granular cost of transport method developed from morphometrics and swimming kinematics, finding that these methods gave similar estimates of energetic expenditure during foraging dives. We then combined expenditure and intake estimates into an exploratory model of daily net energetic balance. Using an estimate of prey size derived from squid beaks collected from a stranded animal, we found that an average of 142±59.8 squid day−1 (52,000±21,800 squid year−1) is enough for an average adult short-finned pilot whale to reach a neutral net energetic balance. This species has an estimated population abundance of ∼8000 individuals in Hawaiian waters, suggesting that the population as a whole would require 416±175 million squid (at an average of 559±126 kJ squid−1) or approximately 88,000±37,000 tonnes of squid annually, assuming similar energetic requirements for each animal.