John A. Totterdell

A predator’s capacity to adapt to environmental change underpins success in modern oceans, particularly within the highly dynamic marine realm facing both natural and human-driven variability....

Aim: Killer whales, Orcinus orca , are cosmopolitan top predators showing highly variable ecology and behaviour across populations. In the Indo‐Pacific, baseline knowledge in general remains scarce, limiting the assessment of their vulnerability to the accelerated environmental changes, including expanding fisheries this region is undergoing. Methodology: This review synthesises 170 sources found between 2000–2025 to evaluate the current knowledge on distribution, population structure, and feeding ecology (including depredation) of killer whales in the Indo‐Pacific, and to identify priorities for future research and management. Results: Occurrence was highly variable, from sporadic sightings in most tropical sectors to seasonal and year‐round presence at temperate and sub‐Antarctic hotspots, reflecting ecological heterogeneity and sampling bias. Seven distinct populations or forms have been confirmed in sub‐Antarctic and temperate regions, but observation and photo‐identification data suggest additional populations. Their connectivity and the presence of putative ecologically and genetically distinct forms remain unresolved. Sixty‐eight prey species were confirmed as taken naturally, notably elasmobranchs, cetaceans, and fish. Generalist diets emerged as a possible dominant pattern although robust dietary inference was concentrated at a few sites. Sixteen species were confirmed as taken through depredation on 17 fisheries, with highly variable rates of interaction with fishing vessels being possibly explained by varying overlaps with killer whale occurrence and diet. Major gaps were identified in killer whale photo‐identification data, genetic sampling, and reporting of interactions with small‐scale fisheries and should be addressed to improve management and conservation of killer whales in the Indo‐Pacific.

Understanding population demographics is crucial for the effective conservation of species. This is particularly important for apex predators, such as the killer whale ( Orcinus orca ), which play important roles in maintaining the structure and function of ecosystems. In this study, we used capture‐mark‐recapture (CMR) modeling to assess killer whale demographics at two distinct aggregation sites in Western Australia: the Ningaloo Reef (NW) and Bremer Sub‐basin (SW). Using 12 years of photo‐identification (photo‐ID) data from the NW and 6 years from the SW, we applied open population models (POPAN and Cormack–Jolly–Seber) to estimate the abundance ( N _total ), apparent survival ( Phi ), capture probability ( p ), and probability of entry ( pent ) of killer whales inhabiting these key areas. Abundance estimates in the NW, which combined females, males, and individuals of unknown sex ( N _total = 47 ± 2, 95% CI = 43–52), revealed a small, well‐marked, and frequently resighted population with high apparent survival ( Phi _female = 0.98 ± 0.016, 95% CI = 0.91–0.99; Phi _male = 0.88 ± 0.060, 95% CI = 0.71–0.96; Phi _unknown = 0.82 ± 0.064, 95% CI = 0.66–0.92). In contrast, abundance estimates in the SW, which separated sexed adults ( N _total = 102 ± 7, 95% CI = 88–117) from the unknown sex group, suggested a much larger and more transient population with variable apparent survival ( Phi _female = 0.98 ± 0.001, 95% CI = 0.97–0.98; Phi _male = 0.82 ± 0.012, 95% CI = 0.79–0.84; Phi _unknown(T) = 0.65 ± 0.177, 95% CI = 0.29–0.90; Phi _unknown(R) = 0.84 ± 0.185, 95% CI = 0.26–0.99). Variation in population demography between the two study areas likely reflects divergent ecological and evolutionary histories shaped by both genetic and environmental factors. Additionally, differences in habitat accessibility, individual distinctiveness, and sampling design may have influenced detectability and model outcomes. These results provide vital baseline demographic data for killer whales in Australian waters and highlight the need for standardized long‐term monitoring to inform conservation management strategies.

Morphological variation within and among species plays a critical role in evolutionary processes, influencing adaptation, survival, and reproductive success. Killer whale ( Orcinus orca ) morphology is known to vary on both an individual and population level with several ecotypes or forms documented worldwide. However, the extent of morphological variation among killer whales in Australian waters remains unclear, both among individuals within the region and in comparison to those in other parts of the southern hemisphere. This study assessed eye patch and dorsal fin shape variation in Australian and Antarctic killer whales to explore the evolutionary relationships among these groups. A large dataset of imagery was compiled and processed to achieve this, which provided representative sample sizes for five separate study groups: northwest Australia (NW), southwest Australia (SW), southeast Australia (SE), Antarctic type A (AA) and Antarctic type B1 (AB). Elliptical Fourier analysis was used to extract the feature outlines and enable multivariate data analyses. Principal component analysis and pairwise comparisons revealed significant morphological differences both within and between Australian and Antarctic killer whales. Eye patch shape variation was driven by the degree of taper and overall width whereas dorsal fin shape variation was driven by falcateness and broadness at its base. Hierarchical cluster analysis revealed considerable variation amongst these features, while linear discriminate analysis indicated that individuals could not be reliably classified into their respective study groups based on eye patch and dorsal fin shape alone. Nonetheless, these findings suggest the presence of both a tropical and temperate form of killer whale in Australia, with the latter resembling both the Antarctic Type A and B2s morphologically. To better understand their connectivity and divergence, dedicated research is needed to assess the evolutionary history of these populations. Such knowledge will be vital in defining global conservation management units for killer whales which are still considered a single, data deficient species by the International Union for Conservation of Nature (IUCN).

The killer whale ( Orcinus orca ) is a globally distributed apex predator. This species is represented by distinct ecotypes or forms, which are well documented in the Northern Hemisphere and Antarctica. However, less is known about killer whales in Australia. While research efforts have been made to study these animals, a broader understanding of their range and drivers of occurrence is lacking. In this study, we model the spatial distribution of killer whales in Australian waters to identify potential areas of habitat suitability and conservation priority. A total of 1310 sightings were compiled, of which 1115 were used alongside a suite of static and dynamic predictor variables to build presence‐only MaxEnt species distribution models (SDMs) in three separate study areas: southeast (SE), southwest (SW) and northwest (NW) Australia. The SDMs identified potential areas of habitat suitability both within and outside of known locations for killer whales in Australia. All three models returned good discriminative power between presence and background points. However, good predictive power was only suggested for the SE and NW. The importance of certain predictor variables indicated a preference for different environmental conditions, supporting the notion of at least two ecologically distinct groups. Killer whales frequenting the SE and SW preferred temperate waters, whereas those in the NW preferred tropical waters. This work greatly increases our understanding of killer whales in Australian waters and identifies potential areas of biological importance for management and monitoring. It also complements ongoing research into their genetics, feeding ecology, and diversification, showcases the utility of citizen science data, and informs the conservation of this species, which is still considered data deficient and remains to be adequately protected under Australian Government legislation.

Admixture is the exchange of genetic variation between differentiated demes, resulting in ancestry within a population coalescing in multiple ancestral source populations. Low‐latitude killer whales ( Orcinus orca ) populations typically have higher genetic diversity than those in more densely populated, high productivity and high‐latitude regions. This has been hypothesized to be due to episodic admixture between populations with distinct genetic backgrounds. We test this hypothesis by estimating variation in local ancestry of whole genome sequences from three genetically differentiated, low‐latitude killer whale populations and comparing them to global genetic variation. We find ‘Antarctic‐like’ ancestry tracts in the genomes of southwestern Australia (SWA) population including recent (within the last 2–4 generations) admixture. Admixed individuals had, on average, shorter and fewer runs of homozygosity than unadmixed individuals and increased effective population size ( N _e ). Thus, connectivity between demes results in the maintenance of N _e of relatively small demes at a level comparable to the sum of N _e across demes. A subset of the admixed regions was inferred to be evolving under selection in the SWA population, suggesting that this admixed variation may be contributing to the population's adaptive potential. This study provides important and rare empirical evidence that small populations can maintain genetic diversity due to sporadic admixture between different genetic backgrounds and that admixed ancestry can promote the long‐term stability of N _e .

Cooperative hunting between humans and killer whales (Orcinus orca) targeting baleen whales was reported in Eden, New South Wales, Australia, for almost a century. By 1928, whaling operations had ceased, and local killer whale sightings became scarce. A killer whale from the group, known as “Old Tom,” washed up dead in 1930 and his skeleton was preserved. How these killer whales from Eden relate to other populations globally and whether their genetic descendants persist today remains unknown. We extracted and sequenced DNA from Old Tom using ancient DNA techniques. Genomic sequences were then compared with a global dataset of mitochondrial and nuclear genomes. Old Tom shared a most recent common ancestor with killer whales from Australasia, the North Atlantic, and the North Pacific, having the highest genetic similarity with contemporary New Zealand killer whales. However, much of the variation found in Old Tom’s genome was not shared with these widespread populations, suggesting ancestral rather than ongoing gene flow. Our genetic comparisons also failed to find any clear descendants of Tom, raising the possibility of local extinction of this group. We integrated Traditional Custodian knowledge to recapture the events in Eden and recognize that Indigenous Australians initiated the relationship with the killer whales before European colonization and the advent of commercial whaling locally. This study rectifies discrepancies in local records and provides new insight into the origins of the killer whales in Eden and the history of Australasian killer whales.

Genome sequences can reveal the extent of inbreeding in small populations. Here, we present the first genomic characterization of type D killer whales, a distinctive eco/morphotype with a circumpolar, subantarctic distribution. Effective population size is the lowest estimated from any killer whale genome and indicates a severe population bottleneck. Consequently, type D genomes show among the highest level of inbreeding reported for any mammalian species (F_ROH ≥ 0.65). Detected recombination cross-over events of different haplotypes are up to an order of magnitude rarer than in other killer whale genomes studied to date. Comparison of genomic data from a museum specimen of a type D killer whale that stranded in New Zealand in 1955, with 3 modern genomes from the Cape Horn area, reveals high covariance and identity-by-state of alleles, suggesting these genomic characteristics and demographic history are shared among geographically dispersed social groups within this morphotype. Limitations to the insights gained in this study stem from the nonindependence of the 3 closely related modern genomes, the recent coalescence time of most variation within the genomes, and the nonequilibrium population history which violates the assumptions of many model-based methods. Long-range linkage disequilibrium and extensive runs of homozygosity found in type D genomes provide the potential basis for both the distinctive morphology, and the coupling of genetic barriers to gene flow with other killer whale populations.