Killer Whales Orcinus Orca Research Articles

Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 549:263-274 (2016) - DOI: https://doi.org/10.3354/meps11676 Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean Ryan R. Reisinger1,5,*, Darren R. Gröcke2, Nico Lübcker1, Erin L. McClymont3, A. Rus Hoelzel4, P. J. Nico de Bruyn1 1Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Private Bag X20, Hatfield 0028, Pretoria, South Africa 2Department of Earth Sciences, Durham University, South Road, Durham DH1 3LE, UK 3Department of Geography, Durham University, South Road, Durham DH1 3LE, UK 4School of Biological and Biomedical Sciences, Durham University, South Road, Durham DH1 3LE, UK 5Present address: Department of Zoology, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa *Corresponding author: ryan.r.reisinger@gmail.com ABSTRACT: Diet seems to be a key factor driving diversity and isolation among killer whale populations. Killer whales at Marion Island, Southern Ocean, have been observed preying on seals and penguins but are also know to depredate Patagonian toothfish from longline fishing vessels. However, their diet is poorly known especially when they occur offshore. We analysed carbon and nitrogen stable isotope ratios in 32 skin samples collected from 24 killer whales belonging to 8 social units. Adult males showed higher δ15N values than adult females or subadults, indicating that they occupy a higher relative trophic level. There were no significant differences in δ13C among social units, but δ15N differed significantly and 2 individuals from social units which have been observed depredating Patagonian toothfish had higher δ15N values. The inshore presence of killer whales at Marion Island was a significant predictor of δ13C values, but not of δ15N values. This suggests some foraging north of Marion Island, potentially on lower trophic level prey. We also analysed tissue samples from seal, penguin and Patagonian toothfish prey and used available values for Antarctic fur seals. Results show that killer whales around Marion Island are apex predators, but that they do not feed exclusively on other high trophic level predators such as elephant seals, fur seals, and Patagonian toothfish. Killer whales had δ15N values similar to those of Patagonian toothfish and adult male elephant seals, implying that the diet of killer whales at Marion Island includes some lower trophic level prey such as cephalopods or fishes. KEY WORDS: Predator · Stable isotopes · Carbon · δ13C · Nitrogen · δ15N · Foraging · Trophic level Full text in pdf format Supplementary material PreviousNextCite this article as: Reisinger RR, Gröcke DR, Lübcker N, McClymont EL, Hoelzel AR, de Bruyn PJN (2016) Variation in the diet of killer whales Orcinus orca at Marion Island, Southern Ocean. Mar Ecol Prog Ser 549:263-274. https://doi.org/10.3354/meps11676 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 549. Online publication date: May 10, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

An Unparalleled Sexual Dimorphism of Sperm Whale Encephalization

The sperm whale Physeter macrocephalus (Linnaeus, 1758) is the largest toothed whales and possesses the highest absolute values for brain weight on the planet (together with the killer whale Orcinus orca). Former calculations of the encephalization quotient (EQ), which is used to compare brain size of different mammalian species, showed that the sperm whale brain is smaller than expected for its body mass. However, the data reported in the literature and formerly used to calculate the sperm whale EQ suffered from a potential bias due to the tendency to measure mostly larger males of this extreme sexually dimorphic species. Accordingly, we found that the brains of female sperm whales are close to the absolute weight range of the males, but, given the much lower body mass of females, their EQ results more than double of what reported before for the whole species, and is thus nearly into the primate range (female EQ = 1.28, male EQ = 0.56). This sexual dimorphism is unique among mammals. Female sperm whales live in large families in which social interactions and inter-individual communication are essential, while adult males live solitarily. Thus the particular sex-specific behavior of SWs may have led to a maternally-driven social evolution, and eventually contributed to achieve female EQ values (but not male EQs) among the highest ever calculated for mammals with respect to their large body mass.

Reproductively isolated ecotypes of killer whales Orcinus orca in the seas of the Russian Far East

Two ecotypes of killer whales—fish-eating and mammal-eating—have been found in the seas of the Russian Far East, but confirmation of their status required genetic studies of animals with known phenotype and foraging specialization. In this paper we combine the results of the analysis of nuclear genetic markers, isotopic composition of tissues and phenetic feature (shape of the saddle patch) of killer whales from different regions of Far Eastern seas. Analysis of allelic composition of 9 microsatellite loci of the nuclear DNA divided the samples into two distinct clusters with the divergence between them high enough to indicate reproductive isolation. The content of nitrogen stable isotope 15N in tissues of whales from the first cluster was significantly lower than that of the second cluster. The difference of δ15N values between individuals from different clusters was about 3‰, which corresponds to the difference between adjacent trophic levels. Apparently, the first cluster comprised fish-eating, and the second—mammal-eating animals. The ratio of saddle patch shape types also differed between the clusters. Whales from the first cluster had five types of patch shape in different proportions, while whales from the second cluster had only “smooth” saddle patches. The differences between the clusters were statistically significant. Thus, killer whales from the seas of the Russian Far East comprise at least two reproductively isolated clusters with stable ecological and morphological differences, that is, two different ecotypes—fish-eating and mammal-eating. Different ecotypes of killer whales should be managed separately during abundance surveys, monitoring, evaluation of human impact and estimates of total allowed takes from the wild populations.

Ecological Knowledge, Leadership, and the Evolution of Menopause in Killer Whales

Summary Classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction [1]. Yet, human females routinely live 30 years after they have stopped reproducing [2]. Only two other species—killer whales ( Orcinus orca ) and short-finned pilot whales ( Globicephala macrorhynchus ) [3, 4]—have comparable postreproductive lifespans. In theory, menopause can evolve via inclusive fitness benefits [5, 6], but the mechanisms by which postreproductive females help their kin remain enigmatic. One hypothesis is that postreproductive females act as repositories of ecological knowledge and thereby buffer kin against environmental hardships [7, 8]. We provide the first test of this hypothesis using a unique long-term dataset on wild resident killer whales. We show three key results. First, postreproductively aged females lead groups during collective movement in salmon foraging grounds. Second, leadership by postreproductively aged females is especially prominent in difficult years when salmon abundance is low. This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales [9, 10]. Third, females are more likely to lead their sons than they are to lead their daughters, supporting predictions of recent models [5] of the evolution of menopause based on kinship dynamics. Our results show that postreproductive females may boost the fitness of kin through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female resident killer whales and humans continue to live long after they have stopped reproducing.

Seasonal movements of killer whales between Iceland and Scotland

Understanding the movements and distribution of killer whales Orcinus orca is important for evaluating the threats they face, as well as their impact as top predators in different ecosystems. Killer whales in the Northeast Atlantic are thought to follow specific prey stocks but their seasonal movements are still poorly understood. Here, we used recent killer whale photo- graphic data collected in Iceland and Scotland to show that some individual whales repeatedly move between these locations. Unlike other killer whales that appear to follow the movements of particular herring stocks, the whales we studied appear to feed on the Icelandic summer-spawning herring stock in winter, and then move outside the summer distribution range of this herring stock. Based on these new photographic recaptures and previously published movements of killer whales between Iceland and Scotland, we infer that movements between both locations have been occurring for several years at least. Although based on only 7 identified individuals, our results provide the first evidence of regular seasonal movements between Iceland and Scotland, and suggest individual or group variability in the movement patterns of killer whales that prey on herring. Understanding killer whale movements will aid our understanding of prey specialization, the whales' potential impacts on local prey resources, and their susceptibility to fluctuations in the availability of different prey species.

On factors for separation of the stock of beluga whale <i>Delphinapterus leucas</i> in the Anadyr Gulf of the Bering Sea

New eco-ethological data on the Anadyr stock of beluga whales are presented based on 14-year (2000-2013) studies by methods of satellite tracking telemetry, multi-spectral aerial surveys and genetic analysis, as well as traditional and ecosystem-based approaches. Possible factors of the separate stock formation in the Anadyr Gulf are discussed, as geographic isolation, environmental conditions, foraging resources, elimination of the beluga whales, and biological isolation (on the results of genetic analysis). The beluga whales are well-adapted to oceanographic conditions and ice regime of the Arctic waters that is realized in their relationship with edge of the sea ice, ability to live in both salt and fresh waters (they enter rivers), and versatility in feeding. Their ice-associating, high sociality, and white protective coloration provide protection against killer whales and other predators and their eury-halinity allows to expand the feeding grounds both to the sea and rivers and hunt for both freshwater, anadromous and marine prey. The food spectrum of beluga whales in the Anadyr estuary is very wide and includes 12 fish species and 1 crustacean species. In the summer-autumn season, the salmons are the most significant part of the diet, as chum salmon Oncorhynchus keta , pink salmon O. gorbuscha and arctic char Salvelinus malma , whereas arctic smelt Osmerus mordax dentex , saffron cod Eleginus gracilis , sculpins Cottidae sp., anadyr whitefish Coregonus anaulorum , and siberian whitefish Coregonus sardinella are presented in the diet to a lesser extent. There is supposed on the base of episodic net surveys, that the beluga whales feeding in marine areas is more diverse, and the most important their prey in the sea are walleye pollock Theragra chalcogramma , pacific cod Gadus macrocephalus , flounders Pleuronectidae sp., sculpins Cottidae sp., capelin Mallotus villosus catervarius , polar cod Boreogadus saida , halibuts Pleuronectidae sp., stingrays Bathyraja , herring Clupeidae sp., and several species of decapod crustaceans Hyppolitidae sp. and Lithodidae sp. Natural enemies of beluga whales are killer whale Orcinus orca , polar bear Ursus maritimus , and predatory form of pacific walrus Odobenus rosmarus . Rather large number of beluga whales are eliminated by the sea ice, up to 80 animals annually, that exceeds in several times the aboriginal landings in Chukotka. Parasitic fauna of the beluga whale is still unclear and requires special investigations; the cases of epizooty are unknown in the Anadyr Gulf. Philopatry is proper to the Anadyr beluga whales, with preference of the Anadyr estuary and the Anadyr Gulf as their habitats, that is explained by optimal for them environments and high food capacity. Unique adaptation of beluga whales to the environments of the Anadyr estuary is their ultrasonic vocalization in the high-turbidity waters. Genetic analysis shows a differentiated distribution of the beluga whales haplotypes in different areas of the North Pacific, so the stock of the Anadyr Gulf is significantly isolated in the post-glacial times. Low anthropogenic pressure on beluga whales in the Anadyr Gulf allows them to maintain their stock there.

Pseudostalked barnacles Xenobalanus globicipitis attached to killer whales Orcinus orca in South African waters

Several records describe pseudostalked barnacles Xenobalanus globicipitis attached to killer whales Orcinus orca, yet little is known of this association in South African waters. Here we describe Xenobalanus prevalence on killer whales in South African waters and assemble previous records. Killer whales were photographed opportunistically between July and September 2013. Sex and age class were determined, and if Xenobalanus were present, attachment site and colony size were noted. A prevalence of 50 % was recorded, with barnacles most commonly observed on the dorsal fin and tail flukes. The high prevalence of Xenobalanus on killer whales in South African waters and lack thereof on killer whales at Marion Island implies that these are separate populations, and thus we suggest Xenobalanus prevalence as an additional means to distinguish between these populations.

Validation of dentine deposition rates in beluga whales by interspecies cross dating of temporal δ13C trends in teeth

Isotopic time series from sequentially sampled growth layer groups (GLGs) in marine mammal teeth can be combined to build chronologies allowing assessment of isotopic variation in marine ecosystems. Synchronous recording of baseline isotopic variation across dentinal GLGs of species with temporal and spatial overlap in foraging offers a unique opportunity for validation of marine mammal age estimation procedures through calibration of GLG deposition rates in one species against another whose GLG deposition has been independently determined. In this study, we compare trends in stable carbon isotope ratios (d13C) across dentinal GLGs of three eastern Canadian Arctic (ECA) beluga (Delphinapterus leucas) populations through the 1960s-2000s with a d13C time series measured across dentinal GLGs of ECA/Northwest Atlantic killer whales (Orcinus orca) from 1944-1999. We use confirmed annual GLG deposition in killer whales as a means to assess beluga GLG deposition, and show linear d13C declines across chronologies of both species were statistically indistinguishable when based on annual GLG deposition in beluga whales, but differed when based on biannual deposition. We suggest d13C declines reflect the oceanic 13C Suess effect, and provide additional support for annual GLG deposition in beluga whales by comparing rates of d13C declines across beluga GLGs with published annual d13C declines attributed to the oceanic 13C Suess effect in the North Atlantic.

Satellite tagging and biopsy sampling of killer whales at subantarctic Marion Island: effectiveness, immediate reactions and long-term responses.

Remote tissue biopsy sampling and satellite tagging are becoming widely used in large marine vertebrate studies because they allow the collection of a diverse suite of otherwise difficult-to-obtain data which are critical in understanding the ecology of these species and to their conservation and management. Researchers must carefully consider their methods not only from an animal welfare perspective, but also to ensure the scientific rigour and validity of their results. We report methods for shore-based, remote biopsy sampling and satellite tagging of killer whales Orcinus orca at Subantarctic Marion Island. The performance of these methods is critically assessed using 1) the attachment duration of low-impact minimally percutaneous satellite tags; 2) the immediate behavioural reactions of animals to biopsy sampling and satellite tagging; 3) the effect of researcher experience on biopsy sampling and satellite tagging; and 4) the mid- (1 month) and long- (24 month) term behavioural consequences. To study mid- and long-term behavioural changes we used multievent capture-recapture models that accommodate imperfect detection and individual heterogeneity. We made 72 biopsy sampling attempts (resulting in 32 tissue samples) and 37 satellite tagging attempts (deploying 19 tags). Biopsy sampling success rates were low (43%), but tagging rates were high with improved tag designs (86%). The improved tags remained attached for 26±14 days (mean ± SD). Individuals most often showed no reaction when attempts missed (66%) and a slight reaction–defined as a slight flinch, slight shake, short acceleration, or immediate dive–when hit (54%). Severe immediate reactions were never observed. Hit or miss and age-sex class were important predictors of the reaction, but the method (tag or biopsy) was unimportant. Multievent trap-dependence modelling revealed considerable variation in individual sighting patterns; however, there were no significant mid- or long-term changes following biopsy sampling or tagging.

Energy content of Pacific salmon as prey of northern and southern resident killer whales

Recovery of depleted species is difficult, but it can be especially complex when the target species interacts strongly with other depleted species. Such is the case for northern and southern resident killer whales Orcinus orca which are listed as 'endangered' under the US Endangered Species Act (ESA) and Canada's Species at Risk Act. These resident killer whales prey heavily on Pacific salmon Oncorhynchus spp., including several 'evolutionarily significant units' also listed under the ESA. In response to concerns that a depleted prey base may affect killer whale recovery, we analyzed proximate composition and calculated caloric content of Pacific salmon to evaluate the importance of salmon species, population, body size, and lipid levels in determining their energy content as prey for killer whales. We sampled all 5 species of Pacific salmon, but emphasized Chinook salmon, a predominant prey of killer whales. Energy density (kcal kg −1 ) was highly correlated with lipid content, whereas total energy value (kcal fish −1 ) was determined primarily by fish mass and secondarily by lipid content. These salmon energetics data can be used to provide better precision and estimates on the caloric value of prey to killer whales. To facilitate application of these results to the co-management of salmon and killer whales, we produced a simple relationship that uses fish length to predict total energy of Chinook salmon as prey where population-specific energy densities and fish masses are lacking. Benefits to killer whales from possible salmon fishery closures, or other activities that affect prey availability, will depend on the salmon species and populations involved.

Habituation to an acoustic harassment device (AHD) by killer whales depredating demersal longlines

AbstractAcoustic harassment devices (AHDs) have been increasingly implemented in various fisheries that suffer significant losses caused by odontocete depredation. However, the efficacy of AHDs to deter odontocetes from fishing gear remains poorly investigated. To determine the effectiveness of AHDs in deterring depredation, we experimentally tested a high amplitude device (195 dB re 1 μPa 6.5 kHz 1 m from the source) from a Patagonian toothfish Dissostichus elegenoides longliner operating off the Crozet Islands, while it was subjected to heavy depredation by killer whales Orcinus orca. This species usually depredates longlines within a 10- to 300-m range from the vessel, as they only have access to fishing gear during hauling. We expected this distance to increase in response to the acoustic disturbance created by the AHD. The distances of 29 killer whales from the vessel (n = 1812 records) were collected during phases of AHD activation and phases during which the AHD was turned off. Two multiexposed killer whale social units fled over 700 m away from the vessel when first exposed to the AHD. However, they remained within a 10- to 300-m range and depredated longlines again past the third and seventh exposures, respectively, showing an insignificant behavioural response to further activations of the AHD. When tested through generalized linear mixed models, the effect of AHD activation was only significant when killer whales were first exposed to the device. However, the effect disappeared after successive exposures suggesting that killer whales became habituated to the AHD and may sustain potentially harmful hearing disturbance to access the resource made available by longliners. In addition to raising significant conservation concerns, this rapid return of initial depredation behaviour strongly suggests that AHDs are ineffective at deterring depredating killer whales, and that fisheries should favour the use of other mitigation techniques when facing repeated depredation by this species.

Recolonizing sea otters spatially segregate from pinnipeds on the Canadian Pacific coastline: The implications of segregation for species conservation

The reintroduction and recolonization of species extirpated from former ranges are key components of species conservation. Resource availability affects recolonization success and resulting distribution patterns, but top-down processes may also play a role through density-mediated or trait-mediated indirect effects that may exclude a species from otherwise suitable habitat. We predicted that the spatial distribution of recolonizing sea otters, Enhydra lutris, on the Canadian Pacific coastline was explained by resources as well as interspecific interactions – spatial segregation from pinnipeds, the preferred prey of killer whales Orcinus orca. We surveyed the summer occurrence of sea otters and pinnipeds on Vancouver Island, Canada. We quantified coastline density and bathymetry at multiple spatial scales as indices of habitat complexity and foraging habitat availability. We used generalized linear model selection to test hypotheses about sea otters’ spatial relationship to resources and heterospecifics. Pinniped presence negatively predicted sea otter presence, even after accounting for complexity and foraging habitat. Sea otters may segregate from pinnipeds due to trait-mediated indirect effects of predation, leading us to hypothesize apparent competition between sea otters and pinnipeds. Research is needed to test this hypothesis; if true, refuge from apparent competitors may be a key component of recolonization habitat for sea otters. Species distribution models should quantify resource landscapes but also species-scapes: the spatial plane of species interactions that combines with resources to drive species distributions. Conservation plans based on recolonization models that include only resources may overestimate available habitat, carrying capacity, and recolonization success.

Observations of killer whales (Orcinus orca) in the fjords of Chilean Patagonia

Killer whales occur in Chilean waters, but their seasonality, diets, and overall distribution are poorly known. Here, we present data on group composition, site fidelity, and prey species of individual killer whales recorded in 63 sightings between 2004 and 2012 in the Chilean Patagonian fjords. Group sizes were small (mean = 5, SD = 2.5 for calf groups; mean = 3, SD = 1.5 for non-calf groups), and occurrence was significantly lower in summer months. Photographs enabled identification of 55 individuals from natural markings, and all resembled Southern Ocean type A killer whales. The species was transient in the area; the average presence was 1.7 days with 60 % of individuals seen only once. Occupancy was 3–44 days, and low levels of site fidelity were recorded (64 % of individuals were seen in only 1 year). Group composition at short time scales (3 months) remained stable, but we detected changes at longer time scales. Prey included fish, otariids, and seabirds. Twelve individual killer whales showed a broad dietary spectrum: 3 ate otariids and fish, 2 ate birds and otariids, and 7 ate otariids, birds, and possibly fish. Further research is needed to increase basic biological knowledge of these killer whales and to determine the relationship with type A killer whales from the Southern Ocean.

Confirmation of the occurrence of a second killer whale morphotype in South African waters

Killer whales Orcinus orca occur worldwide in a number of morphotypes that differ in size, pigmentation, acoustic behaviour, food type and genetics – some may indeed warrant subspecific or even specific status. Until recently, all killer whales in South African waters were referred to a single morphotype, Type A, but three individuals (two males and one female) that have stranded since 1969 differ in several respects from other killer whales examined from the region. Adult length is some 1–1.5 m smaller, appendages such as dorsal fin and flippers tend to be relatively larger, and tooth wear is excessive. Although dietary information is scant, one stomach contained the remains of several elasmobranchs, identified from a DNA subsample as blue sharks Prionace glauca, a dietary item that, if habitual, might account for the tooth wear. This morphotype, referred to here as ‘flat-toothed’ and which in several respects resembles the offshore form in the North Pacific and the Type 1 form in the North Atlantic, does not seem to have been recorded previously from the Southern Hemisphere.

Prey selection of offshore killer whales Orcinus orca in the Northeast Atlantic in late summer: spatial associations with mackerel

The traditional perception of prey species preference of killer whales Orcinus orca L. in the Northeast Atlantic has, to a large extent, been linked to herring Clupea harengus L. Few studies have investigated the feeding ecology of killer whales from the offshore parts of this eco- system. We conducted 2 summer-season ecosystem-based surveys in the Norwegian Sea, when it is most crucial for these animals to build up their energy reserves, using observational, acoustic, oceanographic, plankton net, and pelagic trawl haul data to quantify any spatial overlap between killer whales and the 3 most common and abundant pelagic fish species: herring, mackerel Scomber scombrus L., and blue whiting Micromesistius poutassou R. No spatial relationships were found between killer whales and herring or blue whiting. However, there was a significant rela- tionship and spatial overlap between killer whales and mackerel. Feeding on this epipelagic schooling fish species during summer may incur lower migration costs and higher energetic gain than feeding on alternative prey. Killer whale group size was also correlated to the size of mack- erel trawl catches, indicating active group size adjustment to available prey concentrations.

Inuit Recollections of a 1950s Killer Whale (Orcinus orca) Ice Entrapment in Foxe Basin, Nunavut, Canada

Inuit Recollections of a 1950s Killer Whale (Orcinus orca) Ice Entrapment in Foxe Basin, Nunavut, Canada

On the Behavior and Welfare of Killer Whales in Captivity

The killer whale (Orcinus orca) has proven to be among the most difficult of all species to hold adequately in zoological facilities. The killer whale is a particularly large-brained and long-lived...

Environmental Isolates of Fungi from Aquarium Pools Housing Killer Whales (Orcinus orca)

Systemic mycoses in killer whales (Orcinus orca) are rare diseases, but have been reported. Two killer whales died by fungal infections at the Port of Nagoya Public Aquarium in Japan. In this study, the fungal flora of the pool environment at the aquarium was characterized. Alternaria spp., Aspergillus spp. (A. fumigatus, A. niger, A. versicolor), Fusarium spp. and Penicillium spp. were isolated from the air and the pool surroundings. The other isolates were identified as fungal species non-pathogenic for mammals. However, the species of fungi isolated from the environmental samples in this study were not the same as those isolated from the cases of disease in killer whales previously reported.

Hematological and serum biochemical analytes reflect physiological challenges during gestation and lactation in killer whales (Orcinus orca)

Gestation and lactation result in metabolic alterations of the dam because of varying demands of the fetus and offspring during the different stages of development. Despite killer whales (Orcinus orca) having one of the longest gestations and highest birth weights of all mammals in human care, these metabolic alterations, and their impact on the physiology of the dam have not been measured. The objectives of this analysis were to determine if physiologic demands on the killer whale during pregnancy and lactation have measurable effects on hematology and biochemical analytes and if detectable, to compare these changes to those which are observed in other mammalian species. Forty hematologic and biochemical analytes from seven female killer whales (22 pregnancies, 1,507 samples) were compared between the following stages: (1) non-pregnant or lactating (control); (2) gestation; and (3) the first 12 months of lactation. Decreased hematocrit, hemoglobin, and red blood cell counts were indicative of plasma volume expansion during mid and late gestation. The killer whales exhibited a progressively increasing physiologic inflammatory state leading up to parturition. Gestation and lactation caused significant shifts in the serum lipid profiles. Gestation and lactation cause significant physiologic changes in the killer whale dam. The last 12 months of gestation had greater physiological impact than lactation, but changes associated with and immediately following parturition were the most dramatic. During this period, killer whales may experience increased susceptibility to illness, and anthropogenic and environmental disturbances.

The cetaceans of Aruba, southern Caribbean

Aruba is one of the most densely populated islands in the Caribbean. However, very little is known about its cetaceans. In 2010 and 2011, a total of 19721 km (1686 h) boat-based surveys over nearshore transects resulted in 117 positively-identified sightings comprising eight species. New records are also added for one of three previously-documented species. Five additional species were documented from strandings or reports by others. This brings the total number of cetacean species identified in Aruban waters to 16, of which nine are authenticated here for the first time. Atlantic spotted dolphin (Stenella frontalis(N = 59) and bottlenose dolphin (Tursiops truncatus) (N = 33) were the most frequently observed species, with sightings of both year-round, followed by spinner dolphin (S. longirostris) and false killer whale (Pseudorca crassidens). Additional species recorded are pantropical spotted dolphin (S. attenuata), striped dolphin (S. coeruleoalba), common dolphin (Delphinus capensis), rough-toothed dolphin (Steno bredanensis), short-finned pilot whale (Globicephala macrorhynchus), killer whale (Orcinus orca), Risso's dolphin (Grampus griseus), humpback whale (Megaptera novaeangliae), Bryde's/Eden's whale (Balaenoptera brydei/edeni), sperm whale (Physeter macrocephalus) and an unidentified beaked whale (Mesoplodonsp.). All cetaceans were sighted within 22 km of the coast in relatively shallow waters. Sighting rate was low (0.69 cetacean sightings per 100 km). Sightings of calves and neonates indicate that Aruba may be a nursing or breeding area for some species. The presence of several species of cetaceans in Aruba's coastal waters year-round indicates that status and threat assessments are needed to protect them.