Tracking data reveal both indirect and direct interactions between killer whales and fisheries in subantarctic waters.

Observations of killer whales in the act of predation are rare because feeding bouts are infrequent in relation to sighting opportunities, and they apparently feed at night as well as during the day. A pop-up autonomous recording unit (ARU) was used to expand the observation window of transient (mammal-eating) killer whales by monitoring them continuously from 22 June to 12 July 2006 near a northern fur seal rookery at St. Paul Island, AK, a predation hot-spot in the Bering Sea. The ARU recorded at a sampling rate of 0.5–16<th>000 Hz. Killer whale vocalizations were detected on 19 of 20 days. Most vocalizations occurred from the end of civil twilight (00:26 on 1 July) through mid-morning. Fewest vocalizations occurred between 1800 and 2400. Vocal whales were most likely feeding, based on the paradigm that transients are mostly silent except when attacking prey. Call types are being identified and vocalizations are being correlated with visual observations and fur seal activity at the rookery. Nocturnal hunting is likely one important reason why it has been difficult to understand the foraging behavior of these elusive predators and must be considered when drawing conclusions about the roles transient killer whales play in marine ecosystems.

Community interaction webs describe both direct and indirect interactions among species. Changes in direct interactions often become noticeable soon after a perturbation, but time lags in the responses of many species may delay the appearance of indirect effects and lead to temporal or spatial variation in interaction webs. Accurately identifying these shifts in the field requires time‐specific, spatially differentiated interaction webs. We explore how variation in browsing affects interaction webs in a long‐unburned chaparral shrubland near the central California coast. Most prior work in chaparral focused on rapid changes for <5 years after a wildfire that were assumed to determine community patterns until the next fire. Here, we report the results of the first 15 years of an ongoing experiment monitoring how interaction webs in long‐unburned chaparral (at least 100 years postfire) respond to experimental variation in browsing by deer and rabbits on dominant shrubs (Arctostaphylos pumila, Ceanothus cuneatus var. rigidus, and Ericameria ericoides). We hypothesized that variation in browsing would directly affect foodplants, indirectly modify growth and survival of other shrubs, and impact habitat needed by herbaceous plants. We found a dynamic web of plant–herbivore and plant–plant interactions that responded rapidly to changes in deer browsing on Ceanothus followed by indirect interactions that continued developing over several years, affecting shrubs, open space, herbaceous plants, and small mammals. Experimental variation in the intensity of deer browsing led to temporal and spatial changes in interactions that produced three different community interaction webs. With deer, community webs were complex, having numerous direct and indirect interactions. Removing deer simplified the community web, changed outcomes of interactions, and reduced open space and herbaceous plant densities. Finally, changes in Ceanothus morphology without deer allowed woodrats to browse these shrubs, with negative impacts on Ceanothus growth and survival. General field observations also showed that all three alternative interaction webs occurred naturally at our fieldsite, varying across space and over time. Long‐unburned chaparral communities browsed by deer maintain high biological diversity, but maintenance of this diversity involves many key direct and indirect biotic interactions.

Killer whales (Orcinus orca) are widely distributed in all ocean basins, however, their occurrence, distribution, and ecology in the southeast Pacific, including Peru, is poorly defined. This study aims to describe the occurrence of killer whales in Peruvian waters, with additional description of predatory behaviors. Between 2003 and 2018 there were 29 reports of killer whales in Peruvian waters in which at least 110 individuals were observed, with pod sizes ranging between 1 and 15 individuals. Most sightings occurred in waters within the continental shelf or in close proximity to the shelf break. During eight of the sightings, killer whales displayed predatory behavior towards other marine mammals, including cetaceans (Megaptera novaeangliae and Balaenoptera musculus) and pinnipeds (Otaria flavescens and Arctocephalus australis). In addition, we present the first photo-analysis of the incidence of killer whale tooth rake marks on humpback whale flukes off northern Peru. Between 2009 and 2017, 897 unique individual humpback whales were photo-identified off northern Peru, of which 19.6% (n = 172) displayed rake marks in their flukes, suggesting that humpback whales in the southeast Pacific are exposed to the attack of killer whales. Our findings suggest that the occurrence of killer whales in Peruvian waters are more common than previously documented and that killer whales are preying marine mammals in this region. Further understanding killer whale distribution, foraging habitats, and movement patterns within Peruvian waters will be essential in promoting their conservation.

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 421:229-241 (2011) - DOI: https://doi.org/10.3354/meps08906 Predation on gray whales and prolonged feeding on submerged carcasses by transient killer whales at Unimak Island, Alaska Lance G. Barrett-Lennard1,2,*, Craig O. Matkin3, John W. Durban4,5, Eva L. Saulitis3, David Ellifrit6 1Cetacean Research Program, Vancouver Aquarium, PO Box 3232, Vancouver, British Columbia V6B 3X8, Canada 2Zoology Department, University of British Columbia, #2370-6270 University Blvd., Vancouver, British Columbia V6B 1Z4, Canada 3North Gulf Oceanic Society, 3430 Main St., Suite B1, Homer, Alaska 99603, USA 4National Marine Mammal Laboratory, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, Washington 98115, USA 5Protected Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 8604 La Jolla Shores Dr., La Jolla, California 92037, USA 6Center for Whale Research, 355 Smugglers Cove, Friday Harbor, Washington 98250, USA *Email: lance.barrett-lennard@vanaqua.org ABSTRACT: As apex predators, killer whales Orcinus orca are expected to strongly influence the structure of marine communities by impacting the abundance, distribution, behavior, and evolution of their prey. Empirical assessments of these impacts are difficult, however, because killer whales are sparsely distributed, highly mobile, and difficult to observe. We present a 4 yr time series of observations of foraging and feeding behavior of >150 transient killer whales that aggregate annually during the northbound migration of gray whales past Unimak Island, Alaska. Most predatory attacks were on gray whale Eschrichtius robustus calves or yearlings and were quickly abandoned if calves were aggressively defended by their mothers. Attacks were conducted by groups of 3 to 4 killer whales, which attempted to drown their prey. Gray whales generally tried to move into shallow water along the shoreline when attacked; if they succeeded in reaching depths of 3 m or less, attacks were abandoned. Kills occurred in waters from 15 to 75 m deep or were moved into such areas after death. After some hours of feeding, the carcasses were usually left, but were re-visited and fed on by killer whales over several days. Carcasses or pieces of prey that floated onshore were actively consumed by brown bears Ursus arctos, and carcasses on the bottom were fed on by sleeper sharks Somniosus pacificus, apparently increasing the local density of both species. KEY WORDS: Foraging strategy · Predatory behavior · Prey catching · Scavenger · Killer whale · Gray whale · Brown bear · Sleeper shark Full text in pdf format PreviousNextCite this article as: Barrett-Lennard LG, Matkin CO, Durban JW, Saulitis EL, Ellifrit D (2011) Predation on gray whales and prolonged feeding on submerged carcasses by transient killer whales at Unimak Island, Alaska. Mar Ecol Prog Ser 421:229-241. https://doi.org/10.3354/meps08906 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 421. Online publication date: January 17, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Predation can regulate prey numbers but predator behaviour in multiple‐prey systems can complicate understanding of control mechanisms. We investigate killer whale ( Orcinus orca ) predation in an ocean system where multiple marine mammal prey coexist. Using stochastic models with Monte‐Carlo simulations, we test the most likely outcome of predator selection and compare scenarios where killer whales: (1) focus predation on larger prey which presumably offer more energy per effort, (2) generalize by feeding on prey as encountered during searches, or (3) follow a mixed foraging strategy based on a combination of encounter rate and prey size selection. We test alternative relationships within the Hudson Bay geographic region, where evidence suggests killer whales seasonally concentrate feeding activities on the large‐bodied bowhead whale ( Balaena mysticetus ). However, model results indicate that killer whales do not show strong prey specialization and instead alternatively feed on narwhal ( Monodon monoceros ) and beluga ( Delphinapterus leucas ) whales early and late in the ice‐free season. Evidence does support the conjecture that during the peak of the open water season, killer whale predation can differ regionally and feeding techniques can focus on bowhead whale prey. The mixed foraging strategy used by killer whales includes seasonal predator specialization and has management and conservation significance since killer whale predation may not be constrained by a regulatory functional response.

Killer whale (Orcinus orca) populations specialize in both prey and prey acquisition tactics around the world and may be a primary evolutionary driver of the habits of small cetaceans. Entanglement in fishing gear is the most significant anthropogenic threat to the survival of cetaceans worldwide. Distinguishing between natural and human-caused sources of mortality and injury is a key task in marine mammal conservation and management. In British Columbia (BC), Canada, mammal-eating killer whales co-occur with Pacific white-sided dolphins (Lagenorhynchus obliquidens). Bycatch mortality rates are unknown here due to lack of systematic fisheries observer coverage. Drawing from more than three decades of first-hand observations of killer whale attacks on Pacific white-sided dolphins, we identify common themes with respect to predatory behavior of killer whales and anti-predatory responses of dolphins. With input from veterinary pathologists, we outline clues to distinguish killer whale rake marks from scars and wounds likely to be caused by fishery interactions. We examined photographs of 415 well-marked Pacific white-side dolphins for evidence of injuries and scars consistent with either killer whale attacks or fishery interactions. In this case study, healed scars from interactions with killer whale predators were ∼8× more common than scars from fishery interactions (3.9 vs. 0.5%), suggesting that predation is a much bigger threat to Pacific white-sided dolphins in the study area than anthropogenic impacts, or that dolphins are much less likely to survive a fishery interaction than a predation attempt. To advance our knowledge on poorly studied species, multiple lines of evidence will be needed.

Interactions among species are a fundamental aspect of biodiversity and drive ecosystem functioning and services. Species interactions include direct (pairwise) interactions among two species and indirect interactions that occur when a third species interacts and changes the pairwise direct interaction. In a three‐species interaction network, these interactions can be transitive (where one species outperforms all others) or intransitive (where each species outperforms another). Here, we investigate how direct and indirect interactions influence ecosystem functions in crop systems and how diversification and evolutionary adaptation can influence those interactions and therefore ecosystem functions. A common garden experiment was conducted with crop communities in monocultures, 2‐ and 3‐species mixtures that had either a common or no coexistence history (i.e. co‐adaptation) for the three previous years. Net, direct and indirect interaction intensities were estimated and compared between the diversity levels and coexistence histories. Furthermore, species interaction networks were inspected for transitive/intransitive interactions. We found evidence for less intense competition in mixtures and for reduced negative direct interaction intensity and enhanced facilitative effects upon co‐adaptation. We could further show that indirect interactions were generally less important for co‐adaptation than direct interactions. Additionally, we showed that co‐adaptation has the potential to shift interactions in the species interaction networks from competitive intransitive into pairwise competitive interactions where interactions occurred mainly between two species. Synthesis. Co‐adapted crop species with reduced negative interactions might have the potential to enhance productivity, especially in more diverse cropping systems. This supports the notion that intercropping is a vital part towards a more sustainable agriculture and one with further yield potential when developing cultivars optimised for growth in mixtures.

Killer whales (Orcinus orca) are an apex predator, the largest delphinid odontocete, and have the widest cosmopolitan distribution of all cetacean species. These long-lived animals can be found in life-long matrilineal groups, where fitness-related activities such as cooperative hunting rely on sophisticated group coordination, often mediated by acoustic communication. The effects of anthropogenic noise on the fitness of killer whales is a growing concern, especially for the endangered population of southern resident killer whales. Although modest progress has been made in determining the killer whales’ behavior in response to noise (e.g., Lombard effect), almost nothing is known about how these animals hear in noisy environments. Here, what is known about killer whale hearing is summarized, including behavioral and electrophysiological audiograms, and resulting auditory weighting functions. In addition, new critical ratio data are presented and compared with other odontocete species. These preliminary data are evaluated in a communication space model to predict negative impacts of anthropogenic noise.

Killer whales (Orcinus orca) are highly mobile, large marine apex predators that inhabit all oceans. Despite being the most conspicuous top predator, little is known about their ecology along Patagonia, Argentina. Here, we used carbon (δ13C) and nitrogen (δ15N) isotope analysis of bone and dentine collagen from killer whales (n = 13) stranded in northern Patagonia during the period 1970–2014 to assess their trophic ecology. A model‐based clustering analysis identified three distinct groups related with three large marine ecosystems: the Patagonia (P), Subtropical (ST), and Antarctica (A) groups. Group P (n = 8) is characterized by individuals with high δ13C and δ15N values fitting within the isotopic ratios observed over the Patagonian shelf. Group ST (n = 3) is composed of individuals with high δ13C and low δ15N values, similar to those reported for conspecifics in southern Brazil. Group A (n = 2) is composed of individuals with low δ13C and δ15N values, typical from high latitude areas like sub‐Antarctic/Antarctic waters. The finding of different killer whales' isotopic groups over the Patagonian shelf suggests the existence of individuals or groups exploiting different habitats. Our results expand the limited ecological knowledge for the species while presenting the basis to infer more complex ecological hypotheses.

Thinking flexibly is a skill that enables animals to adapt to changing environments, which enhances survival. Killer whales, Orcinus orca, as the ocean apex predator display a number of complex cognitive abilities, especially flexible thinking or creativity when it comes to foraging. In human care, smaller dolphins and other marine mammals have been trained to think creatively while under stimulus control. The results of these previous studies have demonstrated that bottlenose dolphins, Tursiops truncatus, can create original behaviors in response to an innovative cue. We trained and tested a total of nine killer whales from two different facilities on the innovate concept, using the same methodology. The killer whales ranged in age from 5 to 29 yrs with 4 females and 5 males. The results indicate that the killer whales demonstrated high fluency, originality, some elaboration, and flexibility in their behaviors. Individual variability was observed with younger animals demonstrating more variable behaviors as compared to the older animals. Males seemed to display less complex and lower energy behaviors as compared to females, but this impression may be driven by the age or size of the animal. These results support existing evidence that killer whales are dynamic in their thinking and behavior.

The productive North Pacific waters of the Gulf of Alaska, Aleutian Islands and Bering Sea support a high density of fish-eating “Resident” type killer whales (Orcinus orca), which overlap in distribution with commercial fisheries, producing both direct and indirect interactions. To provide a spatial context for these interactions, we analyzed a 10-year dataset of 3,058 whale photo-identifications from 331 encounters within a large (linear ~4,000 km) coastal study area to investigate the ranging and social patterns of 532 individually identifiable whales photographed in more than one encounter. Although capable of large-scale movements (maximum 1,443 km), we documented ranges generally <200 km, with high site fidelity across summer sampling intervals and also re-sightings during a winter survey. Bayesian analysis of pair-wise associations identified four defined clusters, likely representing groupings of stable matrilines, with distinct ranging patterns, that combined to form a large network of associated whales that ranged across most of the study area. This provides evidence of structure within the Alaska stock of Resident killer whales, important for evaluating ecosystem and fisheries impacts. This network included whales known to depredate groundfish from longline fisheries, and we suggest that such large-scale connectivity has facilitated the spread of depredation.

Killer whales occur in the Gulf of Mexico (GoMex) and the North Atlantic, including off the southeastern United States (SEUS). Data from cetacean surveys during 1990 – 2021 and other sources were combined to assess killer whale biology, including spatial and temporal distribution, social structure, genetics, morphology, acoustics, and predatory behavior. GoMex records occurred predominantly in oceanic waters (&amp;gt;200 m) during spring and summer. SEUS records occurred primarily in winter and spring off the North Carolina region along the shelf-edge and deeper waters, and off the east coast of Florida. Photo-identification analysis of GoMex killer whales resulted in 49 individuals sighted up to seven times with sighting histories up to 26 years, and social analysis provided evidence of long-term relationships up to 16 years. The GoMex genetic samples revealed two mtDNA haplotypes, one of which does not match any outside the GoMex. Most GoMex whales had wide non-faint saddle patches and many had cookiecutter shark scars while no scars were noted on SEUS whales. Three groups recorded in the GoMex made few calls, but a group harassing sperm whales produced many. Cetaceans and tuna are known prey in the GoMex and SEUS, respectively. Directed studies of killer whales in the GoMex areas would be difficult to implement as this species is very rare. It is therefore important to pursue ongoing efforts to collect behavioral, acoustic and any biological samples that will contribute to improve our understanding of the biology and ecology of killer whales in tropical and subtropical regions.

A Killer Whale attack on Narwhals was observed at Kakiak Point in Admiralty Inlet, Nunavut, Canada, in August 2005. Behavioral responses of both Narwhals and Killer Whales were documented by direct observation. Data collected from Narwhals instrumented with satellite-linked transmitters 5 days prior to the arrival of Killer Whales were used to examine changes in Narwhal movement patterns (e.g., dispersal and clumping) five days before the attack, during the attack, and five days after Killer Whales left the area. A minimum of four Narwhals were killed by 12-15 Killer Whales in a period of 6 hours. Narwhals showed a suite of behavioral changes in the immediate presence of Killer Whales including slow, quiet movements, travel close to the beach (&lt;2 m from shore), use of very shallow water, and formation of tight groups at the surface. These behavioral changes are consistent with Inuit accounts of Killer Whale attacks on Narwhals. During the attack, Narwhals dispersed broadly, the groups were less clumped (standard deviation of inter-whale mean latitudes and longitudes), Narwhal space-use doubled from pre-attack home ranges of 347 km2 to 767 km2 (kernel 50% probability), and Narwhals shifted their distribution further south of the attack site. After the disappearance of Killer Whales, north-south dispersal of Narwhals contracted and was similar to pre-attack levels, total space use decreased slightly (599 km2), yet west-east dispersal remained high. Narwhals were distributed significantly (P &lt; 0.001) more broadly offshore in areas not used before the occurrence of Killer Whales. In general, short-term reactions of Narwhals to Killer Whale presence were obvious; yet normal behavior (as observed from shore) resumed shortly after Killer Whales left the area. Long-term (five day) Narwhal behavioral responses included increased dispersal of Narwhal groups over large offshore areas. This is among the few reports of eyewitness Killer Whale attacks on Narwhals in the high Arctic and is the first time changes in Narwhal behavior have been documented in response to a predation event through the use of satellite telemetry.

Assessing the mechanism of DNA damage induced by lead through direct and indirect interactions

Over the past five decades, marine mammal interactions with fisheries have become a major human-wildlife conflict globally. The emergence of longline fishing is concomitant with the development of depredation-type interactions i.e., marine mammals feeding on fish caught on hooks. The killer whale (Orcinus orca) is one of the species most involved in depredation on longline fisheries. The issue was first reported in high latitudes but, with increasing expansion of this fishing method, other fisheries have begun to experience interactions. The present study investigated killer whale interactions with two geographically isolated blue-eye trevalla (Hyperoglyphe antarctica) fisheries operating in temperate waters off Amsterdam/St. Paul Islands (Indian Ocean) and south-eastern Australia. These two fisheries differ in the fishing technique used (vertical vs. demersal longlines), effort, catch, fleet size and fishing area size. Using 7-year (2010–16) long fishing and observation datasets, this study estimated the levels of killer whale interactions and examined the influence of spatio-temporal and operational variables on the probability of vessels to experience interactions. Killer whales interactions occurred during 58.4% and 21.2% of all fishing days, and over 94% and 47.4% of the fishing area for both fisheries, respectively. In south-eastern Australia, the probability of occurrence of killer whale interactions during fishing days varied seasonally with a decrease in spring, increased with the daily fishing effort and decreased with the distance travelled by the vessel between fishing days. In Amsterdam/St. Paul, this probability was only influenced by latitude, with an increase in the southern part of the area. Together, these findings document two previously unreported cases of high killer whale depredation, and provide insights on ways to avoid the issue. The study also emphasizes the need to further examine the local characteristics of fisheries and the ecology of local depredating killer whale populations in as important drivers of depredation.