19 research outputs found
Low-frequency signals produced by Northeast Atlantic killer whales (Orcinus orca)
No full textKiller whale acoustic behavior has been extensively investigated, however most studies have focused on pulsed calls and whistles. This study reports the production of low-frequency signals by killer whales at frequencies below 300 Hz. Recordings of killer whales were made in Iceland and Norway when whales were observed feeding on herring, and no other cetacean species were nearby. Low-frequency sounds were identified in Iceland and ranged in duration between 0.14 and 2.77 seconds and in frequency between 50 and 270 Hz, well below the previously reported lower limit for killer whale tonal sounds of 500 Hz. LFS appeared to be produced close in time to tail slaps, indicative of feeding attempts, suggesting that these sounds may be related to a feeding context. However, their precise function is unknown and they could be the by-product of a non-vocal behavior, rather than a vocal signal deliberately produced by the whales. Although killer whales in Norway exhibit similar feeding behavior, this sound was not detected in recordings from Norway. This study suggests that, like other delphinids, killer whales also produce low-frequency sounds but further studies will be required to understand whether similar sounds exist in other killer whale populations
A multilevel society of herring-eating killer whales indicates adaptation to prey characteristics
No full textThis work was supported by the Fundação para a Ciência e a Tecnologia (grant numbers SFSFRH/BD/30303/2006 and SFRH/BD/84714/2012); Icelandic Research Fund (i. Rannsóknasjóđur, grant number 120248402); National Geographic Society Science and Exploration Europe (grant number GEFNE65-12); Office of Naval Research (grant number N00014-08-10984); and a Russell Trust Award from the University of St. Andrews.Non-social factors can influence animal social structure. In killer whales (Orcinus orca), fish- versus mammal-eating ecological differences are regarded as key ecological drivers of their multilevel society, including group size, but the potential importance of specific target prey remains unclear. Here, we investigate the social structure of herring-eating killer whales in Iceland and compare it to the described social structures of primarily salmon- and seal-eating populations in the Northeast Pacific, which form stable coherent basic units nested within a hierarchical multilevel society. Using 29023 photographs collected over 6 years, we examined the association patterns of 198 individuals combining clustering, social network structure, and temporal patterns of association analysis. The Icelandic population had largely weak but non-random associations, which were not completely assorted by known ranging patterns. A fission–fusion dynamic of constant and temporary associations was observed but this was not due to permanent units joining. The population-level society was significantly structured but not in a clear hierarchical tier system. Social clusters were highly diverse in complexity and there were indications of subsclusters. There was no indication of dispersal nor strong sex differences in associations. These results indicate that the Icelandic herring-eating killer whale population has a multilevel social structure without clear hierarchical tiers or nested coherent social units, different from other populations of killer whales. We suggest that local ecological context, such as the characteristics of the specific target prey (e.g., predictability, biomass, and density) and subsequent foraging strategies may strongly influence killer whale social association patterns.Peer reviewe
Association matrix and individual supplementary details of Icelandic killer whales
No full textFirst sheet with details for each individual (sex-age class, movement pattern, number of records - number of photographs -, number of total days sampled and number of different years seen). Second sheet with the association matrix for all individuals, no restrictions on the number of sightings, calculated using SOCPROG 2.6 software (half-weight index used)
Geographic variation in the time-frequency characteristics of high-frequency whistles produced by killer whales (Orcinus orca)
No full textInvestigating intraspecific variation in acoustic signals can indicate the extent of isolation and divergence between populations and adaptations to local environments. Here we analyze the variation in killer whale high frequency (>17 kHz) whistles recorded off Norway, Iceland, and in the North Pacific. We used a combination of methods including multivariate comparisons of spectral and temporal parameters and categorization of contours to types. Our results show that spectral and temporal characteristics of high-frequency whistles recorded in the North Pacific show significant differences from whistles recorded in the Northeast Atlantic, being generally stereotyped, lower in frequency, and slightly longer in duration. Most high-frequency whistles from the North Pacific were downsweeps, whereas this was one of the least common types recorded in the Northeast Atlantic. The repertoire of whistles recorded in Norway was similar to Iceland, but whistles produced in Norway had significantly lower maximum frequency and frequency range. Most methods were able to discriminate between whistles of the North Pacific and the Northeast Atlantic, but were unable to consistently distinguish whistles from Iceland and Norway. This suggests that macro- and microgeographic differences in high-frequency whistles of killer whales may reflect historical geographic isolation between ocean basins and more recent divergence between adjacent populations
Persistence of skin marks on killer whales (Orcinus orca) caused by the parasitic sea lamprey (Petromyzon marinus) in Iceland
No full textLampreys have long been thought to be a cetacean ectoparasite, due to the observation of round marks on the skin of whales caught during whaling operations. Pike (1951), Nemoto (1955), and van Utrecht (1959) compared such marks on the skin of various cetacean species caught in the Pacific and Atlantic Oceans with the dentition of lampreys and concluded that most round marks had been caused by this parasite. However, lampreys were never collected from captured whales and, due to the lack of direct evidence, some discussion emerged as to the origin of these wounds. Jones (1971) later argued that crescent-shaped marks previously attributed to lampreys were in fact caused by cookie-cutter sharks (Isistius brasiliensis). However, he agreed that other round marks were undoubtedly caused by lampreys. Recently, photographs of sea lampreys (Petromyzon marinus) attached to northern right whales, Eubalaena glacialis (Nichols and Hamilton 2004), and minke whales, Balaenoptera acutorostrata (Nichols and Tscherter 2011), in the western North Atlantic conclusively showed that lampreys do associate with those species. Similar evidence for other cetaceans is still lacking
Killer whales (Orcinus orca) in Iceland show weak genetic structure among diverse isotopic signatures and observed movement patterns
No full textFunding was provided by the Fundação para a Ciência e a Tecnologia (grant number SFRH/BD/84714/2012) and a MASTS (The Marine Alliance for Science and Technology for Scotland) pooling initiative (grant reference SG188) funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions to S.B.T. and the Icelandic Research Fund (Rannsóknasjóđur, grant number 120248042) to F.I.P.S.Local adaption through ecological niche specialization can lead to genetic structure between and within populations. In the Northeast Pacific, killer whales (Orcinus orca) of the same population have uniform specialized diets that are non‐overlapping with other sympatric, genetically divergent, and socially isolated killer whale ecotypes. However, killer whales in Iceland show intrapopulation variation of isotopic niches and observed movement patterns: some individuals appear to specialize on herring and follow it year‐round while others feed upon herring only seasonally or opportunistically. We investigated genetic differentiation among Icelandic killer whales with different isotopic signatures and observed movement patterns. This information is key for management and conservation purposes but also for better understanding how niche specialization drives genetic differentiation. Photo‐identified individuals (N = 61) were genotyped for 22 microsatellites and a 611 bp portion of the mitochondrial DNA (mtDNA) control region. Photo‐identification of individuals allowed linkage of genetic data to existing data on individual isotopic niche, observed movement patterns, and social associations. Population subdivision into three genetic units was supported by a discriminant analysis of principal components (DAPC). Genetic clustering corresponded to the distribution of isotopic signatures, mtDNA haplotypes, and observed movement patterns, but genetic units were not socially segregated. Genetic differentiation was weak (FST < 0.1), suggesting ongoing gene flow or recent separation of the genetic units. Our results show that killer whales in Iceland are not as genetically differentiated, ecologically discrete, or socially isolated as the Northeast Pacific prey‐specialized killer whales. If any process of ecological divergence and niche specialization is taking place among killer whales in Iceland, it is likely at a very early stage and has not led to the patterns observed in the Northeast Pacific.Peer reviewe
Cultural evolution of killer whale calls: background, mechanisms and consequences
No full textCultural evolution is a powerful process shaping behavioural phenotypes of many species including our own. Killer whales are one of the species with relatively well-studied vocal culture. Pods have distinct dialects comprising a mix of unique and shared call types; calves adopt the call repertoire of their matriline through social learning. We review different aspects of killer whale acoustic communication to provide insights into the cultural transmission and gene-culture co- evolution processes that produce the extreme diversity of group and population repertoires. We argue that the cultural evolution of killer whale calls is not a random process driven by steady error accumulation alone: temporal change occurs at different speeds in different components of killer whale repertoires, and constraints in call structure and horizontal transmission often degrade the phylogenetic signal. We discuss the implications from bird song and human linguistic studies, and propose several hypotheses of killer whale dialect evolution
Killer whales (Orcinus orca) produce ultrasonic whistles
No full textThis study reports that killer whales, the largest dolphin, produce whistles with the highest fundamental frequencies ever reported in a delphinid. Using wide-band acoustic sampling from both animal-attached (Dtag) and remotely deployed hydrophone arrays, ultrasonic whistles were detected in three Northeast Atlantic populations but not in two Northeast Pacific populations. These results are inconsistent with analyses suggesting a correlation of maximum frequency of whistles with body size in delphinids, indicate substantial intraspecific variation in whistle production in killer whales, and highlight the importance of appropriate acoustic sampling techniques when conducting comparative analyses of sound repertoires
A comparison of Northeast Atlantic killer whale (Orcinus orca) stereotyped call repertoires
No full textKiller whale call repertoires can provide information on social connections among groups and populations. Killer whales in Iceland and Norway exhibit similar ecology and behavior, are genetically related, and are presumed to have been in contact before the collapse of the Atlanto-Scandian herring stock in the 1960s. However, photo-identification suggests no recent movements between Iceland and Norway but regular movement between Iceland and Shetland. Acoustic recordings collected between 2005–2016 in Iceland, Norway, and Shetland were used to undertake a comprehensive comparison of call repertoires of Northeast Atlantic killer whales. Measurements of time and frequency parameters of calls from Iceland (n = 4,037) and Norway (n = 1,715) largely overlapped in distribution, and a discriminant function analysis had low correct classification rate. No call type matches were confirmed between Iceland and Norway or Shetland and Norway. Three call types matched between Iceland and Shetland. Therefore, this study suggests overall similarities in time and frequency parameters but some divergence in call type repertoires. This argues against presumed past contact between Icelandic and Norwegian killer whales and suggests that they may not have been one completely mixed population
Icelandic herring-eating killer whales feed at night
No full textThis study was funded by an Icelandic Research Fund (i. Rannsóknasjóður, grant number 120248042) supported by a Marie Curie Fellowship.Herring-eating killer whales debilitate herring with underwater tail slaps and likely herd herring into tighter schools using a feeding-specific low-frequency pulsed call (‘herding’ call). Feeding on herring may be dependent upon daylight, as the whales use their white underside to help herd herring; however, feeding at night has not been investigated. The production of feeding-specific sounds provides an opportunity to use passive acoustic monitoring to investigate feeding behaviour at different times of day. We compared the acoustic behaviour of killer whales between day and night, using an autonomous recorder deployed in Iceland during winter. Based upon acoustic detection of underwater tail slaps used to feed upon herring we found that killer whales fed both at night and day: they spent 50% of their time at night and 73% of daytime feeding. Interestingly, there was a significant diel variation in acoustic behaviour. Herding calls were significantly associated with underwater tail slap rate and were recorded significantly more often at night, suggesting that in low-light conditions killer whales rely more on acoustics to herd herring. Communicative sounds were also related to underwater tail slap rate and produced at different rates during day and night. The capability to adapt feeding behaviour to different light conditions may be particularly relevant for predator species occurring in high latitudes during winter, when light availability is limited.Peer reviewe
