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Vocalizations of common minke whales ( Balaenoptera acutorostrata ) in an eastern North Pacific feeding ground
Abstract
The minke whale (Balaenoptera acutorostrata) is the smallest species of baleen whale and has a cosmopolitan distribution. Despite extensive study on the vocalizations of other balaenopterids, the acoustic repertoire of minke whales is not well known. Individuals of the North Pacific subspecies of common minke whale (B. a. scammoni) are known to produce unique vocalizations ("boings") during their putative breeding season from fall to spring. However, no vocalizations have been previously reported for this subspecies in summer feeding grounds. We present four novel call types recorded in the presence of minke whales in Cormorant Channel, in coastal British Columbia, Canada, during the summer of 2012. These calls consist of broadband pulses, tonal wavers, downsweeps, and pulse trains. Calling rates for minke whales in this study region were very low compared to those reported for North Atlantic minke whales on their feeding grounds. We compare our candidate call types with vocalizations described for other minke whale populations and propose predation risk as a cause of the low calling rates observed for minke whales in Cormorant Channel.
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From June to August 2012, we conducted over 500 h of visual surveys from Cormorant Island, British Columbia, to determine behaviour and habitat use patterns of nearby cetaceans. Seven species were documented, but Minke Whales (Balaenoptera acutorostrata) were by far the most common and were observed lunge feeding at the surface on 15 occasions. In addition, this species was documented surface lunge feeding on Pacific Herring (Clupea pallasi) and Pacific Sand Lance (Ammodytes personatus) on 32 occasions during vessel-based cetacean surveys around Cormorant Island between 2010 and 2014. Although Minke Whales are relatively uncommon in British Columbia, these results indicate that they can regularly be found in specific feeding areas during the summer.
Humpback whales produce a wide range of low- to mid-frequency vocalizations throughout their migratory range. Non-song “calls” dominate this species' vocal repertoire while on high-latitude foraging grounds. The source levels of 426 humpback whale calls in four vocal classes were estimated using a four-element planar array deployed in Glacier Bay National Park and Preserve, Southeast Alaska. There was no significant difference in source levels between humpback whale vocal classes. The mean call source level was 137 dBRMS re 1 μPa @ 1 m in the bandwidth of the call (range 113–157 dBRMS re 1 μPa @ 1 m), where bandwidth is defined as the frequency range from the lowest to the highest frequency component of the call. These values represent a robust estimate of humpback whale source levels on foraging grounds and should append earlier estimates.
Source levels of harbor seal breeding vocalizations were estimated using a three-element planar hydrophone array near the Beardslee Islands in Glacier Bay National Park and Preserve, Alaska. The average source level for these calls was 144 dBRMS re 1 μPa at 1 m in the 40–500 Hz frequency band. Source level estimates ranged from 129 to 149 dBRMS re 1 μPa. Four call parameters, including minimum frequency, peak frequency, total duration, and pulse duration, were also measured. These measurements indicated that breeding vocalizations of harbor seals near the Beardslee Islands of Glacier Bay National Park are similar in duration (average total duration: 4.8 s, average pulse duration: 3.0 s) to previously reported values from other populations, but are 170–220 Hz lower in average minimum frequency (78 Hz).
The minke whale is one of the most abundant species of baleen whales worldwide, yet is rarely sighted in subtropical waters. In the North Pacific, they produce a distinctive sound known as the “boing,” which can be used to acoustically localize individuals. A vessel-based survey using both visual and passive acoustic monitoring was conducted during the spring of 2007 in a large (616,000 km2) study area encompassing the Mariana Islands. We applied line transect methods to data collected from a towed hydrophone array to estimate the abundance of calling minke whales in our study area. No minke whales were sighted, but there were hundreds of acoustic detections of boings. Computer algorithms were developed to localize calling minke whales from acoustic recordings, resulting in over 30 independent localizations, a six-fold increase over those estimated during the survey. The two best estimates of abundance of calling minke whales were determined to be 80 and 91 animals (0.13 and 0.15 animals per 1,000 km2, respectively; CV = 34%). These are the first density and abundance estimates for calling minke whales using towed hydrophone array surveys, and the first estimates for this species in the Mariana Islands region. These are considered minimum estimates of the true number of minke whales in the study area.
In the eastern North Pacific Ocean, common minke whales (Balaenoptera acutorostrata) are widespread but encountered relatively infrequently. It is generally believed that they make annual migrations between higher latitudes in the summer and lower latitudes in the winter; however, in some temperate coastal regions where common minke whales have been sighted year-round they have been referred to as resident. To determine movement patterns of common minke whales found in coastal waters of British Columbia and Washington we examined photo-identification data that were collected opportunistically from 2005–12. These data were from four non-overlapping areas between 48°N and 53°N. Despite year-round search efforts, common minke whales were only encountered between April and October. Most of the 44 unique individuals identified in 405 encounters displayed fidelity to areas both within and among years. Five of these whales made relatively large-scale intra-annual movements between areas on six occasions. They were documented to move up to 424km in a northerly direction in spring and up to 398km in a southerly direction in autumn. The seasonal patterns of these movements provide new insights into the foraging ranges and migrations of the individuals. Ecological markers provide evidence that the common minke whales photographed undertake annual long distance migrations. Scars believed to be from cookiecutter shark (Isistius brasiliensis) bites were observed on 43 individuals and the majority of whales documented with good quality images each year had acquired new scars since the previous year. Furthermore, the commensal barnacle Xenobalanus globicipitis was observed on three individuals. Since these sharks and barnacles are from relatively warm waters, it can be inferred that they interacted with the common minke whales at lower latitudes. These findings may have important implications for the definition and management of common minke whale stocks and/or populations in the eastern North Pacific.
A bstract
Density estimation for marine mammal species is performed primarily using visual distance sampling or capture‐recapture. Minke whales in Hawaiian waters are very difficult to sight; however, they produce a distinctive “boing” call, making them ideal candidates for passive acoustic density estimation. We used an array of 14 bottom‐mounted hydrophones, distributed over a 60 × 30 km area off Kauai, Hawaii, to estimate density during 12 d of recordings in early 2006. We converted the number of acoustic cues ( i.e. , boings) detected using signal processing software into a cue density by accounting for the false positive rate and probability of detection. The former was estimated by manual validation, the latter by applying spatially explicit capture‐recapture (SECR) methods to a subset of data where we had determined which hydrophones detected each call. Estimated boing density was 130 boings per hour per 10,000 km ² (95% CI 104–163). Little is known about the population's acoustic behavior, so conversion from boing to animal density is difficult. As a demonstration of the method, we used a tentative boing rate of 6.04 boings per hour, from a single animal tracked in 2009, to give an estimate of 21.5 boing‐calling minke whales per 10,000 km ² .
Vocalizing by natural-living harbour seals has been considered to be rare, limited primarily to aerial threats. A few studies on captive harbour seals, however, indicated that this species produced a wider variety of aerial vocalizations than was previously thought. The objective of this study was to determine whether adult male harbour seals in the wild vocalized under water during the breeding season and whether there was any variation in vocalizations between individuals. Underwater vocalizations of 10 males were tape-recorded at Point Lobos State Reserve, California during the spring and summer of 1991. Females did not vocalize except on land when they threatened other seals. Observational data was taken to identify the vocalizing seal and to determine whether other seals in the vicinity showed any reactions to the vocalizations. Five vocalization types were identified and analysed: grunt, groan, creak, bubbly growl and roar. There were significant differences between males with regard to the frequency measurements of the roars as well as to their entire acoustic displays but there was little intra-individual variation. It is suggested that underwater vocalizations are used in male-male competition and/or as reproductive advertisement displays to attract females.
Passive acoustic monitoring (PAM) is a rapidly growing field, providing valuable
insights in marine ecology. The approach allows for long-term, species-specific monitoring over a
range of spatial scales. For many baleen whales fundamental information on seasonal occurrence
and distribution is still missing. In this study, pulse trains produced by the North Atlantic minke
whale, a highly mobile and cryptic species, are used to examine its seasonality, diel vocalization
patterns and spatial distribution throughout the Stellwagen Bank National Marine Sanctuary
(SBNMS), USA. Three and a half years (2006, 2007 to 2010) of near continuous passive acoustic
data were analyzed using automated detection methods. Random forests and cluster analyses
grouped pulse trains into 3 main categories (slow-down, constant and speed-up), with several subtypes.
Slow-down pulse trains were the most commonly recorded call category. Minke whale
pulse train occurrence was highly seasonal across all years. Detections were made from August
to November, with 88% occurring in September and October. No detections were recorded in
January and February, and only few from March to June. Minke whale pulse trains showed a distinct
diel pattern, with a nighttime peak from approximately 20:00 to 01:00 h Eastern Standard
Time (EST). The highest numbers of pulse trains were detected to the east of Stellwagen Bank,
suggesting that minke whales travel preferably in deeper waters along the outer edge of the sanctuary.
These data show that minke whales consistently use Stellwagen Bank as part of their migration
route to and from the feeding grounds. Unlike other baleen whales in this area they do not
appear to have a persistent year-round acoustic presence.
Laidre, K. L., Heagerty, P. J., Heide-Jørgensen, M. P., Witting, L., and Simon, M. 2009. Sexual segregation of common minke whales (Balaenoptera acutorostrata) in Greenland, and the influence of sea temperature on the sex ratio of catches. – ICES Journal of Marine Science, 66: 2253–2266.
The harvest of common minke whales (Balaenoptera acutorostrata) in West Greenland has historically been skewed towards female whales, yet a complete analysis of spatial and temporal patterns of catch sex ratio has never been conducted. We examined trends in the sex ratio of catches over time, season, space, and relative to sea temperature using 2400 records from inshore Greenland subsistence whaling operations (1960–2006) and 2072 records from offshore Norwegian commercial operations (1968–1985). Logistic regression models were developed to examine the trend in sex ratio in three regions (Northwest, NW; Central West, CW; Southwest, SW) and by latitude. The highly skewed proportion of females in all catches was strongly positively correlated (r² = 0.8) with latitude in the offshore catches (>100 km). Generalized linear models of inshore catches indicated slightly increasing though non-significant trends in the proportion of females taken off CW and NW Greenland and a significant declining trend off SW Greenland. Sensitivity analyses show that the declining inshore SW trend was entirely accounted for by the past 5 years (2002–2006) of data. Models containing both year and temperature interactions suggested that either parameter provided an equivalent explanation of the variation in trends across regions.
Sound production by many fish species has been studied extensively, but little is known about sound production by rockfishes (genus Sebastes), and only a few species have been reported to be soniferous. To determine if additional rockfish species produce sounds, passive acoustic recordings were made during 2007/08 at Hubbs-SeaWorld Research Institute and Southwest Fisheries Science Center in tanks containing Bocaccio (S. paucispinis), Cowcod (S. levis), Starry Rockfish (S. constellatus), and Sunset Rockfish (S. crocotulus). Data were collected using pre-amplified hydrophones (HTI-94-SSQ) and digitized at sample rates of 44,100 or 8,000 Hz (using an Edirol R-09 recorder or Edirol UA-5 sound card and Ishmael software, respectively). Three distinct sounds were recorded in tanks containing only S. paucispinis and two of those sounds occurred at different rates during light and dark conditions. Their common characteristics were low frequency (below 800 Hz), short duration (<4 s), and low source levels (103–113 dB re: 1 µPa at 1 m). Also, there was evidence one or more other species produced sounds. These findings indicate that more rockfishes produce sounds, and suggest passive acoustics could be a useful tool for remotely monitoring their populations.
Balaenoptera acutorostrata (minke whale) is a small and elusive baleen whale that is rarely sighted in the tropical waters of the North Pacific Ocean. During winter and spring, complex sounds called ”boings” are frequently detected around the Hawaiian Islands and other Pacific island regions (Norris et al. 2009; Thompson and Friedl 1982). Although boings were described over 45 years ago (Wenz 1964), they were not attributed to minke whales until very recently (Rankin and Barlow 2005). Sightings of Balaenoptera acutorostrata are uncommon in tropical and subtropical waters; however, boings are frequently detected around the Hawaiian Islands using seafloor hydrophones and from hydrophone arrays towed from research vessels. Even today, very little is known about acoustic behaviors and ecology of Balaenoptera acutorostrata. The long-term objective of this research effort is to improve our understanding of the acoustic ecology and behavior of Balaenoptera acutorostrata in their breeding habitat.
A recently described population of minke whales (Balaenoptera acutorostrata) offered a unique opportunity to study its acoustic behavior. The often-inquisitive dwarf minke whale is seen on the Great Barrier Reef nearly coincident with its suspected calving and breeding seasons. During drifting encounters with whales, a towed hydrophone array was used to record sounds for subsequent localization of sound sources. Shipboard and in-water observers linked these sounds to the closely circling minke whale. A complex and stereotyped sound sequence, the "star-wars" (SW) vocalization, was recorded during a series of visual and acoustic observations. The SW vocalization spanned a wide frequency range (50 Hz-9.4 kHz) and was composed of distinct and stereotypically repeated units with both amplitude and frequency-modulated components. Broadband source levels between 150 and 165 dB re 1 microPa at 1 m were calculated. Passive acoustic studies can utilize this distinct vocalization to help determine the behavior, distribution, and movements of this animal. While the SW vocalization's function remains unknown, the regularly repeated and complex sound sequence was common in low latitude, winter month aggregations of minke whales. At this early stage, the SW vocalization appears similar to the songs of other whale species and has characteristics consistent with those of reproductive advertisement displays.
During a recent cetacean survey of the U.S. waters surrounding the Hawaiian Islands, the probable source of the mysterious "boing" sound of the North Pacific Ocean was identified as a minke whale, Balaenoptera acutorostrata. Examination of boing vocalizations from three research surveys confirms previous work that identified two distinct boing vocalization types in the North Pacific. The eastern boing (n = 22) has a pulse repetition rate of 92 s(-1) and a duration of 3.6 s and was found only east of 138 degrees W. The central boing (n = 106) has a pulse repetition rate of 115 s(-1) and a duration of approximately 2.6 s and was found only west of 135 degrees W. Central boing vocalizations produced by a single source (n = 84) indicate that variation in repetition rate and duration of the calls of the individual were not significantly different than the variation among individuals of the same boing type. Despite a slight latitudinal overlap in the vocalizations, pulse repetition rates of the eastern and central boings were distinct.
Recent speciation events provide important insights into the understanding and conservation of Earth's biodiversity, representing recent adaptations to a changing environment and an important source of future evolutionary potential. However, the most frequently applied criterion for molecular-based speciation investigations, that of reciprocal monophyly of mitochondrial sequences, overlooks recent speciation events where insufficient time has passed for fixed molecular differences to develop between putative species. Two morphologically distinguishable forms of finless porpoise (genus Neophocaena) exist in sympatry in the strait of Taiwan, however the taxonomic relationship of these different forms is controversial. To test the hypothesis that the two forms represent different species, a study was conducted based on morphological characters and microsatellite and mitochondrial markers. The data suggest that the two forms are highly differentiated in terms of both morphology and genetic characteristics, despite being sympatric, and therefore represent different species as defined by the biological species concept. Moreover, the two forms appear to have been reproductively isolated since sharing a common ancestor prior to the last major glaciation event approximately 18 000 years ago. However, this represents an insufficient amount of time for reciprocal monophyly to have developed, and thus previous studies based on this criterion have overlooked this speciation event and resulted in incorrect taxonomic classification of these forms.
During breeding season, male harbor seals (Phoca vitulina) produce underwater calls used in sexual competition and advertisement. Call characteristics vary among populations, and within-population differences are thought to represent individual variation. However, vocalizations have not been described for several populations of this widely-distributed and genetically diverse species. This study describes the vocal repertoire of harbor seals from British Columbia, Canada. Underwater recordings were made near Hornby Island during the summer of 2014 using a single hydrophone. A wide variability was detected in breeding vocalizations within this single breeding site. Four candidate call types were identified, containing six subtypes. Linear discriminant analysis showed 88% agreement with subjective classification of call types, and 74% agreement for call subtypes. Classification tree analysis gave a 92% agreement with candidate call types, with all splits made on the basis of call duration. Differences in duration may have reflected individual differences among seals. This study suggests that the vocal repertoire of harbor seals in this area comprises a vocal continuum rather than discrete call types. Further work with the ability to localize calls may help to determine whether this complexity represents variability due to propagation conditions, animal orientation, or differences among individual seals.
Research has suggested killer whale (Orcinus orca) predation may affect cetacean vocal behavior; however, few data exist to test this hypothesis. Data collected during 40,976 km of visual and acoustic shipboard surveys in the tropical Pacific Ocean, including 1,232 detections of 13 species, were examined to determine if changes in dolphin vocal activity could be attributed to the presence of killer whales. Generalized linear models and Random Forest analyses were used to test the hypothesis that dolphin vocal activity was related to the distance and time to the nearest killer whale sighting. Both results show that dolphin vocalizations were inversely correlated with the temporal proximity of killer whales (P < 0.05). Despite the relative rarity of killer whales in the tropics, they appear to influence vocal behavior of nearby dolphin schools. This disruption in communication may not significantly impact interactions necessary for survival in tropical waters where killer whale density is low. However, in temperate climates, where increased productivity supports a greater abundance of killer whales, this interruption in communication may have a greater impact. The lower incidence of whistling dolphins in temperate waters may be related to the greater abundance of killer whales in these areas. This article is a U.S. Government work and is in the public domain in the USA.
With coverage on all the marine mammals of the world, authors Jefferson, Webber, and Pitman have created a user-friendly guide to identify marine mammals alive in nature (at sea or on the beach), dead specimens in hand, and also to identify marine mammals based on features of the skull. This handy guide provides marine biologists and interested lay people with detailed descriptions of diagnostic features, illustrations of external appearance, beautiful photographs, dichotomous keys, and more. Full color illustrations and vivid photographs of every living marine mammal species are incorporated, as well as comprehendible maps showing a range of information. For readers who desire further consultation, authors have included a list of literature references at the end of each species account. For an enhanced understanding of habitation, this guide also includes recognizable geographic forms described separately with colorful paintings and photographs. All of these essential tools provided make Marine Mammals of the World the most detailed and authoritative guide available! * Contains superb photographs of every species of marine mammal for accurate identification * Authors collective experience adds up to 80 years, and have seen nearly all of the species and distinctive geographic forms described in the guide * Provides the most detailed and anatomically accurate illustrations currently available * Special emphasis is placed on the identification of species in problem groups, such as the beaked whales, long-beaked oceanic dolphin, and southern fur seals * Includes a detailed list of sources for more information at the back of the book.
We determined the gender of deer samples using polymerase chain reaction primers to the sry gene located on the Y chromosome of mammalian males. Primers to the ZFX/ZFY genes were added to the same amplification reaction as a control against amplification failure. The sry fragment amplified from deer DNA was partially sequenced. Sequence alignment with published bp sequences from other mammals and get migration indicate the fragment is 174 bp long. In a blind test, tissue samples from 100 individual deer and elk of known sex were correctly gender-typed. DNA from deer bloodstains and hair samples was successfully amplified and typed. Under known limiting DNA conditions, the duplex reaction results were reliable and no false positive females were observed. DNA detection on gels stained with SYBR green was more sensitive than with ethidium bromide. DNA from wildlife forensic samples confiscated between 1990 and 1997 was extracted with Chelex 100 and tested. Twenty-four out of 31 different evidence items tested were successfully gender-typed: 15 out of 21 bloodstains, 5 out of 6 hairs, and 4 out of 4 tissue samples.
Information on individual calling behaviour and source levels are important for understanding
acoustically mediated social interactions of marine mammals, for which visual observations are
difficult to obtain. Our study, conducted in the Stellwagen Bank National Marine Sanctuary (SB-
NMS), located in the Gulf of Maine, USA, used passive acoustic arrays to track North Atlantic
minke whales and assess the sound production behaviour of individuals. A total of 18 minke whales
were acoustically tracked in this study. Individual calling rates were variable, with a median inter-
call interval (ICI) of 60.3 s. Average source levels (SLrms ) for minke whales pulse trains ranged
between 164 and 168 dB re 1 μPa, resulting in a minimum detection range of 0.4–10.2 km for
these calls in this urban, coastal environment. All tracked animals were actively swimming at a
speed of 5.0 ± 1.2 km/h, which matches swimming speeds of migrating minke whales from other
areas and confirms SBNMS as part of the migration route of this species in the Western North At-
lantic. Tracked minke whales produced 7 discrete call types belonging to 3 main categories, yet no
individual produced all call types. Instead, minke whales produced 2 multisyllabic call sequences
(A and B) by combining 3–4 different call types in a non-random order. While 7 of the tracked
individuals produced calling pattern A, 10 whales used calling pattern B, and only 1 animal com-
bined call types differently. Animals producing different call sequences were in acoustic range of
one another on several occasions, suggesting they may use these sequences for mediating social
interactions. The fact that the same calling patterns were shared by several individuals suggests
that these patterns may contain information related to sex, age or behavioural context.
Underwater soundscapes vary due to the abiotic and biological components of the habitat. We quantitatively characterized the acoustic environments of two coral reef habitats, one in the Tropical Eastern Pacific (Panama) and one in the Caribbean (Florida Keys), over 2-day recording durations in July 2011. We examined the frequency distribution, temporal variability, and biological patterns of sound production and found clear differences. The Pacific reef exhibited clear biological patterns and high temporal variability, such as the onset of snapping shrimp noise at night, as well as a 400-Hz daytime band likely produced by damselfish. In contrast, the Caribbean reef had high sound levels in the lowest frequencies, but lacked clear temporal patterns. We suggest that acoustic measures are an important element to include in reef monitoring programs, as the acoustic environment plays an important role in the ecology of reef organisms at multiple life-history stages.
Recordings of vocalizations in the presence of minke whales Balaenoptera acutorostrata were made from a bottom-mounted hydrophone in the St. Lawrence Estuary, a feeding area for some members of the Northwest Atlantic population. Minke whale activity was observed from a hillside hut and notes were taken with regard to position and swimming direction throughout each recording. The vocalizations were correlated consistently with the occurrence of minkes and sequential sound levels were commensurate with the whale's relative proximity to the hydrophone. Minke calls were heard in 51% of the recordings examined in detail; calling rates were low (0.1 sounds/min—3.6 sounds/min with multiple individuals). The predominant call was a 0.4 sec downsweep in frequency, beginning at 100–200 Hz (median = 118 Hz) and ending below 90 Hz (median = 80 Hz). The change in frequency was variable, between 20 and 70 Hz (median = 42 Hz). Frequency and temporal characteristics of the vocalizations were similar to those recorded from Antarctic minkes by Schevill and Watkins (1972). Comparisons of the minke downsweeps with those from the closely related finback whale B. physalus, which is also common in the area, indicated that minke whale calls had higher initial frequencies, greater changes in frequency, and shorter call durations.
A bstract
A nine‐day acoustic and visual survey was conducted off the West Indies in March 1994 to study the pulse trains that were detected on SOSUS arrays throughout winter in deep water between the West Indies and Bermuda. During the survey, pulse train sounds were consistently recorded in an area 190–350 km northeast of Puerto Rico. Vocalizing animals were never visually observed, but visual sighting conditions were often poor and observation height was low. Pulse trains occurred in two basic forms. The “speed‐up” pulse train was characterized by an accelerating series of pulses with energy in the 200–400 Hz band, with individual pulses lasting 40‐60 msec. Speedup pulse trains started with average pulse rates of 1.5 pulses/sec, lasted 43.7 ± 6.0 sec, and ended with average pulse rates of 2.8 pulses/sec. The less common “slow‐down” pulse train was characterized by a decelerating series of pulses with energy in the 250‐350 Hz band. Slow‐down pulse trains started at pulse rates averaging 4.5 pulses/sec, lasted 60.9 ± 5.8 sec, and ended with average pulse rates of 2.9 pulses/sec. We believe the recorded pulse trains are from minke whales based on careful reanalysis of, and comparison to, minke whale pulse‐train sounds recorded in the Caribbean by Winn and Perkins (1976).
A bstract
Lightweight untethered pneumatic darts were used to biopsy killer whales, Orcinus orca , for genetic and toxicological analysis. Samples of epidermal, dermal, and hypodermal tissue weighing approximately 0.5 g were obtained by 65% of the 91 darts fired during the study. Sufficient DNA for multiple analyses was extracted from the biopsies, which were also used for fatty acid and toxic contaminant analyses. Reactions such as momentary shakes or accelerations were observed after 81% of the dart hits and 53% of the misses. Aversion to the research vessel was assessed by reapproaching target whales after the sampling attempts. In 6% of the hits and 8% of the misses aversion to the research boat increased immediately following the attempt. No similar increases in aversion were seen when killer whales were reapproached one day to one year after being hit. The darts were also tested successfully on humpback whales, Megaptera novaeangliae . In view of the simplicity of the system, its effectiveness in acquiring multipurpose samples, and the apparently short‐term disturbance it caused, it is recommended for future cetacean biopsy studies.
We describe nine incidents of predation or attempted predation of minke whales (Balaenoptera acutorostrata) by mammal-hunting “transient” killer whales (Orcinus orca) in coastal waters of British Columbia, Washington, and southeastern Alaska. Pursuits of minke whales were characterized by prolonged chases on a straight heading at velocities of 15–30 km/h. In four of the nine cases the adultsized minke whale gradually outdistanced the killer whales, which abandoned the high-speed pursuit after 0.5–1 h. In one case the minke beached itself and died. Four attacks were successful. In one instance a subadult minke was killed in open water following a chase. In two cases the fleeing minke entered a confined bay and was killed by the killer whales. One adult minke was taken after apparently attempting to seek cover beside a large sailboat. Minke whales made no attempt to physically defend themselves and were killed by repeated ramming or by asphyxiation. Although killer whales are capable of sprinting speeds greater than those of minke whales, it appears that adult minkes can maintain higher sustained speeds and evade capture if sufficient space for an extended escape trajectory is available. Successful predation of minke whales in coastal waters is rare compared to pinnipeds and small cetaceans, the main prey of transient killer whales.
Interactions of singing humpback whales, Megaptera novaeangliae, with conspecifics nearly were studied during the breeding season off the west coast of Maui, Hawaii. On 35 occasions singing humpbacks were followed by boats (Table 1). The movement patterns of these singing whales and other conspecifics nearby were recorded by observers on land using a theodolite.
Thirteen of 35 singers stopped singing and joined with nonsinging whales either simultaneously or within a few minutes after ceasing to sing. Another 15 also stopped singing while under observation and were not seen to join with another whale, but all singing whales that joined with other whales stopped singing. Singing whales often pursue nonsinging whales, while nonsinging whales usually turn away from singers (Figs. 4, 5).
When a singer joined with a female and calf unaccompanied by another adult, behavior tentatively associated with courtship and mating was observed (Fig. 7). Such behavior also occurred during several interactions between singers and individuals of unknown sex. Aggressive behavior was observed during three interactions between singers and individuals of unknown sex (Fig. 4) and it predominated whenever more than one adult accompanied a cow and calf. During the other occasions when a singer joined another whale, we could not determine the nature of the interaction. Many times the singers and joiner would surface together only once and would then separate. However, on several occasions the singer and joiner would remain together for as long as we could follow them, up to 1.5 h.
The roles of singer and joiner can be interchangeable. For instance, on two occasions a singer joined with a whale that either had been singing or started singing later in the day (Fig. 3). Furthermore, on several occasions, a nonsinging whale appeared to displace the singer. Individual singing humpbacks are not strictly territorial, although singers appear to avoid other singers.
As the breeding season progressed, singers sang for longer periods of time (Fig. 2). In addition, the probability of a whale joining with the singer decreased by 42% from the first half of the observation period to the second half. Furthermore, this increase in duration of song bouts occurred during that section of the season when female reproductive activity as measured by rate of ovulation is reported to be decreasing in other areas.
Our observations support the hypothesis that humpback song plays a reproductive role similar to that of bird song. Humpbacks sing only during the breeding season. If, as seems likely, most singing humpbacks are male, then singing humpbacks probably communicate their species, sex, location, readiness to mate with females, and readiness to engage in agonistic behavior with other whales.
We recorded sounds principally between 4 and 7·5 kHz and with click repetition rates of 6·75 ± 1·02 clicks per second, in the presence of a Minke or Little Piked whale that was circling within tens of meters of a quiet ship. The narrow-band pulses might be suitable for echolocation. These sounds comprise the best of evidence published to date for the possible use of echolocation by Mysticeti.
Northeast Pacific blue whales, Balaenoptera musculus, migrate annually between productive summer feeding grounds off North America and tropical winter breeding grounds off Central America. These migratory movements have been confirmed through acoustic monitoring of the long-duration, low-frequency sounds produced by males (type B calls). However, other calls in the species' repertoire might prove a better proxy for the migratory and foraging behaviour of the population as a whole. To explore the seasonal and daily calling behaviour of this population, we evaluated the occurrence of three blue whale call types (song B, singular B and D) recorded between 2000 and 2004 at Cortez and Tanner Banks, a summer feeding area offshore of southern California. We recorded a significant temporal separation among the type B and D calls, both seasonally and daily, suggesting preferred use of certain call types during different behavioural states. A consistent seasonal pattern was evident, with D calling from April to November and song and singular B calling from June to January. In addition, D calls were heard primarily from dawn through to dusk, in contrast to the crepuscular pattern of song, suggesting that the production of D calls is related to feeding behaviour, which occurs primarily during the day on aggregated krill at depth. An increase in the length of the overall calling season was also observed from 2000 to 2004 and may be related to increased prey availability in the Southern California Bight relative to more southerly feeding areas.
The low-frequency vocalizations of fin and blue whales are the most powerful and ubiquitous biological sounds in the ocean. Here we combine acoustic localization and molecular techniques to show that, in fin whales, only males produce these vocalizations. This finding indicates that they may function as male breeding displays, and will help to focus concern on the impact of human-generated low-frequency sounds on recovering whale populations.
Occurrence of dwarf minke whales (Balaenoptera acutorostrata) on the northern Great Barrier Reef
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Information in support of the identification of critical habitat for transient killer whales (Orcinus orca) off the west coast of Canada
- Jkb Ford
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of critical habitat for transient killer whales (Orcinus orca) off the west coast of Canada. CSAS
Research Document 155.
Minke whale (Balaenoptera acutorostrata) boings detected at the station ALOHA cabled observatory
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