Papers by Susanna B . Blackwell
Bioacoustics-the International Journal of Animal Sound and Its Recording, 2008
bioRxiv (Cold Spring Harbor Laboratory), May 24, 2023
Journal of the Acoustical Society of America, Sep 1, 2018
In August 2013–2017, narwhals from Scoresby Sound, East Greenland, were instrumented with satelli... more In August 2013–2017, narwhals from Scoresby Sound, East Greenland, were instrumented with satellite-linked transmitters and acoustic sound and movement tags (AcousondeTM) over periods of up to 8 days. The records obtained provided continuous information on the whales’ acoustic behavior during foraging and social interactions. Burst-pulses were the most easily recognizable non-feeding vocalization. They tended to occur near the surface and were more common in records that displayed higher rates of clicks from other individuals, i.e., records that presumably would include more social interactions with other narwhals. Over 100 burst pulses detected in eight subjects were analyzed in terms of their overall length and their pattern of successive inter-click intervals (ICIs). While overall length could be somewhat variable, the succession of ICIs was unique for each whale and could therefore have an identity-carrying function, as the signature whistle does in bottlenose dolphins and other odontocetes. The occurrence of these individual-specific burst-pulses in time and space will be examined in relation to other factors provided by the tags, such as the time of day, whale depth, presence of conspecifics, and behavioral state. [Work sponsored in part by the Greenland Institute of Natural Resources.]
Journal of the Acoustical Society of America, 2006
Journal of the Acoustical Society of America, Nov 1, 2004
Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative spec... more Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative species with high seasonal site fidelity, such as the narwhal <i>Monodon monoceros</i>. In this controlled sound exposure study, six narwhals were live-captured and instrumented with animal-borne tags providing movement and behavioural data, and exposed to concurrent ship noise and airgun pulses. All narwhals reacted to sound exposure with reduced buzzing rates, where the response was dependent on the magnitude of exposure defined as 1/distance to ship. Buzzing rate was halved 12 km from the ship, and whales ceased foraging at approximately 7–8 km. The effect of exposure could be detected greater than 40 km from the ship. At only a few kilometres from the ship, the received high-frequency cetacean weighted sound exposure levels were below background noise indicating extreme sensitivity of narwhals towards sound disturbance and demonstrating their ability to detect signals embedde...
These data were used in the statistical analyses presented in the PLoS ONE paper "Spatial an... more These data were used in the statistical analyses presented in the PLoS ONE paper "Spatial and temporal patterns of sound production in East Greenland narwhals". Please consult the paper for the methodology. The database includes 6 columns with the following information:<b><br></b><b>Datetime:</b> date and time.<b><br></b><b>Ind:</b> individual, by name (see paper).<br><b>Depth:</b> diving depth, in meters. Negative depths are considered surface.<b>Area:</b> in which of the four areas defined in the paper (F = Fønfjord, O or Ø = Øfjord, G = Gåsefjord, and OG = Outer Gåsefjord) the subject was found<b>Buzz:</b> 1 if a terminal buzz was begun at that time by the whale carrying the tag, 0 otherwise.<b>Call:</b> 1 if a call was begun at that time by the whale carrying the tag or another whale, 0 otherwise.<br>Permission for capturing, handling, and tagging of ...
Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relati... more Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relative isolation from human perturbation and sustained predation pressures. The resulting naïvety has made this cryptic, deep-diving cetacean highly susceptible to disturbance, although quantifiable effects have been lacking. We deployed a submersible, animal-borne electrocardiograph-accelerometer-depth recorder to monitor physiological and behavioral responses of East Greenland narwhals after release from net entanglement and stranding. Escaping narwhals displayed a paradoxical cardiovascular down-regulation (extreme bradycardia with heart rate ≤4 beats per minute) superimposed on exercise up-regulation (stroke frequency >25 strokes per minute and energetic costs three to six times the resting rate of energy expenditure) that rapidly depleted onboard oxygen stores. We attribute this unusual reaction to opposing cardiovascular signals—from diving, exercise, and neurocognitive fear responses—that challenge physiological homeostasis
Analysis dataset in comma-delimited text format (.csv file extension). This dataset accompanies t... more Analysis dataset in comma-delimited text format (.csv file extension). This dataset accompanies the manuscript submitted in 2017 to PLOS ONE for publication:<br> Blackwell, S.B., C.S. Nations, M.E. Kauffman, A.M. Thode, A.S. Conrad, R.G. Norman, and K.H. Kim. Effects of tones associated with drilling activities on bowhead whale calling rates.<br>There are six fields in the dataset: DASAR, Site, DateTime, Calls, Airguns, and Tones.<br>
PLoS One, 2015
In proximity to seismic operations, bowhead whales (Balaena mysticetus) decrease their calling ra... more In proximity to seismic operations, bowhead whales (Balaena mysticetus) decrease their calling rates. Here, we investigate the transition from normal calling behavior to decreased calling and identify two threshold levels of received sound from airgun pulses at which calling behavior changes. Data were collected in August–October 2007–2010, during the westward autumn migration in the Alaskan Beaufort Sea. Up to 40 directional acoustic recorders (DASARs) were deployed at five sites offshore of the Alaskan North Slope. Using triangulation, whale calls localized within 2 km of each DASAR were identified and tallied every 10 minutes each season, so that the detected call rate could be interpreted as the actual call production rate. Moreover, airgun pulses were identified on each DASAR, analyzed, and a cumulative sound exposure level was computed for each 10-min period each season (CSEL10-min). A Poisson regression model was used to examine the relationship between the received CSEL10-min from airguns and the number of detected bowhead calls. Calling rates increased as soon as airgun pulses were detectable, compared to calling rates in the absence of airgun pulses. After the initial increase, calling rates leveled off at a received CSEL10-min of ~94 dB re 1 μPa2-s (the lower threshold). In contrast, once CSEL10-min exceeded ~127 dB re 1 μPa2- s (the upper threshold), whale calling rates began decreasing, and when CSEL10-min values were above ~160 dB re 1 μPa2-s, the whales were virtually silent.
Scientific Reports, Oct 29, 2020
Arctic top predators are expected to be impacted by increasing temperatures associated with clima... more Arctic top predators are expected to be impacted by increasing temperatures associated with climate change, but the relationship between increasing sea temperatures and population dynamics of Arctic cetaceans remains largely unexplored. Narwhals (Monodon monoceros) are considered to be among the most sensitive of Arctic endemic marine mammals to climate change due to their limited prey selection, strict migratory patterns and high site fidelity. In the context of climate change, we assume that the population dynamics of narwhals are partly influenced by changes in environmental conditions, with warm areas of increasing sea temperatures having lower abundance of narwhals. Using a unique large dataset of 144 satellite tracked narwhals, sea surface temperature (SST) data spanning 25 years (1993-2018) and narwhal abundance estimates from 17 localities, we (1) assessed the thermal exposure of this species, (2) investigated the SST trends at the summer foraging grounds, and (3) assessed the relationship between SST and abundance of narwhals. We showed a sharp SST increase in Northwest, Mideast and Southeast Greenland, whereas no change could be detected in the Canadian Arctic Archipelago (CAA) and in the Greenland Sea. The rising sea temperatures were correlated with the smallest narwhal abundance observed in the Mideast and Southeast Greenland (< 2000 individuals), where the mean summer sea temperatures were the highest (6.3 °C) compared to the cold waters of the CAA (0.7 °C) that were associated with the largest narwhal populations (> 40,000 individuals). These results support the hypothesis that warming ocean waters will restrict the habitat range of the narwhal, further suggesting that narwhals from Mideast and Southeast Greenland may be under pressure to abandon their traditional habitats due to ocean warming, and consequently either migrate further North or locally go extinct. Climate change is affecting almost all regions and ecosystems, with the Arctic demonstrating the greatest, irreversible consequences on marine life. Rapid sea-ice loss and increasing temperatures 1,2 are altering the distribution and abundance of low trophic-level organisms, generating cascading effects through the entire food chain from phytoplankton to mammalian predators 3. Arctic marine mammals have the potential to move over long distances to adapt to changing and erratic resource availability. However, their capacity to adjust long-term adaptations, like site-fidelity and fixed migratory patterns, to climate-induced perturbations remains poorly known 4,5. Among Arctic cetaceans, the narwhal (Monodon monoceros) has a large geographic range extending from the Canadian Arctic Archipelago (CAA) to East Greenland, Svalbard and the western part of the Russian Arctic 6-11. Narwhals are known to exhibit a high degree of site-fidelity and to be closely associated with specific migratory corridors during spring and fall movements between summer and winter grounds 12. During winter, narwhals are mainly found in offshore areas over deep water and often in areas completely covered with pack-ice with only leads available for breathing. In spring the narwhals move towards coastal areas. The inshore summer foraging grounds, where they congregate during the open water season, are considered the primary basis for identifying separate population units of narwhals 13 .
The Journal of Experimental Biology, Nov 1, 2000
All underwater activities of diving mammals are constrained by the need for surface gas exchange.... more All underwater activities of diving mammals are constrained by the need for surface gas exchange. Our aim was to measure respiratory rate (fB) and heart rate (fH) at the surface between dives in free-ranging northern elephant seals Mirounga angustirostris. We recorded fB and fH acoustically in six translocated juveniles, 1.8-2.4 years old, and three migrating adult males from the rookery at Año Nuevo, California, USA. To each seal, we attached a diving instrument to record the diving pattern, a satellite tag to track movements and location, a digital audio tape recorder or acoustic datalogger with an external hydrophone to record the sounds of respiration and fH at the surface, and a VHF transmitter to facilitate recovery. During surface intervals averaging 2.2±0.4 min, adult males breathed a mean of 32.7±5.4 times at a rate of 15.3±1.8 breaths min −1 (means ± S.D., N=57). Mean fH at the surface was 84±3 beats min −1. The fB of juveniles was 26 % faster than that of adult males, averaging 19.2±2.2 breaths min −1 for a mean total of 41.2±5.0 breaths during surface intervals lasting 2.6±0.31 min. Mean fH at the surface was 106±3 beats min −1. fB and fH did not change significantly over the course of surface intervals. Surface fB and fH were not clearly associated with levels of exertion, such as rapid horizontal transit or apparent foraging, or with measures of immediately previous or subsequent diving performance, such as diving duration, diving depth or swimming speed. Together, surface respiration rate and the duration of the preceding dive were significant predictors of surface interval duration. This implies that elephant seals minimize surface time spent loading oxygen depending on rates of oxygen uptake and previous depletion of stores.
Journal of the Acoustical Society of America, Apr 1, 2011
Most bowhead whales from the Bering-Chukchi-Beaufort stock migrate westward from Arctic Canadian ... more Most bowhead whales from the Bering-Chukchi-Beaufort stock migrate westward from Arctic Canadian waters through the Alaskan Beaufort Sea each year from late August to late October. Since 2007 both aerial sighting and acoustic call data have been collected during these fall migrations, as part of a long-term monitoring effort to assess the potential impacts of North Slope oil industry activities on bowhead whales. The aerial sighting efforts recorded the position of bowhead individuals or groups, designating the animals as subadults or adults, and noted whether a calf was present. A five-site array of seven directional autonomous seafloor acoustic recorders (DASARs) each recorded the acoustic data. An automated detection algorithm was used to isolate individual bowhead whale calls and estimate their locations. Here simultaneous acoustic and visual data from 2007, 2008, and 2010 were merged to determine whether potential variations in calling behavior exist between subadults, adults, and adults with calves. Visual measurements of animal course and direction were used to place bounds on call times and locations that may be associated with that animal versus other animals sighted nearby. Potential differences in call rate and call type were statistically examined. [Work supported by the Shell Exploration and Production Company.]
Acoustics research letters online, Oct 1, 2003
A monitoring program documented densities of ringed seals, Phoca hispida, before and during devel... more A monitoring program documented densities of ringed seals, Phoca hispida, before and during development of the Northstar oil field in the central Alaskan Beaufort Sea. Aerial surveys of seals on landfast ice were conducted during the springs of 1997 to 1999 (pre-construction) and 2000-2001 (construction and drilling). Acoustic and vibration data were acquired during the ice-covered seasons of 2000 and 2001. Underwater sounds, in-air sounds, and iceborne vibrations from Northstar were above background levels to distances of 1-5, 0.5-4, and 1-4 km, respectively.
Journal of the Acoustical Society of America, Jul 1, 2014
Science, Dec 8, 2017
Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relati... more Until recent declines in Arctic sea ice levels, narwhals (Monodon monoceros) have lived in relative isolation from human perturbation and sustained predation pressures. The resulting naïvety has made this cryptic, deep-diving cetacean highly susceptible to disturbance, although quantifiable effects have been lacking. We deployed a submersible, animal-borne electrocardiograph-accelerometer-depth recorder to monitor physiological and behavioral responses of East Greenland narwhals after release from net entanglement and stranding. Escaping narwhals displayed a paradoxical cardiovascular down-regulation (extreme bradycardia with heart rate ≤4 beats per minute) superimposed on exercise up-regulation (stroke frequency >25 strokes per minute and energetic costs three to six times the resting rate of energy expenditure) that rapidly depleted onboard oxygen stores. We attribute this unusual reaction to opposing cardiovascular signals-from diving, exercise, and neurocognitive fear responses-that challenge physiological homeostasis.
Journal of Zoology, Nov 1, 1993
With 3 figures in the text) Northern elephant seals, Miroungu angus/irostri.s, breathe irregularl... more With 3 figures in the text) Northern elephant seals, Miroungu angus/irostri.s, breathe irregularly while sleeping on land, alternating bouts of breath-holding (apnoea) that can last up to 25 min with periods of breathing (eupnoea). Our aims were to quantify changes in this behaviour during development and to determine the correspondence between these ontogenetic changes and those indcpendently recorded in the dive durations of free-ranging seals. We observed 163 seals during periods of apparent sleep, ranging in age from newborn to adult. at Afio Nuevo, California. Mean length of apnoea and percentage time spent in apnoea were 3.1 min and 59'%, in neonates (0-4 days old). These values decreased to 1.8 min and 37% in suckling pups (5 28 days old), then increased with age thereaftcr, reachingabout 8.0 min and 60% in adults ofboth sexes. Sleep apnoeaduration and percentage time spent in sleep apnoea increascd most markedly after wcaning, when the animals were learning to swim and dive. Mean sleep apnoea duration and mean dive duration increased in a similar way during the first year of life; thereafter. mean sleep apnoea duration reached an asymptote while mean dive duration continued to increase. We conclude that the elephant seal's ability to sustain long apnoeas is not only an adaptation for foraging underwater but also :.I means for conserving water and energy while fasting on land.
Science Advances, Jul 28, 2023
Niche-conservative species are especially susceptible to changes in their environment, and detect... more Niche-conservative species are especially susceptible to changes in their environment, and detecting the negative effects of new stressors in their habitats is vital for safeguarding of these species. In the Arctic, human disturbance including marine traffic and exploration of resources is increasing rapidly due to climate change–induced reduction of sea ice. Here, we show that the narwhal, Monodon monoceros , is extremely sensitive to human-made noise. Narwhals avoided deep diving (&gt; 350 m) with simultaneous reduction of foraging and increased shallow diving activity as a response to either ship sound alone or ship sound with concurrent seismic airgun pulses. Normal behavior decreased by 50 to 75% at distances where received sound levels were below background noise. Narwhals were equally responsive to both disturbance types, hence demonstrating their acute sensitivity to ship sound. This sensitivity coupled with their special behavioral-ecological strategy including a narrow ecological niche and high site fidelity makes them thus especially vulnerable to human impacts in the Arctic.
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Papers by Susanna B . Blackwell