DiMarzio Nancy A.

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Nancy A.

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Now showing 1 - 5 of 5
  • Article
    Vessel noise affects beaked whale behavior : results of a dedicated acoustic response study
    (Public Library of Science, 2012-08-03) Pirotta, Enrico ; Milor, Rachael ; Quick, Nicola ; Moretti, David J. ; DiMarzio, Nancy A. ; Tyack, Peter L. ; Boyd, Ian L. ; Hastie, Gordon
    Some beaked whale species are susceptible to the detrimental effects of anthropogenic noise. Most studies have concentrated on the effects of military sonar, but other forms of acoustic disturbance (e.g. shipping noise) may disrupt behavior. An experiment involving the exposure of target whale groups to intense vessel-generated noise tested how these exposures influenced the foraging behavior of Blainville’s beaked whales (Mesoplodon densirostris) in the Tongue of the Ocean (Bahamas). A military array of bottom-mounted hydrophones was used to measure the response based upon changes in the spatial and temporal pattern of vocalizations. The archived acoustic data were used to compute metrics of the echolocation-based foraging behavior for 16 targeted groups, 10 groups further away on the range, and 26 nonexposed groups. The duration of foraging bouts was not significantly affected by the exposure. Changes in the hydrophone over which the group was most frequently detected occurred as the animals moved around within a foraging bout, and their number was significantly less the closer the whales were to the sound source. Non-exposed groups also had significantly more changes in the primary hydrophone than exposed groups irrespective of distance. Our results suggested that broadband ship noise caused a significant change in beaked whale behavior up to at least 5.2 kilometers away from the vessel. The observed change could potentially correspond to a restriction in the movement of groups, a period of more directional travel, a reduction in the number of individuals clicking within the group, or a response to changes in prey movement.
  • Technical Report
    Whale call data for the North Pacific : November 1995 through July 1999 occurrence of calling whales and source locations from SOSUS and other acoustic systems
    (Woods Hole Oceanographic Institution, 2000-02) Watkins, William A. ; George, Joseph E. ; Daher, Mary Ann ; Mullin, Kristina ; Martin, Darel L. ; Haga, Scott H. ; DiMarzio, Nancy A.
    Calls of blue whales (Balaenoptera musculus), fin whales (Balaenoptera physalus), and humpback whales (Megaptera novaeangliae) were identified in the data from U.S. Navy Sound Surveilance System (SOSUS) and other hydrophone arrays. These data on calling whales from November 1995 through July 1999 have been listed here for four offshore, deep-water Regions along continental margins of the North and Northeast Pacific. The occurrence of calling whales was monitored during two-day periods each week. Call data recorded from each array identified species, call occurrence, variation, received beam, and relative numbers of calling whales. This allowed assessment of seasonal distribution of calls for the different species, and provided locations for sources received at multiple arrays. Blue whale tonal sounds were distributed widely, received most in the NW Region, with a peak in occurrence in the fall. Fin whale "20-Hz" repetitive pulse sequences were received from whales grouped in local areas in all Regions, with a peak in occurrence in midwinter. Humpback songs were received from December through May particularly in the SE Region. The offshore listening systems allowed basin-wide monitoring of the seasonal distribution of these callng whales.
  • Technical Report
    Distinctions in sound patterns of calls by killer whales (Orcinus Orca) from analysis of computer sound features
    (Woods Hole Oceanographic Institution, 1998-03) Watkins, William A. ; Daher, Mary Ann ; DiMarzio, Nancy A. ; Reppucci, Gina
    Calls of killer whales, Orcinus orca, were analyzed using computed sound features to classify sound patterns and identify call similarties. Calls were classified and separated according to the podfamily group within clans identified previously by John Ford (U. BC) in the Vancouver whale populations. Acoustic characteristics of the same call type from different individuals were extremely similar, so that discriminating these different sounds was the goal. The WHOI AcouStat program and associated database systems were used to define numerical statistics for each call, and then, these were compared to sort and classify the sounds. The results were in agreement with Ford's descriptions of the calls derived from visual inspection of sound spectrograms of calls. The classification analyses demonstrated that although specific shared calls from different killer whales were much alike, they could be sorted by the pod/subpod of the whales producing the calls. A typical analysis, for example, of the N4 call from Clan A (Vancouver, BC), classified 97% of the calls correctly according to the pod/family of the whales producing the calls. Remaining calls were variant, and likely a result of individual differences in call sounds. Similar classification analysis were tested on unsorted, unalyzed recordings from different populations of whales, and these too could be distinguished, with 98.5% correct separation of the calls.
  • Article
    Estimating cetacean population density using fixed passive acoustic sensors : an example with Blainville's beaked whales
    (Acoustical Society of America, 2009-04) Marques, Tiago A. ; Thomas, Len ; Ward, Jessica ; DiMarzio, Nancy A. ; Tyack, Peter L.
    Methods are developed for estimating the size/density of cetacean populations using data from a set of fixed passive acoustic sensors. The methods convert the number of detected acoustic cues into animal density by accounting for (i) the probability of detecting cues, (ii) the rate at which animals produce cues, and (iii) the proportion of false positive detections. Additional information is often required for estimation of these quantities, for example, from an acoustic tag applied to a sample of animals. Methods are illustrated with a case study: estimation of Blainville's beaked whale density over a 6 day period in spring 2005, using an 82 hydrophone wide-baseline array located in the Tongue of the Ocean, Bahamas. To estimate the required quantities, additional data are used from digital acoustic tags, attached to five whales over 21 deep dives, where cues recorded on some of the dives are associated with those received on the fixed hydrophones. Estimated density was 25.3 or 22.5 animals/1000 km2, depending on assumptions about false positive detections, with 95% confidence intervals 17.3–36.9 and 15.4–32.9. These methods are potentially applicable to a wide variety of marine and terrestrial species that are hard to survey using conventional visual methods.
  • Article
    Beaked whales respond to simulated and actual navy sonar
    (Public Library of Science, 2011-03-14) Tyack, Peter L. ; Zimmer, Walter M. X. ; Moretti, David J. ; Southall, Brandon L. ; Claridge, Diane E. ; Durban, John W. ; Clark, Christopher W. ; D'Amico, Angela ; DiMarzio, Nancy A. ; Jarvis, Susan ; McCarthy, Elena ; Morrissey, Ronald ; Ward, Jessica ; Boyd, Ian L.
    Beaked whales have mass stranded during some naval sonar exercises, but the cause is unknown. They are difficult to sight but can reliably be detected by listening for echolocation clicks produced during deep foraging dives. Listening for these clicks, we documented Blainville's beaked whales, Mesoplodon densirostris, in a naval underwater range where sonars are in regular use near Andros Island, Bahamas. An array of bottom-mounted hydrophones can detect beaked whales when they click anywhere within the range. We used two complementary methods to investigate behavioral responses of beaked whales to sonar: an opportunistic approach that monitored whale responses to multi-day naval exercises involving tactical mid-frequency sonars, and an experimental approach using playbacks of simulated sonar and control sounds to whales tagged with a device that records sound, movement, and orientation. Here we show that in both exposure conditions beaked whales stopped echolocating during deep foraging dives and moved away. During actual sonar exercises, beaked whales were primarily detected near the periphery of the range, on average 16 km away from the sonar transmissions. Once the exercise stopped, beaked whales gradually filled in the center of the range over 2–3 days. A satellite tagged whale moved outside the range during an exercise, returning over 2–3 days post-exercise. The experimental approach used tags to measure acoustic exposure and behavioral reactions of beaked whales to one controlled exposure each of simulated military sonar, killer whale calls, and band-limited noise. The beaked whales reacted to these three sound playbacks at sound pressure levels below 142 dB re 1 µPa by stopping echolocation followed by unusually long and slow ascents from their foraging dives. The combined results indicate similar disruption of foraging behavior and avoidance by beaked whales in the two different contexts, at exposures well below those used by regulators to define disturbance.