Export 6 results:
Sort by: Author [ Title  (Asc)] Type Year
A B C D E F G H I J K L M N O P Q R S [T] U V W X Y Z   [Show ALL]
Johnston, DW, McDonald M, Polovina J, Domokos R, Wiggins S, Hildebrand J.  2008.  Temporal patterns in the acoustic signals of beaked whales at Cross Seamount. Biology Letters. 4:208-211.   10.1098/rsbl.2007.0614   AbstractWebsite

Seamounts may influence the distribution of marine mammals through a combination of increased ocean mixing, enhanced local productivity and greater prey availability. To study the effects of seamounts on the presence and acoustic behaviour of cetaceans, we deployed a high-frequency acoustic recording package on the summit of Cross Seamount during April through October 2005. The most frequently detected cetacean vocalizations were echolocation sounds similar to those produced by ziphiid and mesoplodont beaked whales together with buzz-type signals consistent with prey-capture attempts. Beaked whale signals occurred almost entirely at night throughout the six-month deployment. Measurements of prey presence with a Simrad EK-60 fisheries acoustics echo sounder indicate that Cross Seamount may enhance local productivity in near-surface waters. Concentrations of micronekton were aggregated over the seamount in near-surface waters at night, and dense concentrations of nekton were detected across the surface of the summit. Our results suggest that seamounts may provide enhanced foraging opportunities for beaked whales during the night through a combination of increased productivity, vertical migrations by micronekton and local retention of prey. Furthermore, the summit of the seamount may act as a barrier against which whales concentrate prey.

Oleson, EM, Wiggins SM, Hildebrand JA.  2007.  Temporal separation of blue whale call types on a southern California feeding ground. Animal Behaviour. 74:881-894.   10.1016/j.anbehav.2007.01.022   AbstractWebsite

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.

Sirovic, A, Williams LN, Kerosky SM, Wiggins SM, Hildebrand JA.  2012.  Temporal separation of two fin whale call types across the eastern North Pacific. Marine Biology. 160:47-57.   10.1007/s00227-012-2061-z   AbstractWebsite

Fin whales (Balaenoptera physalus) produce a variety of low-frequency, short-duration, frequency-modulated calls. The differences in temporal patterns between two fin whale call types are described from long-term passive acoustic data collected intermittently between 2005 and 2011 at three locations across the eastern North Pacific: the Bering Sea, off Southern California, and in Canal de Ballenas in the northern Gulf of California. Fin whale calls were detected at all sites year-round, during all periods with recordings. At all three locations, 40-Hz calls peaked in June, preceding a peak in 20-Hz calls by 3-5 months. Monitoring both call types may provide a more accurate insight into the seasonal presence of fin whales across the eastern North Pacific than can be obtained from a single call type. The 40-Hz call may be associated with a foraging function, and temporal separation between 40- and 20-Hz calls may indicate the separation between predominately feeding behavior and other social interactions.

Gassmann, M, Wiggins SM, Hildebrand JA.  2015.  Three-dimensional tracking of Cuvier's beaked whales' echolocation sounds using nested hydrophone arrays. Journal of the Acoustical Society of America. 138:2483-2494.   10.1121/1.4927417   AbstractWebsite

Cuvier's beaked whales (Ziphius cavirostris) were tracked using two volumetric small-aperture (similar to 1 m element spacing) hydrophone arrays, embedded into a large-aperture (similar to 1 km element spacing) seafloor hydrophone array of five nodes. This array design can reduce the minimum number of nodes that are needed to record the arrival of a strongly directional echolocation sound from 5 to 2, while providing enough time-differences of arrivals for a three-dimensional localization without depending on any additional information such as multipath arrivals. To illustrate the capabilities of this technique, six encounters of up to three Cuvier's beaked whales were tracked over a two-month recording period within an area of 20 km(2) in the Southern California Bight. Encounter periods ranged from 11 min to 33 min. Cuvier's beaked whales were found to reduce the time interval between echolocation clicks while alternating between two inter-click-interval regimes during their descent towards the seafloor. Maximum peak-to-peak source levels of 179 and 224 dB re 1 mu Pa @ 1 m were estimated for buzz sounds and on-axis echolocation clicks (directivity index = 30 dB), respectively. Source energy spectra of the on-axis clicks show significant frequency components between 70 and 90 kHz, in addition to their typically noted FM upsweep at 40-60 kHz. (C) 2015 Acoustical Society of America.

Wiggins, SM, Dorman LM, Cornuelle BD.  1997.  Topography can affect linearization in tomographic inversions. Geophysics. 62:1797-1803.   10.1190/1.1444280   AbstractWebsite

Linearized inverse techniques commonly are used to solve for velocity models from traveltime data. The amount that a model may change without producing large, nonlinear changes in the predicted traveltime data is dependent on the surface topography and parameterization. Simple, one-layer, laterally homogeneous, constant-gradient models are used to study analytically and empirically the effect of topography and parameterization on the linearity of the model-data relationship. If, in a weak-velocity-gradient model, rays turn beneath a valley with topography similar to the radius of curvature of the raypaths, then large nonlinearities will result from small model perturbations. Hills, conversely, create environments in which the data are more nearly linearly related to models with the same model perturbations.

Wiggins, SM, Frasier KE, Henderson EE, Hildebrand JA.  2013.  Tracking dolphin whistles using an autonomous acoustic recorder array. The Journal of the Acoustical Society of America. 133:3813-3818.: ASA   AbstractWebsite

Dolphins are known to produce nearly omnidirectional whistles that can propagate several kilometers, allowing these sounds to be localized and tracked using acoustic arrays. During the fall of 2007, a km-scale array of four autonomous acoustic recorders was deployed offshore of southern California in a known dolphin habitat at ∼800 m depth. Concurrently with the one-month recording, a fixed-point marine mammal visual survey was conducted from a moored research platform in the center of the array, providing daytime species and behavior visual confirmation. The recordings showed three main types of dolphin acoustic activity during distinct times: primarily whistling during daytime, whistling and clicking during early night, and primarily clicking during late night. Tracks from periods of daytime whistling typically were tightly grouped and traveled at a moderate rate. In one example with visual observations, traveling common dolphins (Delphinus sp.) were tracked for about 10 km with an average speed of ∼2.5 m s−1 (9 km h−1). Early night recordings had whistle localizations with wider spatial distribution and slower travel speed than daytime recordings, presumably associated with foraging behavior. Localization and tracking of dolphins over long periods has the potential to provide insight into their ecology, behavior, and potential response to stimuli.