Jason Wood

Wild African elephants (Loxodonta africana) discriminate between familiar and unfamiliar conspecific seismic alarm calls.

The ability to discriminate between call types and callers as well as more subtle information about the importance of a call has been documented in a range of species. This type of discrimination is also important in the vibrotactile environment for species that communicate via vibrations. It has recently been shown that African elephants (Loxodonta africana) can detect seismic cues, but it is not known whether they discriminate seismic information from noise. In a series of experiments, familiar and unfamiliar alarm calls were transmitted seismically to wild African elephant family groups. Elephants respond significantly to the alarm calls of familiar herds (p=0.004) but not to the unfamiliar calls and two different controls, thus demonstrating the ability of elephants to discriminate subtle differences between seismic calls given in the same context. If elephants use the seismic environment to detect and discriminate between conspecific calls, based on the familiarity of the caller or some other physical property, they may be using the ground as a very sophisticated sounding board.

Wild elephant (Loxodonta africana) breeding herds respond to artificially transmitted seismic stimuli

Seismic communication is known to be utilized in insects, amphibians, reptiles, and small mammals, but its use has not yet been documented in large mammals. Elephants produce low-frequency vocalizations, and these vocalizations have seismic components that propagate in the ground, but it has not yet been demonstrated that elephants can detect or interpret these seismic signals. In this study, we played back seismic replicates of elephant alarm vocalizations to herds of wild African elephants in their natural environment and observed significant behavioral changes indicating that they had detected these signals. Seismic communication may provide an important complement to existing communication modes used by elephants. Seismic sensitivity may also provide elephants with an additional modality for sensing important environmental cues such as changes in weather patterns or seismic disturbances.

CLASSIFICATION OF AFRICAN ELEPHANT LOXODONTA AFRICANA RUMBLES USING ACOUSTIC PARAMETERS AND CLUSTER ANALYSIS

ABSTRACT It has been suggested that African savanna elephants Loxodonta africana produce 31 different call types (Langbauer 2000). Various researchers have described these calls by associating them with specific behavioural contexts. More recently Leong et al. (2003) have attempted to classify elephant call types based on their physical properties. They classified 8 acoustically distinct call types from a population of captive elephants. This study focuses on one of these call types, the rumble, in a wild population of elephants in Kruger National Park, South Africa. A single family group of elephants was followed to record group behaviours and vocalizations from January through August 2001. By measuring the physical properties of 663 rumbles and subjecting these to cluster analysis, we present evidence that shows that rumbles can be categorized by their physical properties and that the resulting rumble types are associated with specific group behaviours. We characterize three types of rumbles that differ significantly by ten acoustic parameters. Two rumble types were associated with the elephant group feeding and resting, while the third was associated with socializing and agitation.

Ship noise extends to frequencies used for echolocation by endangered killer whales

Combining calibrated hydrophone measurements with vessel location data from the Automatic Identification System, we estimate underwater sound pressure levels for 1,582 unique ships that transited the core critical habitat of the endangered Southern Resident killer whales during 28 months between March, 2011, and October, 2013. Median received spectrum levels of noise from 2,809 isolated transits are elevated relative to median background levels not only at low frequencies (20–30 dB re 1 µPa2/Hz from 100 to 1,000 Hz), but also at high frequencies (5–13 dB from 10,000 to 96,000 Hz). Thus, noise received from ships at ranges less than 3 km extends to frequencies used by odontocetes. Broadband received levels (11.5–40,000 Hz) near the shoreline in Haro Strait (WA, USA) for the entire ship population were 110 ± 7 dB re 1 µPa on average. Assuming near-spherical spreading based on a transmission loss experiment we compute mean broadband source levels for the ship population of 173 ± 7 dB re 1 µPa 1 m without accounting for frequency-dependent absorption. Mean ship speed was 7.3 ± 2.0 m/s (14.1 ± 3.9 knots). Most ship classes show a linear relationship between source level and speed with a slope near +2 dB per m/s (+1 dB/knot). Spectrum, 1/12-octave, and 1/3-octave source levels for the whole population have median values that are comparable to previous measurements and models at most frequencies, but for select studies may be relatively low below 200 Hz and high above 20,000 Hz. Median source spectrum levels peak near 50 Hz for all 12 ship classes, have a maximum of 159 dB re 1 µPa2/Hz @ 1 m for container ships, and vary between classes. Below 200 Hz, the class-specific median spectrum levels bifurcate with large commercial ships grouping as higher power noise sources. Within all ship classes spectrum levels vary more at low frequencies than at high frequencies, and the degree of variability is almost halved for classes that have smaller speed standard deviations. This is the first study to present source spectra for populations of different ship classes operating in coastal habitats, including at higher frequencies used by killer whales for both communication and echolocation.

Exploring the use of acoustics as a tool in male elephant/human conflict mitigation

Elephant/human conflict mitigation solutions have been explored with varying degrees of success. We present findings on a potential acoustic tool to reduce negative outcomes of male elephants entering agricultural areas in the region northeast of Etosha National Park, Namibia. We monitored elephant traffic within and outside the park boundary using GPS collars on five male elephants with known hormonal status as well as information on the frequency and location of fence breaks. Male elephants in the hormonal state of musth have an increased range, often extending outside the protected area. We explored the feasibility of attracting musth males away from potential conflict areas noninvasively, using estrus calls. We played back estrus calls to known individual subadult (n = 9) and adult musth (n = 9) and nonmusth (n = 6) male elephants and show that adult musth and subadult nonmusth males were much more likely to respond and approach the source than nonmusth adult males (p = 0.029 and p = 0.009, respectively) with an equal level of intensity (p = 0.822). Our findings suggest that the use of acoustics may serve as an effective tool in noninvasive male elephant/human conflict mitigation, depending on the age and hormonal status.

Killer whale scouting: Listen live for troops J, K, and L.

The southern resident killer whales are highly vocal, sharing almost 40 distinct calls. The endangered population of about 87 orcas live in matriarchal groups (like troops) known as J, K, and L pods. Each pod has a favorite call that is used about half the time pod members vocalize. If you hear a favorite call you can guess (or infer) which pod is present. A new way to listen for orcas is with hydrophones (underwater microphones) that are connected to the internet. The Northeast Pacific Hydrophone Network—http://orcasound.net—includes five hydrophones located near Seattle, WA within the summertime range of the orcas. You can listen live through iTunes to discover which pods are calling or to monitor the environment for noise pollution that could be a problem for the whales. This hands‐on activity teaches you how to listen, identify the three pods based on their favorite calls, and share your observations with other listeners. High school students can use free software to record orca calls, whistles, and c...

Empirical measures of harbor seal behavior and avoidance of an operational tidal turbine

There is global interest in marine renewable energy from underwater tidal turbines. Due to overlap in animal habitat with locations for tidal turbines, the potential for collisions has led to concern around strike risk. Using data from tagged harbor seals collected before construction and after operation of the SeaGen tidal turbine in Northern Ireland, this study quantifies risks of an operational turbine to harbor seals by taking into account turbine characteristics, tidal state, and seal behavior. We found 68% spatial avoidance (95% C.I., 37%, 83%) by harbor seals within 200 m of the turbine. When additionally accounting for variation in seal occupancy over depth and tidal flows, there is an overall reduction in collision risk from 1.29 to 0.125 seals per tidal cycle (90.3% reduction; (95% C.I., 83%, 98%)) compared to risk calculated under assumptions of uniform habitat use. This demonstrates the need to incorporate environmental conditions to properly assess strike risk.

Sperm whale inter-pulse intervals and size: The anomaly called Yukusam

Yukusam is the name given to a male sperm whale who was first documented off northeastern Vancouver Island in February 2018. He spent several weeks in this area before traveling south to the inland waters of the Salish Sea in late March 2018. Sperm whale clicks have been used as a proxy to determine overall size by using the time difference of arrival between the initial noise pulse and its reflections within the spermaceti organ. Different equations have been derived in order to use this Inter-Pulse Interval (IPI) to estimate overall length. Here we use Yukusam’s usual clicks recorded from the Lime Kiln hydrophone on the west side of San Juan Island (WA State, USA) to compare IPI-based length estimates with visual observations. Photo and video documentation indicate that this whale is ~15 m in length. Our initial acoustic results indicate that equations in the literature underestimate his length by at least a few meters. The potential reasons behind these anomalies are explored in this presentation.Yukusam is the name given to a male sperm whale who was first documented off northeastern Vancouver Island in February 2018. He spent several weeks in this area before traveling south to the inland waters of the Salish Sea in late March 2018. Sperm whale clicks have been used as a proxy to determine overall size by using the time difference of arrival between the initial noise pulse and its reflections within the spermaceti organ. Different equations have been derived in order to use this Inter-Pulse Interval (IPI) to estimate overall length. Here we use Yukusam’s usual clicks recorded from the Lime Kiln hydrophone on the west side of San Juan Island (WA State, USA) to compare IPI-based length estimates with visual observations. Photo and video documentation indicate that this whale is ~15 m in length. Our initial acoustic results indicate that equations in the literature underestimate his length by at least a few meters. The potential reasons behind these anomalies are explored in this presentation.

Ship speed reduction is an effective mitigation for underwater noise effects

The Vancouver Fraser Port Authority’s ECHO Program led a voluntary 2-month ship slowdown trial during which 56% of piloted ships slowed down to <13 knots in a 16 nautical mile corridor. The goal was to determine if a slowdown could be used as a mitigation measure to reduce ship related underwater noise effects in core Southern Resident killer whale habitat. A calibrated hydrophone system was used to measure ambient noise levels from 10 Hz to 100 kHz during the trial and a representative 2-month baseline period. The hydrophone was located 2.3 (inbound) and 5 km (outbound) from the center of the shipping lanes at 23 m depth. Analyses of data with ships present showed a median broadband noise reduction of 2.5 dB. This reduction was highest in the 10–100 Hz decade band (3.1 dB) and lowest in the 10,000–100,000 Hz band (0.3 dB). A statistical model found that received noise levels were best described by the distance to ships, the presence of small boats, water velocity, slowdown period, ship speed through water, and wind speed. This highlights that appropriate temporal scales and the inclusion of covariate data are needed to adequately measure ship related changes in underwater ambient noise levels. The Vancouver Fraser Port Authority’s ECHO Program led a voluntary 2-month ship slowdown trial during which 56% of piloted ships slowed down to <13 knots in a 16 nautical mile corridor. The goal was to determine if a slowdown could be used as a mitigation measure to reduce ship related underwater noise effects in core Southern Resident killer whale habitat. A calibrated hydrophone system was used to measure ambient noise levels from 10 Hz to 100 kHz during the trial and a representative 2-month baseline period. The hydrophone was located 2.3 (inbound) and 5 km (outbound) from the center of the shipping lanes at 23 m depth. Analyses of data with ships present showed a median broadband noise reduction of 2.5 dB. This reduction was highest in the 10–100 Hz decade band (3.1 dB) and lowest in the 10,000–100,000 Hz band (0.3 dB). A statistical model found that received noise levels were best described by the distance to ships, the presence of small boats, water velocity, slowdown period, ship speed through wat...

Development of beluga calf calls (Delphinapterus leucas) in the first six months of life

As part of an ongoing effort to understand beluga mother-calf communication and impacts of anthropogenic noise on neonate calls, we investigated a male beluga calf’s vocal development at Oceanografic, using a calibrated digital hydrophone with a sampling rate of 256 kHz. His initial vocalizations were broadband pulse-trains with upper frequency limits reaching ≥128 kHz on his first day of life, higher than reported by earlier studies limited by lower sampling rates. Over the calf’s first six months, pulsed trains were the predominant call type, increasing significantly in peak and first quartile frequencies and pulse repetition rate during this period. First and third quartile frequencies also increased significantly over the calf’s first month, indicating an early and continuous shift in pulse train energy distribution towards higher frequencies. While mixed and tonal calls appeared sporadically in the calf’s first month of life, they were not common until his third month, when they comprised 13% of his vocalizations. Additionally, estimated source levels of the calf’s calls increased throughout his first month, but were lower than those for adult belugas. This, coupled with the progressive shift in energy distribution, has important implications regarding a neonate’s ability to compensate for noise.As part of an ongoing effort to understand beluga mother-calf communication and impacts of anthropogenic noise on neonate calls, we investigated a male beluga calf’s vocal development at Oceanografic, using a calibrated digital hydrophone with a sampling rate of 256 kHz. His initial vocalizations were broadband pulse-trains with upper frequency limits reaching ≥128 kHz on his first day of life, higher than reported by earlier studies limited by lower sampling rates. Over the calf’s first six months, pulsed trains were the predominant call type, increasing significantly in peak and first quartile frequencies and pulse repetition rate during this period. First and third quartile frequencies also increased significantly over the calf’s first month, indicating an early and continuous shift in pulse train energy distribution towards higher frequencies. While mixed and tonal calls appeared sporadically in the calf’s first month of life, they were not common until his third month, when they comprised 13% of his ...