2pPPa1 – Flying bats modify their biosonar sounds to avoid interference from other bats

Andrea M. Simmons, andrea_simmons@brown.edu
Charlotte R. Thorson, charlotte_thorson@alumni.brown.edu
Madeline McLaughlin, madeline_mclaughlin1@brown.edu
Pedro Polanco, pedro_polanco@alumni.brown.edu
Amaro Tuninetti, amaro_tuninetti@brown.edu
James A. Simmons, james_simmons@brown.edu
Brown University
Providence RI 02912

Popular version of 2pPPa1 – Echolocating bats modify biosonar emissions when avoiding obstacles during difficult navigation tasks
Presented Tuesday afternoon, December 2, 2021
181th ASA Meeting, Seattle WA
Click here to read the abstract

Bats use echolocation, an active biological sonar, to find their way in the dark. By broadcasting trains of intense ultrasonic sounds and listening to returning echoes, they can locate and identify obstacles to their flight (vegetation, buildings) and capture small insect prey. Bats often fly and forage in groups. When other flying bats are present, they face the added challenge of separating out the echoes from their own broadcasts from the broadcasts and echoes created by these other bats, while still maintaining their flight path. To assess how bats address these challenges, we flew individual and then pairs of big brown bats (Eptesicus fuscus) through a curved flight corridor bounded by rows of closely spaced vertical hanging plastic chains that produced echoes mimicking those produced by dense vegetation. When flying alone, each bat broadcasts sonar sounds containing frequencies from 100-25 kHz in a characteristic pattern of alternating long and short time intervals. These short time intervals allow fast reactions to immediate collision hazards, while the long intervals allow the bat to peer deep into its surroundings to plan its upcoming flight path. When two bats fly towards each other from opposite ends of the curved corridor, they maneuver to avoid colliding. There are three distinctive biosonar reactions tied to these maneuvers. First, both bats increase the strength of their broadcasts (Lombard effect) during the brief time they are in close proximity. Second, they produce more short time intervals, speeding up their broadcast rate. Third, at the point where they are in closest proximity and the need for each bat to avoid being interfered with by the other bat is most acute, one of them sharply decreases the low-frequency end of its broadcasts to about 15 kHz. This unusual, asymmetric response allows this bat to distinguish echoes of its own broadcasts from those of the other bat, even though the total range of frequencies remains large. Bats place particular priority on the lowest frequencies in echoes, and having different lowest frequencies lets them separate out each other’s biosonar broadcasts and prevent mutual interference when close together.

5aABb2 – A tale of two singers: how do bats and bird mixed-flocks respond to petroleum industry noise in the Ecuadorian Amazon

Rivera-Parra, JL, jose.riverap@epn.edu.ec
De la Cruz, I.
Viscarra, S.
Vasconez, C.
Dueñas, A.
Xulvi, R.
Sorriso-Valvo, L.

Popular version of 5aABb2 – A tale of two singers: how do bats and bird mixed-flocks respond to petroleum industry noise in the Ecuadorian Amazon
Presented Friday morning, December 3, 2021
181st ASA Meeting, Seattle, WA
Click here to read the abstract

Industrial noise can have a significant impact on animal groups that rely on acoustic communication for fundamental survival activities. Our research focuses on two of these groups: insectivorous bats, which use ultrasound to navigate and find food; and mixed flocks of insectivorous birds, that rely on vocalizations to communicate about foraging direction and potential threats. The Yasuni Bio-sphere Reserve in the Ecuadorian Amazon is one of the most biodiverse spots in the world, but it is also a place with thriving oil exploitation activities.

It is well known that some disturbance, such as roads, or industrial noise, can be related to biodiversity loss, however, how much of these effects can be attributable to the noise caused by the oil exploitation have never been measured, nor has it been characterized. Furthermore, characterization of noise is usually done only in the audible spectrum, meaning the frequencies that us as hu-mans can hear, but is not done taking into account ultrasound.

To characterize the noise caused by oil exploitation we selected three different places, based on the potential source related to the oil industry, plus a control point: 1) drilling site, 2) processing facilities, 3) a control site, a forest with no disturbance. For all three sites recordings of both audible and ultrasonic sound were made in a transect from the border of the source of industrial noise to-wards the forest. To further analyze the effects of the noise, biological surveys were made both in birds and bats. We characterized bats and birds vocalizations, and the industrial noise profile, both in ultrasound and audible frequencies.

Our results suggest, in both groups, the immediate response is avoidance; this results, in the short and long term, in a biodiversity loss. These effects are proportional to how much noise the habitat itself absorbs, the complexity of the habitat, the complexity of the noise, and the distance from the source. In the long term the effects seem to include a change on habitat use, and modification on community composition. Thus is possible it can cause a disruption of ecosystem services by bats and birds, such as natural pest control, polinization, and seed dispersal, which can lead to a broader change in forest dynamic.

petroleum industry noise

1pABb6 – Eavesdropping on a bald eagle breeding pair

JoAnn McGee – mcgeej@umn.edu
VA Loma Linda Healthcare System, Loma Linda, CA 92357
Center for Applied and Translational Sensory Science,
University of Minnesota,
Minneapolis, MN 55455

Peggy B. Nelson – nelso477@umn.edu
Department of Speech-Language-Hearing Sciences and the Center for Applied and Translational Sensory Science,
University of Minnesota,
Minneapolis, MN 55455

Julia B. Ponder – ponde003@umn.edu
The Raptor Center,
College of Veterinary Medicine, University of Minnesota, St. Paul, MN 55108

Christopher Feist – feist020@umn.edu
Christopher Milliren – milli079@umn.edu
St. Anthony Falls Laboratory,
University of Minnesota,
Minneapolis, MN 55414

Edward J. Walsh – ewalsh@umn.edu
VA Loma Linda Healthcare System,
Loma Linda, CA 92357
Center for Applied and Translational Sensory Science,
University of Minnesota,
Minneapolis, MN 55455

Popular version of 1pABb6 – A study of the vocal behavior of adult bald eagles during breeding and chick-rearing
Presented at the 181st ASA Meeting in Seattle, Washington
Click here to read the abstract

One of the many challenges associated with efforts to characterize the acoustic properties of free-ranging bald eagle (Haliaeetus leucocephalus) vocalizations in a behavioral context is the relative inaccessibility of individual, interacting signalers. Here, we take advantage of the opportunity to eavesdrop on vocal exchanges between a breeding pair inhabiting a nest furnished with a webcam and microphone located in Decorah, Iowa and managed by the Raptor Resource Project (www.raptorresource.org).

In a previous study centered on captive bald eagles at the University of Minnesota Raptor Center, five call categories, including so-called grunts, screams, squeals, chirps and cackles, were identified. The primary goal of this study was to extend the investigation into the field to begin efforts to characterize and compare the acoustic properties of calls produced in captivity and in the wild.

Predictably, many of the acoustic features of calls produced in captivity and in the wild are generously shared. However, preliminary findings suggest that at least a subset of calls exchanged by breeding pairs may take on a hybrid character, exhibiting blended variations of the chirps, squeals and screams characterized previously in captive birds. Calls analyzed here were taken from a variety of settings that include mating, exchanges associated with feeding at the nest, vocal reaction to intruders near the nest, and short distance call exchanges that appear to function as hailing signals.

The source of raw materials used to relate the behavior of the interacting pair to their vocal exchanges can be appreciated by observing the following audiovisual recording examples.

VIDEO 1
In this video, the female of the pair, an eagle known affectionately as Mom, is not so patiently awaiting the arrival of her partner, known by the less endearing name DM2. As DM2 arrives at the nest with a meal, Mom produces a call sounding a lot like the call of a sea gull; a call with the characteristics of a lower frequency version of the scream observed in captive eagles.

VIDEO 2
Here, Mom appears to be calling out to DM2 for a break from nesting. DM2 arrived shortly after the footage shown here and Mom takes off for higher ground. The call appears to be a commonly produced, seemingly multipurpose utterance closely resembling a spectrally complex version of a call observed in captive eagles known as the chirp.

VIDEO 3
In this sequence, Mom appears to summon DM2 in response to what appears to be an intruder, possibly another bald eagle, in the airspace surrounding their nest. Again, a complex variation of the chirp observed in captive eagles appears to serve as a territorial marker.

The take-home message of preliminary findings reported here is that the acoustic structure of at least a subset of calls produced by free-ranging bald eagles appears to be more nuanced and complex than those representing their captive counterparts. Elements typically representative of three primary call types in captive birds, namely chirps, screams and squeals, intermix in calls produced by free-ranging eagles, creating a vocal repertoire with subtle, but potentially meaningful structural variation. If differences reported here remain stable across a larger sample size, these findings will serve to underline the relative importance of our work in the field.

1pAB6 – Oscillatory whistles – the ups and downs of identifying species in passive acoustic recordings

Julie N. Oswald – jno@st-andrews.ac.uk
Sam F. Walmsley – sjfw@st-andrews.ac.uk
Scottish Oceans Institute
School of Biology
University of St Andrews, UK

Caroline Casey – cbcasey@ucsc.edu
Selene Fregosi – selene.fregosi@gmail.com
Brandon Southall – brandon.southall@sea-inc.net
SEA Inc.,
9099 Soquel Drive,
Aptos, CA 95003

Vincent M. Janik – vj@st-andrews.ac.uk
Scottish Oceans Institute
School of Biology
University of St Andrews, UK

Popular version of paper 1pAB6 Oscillatory whistles—The ups and downs of identifying species in passive acoustic recordings
Presented Tuesday afternoon, June 8, 2021
180th ASA Meeting, Acoustics in Focus

Many dolphin species communicate using whistles. Because whistles are produced so frequently and travel well under water, they are the focus of a wide range of passive acoustic studies. A challenge inherent to this type of work is that many acoustic recordings do not have associated visual observations and so species in the recordings must be identified based on the sounds that they make.

Acoustic species identification can be challenging for several reasons. First, the frequency contours of dolphin whistles are variable, and each species produces many different whistle types. Also, whistles often exhibit significant overlap in their characteristics between species. Traditionally, acoustic species classifiers use variables measured from all whistles, regardless of what type they are. An assumption of this approach is that there are underlying features in every whistle that provide information about species identity. In human terms, we can tell a human scream or grunt from those of a chimpanzee because they sound different. But is this the case for dolphin whistles? Can a dolphin tell whether a whistle it hears is produced by another species? If so, is species information carried in all whistles?

To investigate these questions, we analyzed whistles produced by short- and long-beaked common dolphins in the Southern California Bight. Our previous work has shown that the whistles of these closely related species overlap significantly in time and frequency characteristics measured from all whistles, so we hypothesized that species information may be carried in the shape of specific whistle contours rather than by general characteristics of all whistles. We used artificial neural networks to organize whistles into categories, or whistle types. Most of the resulting whistle types were produced by both species (we called these shared whistle types), but each species also had distinctive whistle types that only they produced (we called these species-specific whistle types). Almost half of the species-specific whistles produced by short-beaked common dolphins had oscillations in their contours, while oscillations were very rare for both long-beaked common dolphins and shared whistle types. This clear difference between species in the use of one specific whistle shape suggests that whistle type is important for species identification.

We further tested the role of species-specific whistle types in acoustic species identification by creating three different classifiers for the two species – one using all whistles, one using only whistles from shared whistle types and one using only whistles from species-specific whistle types. The classifier that used whistles from species-specific whistle types performed significantly better than the other two classifiers, demonstrating that species-specific whistle types collectively carry more species information than other whistle types, and the assumption that all whistles carry species information is not correct.

The results of this study show that we should re-evaluate our approach to acoustic species identification. Instead of measuring variables from whistles regardless of type, we should focus on identifying species-specific whistle types and creating classifiers based on those whistles alone. This new focus on species-specific whistle types would pave the way for more accurate tools for identifying species in passive acoustic recordings.

1aABa1 – Ending the day with a song: patterns of calling behavior in a species of rockfish

Annebelle Kok – akok@ucsd.edu
Ella Kim – ebkim@ucsd.edu
Simone Baumann-Pickering – sbaumann@ucsd.edu
Scripps Institution of Oceanography – University of California San Diego
9500 Gilman Drive
La Jolla, CA 92093

Kelly Bishop – kellybishop@ucsb.edu
University of California Santa Barbara
Santa Barbara, CA 93106

Tetyana Margolina – tmargoli@nps.edu
John Joseph – jejoseph@nps.edu
Naval Postgraduate School
1 University Circle
Monterey, CA 93943

Lindsey Peavey Reeves – lindsey.peavey@noaa.gov
NOAA Office of National Marine Sanctuaries
1305 East-West Highway, 11th Floor
Silver Spring, MD 20910

Leila Hatch – leila.hatch@noaa.gov
NOAA Stellwagen Bank National Marine Santuary
175 Edward Foster Road
Scituate, MA 02474

Popular version of paper 1aABa1 Ending the day with a song: Patterns of calling behavior in a species of rockfish
Presented Tuesday morning, June 8, 2021
180th ASA Meeting, Acoustics in Focus

Fish can be seen as ‘birds’ of the sea. Like birds, they sing during the mating season to attract potential partners to and to repel rival singers. At the height of the mating season, fish singing can become so prominent that it is a dominant feature of the acoustic landscape, or soundscape, of the ocean. Even though this phenomenon is widespread in fish species, not much is known about fish calling behavior, a stark contrast to what we’ve learned about bird calling behavior. As part of SanctSound, a large collaboration of over 20 organizations investigating soundscapes of US National Marine Sanctuaries, we have investigated the calling behavior of bocaccio (Sebastes paucispinis), a species of rockfish residing along the west coast of North America. Bocaccio produce helicopter-like drumming sounds that increase in amplitude.

We deployed acoustic recorders at five sites across the Channel Islands National Marine Sanctuary for about a year to record bocaccio, and used an automated detection algorithm to extract their calls from the data. Next, we investigated how their calling behavior varied with time of day, moon phase and season. Bocaccio predominantly called at night, with peaks at sunset and sunrise. Shallow sites had a peak early in the night, while the peak at deeper sites was more towards the end of the night, suggesting that bocaccio might move up and down in the water column over the course of the night. Bocaccio avoided calling during full moon, preferentially producing their calls when there was little lunar illumination. Nevertheless, bocaccio were never truly quiet: they called throughout the year, with peaks in winter and early spring.

The southern population of bocaccio on the US west coast was considered overfished by commercial and recreational fisheries prior to 2017, and has been rebuilt to be a sustainably fished stock today. One of the keys to this sustainability is reproductive success: bocaccio are very long-lived fish that don’t reproduce until they are 4-7 years old, and they can live to be 50 years old. They are known to spawn in the Channel Islands National Marine Sanctuary region from October to July, peaking in January, and studying their calling patterns can help us ensure that we keep this population and its habitat viable well into the future. Characterizing their acoustic ecology can tell us more about where in the sanctuary they reside and spawn, and understanding their reproductive calling behavior can help tell us which time of the year they are most vulnerable to noise pollution. More importantly, these results give us more insight into the wondrous marine soundscape and let us imagine what life must be like for marine creatures that contribute to and rely on it.

3aAB2 – Assembling an acoustic catalogue for different dolphin species in the Colombian Pacific coast: an opportunity to parameterize whistles before rising noise pollution levels.

Daniel Noreña – d.norena@uniandes.edu.co
Kerri D. Seger
Susana Caballero

Laboratorio de Ecologia Molecular de Vertebrados Marinos
Universidad de los Andes
Bogotá, Colombia

Popular version of paper 3aAB2
Presented Wednesday morning, December 9 , 2020
179th ASA Meeting, Acoustics Virtually Everywhere

Growing ship traffic worldwide has led to a relatively recent increase in underwater noise, raising concerns about effects on marine mammal communication. Many populations of several dolphin species inhabit the eastern Pacific Ocean, particularly along the Chocó coast of Colombia. Recent research has confirmed that anthropologic noise pollution levels in this region are one of the lowest in any studied area around the globe, allowing an opportunity for scientists to listen and analyze a relatively undisturbed soundscape in our oceans.

Figure 1. Vessel traffic in the Americas (a) and in (b) Colombia in particular. Red indicates high traffic and blue areas have no traffic. Note the gap in traffic in the Colombian Pacific coast where the Gulf of Tribugá is located (inside black/red box) as compared to all other coastal regions.

Currently, the CPC is slated for the construction of a port in the Gulf of Tribugá, pending permits. Previous port construction projects in other countries have shown that this will change the acoustic environment and could compromise marine fauna, such as dolphin communication. This is the first study to document the whistle acoustic parameters from several dolphin species in the region before any disturbance. Opportunistic recordings were made in two different locations alongside the coast: Coquí, Chocó, and a few hundred kilometers north Bahía Solano, Chocó.

Figure 1. (a) The Colombian Pacific coast and (b) whale-watching locations and ports of the Pacific coast of Colombia. Ports are red markers and whale-watching spots are blue markers.

Five different delphinid species were recorded: Common bottlenose dolphin (Tursiops truncatus), Pantropical spotted dolphin (Stenella attenuata), Spinner dolphin (Stenella longirostris), False killer whale (Pseudorca crassidens) and Short- beaked common dolphin (Delphinus delphis). Comparing these recordings to those made from dolphin populations in more disturbed areas around the globe showed that the repertoires of four of the five species were different. These differences could be because the Chocó dolphins represent populations that use whistles with more natural features while the other, more disturbed, populations may have already changed their whistle features to avoid overlapping with boat traffic noise.

However, avoiding overlap with other conspecifics or other species in the same habitat is natural, too. This is called the acoustic niche hypothesis (ANH). The ANH states that geographically sympatric species should occupy specific frequency bands to avoid overlapping with each other. A Linear Discriminant Analysis (LDA) was done to explore whether the five different species have already adjusted their whistle features to avoid overlapping with other species. Frequency band separation is not the only feature of whistles that dolphins could adjust. The LDA used nine different features to observe if there is any natural division between any of the features.

dolphinFigure 2. LDA plot for nine whistle variables among the five species.

Tracking these whistle features in Chocó over time will help determine whether the different whistle features between the Chocó dolphins and dolphins from more disturbed areas are a result of the natural acoustic niche hypothesis or a result of noise pollution avoidance. If constructed, the port could force species to adjust their whistle features like populations from noisier habitats already have, and that could disrupt the acoustic niches that already exist, some of their whistles may still be interrupted by boat noise. Such disturbances could increase their stress levels or could lead to area abandonment, which would cause economic and ecological disasters for the region that relies on artisanal fishing and ecotourism.