Coconut Wireless: Understanding endangered Hawaiian false killer whale communication

Brijonnay Madrigal – bcm2@hawaii.edu
Instagram: @brijonnay
Marine Mammal Research Program
University of Hawaiʻi at Mānoa
46-007 Lilipuna Rd
Kaneohe, HI 96744
United States

Marine Mammal Research Program @mmrp_uh

Popular version of 5aAB – Acoustic behavior of endangered false killer whales (Pseudorca crassidens) using biologging devices in Hawaiʻi
Presented at the 188th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0038276

–The research described in this Acoustics Lay Language Paper may not have yet been peer reviewed–

Photo Credit: Grace Olson (Pacific Whale Foundation)

How do scientists better understand the communication of individual animals when we don’t know who is speaking and what they are doing underwater? For cetaceans (whales/dolphins/porpoises), passive acoustic monitoring is an important approach to study these animals that spend most of their time underwater and rely on acoustic signaling to communicate. The use of acoustic biologging tags has enabled the collection of high-resolution data to study acoustic behavior of top predators. The Main Hawaiian Islands (MHI) insular population of false killer whales (Pseudorca crassidens) is the most endangered toothed whale population in Hawaiʻi under the Endangered Species Act. Despite ongoing management efforts to address threats, the population has continued to decline to a current population size of less than 150 individuals. Therefore, it is crucial to understand the behavior of this population to better inform conservation measures critical for the protection of this species. Our understanding of the social context of individual false killer whales has generally been limited, until now.

The goal of this study was to use data recorded from non-invasive archival , suction-cup tags, to describe the acoustic behavior of MHI insular false killer whales to better understand the behavioral context of social signals. Our objectives were to (1) classify and characterize the repertoire of individual false killer whales; (2) describe nonlinear features observed in calls that enhance communication between individuals; and (3) analyze the relationship between social sound production and diving behavior. These findings can help us evaluate social context on a small scale and provide foundational information to determine the potential function of these signals.

Our results show that MHI insular false killer whales have a more diverse repertoire than previously described. Some call types are shared between individuals, and some are unique to individuals. We identified predominate call types that are repeated or favored by specific individuals and call rates vary by individual across dive states (for example – descent, ascent) (Figure 1). Most calls are biphonic, where the animals produce a call and clicks simultaneously (Audio 1). Although clicks are commonly used for echolocation to navigate and locate prey, the clicks produced by these animals occur with calls at the same time in distinct patterns, so they likely function in communication and encode additional information for individuals. This study provides invaluable insights into this species’ social behavior and by intercepting the coconut wireless of Hawaiʻi false killer whales using tag technology, our findings can inform management strategies necessary to advance conservation efforts of this top predator to the Hawaiʻi ecosystem.

Figure 1: A spectrogram of three predominate call types produced by one tagged false killer whale from the Main Hawaiian Islands insular population. Calls are biphonic which means a call and clicks are produced simultaneously, as indicated by the arrows in the first panel. A spectrogram is a visual representation of sound with time on the x-axis, frequency (or pitch) on the y-axis, and color representing the relative amplitude (loudness) of the sound.

Figure 1: A spectrogram of three predominate call types produced by one tagged false killer whale from the Main Hawaiian Islands insular population. Calls are biphonic which means a call and clicks are produced simultaneously, as indicated by the arrows in the first panel. A spectrogram is a visual representation of sound with time on the x-axis, frequency (or pitch) on the y-axis, and color representing the relative amplitude (loudness) of the sound.

Image credit: Grace Olson (Pacific Whale Foundation)

Customized animal tracking solutions (CATS) tags audio recording of calls produced by a tagged MHI insular false killer whale.

Exploring the Impact of Offshore Wind on Whale Deaths #ASA187

Exploring the Impact of Offshore Wind on Whale Deaths #ASA187

Some experts are worried wind farm survey noise adds stress and increases whale deaths.

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MELVILLE, N.Y., Nov. 21, 2024 – In the winter of 2022-2023, nearly a dozen whales died off the coast of New Jersey, near the sites of several proposed wind farms. Their deaths prompted concern that related survey work being conducted in the area somehow contributed to their deaths.

Michael Stocker of Ocean Conservation Research will present his work Thursday, Nov. 21, at 3:29 p.m. ET in a session dedicated to examining the circumstances surrounding these whale deaths, as part of the virtual 187th Meeting of the Acoustical Society of America, running Nov. 18-22, 2024.

Researchers retrieve an instrument package from the Cook Inlet. Could noise from these surveys like these have led to the death of almost a dozen whales during winter of 2022-2023? Credit: Michael Stocker

In pursuit of clean energy goals and to reduce atmospheric carbon emissions, developers are increasingly exploring building wind turbines in the waters off the East Coast of the United States. Three offshore wind farms are already in operation, with several more planned or underway. These wind farms stand to generate a significant amount of carbon-free electricity, which can help coastal states meet their decarbonization goals.

The increased presence of these turbines in coastal waters, along with the noise from construction and surveys, has led to concerns of their impact on marine life. In particular, cetaceans such as whales and dolphins are likely to be sensitive to the noises and increased marine traffic brought by these turbines.

However, the Marine Mammal Commission, a federal oversight agency, states there is no evidence linking the whales that died in the New Jersey region in the winter of 2022-2023 to wind energy development.

According to necropsies performed on recovered whales, many of them died from collisions with ships. The Marine Mammal Commission notes that this is not a particularly unusual occurrence, nor is the number of whale deaths in this period higher than average. A rise in ship strikes over the last decade is mostly due to a simple combination of more whales plus more ships.

“In the case of a lot of whales, population recoveries since the cessation of commercial whaling are coincident with increasing shipping traffic and increasing fishing efforts,” said Stocker. “This is resulting in increased interactions between whales and the industrialization of the ocean.”

Stocker, however, is concerned that the increased presence of survey ships in and around New Jersey waters may have exacerbated this issue.

“Were the ship strikes just a coincidence?” asked Stocker. “Or were they a product of compromised whale vigilance due to aggregated stress factors?”

Survey ships are employed by wind farm developers to map the seafloor in preparation for construction. These ships use underwater acoustic devices in their efforts, which can stress marine mammals such as whales. While one survey ship likely has little effect, Stocker highlights that 11 different surveys were operating in the region from December 2022 to March 2023, and that the cumulative impact of these surveys has not been properly evaluated.

Stocker hopes his Thursday session will spark a discussion among attendees with the goal of identifying approaches to minimize whale deaths in the future.

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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.

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.