Mapping Whale Presence in the Gulf of Mexico: Sound and Habitat Connections

Alba Solsona-Berga – asolsonaberga@ucsd.edu
Scripps Institution of Oceanography
University of California San Diego
La Jolla, CA 92037
United States

Instagram: @sripps_mbarc

Popular version of 2pAO5 – Shaping the acoustic field in the Gulf of Mexico: marine mammals linked to topography and oceanographic features
Presented at the 188th ASA Meeting
Read the abstract at https://eppro01.ativ.me/appinfo.php?page=Session&project=ASAICA25&id=3859319&server=eppro01.ativ.me

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

Exploring the Lives of the Ocean’s Deepest Divers
After the Deepwater Horizon oil spill, restoring marine mammal populations in the Gulf of Mexico became a priority. Protecting these animals starts with understanding how they use their habitat and where they go. Sperm whales and beaked whales are some of the ocean’s most extreme divers, spending much of their lives navigating the dark depths. They rely on bursts of sound called echolocation clicks to find their prey and navigate. These clicks act like acoustic fingerprints, helping us figure out where whales go and what environments they prefer.

Deepwater habitat

To track their movements, we set up 18 underwater listening stations throughout the Gulf. These instruments recorded sounds continuously for three years. By analyzing this data, we discovered patterns in where the whales appeared and how those locations were linked to oceanographic features like currents and slopes.

Video: Deploying the instruments.

Where Whales Go
Different whale species tend to favor different parts of the deep Gulf. Goose-beaked whales often stay near deep eddies and steep slopes. Gervais’ beaked whales are more likely to follow surface and midwater eddies, while sperm whales mostly stick to areas where freshwater from rivers mixes with the open ocean. They tend to avoid the tropical Loop Current, a warm flow from the Caribbean into the Gulf, that seems to create conditions less favorable for these whales.

An example of how marine mammals use different parts of the Gulf of Mexico. The maps show ocean features at three depth ranges: surface (0-250 m), mid-depth (700-1250 m), and deep (1500-3000 m). Dolphins are shown in the surface plot, sperm whales in the mid-depth plot, and goose-beaked whales in the deep plot. Colors indicate water movement, with red showing strong currents and blue showing calmer areas. Circles mark recording stations, with bigger circles showing more animals detected.

Whales Shape Their Environment
Whales don’t just adapt to their surroundings, they also shape them. Their powerful clicks, produced by the millions, bounce off the seafloor and underwater features, making their presence a key part of the local acoustic environment. Where whales occur, the acoustic environment changes, influenced both by their vocalizations and by the prey that may be present. Prey layers can influence how sound propagates through the water, adding complexity to the acoustic field. Detecting whales in specific areas helps us understand how the acoustic environment might vary under different conditions. Mapping where whales are present also reveals potential biological hotspots and helps us understand how sound behaves in these deep-sea habitats.

Why This Matters
This research is a collaboration between scientists from the United States and Mexico, supported by NOAA’s RESTORE Science Program, the Deepwater Horizon Restoration Open Ocean Marine Mammal Trustee Implementation Group, and the Office of Naval Research Task Force Ocean. These detailed maps of whale distribution are vital for identifying critical habitats and guiding conservation strategies. They help us understand how threats like oil spills, industrial activity, and environmental changes impact whale populations, allowing us to plan effective mitigation and restoration efforts to maintain healthy ecosystems.

New scientific tools help national parks learn more about wildlife and natural sounds

Cathleen Balantic – cathleen_balantic@nps.gov

Biologist, National Park Service, Natural Sounds and Night Skies Division
1201 Oakridge Drive Suite 100
Fort Collins, CO, 80524, United States

Popular version of 2aAB5 – From sounds to science on public lands: using emerging tools in terrestrial bioacoustics to understand national park soundscapes
Presented at the 186th ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0026931

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

In recent decades, audio recordings have helped scientists learn more about wildlife. Natural sounds help answer questions such as: which animals are present or absent from the environment? When do frogs and birds start calling in the spring? How are wildlife reacting to something humans are doing on a landscape?

As audio recordings have become less expensive and easier to collect, scientists can rapidly amass thousands of hours of data. To absorb this volume of data, instead of listening ourselves, we create automated detectors to find animal sounds in the recordings. However, it is a daunting and time-consuming task to create detectors for a diversity of species, habitats, and types of research.

This is a familiar challenge to researchers in the National Park Service Natural Sounds and Night Skies Division. Our division is a national service office that provides scientific expertise and specialized technical assistance to parks, and we need to be prepared to help any of the 400+ national parks that have questions about bioacoustics. Each park has distinct research questions, varied habitats, and different wildlife (Fig. 1, Sound Clip 1).

national parks

Figure 1. Varied Thrush at Glacier Bay National Park and Preserve in 2015. Image courtesy of the National Park Service.

Several bird species vocalize at an acoustic monitoring station at Glacier Bay National Park and Preserve, including Pacific Wren, American Robin, and Varied Thrush. This example was recorded on June 13, 2017, at 3:22am local time. Audio recording courtesy of the National Park Service.

As more parks collect audio data to answer pressing research and management questions, building a unique automated detector for a single park project is no longer tenable. Instead, we are adopting emerging technology like BirdNET, a machine learning model trained on thousands of species worldwide (not just birds!). BirdNET provides us with more capacity. Instead of painstakingly building one detector for one project, BirdNET enables us to answer questions across multiple national parks.

But emerging technology poses more questions, too. How do we access these tools? What are the best practices for analyzing and interpreting outputs? How do we adapt new methods to answer many diverse park questions? We don’t all have the answers yet, but now we have code and workflows that help us process terabytes of audio, wrangle millions of rows of output, and produce plots to visualize and explore the data.

We are learning even more by collaborating with other scientists and land managers. So far, we’re exploring avian soundscapes at Glacier Bay National Park and Preserve across a decade of monitoring – from when birds are most vocally active during the spring (Fig.2), to when they are most active during the dawn chorus (Fig. 3). We are learning more about wildlife in the Chihuahuan Desert, wood frogs in Alaska, and how birds respond to simulated beaver structures at Rocky Mountain National Park.

The information we provide and interpret from audio data helps parks understand more about wildlife and actions to protect park resources. Translating huge piles of raw audio data into research insights is still a challenging task, but emerging tools are making it easier.

 

Figure 2. Heat map of BirdNET detection volume for selected focal species at Glacier Bay National Park and Preserve. (a) Hermit Thrush, (b) Pacific-slope Flycatcher, (c) Pacific Wren, (d) Ruby-crowned Kinglet, (e) Townsend’s Warbler, and (f) Varied Thrush. Dates ranging in color from purple to yellow indicate increasing numbers of detections. Dates colored gray had zero detections. White areas show dates where no recordings were collected. Image courtesy of the National Park Service.

 

Figure 3. Heat map of Varied Thrush detections across date and time of day at Glacier Bay National Park and Preserve. Timesteps ranging in color from purple to yellow indicate increasing numbers of detections. Timesteps colored gray had zero detections. White areas show times when no recordings were collected. Audio recordings were scheduled based on sunrise times. Image courtesy of the National Park Service.

I know what you did last winter: Bowhead whale unusual winter presence in the Beaufort Sea

Nikoletta Diogou – niki.diogou@gmail.com

Twitter: @NikiDiogou
Instagram: @existentialnyquist

University of Victoria
Victoria, BC V5T 4H3
Canada

Additional authors: William Halliday, Stan E. Dosso, Xavier Mouy, Andrea Niemi, Stephen Insley

Popular version of 1aAB8 – I know what you did last winter: Bowhead whale anomalous winter acoustic occurrence patterns in the Beaufort Sea, 2018-2020
Presented at the 184 ASA Meeting
Read the abstract at https://doi.org/10.1121/10.0018030

The Arctic is warming at an alarming pace due to climate change. As waters are warming and sea ice is shrinking, the arctic ecosystems are responding with adaptations that we only recently started to observe and strive to understand. Here we present the first evidence of bowhead whales, endemic baleen whales to the Arctic, breaking their annual migration and being detected year-round at their summer grounds.

Whales, positioned at the top of the food web, serve as excellent bio-indicators of environmental change and the health of marine ecosystems. There are more than 16,000 bowhead whales in the Bering-Chukchi-Beaufort (BCB) population in the Western Arctic. The BCB bowheads spend their winters in the ice-free Bering Sea, and typically start a journey early each spring of over 6000 km to summer feeding grounds in the Beaufort Sea, returning to the Bering Sea in early fall when ice forms on the Beaufort Sea (Figure 1). But how stable is this journey in our changing climate?

Figure 1. Map showing migration route of BCB bowhead whales and the wider study area.

The Amundsen Gulf (Figure 1), in the Canadian Arctic Archipelago of the Beaufort Sea, is an important summer-feeding area for the BCB whales. However, winter inaccessibility and harsh conditions year-round make long-term observation of marine wildlife here challenging. Passive acoustic monitoring has proven particularly useful for monitoring vocal marine animals such as whales in remote areas, and offers a remarkable opportunity to explore where and when whales are present in the cold darkness of Arctic waters. Figure 2 shows examples of two types of bowhead whale vocalizations (songs and moans) together with other biological and environmental sounds recorded in the Amundsen Gulf.

Figure 2. Examples of spectrograms recorded in the Amundsen Gulf of bowhead whale songs on the left, and bowhead whale moans on the right. Spectrograms are visual representations of sound, indicating the pitch (frequency) and loudness of sounds as a function of time. Spectrograms on the left include bearded seal calls (trills) interfering with the bowhead songs. Spectrograms on the right include other ambient sounds (ice noise) that interfere with the bowhead moans. Image adapted from authors’ original paper.

Examples of characteristic calls of bowhead whales recorded during 2018-2019 in the southern Amundsen Gulf.

In September of 2018 and 2019 we deployed underwater acoustic recorders at five sites in the southern Amundsen Gulf and recorded the ocean sound for two years to detect bowhead whale calls and quantify the whale’s seasonal and geographic distribution. In particular, we looked for any disruptions to their typical migration patterns. And sure enough, there it was.

A combination of automated and manual analysis of the acoustic recordings revealed that bowhead whales were present at all sites, as shown for 3 sites (CB50, CB300 and PP) in Figure 3. Bowhead calls dominated the acoustic data from early spring to early fall, during their summer migration, confirming the importance of the area as a core foraging site for this whale population. But surprisingly, the analysis uncovered a fascinating anomaly in bowhead whale behavior: bowhead calls were detected at each site through the winter of 2018-2019, representing the first clear evidence of bowhead whales overwintering at their summer foraging grounds (Figure 3). This is a significant departure from their usual migratory pattern. However, analysis of the 2019-2020 recordings did not indicate whales over-wintering that year. Hence, it is not yet clear if the over-wintering was a one-time event or the start of a more stable shift in bowhead whale ecology due to climate change. The variability in bowhead acoustic presence between the two years may be partly explained by differences in sea ice coverage and prey density (zooplankton), as summarized in Figure 4.

Figure 3. Number of days with acoustic detections per month for bowhead whales for sites CB50 (blue), CB300 (green), and PP (red) in 2018-2019. The yellow shaded areas represent time periods at each station when the ice concentration was below 20% (“ice-free”), grey areas when ice concentration was 20%-70% (“shoulder season”), and white areas when ice concentration was greater than 70%. Image adapted from authors’ original paper.

Figure 4. Graphical summary of the objectives and major results of the study.

The findings of this study have important implications for understanding how climate change is affecting the Arctic ecosystem, and highlights the need for continued monitoring of Arctic wildlife. Passive acoustic monitoring can provide data on how whale ecology is responding to a changing environment, which can be used to inform conservation efforts to better protect Arctic ecosystems and their inhabitants.