The Knowledge
How dolphins communicate – new discoveries from a long‑term study in Sarasota, Florida
Laela Sayigh, Woods Hole Oceanographic Institution
Human fascination with bottlenose dolphins goes back thousands of years, at least as early as Greek mythology.
But it wasn’t until the 1960s that methodical research into dolphin communication began. Scientists like John Lilly and the husband-and-wife team of Melba and David Caldwell tried various experiments to decipher the sounds dolphins can make.
The Caldwells figured out a way to record isolated animals in human care. They discovered that each individual dolphin communicated mostly with one unique whistle, which they called the “signature whistle.” Researchers now know that these whistles convey identities much like human names do. Dolphins use them to stay in touch with each other in their murky habitat, where vision is limited. It’s like announcing “I’m over here!” when someone can’t see you.
This discovery is foundational to my own research. I’ve been studying communication in wild dolphins since the mid-1980s, when I joined my mentor Peter Tyack in documenting signature whistles in wild dolphins for the first time. Our team’s research focused on a resident community of free-ranging bottlenose dolphins in waters near Sarasota, Florida, where I continue to work today.
This collaborative study, led by Randall Wells of Brookfield Zoo Chicago’s Sarasota Dolphin Research Program, involves numerous researchers from a variety of institutions, who study different aspects of dolphin biology, health, ecology and behavior. Begun in 1970, this is the longest-running research project on a population of wild cetaceans – whales, dolphins and porpoises – in the world.
Recording and observing
Researchers know the age, sex and maternal relatedness of almost all of the approximately 170 dolphins in the Sarasota community. This depth of knowledge provides an unprecedented opportunity to study communication in a wild cetacean species.
The dolphins in the Sarasota project are periodically subject to brief catch-and-release health assessments, during which researchers, including me, briefly handle individual dolphins.
Our team attaches suction-cup hydrophones directly onto each dolphin’s melon – that is, its forehead. We then record the dolphins continuously throughout the health assessments, taking notes on who is being recorded when, and what is happening at the time.
This is how my colleagues and I were able to confirm that wild dolphins, like captive animals, produced large numbers of individually distinctive signature whistles when briefly isolated from other dolphins. Through observations and recordings of known free-swimming dolphins, we were further able to confirm that they produced these same signature whistles in undisturbed contexts.
We have organized these recordings into the Sarasota Dolphin Whistle Database, which now contains nearly 1,000 recording sessions of 324 individual dolphins. More than half of the dolphins in the database have been recorded more than once.
We identify each dolphin’s signature whistle based on its prevalence: In the catch-and-release context, about 85% of the whistles that dolphins produced are signature whistles. We can identify these visually, by viewing plots of frequency vs. time called spectrograms.
Signature whistles and ‘motherese’
The Sarasota Dolphin Whistle Database has proved to be a rich resource for understanding dolphin communication. For instance, we have discovered that some calves develop signature whistles similar to those of their mothers, but many do not, raising questions about what factors influence signature whistle development.
We have also found that once developed, signature whistles are highly stable over an animal’s lifetime, especially for females. Males often form strong pair bonds with another adult male, and in some instances, their whistles become more similar to one another over time. We are still trying to understand when and why this occurs.
Dolphin mothers modify their signature whistles when communicating with their calves by increasing the maximum frequency, or pitch. This is similar to human caregivers using a higher-pitched voice when communicating with young children – a phenomenon known as “motherese.”
Slowed recording of a bottle-nosed dolphin without her calf, then with her calf. Courtesy of Laela Sayigh of Woods Hole Oceanographic Institution, and Brookfield Zoo Chicago’s Sarasota Dolphin Research Program. These sounds were obtained under a federal scientific research permit issued to R. Wells of SDRP.72 KB (download)
Also similar to humans is how dolphins will initiate contact with another dolphin by imitating their signature whistle – what we call a signature whistle copy. This is similar to how you would use someone’s name to call out to them.
Our team is interested in finding out if dolphins also copy whistles of others who aren’t present, potentially talking about them. We have seen evidence of this in our recordings of dolphins during health assessments, which provide a rare context to document this phenomenon convincingly. But we still have more work to do to confirm that these are more than chance similarities in whistles.
Shared whistle types
Another exciting development has been our recent discovery of shared whistle types — ones that are used by multiple animals and that are not signature whistles. We call these non-signature whistles.
I could hardly believe my ears when I first discovered a repeated, shared non-signature whistle type being produced by multiple dolphins in response to sounds we play back to them through an underwater speaker. We had previously believed that these non-signature whistles were somewhat random, but now I was hearing many different dolphins making a similar whistle type.
Our team originally had been using the playbacks to try to determine whether dolphins use “voice cues” to recognize each other – similar to how you can recognize the voice of someone you know. Although we found that dolphins did not use voice cues, our discovery of shared non-signature whistle types has led to an entirely new research direction.
So far, I’ve identified at least 20 different shared non-signature whistle types, and I am continuing to build our catalog. We are hoping that artificial intelligence methods may help us categorize these whistle types in the future.
To understand how these shared non-signature whistle types function, we are carrying out more playback experiments, filming the dolphins’ responses with drones. We’ve found that one such whistle often leads the dolphins to swim away, suggesting a possible alarm-type function. We have also found that another type might be an expression of surprise, as we have seen animals produce it when they hear unexpected stimuli.
More difficult, more interesting
So far, the main takeaway from our experiments has been that dolphin communication is complex and that there are not going to be one-size-fits-all responses to any non-signature whistle type. This isn’t surprising, given that, like us, these animals have complicated social relationships that could affect how they respond to different sound types.
For instance, when you hear someone call your name, you may respond differently if you are with a group of people or alone, or if you recently had an argument with someone, or if you’re hungry and on your way to eat.
Our team has a lot more work ahead to sample as many dolphins in as many contexts as possible, such as different ages, sexes, group compositions and activities.
This makes my job more difficult – and far more interesting. I feel lucky every day I am able to spend working on the seemingly infinite number of fascinating research questions about dolphin communication that await answers.
This article has been corrected to better describe how dolphins respond to playback whistles.
Read more stories from The Conversation about Florida.
Laela Sayigh, Senior Research Specialist, Cetacean Communication, Woods Hole Oceanographic Institution
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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The Long Track Back
LA Metro Approves $71 Million Bus Engine Program and Advances Antelope Valley Line Safety Work
LA Metro will replace engines in as many as 680 natural-gas buses while advancing safety improvements at two Antelope Valley Line crossings in Sylmar.
Two newly confirmed Board actions will keep hundreds of Metro buses in service while moving two Sylmar rail crossings toward construction.
LOS ANGELES — October 28, 2026 — The Los Angeles County Metropolitan Transportation Authority has approved two major investments affecting bus reliability and regional rail safety: a nearly $71 million engine-replacement program for as many as 680 buses and a $27.6 million construction budget for two Antelope Valley Line crossings in Sylmar.
The Metro Board approved both actions on October 22.
Hundreds of natural-gas buses will receive new engines
Metro awarded Cummins Sales and Service a five-year, single-source contract worth up to $70.99 million for 680 near-zero-emission natural-gas engines. The engines will be installed in El Dorado National 40-foot buses and New Flyer 60-foot articulated buses during fiscal years 2027 through 2031.
The engines will operate on renewable compressed natural gas and replace older engines as part of Metro’s midlife bus-refurbishment program. Metro mechanics will perform the installations.
According to the Board report, replacing high-mileage engines should reduce engine-related road calls and improve the reliability of buses that remain in daily service. Metro estimates that the replacements will reduce nitrogen-oxide emissions by 90 percent and greenhouse-gas emissions by 9 percent compared with the engines being removed.
The decision also provides more context for Metro’s transition to electric buses. In September, the agency approved the purchase of 220 battery-electric buses, with deliveries expected to begin in 2028. The new Cummins contract shows that Metro will continue investing in its existing natural-gas fleet while electric buses and the charging infrastructure needed to support them are introduced.
Metro has not changed its zero-emission goal through this action. The engine replacements are intended to keep current buses dependable during the transition and do not obligate the agency to order all 680 engines.
Two Sylmar rail crossings move toward construction
In a separate action, the Board established a $27.62 million life-of-project budget for improvements at the Astoria Street pedestrian crossing and the Polk Street roadway crossing along the Metrolink Antelope Valley Line.
The crossings are part of Segment 4 of Metro’s Brighton-to-Roxford Double Track Project. Although the broader project remains in different stages of design, the Astoria and Polk plans are sufficiently advanced to proceed as separate construction packages.
Planned improvements include coordinated traffic signals, pedestrian gates and additional roadway gates. Polk Street will receive a four-quadrant gate system intended to make it harder for motorists to enter or drive around the crossing when a train approaches. Both locations will also be prepared for possible future quiet-zone operations.
The work supports Metro’s larger effort to improve safety, reliability and capacity on the Antelope Valley Line. Advancing the two crossings now also protects state Transit and Intercity Rail Capital Program funding that must be spent and submitted for reimbursement by June 30, 2027.
Metro will conduct community outreach and execute the construction contracts following the Board’s approval. A specific construction-start date has not yet been announced.
Primary sources
● Metro Board Report 2026-0644: Near-Zero Natural Gas-Fueled Engines
● Metro Board Report 2026-0640: Astoria and Polk Crossing Improvements
This story is part of The Long Track Back, STM Daily News’ continuing coverage of Los Angeles transit projects, service and regional mobility.
Daily News
Major Construction Begins on Metro’s East San Fernando Valley Light Rail Line
LA Metro has moved the East San Fernando Valley Light Rail Transit Project into major construction. The 6.7-mile Van Nuys Boulevard line will add 11 stations, connect with the G Line and regional rail services, and is now targeted for completion in early 2032.
After years of utility relocation and planning, LA Metro is moving into major construction on a new rail line along Van Nuys Boulevard. The milestone also comes with a revised early-2032 completion target.
LA Metro has officially marked the beginning of major construction on the East San Fernando Valley Light Rail Transit Project, moving one of the region’s most important rail projects from preparatory work into full-scale construction.
Metro held a groundbreaking ceremony on October 19, 2026, for the 6.7-mile line, which will run along Van Nuys Boulevard from the G Line busway north to San Fernando Road in Pacoima. The project will add 11 light-rail stations serving Van Nuys, Panorama City, Arleta and Pacoima.
This was not the project’s first groundbreaking. Metro held an earlier ceremony in December 2022 when crews began relocating utility infrastructure. The new milestone is more consequential for riders: the major-construction phase covers the guideway, stations, traction-power substations, rail systems and a maintenance and storage facility.
From utility work to a new rail corridor
The project has spent several years in utility relocation, property acquisition, design and other early work. Metro’s current construction timeline shows major work continuing from 2026 through 2032, with phased traffic changes and K-rail installations expected along Van Nuys Boulevard.
When completed, trains are expected to operate every seven to 10 minutes during peak periods. The line will connect directly with the G Line and provide access to the Van Nuys Metrolink and Amtrak station. It is also expected to become an important transfer point for the future Sepulveda Transit Corridor and a planned Metrolink station in Pacoima.
The corridor already has a substantial transit market. Metro reported that bus Lines 233 and 761, which serve Van Nuys Boulevard, recorded nearly 20,000 boardings in September 2026. The agency also says approximately 19 percent of households in the project area lack access to a car, compared with about 8 percent countywide.
Those figures help explain why this project matters beyond its construction footprint. It is intended to give residents in some of the Valley’s most transit-dependent communities more reliable access to jobs, schools, healthcare and the wider regional transit network.
The opening target has moved to 2032
Metro’s current project page lists an estimated completion date of early 2032. That is later than the 2031 opening forecast the agency publicized when it celebrated an $893-million federal grant in September 2024. Earlier plans were more optimistic still: when utility work began in 2022, Metro said the first segment could open between 2028 and 2030.
The project’s financial scale has also grown clearer. In May 2026, the Metro Board established a life-of-project budget of approximately $3.999 billion and authorized the next phase of its progressive design-build contract with San Fernando Transit Constructors, a joint venture of Skanska and Stacy and Witbeck.
That authorization increased the construction contract’s value to roughly $2.431 billion. Funding for the larger project combines federal, state and local sources, including revenue from Los Angeles County’s Measure M transportation sales tax.
Rail returns to Van Nuys Boulevard
The East San Fernando Valley line will restore passenger rail to Van Nuys Boulevard for the first time since Pacific Electric ended streetcar service there in 1952. It will also become the first major new Metro rail project in the San Fernando Valley since the subway reached North Hollywood in 2000.
The historical parallel is significant. Van Nuys Boulevard once developed around electric railway service before the region shifted heavily toward automobiles and buses. Metro is now rebuilding rail in the same broad corridor, but as part of a modern network designed to connect local riders with bus rapid transit, regional rail and future high-capacity projects.
The current project ends in Pacoima. Metro continues to study a separate 2.5-mile northern extension that would reach the Sylmar/San Fernando Metrolink station. That extension is not included in the segment now entering major construction.
For riders, the October groundbreaking does not mean trains are imminent. Several years of disruptive and technically complex work remain, and the schedule has already moved beyond earlier forecasts. Still, it represents a tangible transition: the East San Fernando Valley line is no longer primarily a planning exercise or utility-relocation program. Metro has begun building the infrastructure that will carry trains.
That makes this a major step in Los Angeles County’s long effort to restore frequent rail transit to communities that lost it generations ago—and another chapter in The Long Track Back.
Primary sources
- LA Metro: Major construction will soon be underway
- LA Metro project page: East San Fernando Valley Light Rail Transit
- LA Metro Board meeting, May 28, 2026 — project budget and contract authorization
- LA Metro: $893 million federal grant announcement, September 6, 2024
- LA Metro: Advanced utility-work groundbreaking, December 2, 2022
This article is part of The Long Track Back, STM Daily News’ continuing coverage of how Los Angeles is rebuilding and expanding a passenger-rail network after decades of automobile-centered grow
For generations, the Santa Monica Pier sign has marked the start of a day at the beach. Now, the familiar blue neon landmark is preparing for a journey of its own.
Santa Monica scheduled removal of the 1941 sign for October 20–22, with shipment to Las Vegas anticipated October 26. The timetable is subject to change, according to the city’s October 19 announcement.
The temporary removal accompanies replacement of the aging bridge connecting Ocean Avenue to the pier. It also creates an opportunity to preserve the historic sign.
YESCO will restore it at its Las Vegas facility. The company’s experience includes work on the “Welcome to Fabulous Las Vegas” sign.
Crews will repair neon tubing, treat rust, repaint components and address structural needs while retaining historic features. The sign will remain in secure storage during bridge construction.
Once the project is finished, it will return above the new bridge at a slightly greater height for visibility and vehicle clearance. The city’s latest announcement targets project completion by 2028, ahead of the Los Angeles Olympics and Paralympics.
Meanwhile, visitors can photograph a lighted, half-scale replica near Pier Burger.
For anyone who associates that glowing arch with Southern California memories, its absence will be noticeable. The restoration is intended to ensure future generations can make memories beneath it, too.
Source: City of Santa Monica — October 19, 2026 announcement
Related Links
- City of Santa Monica: Official sign restoration announcement — October 19, 2026. Primary source for removal dates, shipment to Las Vegas, YESCO’s restoration work and the sign’s planned return.
- Santa Monica Daily Press: Sign restoration during bridge rebuild — October 20, 2026. Additional local reporting on the project and visitor access.
- LAist: Sign removal and how to watch — Reporting on the removal schedule and public viewing opportunities.
Follow more Southern California stories at STM Daily News.
