Kendra Pierre-Louis: For Scientific American’s Science Rapidly, I’m Kendra Pierre-Louis, in for Rachel Feltman.
With some estimates inserting the variety of Hawaiian monk seals left within the wild at simply 1,600, the species is among the world’s most endangered kinds of seals. Though scientists have studied the creatures’ biology, actions and inhabitants modifications in depth, little or no was recognized about their communication—till now.
By placing underwater recorders in a handful of vital monk-seal habitats throughout the Hawaiian archipelago, scientists have uncovered 20 new calls.
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Freelance ocean author Melissa Hobson talked to the researchers behind the invention, in addition to different seal consultants, to search out out what this discovery reveals about Hawaiian monk seals and why it’s vital to take heed to the animals’ calls. Over to you, Melissa.
[CLIP: Monk seal vocalizations]
Melissa Hobson: That unusual noise is the decision of a Hawaiian monk seal, one among solely two species of monk seal on the earth.
The decision was recorded underwater off the coast of Hawaii as a part of a brand new research. Researchers from the College of Hawaii at Mānoa analyzed 4,500-plus hours of acoustic knowledge and heard greater than 23,000 vocalizations. Inside these sounds the scientists recognized 25 distinct calls, 20 of which have by no means been described earlier than.
Though most individuals in all probability haven’t ever heard the noises these monk seals make, Dana Jones, govt director for volunteer group Hawaiian Monk Seal Preservation Ohana, is aware of firsthand how vocal these animals might be.
Dana Jones: Most individuals who see monk seals normally see them asleep on the seaside, and except they disturb them they’re not going to listen to an entire lot of vocalization.
Hobson: Dana wasn’t concerned within the new research, however she’s an knowledgeable in rescuing and rehabbing monk seals.
In 2008 she was a part of a staff that took care of a pup who was rescued after being orphaned lower than 48 hours after his start.
Jones: His title is Hōʻailona, however we at all times confer with him as “KP2” ’trigger he was from Kauai. “Kauai Pup Two” is what that stands for.
So he was one among my first infants.
Hobson: The volunteers discovered later that KP2 had developed cataracts that rendered him virtually fully blind and couldn’t be re-released. Some additionally thought that he’d grow to be too habituated to being round people.
However when he was first taken in Dana and the opposite educated volunteers hoped they could be capable to return him to the wild when he was wholesome once more.
Jones: I used to be one of many caretakers that slept on the concrete ground subsequent to his pool in a single day many, many, many occasions, and he—we weren’t allowed to speak to him as a result of we had been instructed that he was gonna be launched, however he didn’t get the memo. So he would speak all evening lengthy. [Laughs.] And he has these little bubble sounds that he would make, and he would go slightly, “Mm mm, mm mm,” and in the event you didn’t reply him, he would get way more vocal.
So once I noticed this factor from UH Mānoa speaking about monk seals speaking, I’m going, “Effectively, no kidding, duh,” [Laughs] ’trigger he was an enormous communicator.
Hobson: For marine mammals similar to Hawaiian monk seals, sound is essential. They use it for varied functions, together with discovering meals or mates, navigating, speaking and fascinating in social interactions.
Regardless of being an important facet of the species’s lives their vocalizations aren’t properly studied.
John Terhune: Underwater sound is the one technique of long-range communication.
Hobson: That’s John Terhune, a professor emeritus at Canada’s College of New Brunswick. He’s an knowledgeable in seals, having studied their listening to and vocalizations for greater than 50 years.
Terhune: Imaginative and prescient will work in very clear water for a number of tens of meters or such. And so, actually, the marine mammals on the whole, and seals particularly, make the most of sound to keep up contact for varied social behaviors—particular person interactions, interactions with the group.
Hobson: John additionally wasn’t concerned within the research, however he’s within the novel outcomes.
The authors scientifically described 20 Hawaiian monk seal vocalizations for the primary time and located that a few of their calls have been surprisingly complicated. The undertaking was led by Kirby Parnell.
Kirby Parnell: I’m a Ph.D. candidate on the College of Hawaii at Mānoa, the place I work within the Marine Mammal Analysis Program.
Hobson: That’s Kirby. Her work on monk seal calls began in 2016, whereas she was doing her grasp’s on the College of California, Santa Cruz.
The college had entry to a monk seal in human care and thought it might be alternative to report and describe the animal’s vocalizations underwater, which she says had by no means been finished earlier than.
Parnell: There’s some papers again within the ’90s [and 2000s] that, you recognize, talked about, “Oh, monk seals bark and bubble on land and produce foghorn calls underwater,” however these are, in fact, anecdotal, and no one had ever actually described them earlier than.
Hobson: To scientifically describe the animals’ calls Kirby and her fellow researchers systematically recorded the options of the sounds, such because the size, quantity and frequency.
That analysis, printed in 2021, was the primary examination of underwater calls from Hawaiian monk seals, in accordance with the research. As soon as the undertaking was completed the pure development from finding out a seal in human care was to look at the calls of untamed monk seals.
To do that the researchers used passive acoustic recorders referred to as SoundTraps.
Parnell: Mainly, they’re these units that report sounds underwater.
Hobson: These self-contained underwater recorders, that are referred to as hydrophones, don’t essentially appear like essentially the most snazzy gear. These small titanium cylinders weigh only a few kilos, so that they need to be secured to a concrete block to maintain them in place on the seabed.
The staff lowered the units into the water utilizing ropes …
[CLIP: Splash sound]
Hobson: And left them recording the underwater setting, usually for weeks or months at a time.
Kirby knew males typically patrol the seashores and swim in waters near shore in search of mates, so she determined to put her recorders in shallow waters, sometimes lower than 10 meters deep.
Parnell: You simply need to deploy them in areas the place you assume monk seals are, and, you recognize, they’ll choose up sounds, every little thing from monk seal vocalizations …
[CLIP: Monk seal vocalizations]
Parnell: To sounds from storms.
[CLIP: Storm sounds]
Parnell: I’ve even picked up some earthquake sounds …
[CLIP: Earthquake sounds]
Parnell: In addition to snapping shrimp …
[CLIP: Snapping shrimp sounds]
Parnell: And fish and different organic, in addition to anthropogenic, noise.
Hobson: One of many recorders needed to be introduced up after seven days as a result of a curious monk seal chewed on the gadget and broke it. However some recorded constantly for almost three months.
Hobson: After the researchers introduced the units again up and cleaned them, they have been prepared to search out out what they’d captured. Downloading the info alone took days on finish.
Parnell: I’d say that was some of the thrilling issues for me all through this Ph.D., is getting the SoundTraps again and off-loading the info and opening it up to take a look at the spectrogram and seeing, “Oh, my gosh, we’ve knowledge!” [Laughs.] “There’s fish, and oh, my gosh, there’s monk seal sounds. Oh, my gosh, we did it.”
Hobson: And manually processing all of it was extremely time-consuming.
Parnell: They’re vocalizing rather a lot, and we’re logging each single one among their calls—the beginning and the tip time to each single one among their calls. So inside a five-minute interval you may discover, you recognize, as much as 60 totally different vocalizations, and which may take anyone half-hour or so to get by.
I’ve to offer a lot credit score to my interns as a result of they’ve finished this now for 4 years—processing knowledge for 4 years. Discovered 23,000 calls. That takes so lengthy.
Hobson: Listening again to the audio the researchers have been capable of determine 25 totally different name sorts in whole, 20 of that are new to science.
Parnell: Six name sorts have been elemental name sorts, that are simply singular models of sound.
The croak is like: [Croaks twice].
[CLIP: Monk seal croaks]
Parnell: And the growl is like: [Growls]. [Laughs.]
[CLIP: Monk seal growls]
Parnell: After which everyone’s favourite, which you are able to do too, in the event you wanna report your self, is the whoop, which is: [Whoops five times].
[CLIP: Monk seal whoops]
Hobson: Okay, I’m gonna attempt: [Whoops three times].
The opposite 19 have been combinational calls, which be a part of the basic calls collectively with none silence in between.
So that you may need one name that’s made up of the croak, hum, growl and whoop. It sounds a bit like a abdomen rumbling loudly.
[CLIP: Monk seal croak, hum, growl, whoop]
Hobson: Then there’s the growl, rumble, whoop.
[CLIP: Monk seal growl, rumble, whoop]
Hobson: And the hum, growl, rumble.
[CLIP: Monk seal hum, growl, rumble]
Hobson: You get the image.
With the ability to mix these totally different sounds collectively on this means is uncommon for a lot of these marine mammals.
Parnell: I’m unaware of another pinnipeds—you recognize, seals, sea lions and walruses—which might be capable of string these singular models of sound along with, with no silence between them.
Hobson: John says these complicated combos are noteworthy as a result of they may permit monk seals to extra intently tie particular sounds to sure behaviors.
Terhune: The impact of mixture calls is that it does open a chance for extra exact behavioral calls. By ordering a name, say, sort A, B, C, it might be [different] than C, B, A, for instance.
Though they recognized about 20 combos, when you’ve got 5 name sorts and [are] making three calls in a row, then that’s a chance of 125 totally different patterns. And so there appears to be some specification as to which name sorts are being given wherein order.
Hobson: Now the scientists know that the seals make these noises underwater, they need to discover out why the animals are doing so.
To dive into this query the researchers plan to deploy extra recorders for longer durations—as much as a 12 months or extra—to see if they’ll spot any seasonal patterns. For instance, in the event that they hear sure calls extra throughout breeding season, it would counsel that these kinds of vocalizations are associated to copy.
The scientists additionally need to collect extra context concerning the seals’ conduct as they make these sounds. To do that the researchers have began utilizing seal-mounted monitoring units with the flexibility to report video and audio and seize quite a lot of knowledge factors, together with how deep underwater an animal is and the way shortly it’s shifting.
Parnell: It’s mainly like a seal Fitbit with a video digicam and acoustic recorder, so that you form of get, like, a hen’s-eye view of monk seal conduct underwater.
Hobson: The researchers hope the video will seize what the monk seals are doing when making sure vocalizations to allow them to hyperlink kinds of calls to particular behaviors.
The staff already has a concept about one of many elemental calls, dubbed the whine.
Parnell: So the whine, it feels like: [Whines]. [Laughs.]
[CLIP: Monk seal whines and snapping shrimp sounds]
Hobson: Throughout her Ph.D., Kirby got here throughout social media clips of Hawaiian monk seals foraging and observed that the animals produced this noise whereas in search of meals. She hypothesizes that the decision may need one thing to do with discovering a meal and is hopeful the seal spy cameras will assist the staff verify whether or not that’s true.
It will be an thrilling discovery as a result of she isn’t conscious of many different seals doing this.
Parnell: Just one different publication has talked about a phocid seal, or a real seal, producing a vocalization for foraging functions, and that was the elephant seal, who’s intently associated to monk seals.
Hobson: Dana remembers a monk seal whose loud searches for meals precipitated fairly a stir in the area people.
Jones: We had a seal that got here from Nīhoa, which is among the Northwestern Hawaiian Islands, and she or he turned fairly a vocal lady in one of many canals on the west facet. And other people would complain that she stored them awake all evening ’trigger she would go into the canal to hunt for tilapia, and she or he would scrounge and grunt and moan and do every kind of stuff.
Hobson: The seal was so noisy that folks have been nervous about it, to not point out irritated at being stored up all evening by a grunting animal, and Dana needed to go to a group assembly to clarify that it wasn’t damage.
Scientifically recording all this data is vital as a result of if we don’t know concerning the lives of those creatures, we will’t defend them.
Parnell: These are foundational research and simply tiny items of the general puzzle, proper? Working with an endangered species, we have to perceive every little thing that we will, and that is one piece of the puzzle.
Hobson: Gathering this details about the several types of monk seal calls is a vital first step. Figuring out that they make the calls might result in a greater understanding of what these vocalizations are for. These insights will hopefully assist make clear how human exercise impacts their lives.
Scientists already know that, for different marine mammals, loud noises made by people’ exercise can interrupt their communication, alter their conduct and even briefly or completely harm their listening to. And it may well make it harder for them to listen to calls from far-off.
The researchers need to know whether or not that’s the case for Hawaiian monk seals as properly. Within the research the staff discovered that the seals vocalize at a really low frequency—sometimes under one kilohertz.
Terhune: That is vital as a result of this matches the frequency vary that’s produced by giant ships, and the ship noise, which might journey—as a result of it’s very excessive supply ranges, usually—can journey for tens to a whole bunch of kilometers, may have the impact of masking the calls.
And so when you’ve got a superbly quiet time, say, within the night, with no waves and no close by vessels, in that case the seals might be able to detect one another over ranges of as much as, say, two or three or 4 kilometers. But when a ship noise comes alongside, that may be diminished very quickly right down to properly beneath 100 meters.
Hobson: If the noise of ships is masking the seals’ calls to allow them to’t hear one another correctly, it would even intrude with their skill to search out mates.
Terhune: The monk seals additionally are likely to reside roughly individually more often than not. And in the course of the breeding seasons the females with their pups might be up, usually, on shore, and the males are likely to patrol backwards and forwards alongside the seashores, basically in search of mates.
Hobson: The sound of seals serenading potential companions is one thing Dana has heard many occasions.
Jones: We might undoubtedly inform when the males have been on the transfer, in search of a girlfriend. They’d get fairly vocal once they would haul up on the seaside after a feminine.
The males are fairly aggressive in the case of getting out of the water and developing, and the females [seem to get] fairly aggressive, too, in the event that they don’t need to be bothered. So that you—we’ve some very vocal [Laughs] movies of, mainly, fights. And I couldn’t let you know—I wouldn’t need to translate what they’re saying. [Laughs.] “Get away from me, large boy!” No matter they’re saying.
Hobson: If human actions have been to interrupt these courtship calls, it might find yourself being actually problematic for the species.
Terhune: By the women and men calling they’re presumably capable of find one another, after which that may facilitate a profitable mating. And [it] carries, if there was a really steady excessive ranges of enormous vessel noises, then that might be interfered with, and you might get barely diminished mating alternatives. And over a protracted time period that might have an effect on the inhabitants.
Hobson: And in the case of getting sufficient meals, noise air pollution might be a barrier if a vocalization just like the whine is, the truth is, linked to foraging.
Terhune: They might feed rather less, notably in the event that they’re feeding on a fish species that’s truly making calls. So in the event that they’re capable of determine the fish and find them by listening to their calls, then that may affect their skill to—for profitable foraging.
Hobson: It’s additionally value remembering that spending time within the water is a well-liked pastime for a lot of Hawaiian residents, seal and human alike.
Parnell: We have now about 1.4 million those who reside right here, in the primary Hawaiian Islands, and about 400 seals, so we’ve a big overlap between seals and people.
And naturally, it’s Hawaii—we love going out into the water. We love, you recognize, snorkeling, free diving, being on boats, fishing, ecotourism.
Hobson: All these water actions imply a lot of vessels within the seals’ territory, making noise which may disturb the animals.
The researchers hope that this research might result in improved conservation measures as a result of now that scientists have a greater thought of what Hawaiian monk seal calls sound like, they’ll use audio recordings to find out precisely the place the seals spend time throughout totally different elements of the 12 months. That provides them the information to place safety measures in place, similar to velocity limits for boats.
Within the meantime, in the event you’re ever fortunate sufficient to see a Hawaiian monk seal within the wild, don’t method it, give it loads of area, and savor the uncommon encounter.
Parnell: If I’m within the water, there’s a monk seal round, you recognize, you’re, you’re actually supposed to maneuver away from the animals. However once more, they’re curious, and typically they do comply with you.
That is an endangered species. You higher take pleasure in that second as a result of that’s unbelievable. Like, the truth that you’re seeing one particular person of this endangered species out in its habitat is simply—ah, what a, what a particular expertise, so. So thrilling. [Laughs.]
[CLIP: Monk seal vocalizations and snapping shrimp sounds]
Pierre-Louis: That’s it for right this moment! Tune in on Monday for a particular roundup of 2025.
Science Rapidly is produced by me, Kendra Pierre-Louis, together with Fonda Mwangi and Jeff DelViscio. This episode was reported and co-hosted by Melissa Hobson and edited by Alex Sugiura. Shayna Posses and Aaron Shattuck fact-check our present. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for extra up-to-date and in-depth science information.
For Scientific American, that is Kendra Pierre-Louis. Have an ideal weekend.
