By: Valeria Vergara, Research Scientist
It is late in the evening, the Arctic sun still bright on the horizon, and I am recording a group of belugas that has become temporarily entrapped at low tide in a river channel. It is not the first time this has happened; two other groups were recently entrapped in the same channel – swimming out hours later with the rising tide. Every time this occurs, I run across the muddy flats of the delta to deploy my hydrophone in the river-pool and listen.
It is 2015 and I am in Cunningham Inlet, Nunavut, a traditional summer nursery area for up to 2,000 beluga whales from the Eastern High Arctic-Baffin Bay population, to study how this species communicates in a still-pristine environment. Human-made noise pollution – a pervasive threat to many species of whales and dolphin – is entirely absent here. These temporary river entrapments have added an unexpected dimension to my study!
Contact calls blast loud and clear through my speakers. These calls are the “hello, I am here” of the species. I discovered this over 15 years ago, shortly after I began to study how these loquacious whales communicate acoustically. Contact calls sound nothing like the typical chirps and whistles that form the majority of their sophisticated vocal repertoire, but more like loud chainsaws or creaky rusty doors. Their distinctiveness makes it easier for us to identify them reliably, and therefore to study them.
As I listen, transfixed, I think, not for the first time, that the contact calls I am hearing do not all sound the same. And today, with fewer whales, I also notice something else: there seems to be less variety in the acoustic quality of the contact calls that the they exchange. What if… what if each whale produces its own individual contact call to identify itself to the group? What if the entrapments continue to happen, and I could document this? If I could find out exactly how many individuals were trapped in the river channel each time, and if I could correlate the number of individuals with the number of distinct contact calls I recorded each time…well, that may just offer us a first glimpse into the answer!
I remember the “Eureka” moment as if it was yesterday. As is often the case with fieldwork, the best ideas can emerge once you’ve been in a location for a while, and you become attuned to the animals you are studying. Arriving to the field with a protocol in mind is of course essential, but it is also important to pay attention to the questions that arise, and to be flexible enough to pursue those questions. So an unplanned study was quickly put in place. A film crew made it possible to fly a drone over the whales during each ensuing entrapment, which allowed me to count the whales much more precisely than I could have at eye level. I used my hydrophone to record fourteen of these natural entrapments. I also periodically recorded the free-ranging herd, for comparison.
Back at the Marine Mammal Conservation Research Lab, Marie-Ana Mikus, beluga research technician extraordinaire, and I, spent many hours analyzing these recordings and discussing our findings excitedly every chance we had. It became very clear that when the whales were entrapped in the channel, they resorted to contact-calling. Were they calling their companions on the other side of the sandbar? Were they keeping track of one another in a situation perceived as dangerous? We do not know, but contact-calls comprise only 10% of the vocalizations produced by the free ranging herd, while more than half (61%) of the calls produced by entrapped whales were contact calls. Many of these had clearly identifiable characteristics that we were delighted to observe in spectrograms (visual representations of a sound). In total, we classified 87 distinct contact call types produced during the entrapments. But don’t just take our word for it: we recruited 55 naïve judges to verify our classification, a commonly used technique in the field of bioacoustics. Some of the judges had never looked at a spectrogram and some were biologists who had worked with animal sounds before, even with beluga sounds, but had no experience with our study population. There was an overwhelming agreement with our classification.
We also found a strong relationship between the number of whales and the number of contact call types recorded in an entrapment. This could mean one of two things: that each individual produced its own distinct contact call type, or, if the entrapments contained groups of associated individuals (the larger the entrapment, the larger the potential number of such associations), that each contact call type was potentially shared by a few close associates. These preliminary findings that beluga contact calls may be what biologists refer to as vocal signatures were published last year1.
Why is this exciting? Don’t individuals of all vocal species, including humans, have their own voice characteristics that help tell them apart? True! But a vocal signature is a call type that shows individual differences that are much more accentuated than the often-subtle differences in voice characteristics. What’s more, vocal signatures need to be learned – much like human toddlers must learn to pronounce their own names. This fits our research very well: beluga whales must indeed learn to pronounce these contact calls, they learn them from their mother, and it takes them one to two years to perfect this call type, as our most recent study, just published, corroborated2.
One of the handful of species for which vocal signatures have been documented is the bottlenose dolphin. Their well-known signature whistles act as names of sorts and play an important role in helping individuals keep track of one another in their fission-fusion societies, in which the size and composition of social groups changes periodically and often drastically. So does it make evolutionary sense to expect that belugas would have vocal signatures as well?
We think so. A ground-breaking recent study3 illuminates strong parallels between belugas and human societies. We are both long-lived, profoundly social and cultural species. Beluga societies seem to be fission-fusion and involve close and fluid long-term associations with both kin and non-kin, cooperation, and strong cultural traditions in the context of communities that include large numbers of individuals of all sexes and ages. Males form friendships and alliances that can last years, nonrelated females travel together, presumably helping to raise each other’s young, and juveniles of multiple ages and different maternal lineages gather together in bands to play and socialize.
So how do belugas mediate these complex and fluid social relationships? How do they recognize and keep track of one another in an aquatic, dark environment where vision would not be very helpful? Identity calls may be the answer, helping them stay in acoustic contact with both close relatives and friends amidst the chaotic comings and goings of their intensely sociable communities.
But until we gather more robust data, our answer is still a maybe. After all, we are still missing the most important part of the puzzle: identifying the individual callers! Can we put a face (or rather, a dorsal ridge!) to a call? Perhaps! When Marie-Ana and I found that our colleagues at Fisheries and Oceans Canada (DFO) and the Group for Research and Education on Marine Mammals (GREMM) were deploying temporary non-invasive Digital Recording Tags (DTAGS, which attach to the whales via suction cups) on St. Lawrence Estuary belugas, we jumped at the opportunity to collaborate with them. Our role? To pair the contact-calls produced by individuals carrying these temporary DTAGS with photo-IDs of those individuals (matching the photos to GREMM’s extensive photographic catalogue of this endangered population). We will soon receive the Dtag recordings from 2020, the third and last season! This is how science works: findings build upon each other, new ideas emerge, and collaborations allow for those ideas to be tested. Some ideas are quickly discarded. Some take years to be proven right…or wrong! We hope that the St. Lawrence data will illuminate whether beluga contact-calls are strictly individual or shared with close relatives or friends.
There is no doubt that this is a fascinating area of inquiry. I am profoundly curious; I simply ache to learn more about a species that resembles us so closely. But curiosity aside, recognising and thus monitoring individuals, groups, and even communities acoustically also has important conservation implications for declining populations. If we confirm that contact calls are indeed vocal signatures, then it follows that we could use acoustic monitoring alone to understand habitat use and ranging patterns of individual beluga whales and their close associates. Moreover, how these sound-centered whales use sound is a particularly important aspect of their ecology that needs to be understood to gain insight into the effects of anthropogenic noise on their ability to communicate effectively, and to survive.
1. Vergara, V. & Mikus, M.-A. Contact call diversity in natural beluga entrapments in an Arctic estuary: Preliminary evidence of vocal signatures in wild belugas. 35, 434–465 (2019).
2. Ames, A. E. & Vergara, V. Trajectories of vocal repertoire development in beluga (Delphinapterus leucas) calves: insights from studies a decade apart. Aquat. Mamm. 46, 344–366 (2020).
3. O’Corry-Crowe, G. et al. Group structure and kinship in beluga whale societies. Sci. Rep. 10, 1–21 (2020).