Posts tagged with "whale research"

New Study Examines the Effect of Vessel Noises on Humpback Whale Singers by Callie Cho

As anthropogenic noise continues to increase in our oceans, animals who employ acoustic communication have become increasingly challenged to make their sounds heard and understood by other members of their species. This artificial noise interferes with behaviors essential to individual and species survival, such as acts of courtship, displays of dominance, communication of resources, feeding behaviors, and navigation.

One animal whose form of communication has become increasingly encroached upon by anthropogenic noise is the humpback whale (Megaptera novaeangliae). While it is not completely known why male humpbacks sing, this behavior mainly occurs in breeding grounds and migratory corridors, indicating that it is important for comparing and communicating fitness to females and to other male singers. Understanding the effect of human-created noises such as boat sounds on humpback song is essential in advancing productive conservation initiatives.

Humpback whales naturally adapt their singing intensity in response to the given amount of naturally occurring noise in their environment; noises such as wind, water, and reef sounds. The unconscious act of adjusting vocal effort in the presence of other sounds is known as the Lombard effect and is present in many acoustically communicating animals. However, it is unknown if the Lombard effect is present in singing humpback males in relation to vessel noise.

A recent study conducted by Girola et al. (April 2023) at the University of Queensland sought to answer this question by studying eastern Australia’s singing males’ Lombard response to ambient wind noise as compared to wind noise accompanied by vessel noise. The scientists hypothesized that if the males’ Lombard effect accounted for vessel noise as well as wind noise, then their singing would change accordingly in the presence of a vessel as compared to when no vessel was present.

In September and October of 2010, Girola et al. recorded humpback song in Peregian Beach, a migratory corridor for humpbacks moving southbound towards Antarctica from breeding grounds in the Great Barrier Reef. The researchers employed the use of four stationary buoys to record singers within 5km of the designated study area, and they methodically drove a vessel along an established route. Recordings disturbed by the sounds of rain, other vessels, or loud fish choruses were excluded from the study to isolate the sounds of wind and the research vessel noises.

After extensive song unit analysis, the authors concluded that while humpback singers adjust their songs according to wind levels, they do not do so for vessel noises. In other words, the Lombard effect is present in response to varying levels of wind noise but not present in response to vessel noises. While this result suggests that other coping strategies could be at play, no other ones have been scientifically studied.

In conclusion, this study reinforces the importance of understanding the effect of anthropogenic noises on humpback whale behavior. Knowing that singers do not employ the Lombard effect when accounting for vessel noise opens doors for more studies to be done on alternate coping mechanisms. This result could also suggest that whales do not, in fact, have a fixed strategy in place to deal with this type of anthropogenic noise, considering their lack of song adjustment in response to vessel noise. If the latter is true, then anthropogenic noise could pose a detrimental problem for humpback whale vocalization and its associated behaviors.

Specifically in relation to our research, the waters around Rarotonga are part of the migratory corridor of the last population of endangered migrating humpback whales in the world. In these waters, humpbacks opportunistically breed and birth their young. Therefore, conservation initiatives in the Cook Islands should aim to control vessel noise in proximity to singing males. It is imperative to understand the effects of vessel noise to best protect these amazing animals.

References:

¹ Payne R, McVay S. 1971 Songs of Humpback whales. Science 173, 585-597. (doi: 10.1126/science.173.3997.585)

² Dunlop RA, Cato DH, Noad MJ. 2014 Evidence of a Lombard Response in migrating humpback whales (Megaptera novaeangliae). J. Acoust. Soc. Am. 136, 430-437. (doi:10.1121/1.4883598)

³ Whitlock, J. (2012). Understanding the Lombard Effect. New Zealand Acoustics, 25(2), 14–17.

⁴ Girola E, Dunlop RA, Noad MJ. 2023 Singing humpback whales respond to wind noise, but not to vessel noise. Proc. R. Soc. B 290: 20230204. https://doi.org/10.1098/rspb.2023.0204

Meditation on Time with Whales at Sunset By Callie Cho

Photograph by Callie Cho

Time passes differently on the open ocean, a passive presence that lulls in and out of one’s consciousness with the rhythms of swells. Quiet moments on still water can drag on: time looms over you like a vampiric presence, elongated by the possibility of a whale-induced ripple. Eyes become strained, focused, and red-rimmed; backs and butts sit torqued between pelican cases; core muscles remain tensed and fight the rocking of your boat. And you, the observer, feel completely embodied in your discomfort. Minutes become hours and become a persistent feeling of shifty anticipation.

But, in an instant, time can disappear again: Maybe, a whale, inhabiting an otherworldly dimension, passes directly under your boat. Its shadow unveils the edges of your plane of existence, offering you a glimpse into the dimension beneath your own.

Curious, you free dive into the deep blue, descending from one plane into the next. Your ears crackle and pop, adjusting from a life of ease in a visual existence to life in a purely auditory one. Sound travels four times faster in water than in air. You become immersed in a womb of song: alien whines and groans, patterned and repeated in a manner that envelops and penetrates you, evoking a sense of profound longing, an anguish that makes your toes curl.

Returning to the buoyant white speck that constitutes your plane of reality on this ocean, you humbly present the humpback’s song, a treasure that makes your heart tremble. The song recalls the sea in its romantic melancholy.

Then, from above. The sun burns the sky from blue to purple to orange, a spectacle that rivals the majesty of the whales below. The idea of nature as peaceful and serene is a gross misconception. Nature exists in constant competition with itself, and tonight’s performance is no exception: A calf, not ten days old with a dorsal fin still flopping to its side, briefly eclipses the sun in an offensive play consisting of breaches and tail slaps. The sun responds by painting wave crests in a brilliant shade of hibiscus pink.

The battle rages on. You, the observer, are helpless but to marvel in its heat and divinity.

As the light finally fades, the horizon disappears along with it, hazy and greying into itself. The sun’s last laugh: an absence of light signifying the closing of the curtains.

As you head home, the cold, falling darkness encourages the sea spray to sting your cheeks. Suddenly, the whales respond with an encore: a breach that forces the day’s last remaining photons to reflect ghostly white on the sea foam. And, even more astounding, the triumphant sound of water parted by a surprising and violent crash. The final act.

To receive and to revel.

Photograph by Julia Grater

Journal Entry of a Whale’s Ungrounding by Callie Cho

You’d spent five hours on the boat, moving with and observing the behaviors of whales off the coast of Rarotonga. Very little water had been consumed. Your soggy egg sandwich had been scarfed down in haste, between futile attempts to collect the skin samples of three fighting male bulls. Participation in the demolition of a 2-liter tub of chocolate ice cream had, in turn, demolished your digestive tract, and you were feeling the repercussions.

You had watched, enthralled by the ecstasy of the presence of a wild new life, as a newborn calf joyfully breached along the reef break; its mother, protective and warding off the advances of an escort. The day had been long and windy, the only sun glinting through patches of clouds and reflecting pensively off inky blue water. It was beautiful, though like most beautiful things, it provided little warmth. Your guard down — tired, cold, and satiated by a full day’s work — you begin your journey back to port.

Nature always chooses to astonish when you least expect it: A whale, rising ethereally from the sea’s unbothered surface, careening itself heavenwards, the tip of its cranium seeming to graze the blazing edge of the sun — time tends to freeze for moments like these. One, two. And then, crash a gloriously auditory experience: giant cymbals of blubber on water create a cacophony that pinches you (the observer) back into reality’s timeline, just as the whale is sucked back into its physical form from its moment of inarticulable majesty by the sheer weight of its gravity. A sinking mass of chaos, pulling you down with it.

But remember, you are a researcher. Remember, while you remain slightly dislocated from your little crux of reality, you must find footing in the scientific method. Its construct provides mild comfort, a framework through which to understand this wonderous experience and consolidate it into part of the human experience. When a whale surfaces, the water where it had been becomes altered – smoothened — by its movement, leaving what is known as a footprint. You are looking for skin: little flakes that the whale had dislodged, just as you had been.

: Francesca after a wonderful day of so many whales that we lost count

: Ella with the whale skin DNA sample on ice

So, you jump into the expansive teal blue water, armed with a sample net and a snorkel. Swimming in the open ocean is akin to moving through a dimensionless space: there are no boundaries or landmarks, and again you feel yourself becoming increasingly disembodied, uprooted from time the further you swim. Flat, blue expanse consumes you, and not even the light seems to provide dimension. It’s terrifying and thrilling.

And then, in the footprint, skin falls like snow with nowhere to land. Grey and white flecks speckle your vision and a feeling of ecstasy ripples through your body. There, a large flake falls slowly towards nothing. But you will not let it escape you, this skin is grounding. This skin is important. This skin is a relic. Diving down net-first, you successfully collect it, sacrificing breath for skin — the burning in your lungs signifying a pilgrimage – this must be what it feels like to touch the shroud of Turin; the staff of Moses; the statue of Shiva.

You breach the surface of the water, human and holding the only tangible evidence of a fleeting transcendence.

Happy Researcher on whale research project

The research team feeling happy after a hard day’s work