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Sea Search Monthly
 January 2022
News from the marine world and more
The table talk of giants
If someone was to mention the word humpback whale, what would be the first thing to pop into your head? Other than their colossal size and huge fins, you would most probably think of whale song. Most of us know humpback whales for their extraordinarily long and complex songs, but did you know that they also use a wide variety of vocalisations to communicate in their everyday life? Living in an underwater environment means that seeing isn’t all that easy and humpback whales, like many marine mammals, must rely more heavily on sound during their day-to-day activities. Understanding the acoustic communication of humpback whales is, therefore, key to understanding their world.
In more recent years here in South Africa we have been blessed with yearly congregations of humpback whales, that gather by the hundreds to feed in our waters. These dinner parties are some of the largest in the marine world, and we here at Sea Search have grasped this extremely exciting and unique opportunity to uncover the mysteries of this astonishing phenomenon.

Like we all enjoy having a good chat at the dinner table, humpback whales are also very talkative when dining in groups. Their conversations, however, aren’t revolved around catching up on the most recent happenings. Instead, humpback whales may actually communicate to coordinate their movements and work together to catch more prey, more efficiently. In some populations individuals produce specific sounds that might even manipulate the beahviour of prey species, such as fish, to make them easier to catch. 
A bunch of our team members- including myself (Catherine Nadin)- are working to reveal how the conversations of our humpback whales facilitate the formation of these colossal groups, along with, potentially helping these tightly packed giants to coordinate their feeding behaviours. We are doing so by recording their sounds and observing their behaviours during these epic dining experiences. This will allow us to match specific sounds to specific behaviours, to discover the function of these sounds and decode the language of these captivating creatures.
This information can then be used in the long run to monitor the behaviour and health of these groups over broader areas, without the need for human observations, using underwater microphones deployed for long periods of time. This is becoming ever-more important because, as this population of majestic giants increases, so too do their negative interactions with humans. The home of these humpback whale ‘super-groups’ overlaps with one of the busiest shipping routes in the Southern Hemisphere, increasing their chances of ship strikes and noise disturbance. Within our work we are also investigating the sensitivity and response of these groups to large and small vessels, which will allow for important assessment of their vulnerability to boat traffic.

All of our photographs and animal approaches are conducted under relevant permit and ethics clearances.
Sound may just save the humpback dolphin
As we take the time to share the important work of our PhD students, this month we turn our focus to Sasha Dines. Sasha is working to monitor and conserve the most endangered marine mammal in South Africa. With only 500 Indian Ocean humpback dolphins left along the eastern coastline of South Africa, and drastically decreasing numbers in more recent times, scientists are highly concerned that this species may well be facing extinction. Living in coastal waters and estuaries, humpback dolphins are exposed to numerous threats such as: shark nets, coastal expansions, and polluted rivers. Immediate action to understand the movements and behaviour of this species, along with, its current threats has never been more imperative.
Just as living in coastal waters now limits the humpback dolphin’s chances of survival, it limits our chances of documenting their movements and behaviours. In these rough and choppy waters traditional boat-based surveying methods, during which scientists document individuals by taking photos and building up a photographic catalogue (see pictures below), are just not feasible. But this has not deterred Sasha and other Sea Search members from trying to help this species. Instead it has resulted in them developing new methods to better study and conserve these mysterious animals.
Humpback dolphins are one the few members of the animal kingdom that use particular sounds that are completely unique to each individual. Marine mammal scientists call these individually specific sounds ‘signature whistles’. In the human world we could compare signature whistles to a person’s name, per say. Individuals develop signature whistles at a young age and use them throughout their daily conversations to keep in touch with each other and stick together. Sasha and the team are taking advantage of this extraordinary trait by using these whistles to locate and track the movements of humpback dolphins along our coastline, but how? Well, it involves setting up a large arrangement of underwater microphones, across areas where these dolphins hang out, to record their signature whistles.
Once retrieved from the ocean Sasha spends her time searching through the audio recordings made by these underwater microphones (called hydrophones) to find and document signature whistles. To do so, however, takes an incredibly long time, which we don’t realistically have. This is where, once again, new technology is becoming ‘man’s best friend’. Dr Gui Frainer is helping Sasha to complete this near impossible task by developing a machine learning program that will automatically select signature whistles from her audio files. This means Sasha can rapidly gain crucial information needed to advise the government on the steps necessary to save this species.
Developing such methods to understand how to save these charming creatures is unfortunately a rather expensive endeavour and Sasha is forever trying to find ways to fund her work. If you can spare a small amount to help Sasha help the humpback dolphin, any donations would be highly appreciated: https://www.givengain.com/cc/saving-humpback-dolphins/. Thank you!
There's an art in eavesdropping
As we delve deeper into the acoustic realms of our planet it is becoming clearer and clearer how important sound is when trying to conserve the animal kingdom. Passive Acoustic Monitoring (PAM) is an incredibly useful tool that can be used to assess the presence of species, study animal behaviour, and inspect the health of an ecosystem. Passive Acoustic Monitoring essentially allows us to eavesdrop on our environment by using acoustic recording devices. In doing so, we can gain a picture of the ‘soundscape’ (the combination of all the different sounds within an ecosystem) of different environments. This provides us with crucial information on how the health and biodiversity of ecosystems varies within different areas and over time, along with, shedding light on occurrences of human disturbance.
When studying terrestrial environments Passive Acoustic Monitoring is extremely feasible, however, when we submerge ourselves into the aquatic world things become little less attainable. This is typically due to extreme financial constraints, as underwater microphones (like the hydrophone in the pictures above) do not come cheap! On average, underwater recording devices are five times more expensive than terrestrial audio recorders and the cheapest underwater recorder is over 40 times more expensive than the cheapest terrestrial recorder.
To address this issue, a company called Open Acoustic Devices created a much cheaper underwater device called the ‘HydroMoth’ (see picture above). They did this by building a waterproof case for a well-used terrestrial recording device, the ‘AudioMoth’. Members of our team joined forces with scientists at Exeter University in the UK to test this device. They found that this modified, low-cost recording device can be used to identify different fish and marine mammal species, as well, assess the biodiversity of marine soundscapes. This opens up a whole lot of new possibilities with regards to studying and monitoring our oceanic ecosystems. ‘That is one small step for man, one giant leap for marine-kind.'
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Copyright © 2022 Sea Search Research and Conservation, written & created by Catherine Nadin (MRes),
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