Clicks and Whistles

MascallDance welcomes Nicholas Macfarlane, a senior scientist at the International Union for the Conservation of Nature (IUCN).  He is a marine biologist who spent five years in the Straits of Gibraltar studying pilot whales.  Recently he was part of a group of scientists who developed a way of measuring species extinction risk to quantify how specific actions can safeguard biodiversity.

I want to talk about three ideas that relate to the way we think about fresh and salt water, and how that might be different from what’s going actually going on in those places. Then a little a bit about how sight and sound work underwater, and what that might mean for those who have to live in aquatic environments.

In our everyday lives, we don’t think about aquatic environments.  They’re big and they’re out there… but that’s really about it. Many people go to the beach, and see the surface of the water, and if they go swimming, they’re just at the very top of the surface, and we really don’t dwell on the fact that these places are the reason that we have air that we can breathe and a climate that we can live in – and really, life at all.

We see this all the time in environmental legislation.  We have so many rules that protect life on land, but relatively few protect life underwater. We just don’t think about it, and we’re not very good at understanding how to think about it. Sometimes the way that we don’t think about water is called ‘seablindness’.  

Part of the reason is that it’s pretty alien to us and hard to imagine.

As humans -or really, most terrestrial animals - we’re very visual. Our brains almost completely prioritize seeing and sight over all our other senses. Underwater, that’s not particularly useful. 

We see these beautiful pictures of coral reefs and lots of light. But once you drop below 10 or 20 meters, depending on where you are, it’s pitch black. Vision just doesn’t matter.  Sound is what matters.  And sound behaves very differently in water than it does in the air - so we have a hard time imagining how things that live in the water may be perceiving their environment.

Underwater, sound can travel much, much further than it can up in the air. Hundreds, thousands of kilometres in some cases.  So - you might be able to see across the room.  On the surface of the ocean, you can “see” 4  or 5 kilometres into the distance before the earth curves and it goes out of sight.

Underwater, the space that’s available to the awareness of things that live there can be much, much bigger. We continually make more and more things, and the way that the economy is set up right now, we send them increasingly around the world in ships. Ships – and shipping noise – are drowning out the ability of animals in the ocean to communicate. And every year, the oceans are getting louder in the frequencies that are the same ones that animals use to communicate.

You can sort of imagine that – well, pre-COVID – you were going out to a bar. You arrive there early, there’s no one in the bar; having a conversation with someone you sit with is no problem.  But as more and more people arrive, and background noise increases, it gets harder and harder to communicate.  And now maybe imagine that you have to wander around the bar to find this person and its’ dark.  So sound is all you have.  As the background keeps getting louder, it’s going to get harder and harder to have a conversation or find your person.

COVID is actually a bit of an experiment.  because the first thing that happened when countries went into lockdown is that industrial activity just stopped. Shipping stopped. This has been the quietest year in the ocean in ages. COVID has been rough on us as humans but some species that live in the ocean have thrived. It has been so quiet. The last time anything like this happened was the September 11th terrorist attacks – shipping just stopped for a couple of weeks.  And in those weeks, background noise in the ocean just plummeted.  Researchers studying stress in critically endangered North Atlantic Right Whales could measure the drop in stress levels in these creatures over that tiny period.   

We have this massive aquatic environment - far bigger than the terrestrial environment, where our normal senses are much less useful than we’re used to. We don’t think about it. But stuff lives there. And one of the things that I want to talk about with you, as I draw this to a close, is one of the interesting challenges that things in water face.

Like us, many animals live in groups. And they get a lot of good things from living in groups such as social benefits, decreased predation risk.

In Washington DC as we speak, trillions of ciccadas are about to emerge from the ground and literally blanket everything around us. By being pressed so close together, every predator can eat more of them than they can possibly dream of, but even so, many of the ciccadas will survive to lay eggs and produce the next generation. 

A group could even reduce your cost of movement if all of you are moving together, cyclists, say, in a peloton, can work less hard because they are all together, producing drafts.  Probably this year, all these things that result from being in a group are especially salient, as we had our ability to have social groups taken from us. 

At a fundamental level, being in a group requires being in the same place at the same time, whether in physical or virtual space.  And this isn’t a trivial thing. Despite individual motivations and desires, right now might not have been the most convenient time for all of us in all our corners of the world with all the things we wanted to be doing, if we are not together, we lose the critical benefits of being part of that group. We’re each making trade-offs between what we might be able to do on our own, and what we get from being together with the group.

And I bring all this up because for animals that live underwater, this is a big deal.

Aquatic environments are huge, and these animals are exposed.  There is often no safe home to hide in. Home is your group and separating from your group can just be disastrous – or lethal.  And you can’t say “Hey, if you get lost just meet me at home, or meet me at the Mascall Dance office” because there’s no home, or offices.  All you have in this enormous environment is your group.  This is very different from how we and many terrestrial animals live our lives. 
This is a serious concern for strongly bonded individuals, like mother and calf dolphins, where the calf is totally dependent on its’ mum for survival. Every single time they separate is potentially life threatening for the calf.

The image that I want you to have in your mind is that you’re in a dark, crowded airport trying to keep track of a toddler, and you can’t hold the toddler’s hand. That’s the situation that they’re in.   It’s kind of a wild thing to think about, and it is unique among all the animals that we know about.  Dolphins have this pretty incredible and special way of managing this problem. 

These are bottlenose dolphins, a mom and calf, in Sarasota Florida, a site where people have been studying these animals since the 1970s.  Dolphins make two kinds of sounds. They explore their environment with echolocation clicks, kind of like bats, and then they have these very unique signature whistles that are distinct for each dolphin.[MN1] 

Scientists believe that these whistles broadcast their identity and signal that it’s time to reunite with each other.

First, Dolphins and pilot whales use clicks, and the echoes that bounce back, to explore their environment. This is a distance sense that tells you how far away things are, but because they are doing it on many, many things all at once, they can recreate this mental picture of what they are “seeing” with sound when they’re underwater.   

Now, since the issue they are trying to solve is keeping track of each other, and this is a distance sense, they can likely use these echolocation clicks to track each other when they are close together. Or even, because these animals are making these clicks as they are exploring their environment, they can do it by listening to each other’s signals as well.  It’s like being with your partner in your house – you can’t see them, but you know from the sounds that they’re puttering around somewhere.

The other sounds bottlenosed dolphins make are many types of whistles, including a particular subset of tonal whistles called “signature whistles.” Each dolphin has this stable, stereotyped, individually distinct signature whistle that conveys their identity to the other dolphins that know them.

This is what bottlenose dolphins have that very few other animals do.

So: what does a separation and reunion of mother and calf dolphin look like? Two animals, highly motivated to stay together. When they’re close, they can see each other, unless they’re down too deep and it’s black or the water is too murky. They don’t really need sounds; they can keep track of where they are.

As they separate, they can use this eavesdropping we talked about, where they are listening to each other’s whistles and clicks while they’re off doing their own thing, and still keep track of each other. 

But at some point, they’re going to drift out of range. This is the potentially dangerous situation in which the whistles become so important – the signature is an active information flow, not the passive noises they made on their own.  They signal “Hey- time to start going back to the last place where we heard each other”.  It’s a contingency plan for this environment where you have no boundary markers to use to reunite.

That’s how dolphins do it.

ABOUT NICHOLAS MACFARLANE:

NICHOLAS MACFARLANE

is a Senior Scientist, International Union for Conservation of Nature (IUCN). Nicholas is a marine biologist who started his career tagging toothed whales to study changes in spatial behaviour, and social cohesion resulting from human disturbance.

At IUCN, he leads the execution of IUCN science and knowledge projects developing science-based targets for biodiversity and deploying global datasets to analyse the interactions between biodiversity and key human interfaces such as violent conflict, migration, synthetic biology, and palm oil.

A lead author on the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services Americas Assessment, Nicholas came to IUCN from the US National Academy of Sciences, where he assessed restoration monitoring efforts following the Deep Water Horizon oil spill and analysed the cumulative impacts of stressors on marine mammals.

He holds a Ph.D. in Biology and Oceanography from MIT and the Woods Hole Oceanographic Institution, a Master’s in technology and Policy from MIT, and a BA in Psychology and Neuroscience from Princeton University.