# Sonar Jamming Squids

### Context

In the arms race of survival many animals have developed ways of evading predators, but the animal I am interested in for this question would be the tiger moth. So basically these guys jam bat echolocation through their wing flapping patterns, this causes the bat to get mixed signals and be confused so the moth can get away. It just so happens another predatory animal uses echolocation to hunt, the sperm whale, and what they hunt are giant/colossal squids...

### Question

What sort of biological or technological adaptation of an already existing giant/colossal squid part could be used to manipulate sperm whale sonar to lead them into traps and cancel out the sonar to avoid being stunned by it?

• I thought this would be about jamming ship sonar using squid. I am sad. Jun 1 '18 at 15:00
• @JoeBloggs in principle maybe it could? Jun 1 '18 at 15:02
• My first thought when I read the question title was "Wait, really, how does it work?", and then I realized that this was a worldbuilding question. You're on to something!
– user32463
Jun 1 '18 at 19:59
• To offer up a piece of the puzzle, most fish finders actually detect the fish's swim bladder and not the entire fish.
– Todd
Jun 1 '18 at 21:59
• There is no evidence at all to support sperm whales stunning squid, only speculation in one paper 40 years ago. The one squid species, not giant squid, that has been studied showed no reaction to clicks as loud as sperm whales produce. Jun 2 '18 at 0:47

A cloud of smaller host creatures scatters the sonar.

The squid is followed by a cloud of small creatures that scavenge the scraps of the squid's food. In return they serve to scatter the sonar waves of a sperm whale.

In order to scatter the sonar properly, the space between the creatures should be on the same scale as the wavelength of the sonar. We can calculate that.

The wavelength of the sonar is $S \ /\ F$ for $S$ the speed of sound in water (metres per second) and $F$ the frequency (hertz). Since we're in the deep ocean let's say the water temperature is $2 C$ and we're 2km down. Then there are $200$ atmospheres of pressure and Wolfram Alpha says $S = 1445$. This BBC article claims a Sperm whale clicks at about $10 \text{ kHz}$ so we get $F = 10,000$. Dividing gives the wavelength of $14.45\text{cm}$.

So I suggest a cloud of small creatures a few metres across with about $15\text{cm}$ distance between each member. Perhaps these creatures can anchor themselves to the squid like remoras and only detach when they hear the first click.

A hunting whale is still able to detect the presence of a squid but with less precision depending on how effective the scattering is. They know the squid is is over there but that might be 30km away and they have to guess exactly where to aim. By the time they get there the squid has moved somewhere else. After a while the whale evolves to ignore these blurred signals and specialises hunting non-jamming squids.

• Chaffish. Excellent idea! Jun 1 '18 at 17:42

I've a few thoughts:

1. Similar to the use of specific geometry and materials in stealth aircraft and watercraft to foozle radar, one could envision a very bright colossal squid draping itself with carefully-orchestrated kelp stalks and fronds to disguise its form, and to both absorb and randomly scatter the acoustic energy of a sonar ping...
2. Or possibly there's another simpler answer - if the squid's tissues were in fact close to water's density (and acoustic properties), and the surface tissues were carunculated enough (convoluted like the brain) to scatter sonar to hide the transitionary edge condition from glancing angle pings...
3. We could also consider aggressive countermeasures: what if the squid had incredibly sensitive hearing in the frequency range most commonly used by its typical predators (5 to 50 kHz.), and what if that hearing was across the whole body surface (with cephalopods, this is quite possible) and upon detecting sonar pings the squid could rapidly triangulate and get the approach vector of the predator in two to three pings, and then fired a massive sonic response on that same frequency with very tightly focussed sound (see second reference below) along exactly the same vector, hoping to overwhelm the predator's auditory receptors? Given the auditory sensitivity of the most common predators (30 and 50 dB re 1 μPa) this might not only act as a locational countermeasure, but could possibly induce pain or damage, protecting more than just the individual squid.
• for 3 what formations in the squid could do the job? Jun 1 '18 at 16:03
• You asked about technological adaptions - adding an acoustic generator with the capabilities discussed would fit the bill! Jun 1 '18 at 16:40
• It is my understanding that spermwhales use a version of 3 on squid though the science of it actually hurting anything is weak and their generator can weigh more than a ton.
– user25818
Jun 1 '18 at 17:39
• @Amoeba the lateral line organ of fish is pretty close, possibly exactly, what you need for the detection and localization. The offensive part sounds like a long range acoustic device. Jun 2 '18 at 1:37

Bubble decoy

Bubbles are very bright acoustically. Bubble containing solutions are used as contrast for echocardiograms.
https://www.londoncardiovascularclinic.co.uk/cardiology-info/investigation/bubble-contrast-echocardiography

This principle was used as an early antisonar measure: a bubble generating decoy. https://en.wikipedia.org/wiki/Bold_(decoy)

So too the squids. Along with ink, they can eject a cloud of bubbles which serve as a decoy while the squid quietly slips away.

Squids generate these bubbles internally by including copious quantities of sea vegetables in their diet.

Tiger moths can do this! The mechanism seems similar to GerardFalla's third answer, though they can also create ghost images.

@Joe Bloggs: I don't see any reason the squid couldn't do this at a range of frequencies. I haven't done the research, but I wouldn't imagine the frequencies for whale and ship sonar are terribly different

Noise cancellation. Just send a sound back at the source that is identical to the sonar but exactly out of phase with it. This will result in no noise being returned to the sonar's source.

So what part of a squid could evolve to generate this sort of noise? I'd suggest a modification of their mantle cavity. Squids can suck water into their mantle cavity and squeeze it out to propel themselves. They are string to propel themselves out of the water for short distances [wikipedia]. This organ could conceivably be modified to produce sound by vibrating the cavity.