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Shreya’s Electric Fish Detector

Hi, the electric fish project is going swimmingly! I designed a bandpass filter circuit with cut-off frequencies = 159.155 Hz and 15.9155 kHz to remove unwanted noise from the recorded electric organ discharges (collected using electrodes placed close to the elephant nose fish inside the fish tank), and an amplifier with a gain of around 20 to amplify the signal. I had to adjust the gain and supply voltages so that the voltage level of the signal input to the Arduino doesn’t exceed its voltage limit. The Arduino converts the analog input signal to digital using its 12 bit ADC (analog to digital converter) and detects “spikes” when the value read differs from the average by 100 ADC units or more. Here’s the first spike I recorded on the SD card-

This is the electrode I used to record EODs from the fish-

It’s easy to make- just wind 3 pieces of wire at equal distances on a long plastic stick and connect the 3 wires to an audio jack that can be connected to the rest of the circuit. Here’s a picture of the PCB, which is made in the form of an Arduino shield that works on an Arduino M0 pro-

I also observed that there is a noticeable inversion of the EOD spike when the fish turns using which we can tell which direction the fish was facing with respect to the electrode.

Next, I varied the distance of the electrode from the fish and measured the average peak to peak height of the spikes recorded.

I took 2 minute readings for each distance (taken 3 cm apart from 0 to 55 cm) and averaged the values which are plotted in the graph below. Beyond around 27 cm, the EOD spikes were too weak to be detected and were hence, not always detected, but the few that were, had a peak to peak height of around 50 to 53 ADC units tall at 55cm, and around 60 to 65 ADC units at 45cm.

The time taken to write to the SD card is around 25ms when the buffer size is 100 samples.

To improve the accuracy of detecting EOD spikes at distances greater than 30 cm, I increased the gain of the amplifier, which helped but caused the spikes to be clipped when the distance was small, like 10 to 15 cm. To overcome this problem, I made another PCB incorporating a digital potentiometer in the amplifier stage so that the gain could be varied depending on the distance of the electrode from the fish. Currently, I am testing this new board.

When Computers Hear the Birds Sing…

Hey there! Zach here with the Songbird Identification project for a quick update. Since the last post, I’ve been hard at work creating a prototype device to listen for and record songbirds. I began by creating a small circuit using a microphone and amplifier chip. This acts as a sound recorder and also includes circuitry to act as a trigger to start recording when sound is detected. Currently, the sound level can be set using an adjuster on the board and an LED light indicates when sound is detected. This worked, but I needed more power and a dedicated board before I could begin field-testing…

After proof of concept, I began work on the actual recording device using an Arduino M0 Pro microcontroller. I connected this to my circuit and an SD card reader and programmed the board to automatically record as a .wav file to the card when sound is detected. Having completed this initial prototype, I had the circuit turned into a PCB “shield” (an extender for the Arduino microcontroller). Once put together, the initial prototype boards looked like this:

At this point, it was about time to do a field test, so I took the board out into the woods near the Nichols Arboretum to see how well the board would pick up birds in the wild. Check out the video below to see it in action. When you hear the birds, watch the red LED on my board… it flickers as the birds sing! This is the visual indicator that the board hears the bird and has started recording!

Bird Box in Action

The next step will be to develop a weatherproof housing for the board. This is an important step for two reasons. First, I need longer term test recordings to make sure that my hardware isn’t running into any issues. Second, the housing itself is a key element to this project, as the end goal is to deploy these boxes for days, maybe even weeks, at a time. Be on the lookout for an update once I have my enclosure built!

My 4th of July Parade Hat, Ft. Acrylic, Laser cut songbirds!

Thanks for following the project thus far and stay tuned for more!

Studying the Aggressive Behavior of Octopodes

Oh hey there! Long time no see, why don’t you have a seat and hear what I’ve been up to since my last blog update.

If you were at the Ann Arbor 4th of July parade you might have seen me dressed up as a beautiful purple octopus (or maybe it was a squid? The costume was quite ambiguous). The costume was an elegant combination of recycled foam, acrylic paint, paper mache, and hope.

For the behavioral analysis part of my project I have decided to forgo maze solving, as forcing an octopus to run a maze over and over for data proves both more difficult than previously thought and honestly doesn’t seem that fun for the octopus itself.

Instead, I have decided to delve deeply into deciphering the ancient mystery of Octopus wrestling. Believe it or not, if left to their own devices, bimac octopuses absolutely love to have wrestling matches, pushing around their opponent with their tentacles to figure out who among them is truly the dominant bimac. They then take a short break (only a couple minutes at max) and go back at it again, in a rematch to see if the underdog can take a round off the reigning champion.

Before you get too worried for the safety of our small aquatic friends, know that I’m not forcing or aggravating them into wrestling and that it’s actually quite difficult to prevent them from tusseling. Additionally, I keep a close watch on them to make sure no one is trying any dirty tricks like biting or going for the eyes.

This unique behavior prompted me to laser cut some custom housing arrangements for these 8 legged boxers. They are very territorial, so I had to construct some acrylic dividers with nylon mesh windows to promote water circulation. I inserted these into their aquarium to separate it into three individual tanks for the octopus because I’d prefer them not to fight unsupervised.

Next, to film the matches I constructed an acrylic wrestling chamber with a rack to hold the video camera for recording. This way they have an area to fight and my camera is guaranteed to give me the same angle of video every time.

I mount a go-pro facing directly down into the white, open-faced tank. This way I get identically framed footage every time, very important for later analysis

One tank becomes three…

There are many intricacies to an octopus wrestling match, many behaviors and patterns that we can try to decompose and comprehend with the help of computation. They circle each other, they taunt their opponent with their curled tentacles, they sometimes even act almost coy towards each other. This is where I switch to a completely different animal, Python, to analyze the speeds, positions, angles, and even colorings of the octopuses.

Why won’t you Look me in the Eyes?

Our confidently wrestling octopuses seem to have a bit of a shy side when it comes to making eye contact with each other. As you can see in the two frames from footage recorded of the octopuses before a wrestling bout, they do not appear to be facing each other at all, and watching the footage confirms this; they approach one another by moving sideways, not with their tentacles leading the movement as one would expect.

This however drastically changes as the distance between them closes, as seen in the above graph, as the distance lowers beyond a certain point, the angle between the two octopus rapidly drops to zero (zero meaning they are directly facing each other).

This seems to indicate a certain “fight zone” or, dare I say, a “danger zone”, where if the distance between the two enters this zone they will rapidly spin around to face their opponent with tentacles at the ready. This is most curious since it’s not only octopuses that display this kind of behavior.

Link to Gorilla Fight: Keep an eye out for how they approach eachother at a weird angle…

Even Silverback Gorillas tend to go into a fight sideways, spinning to face their opponent at the last moment of their approach, and black iguanas are suggested to use eye contact and approach to discriminate risk from an approaching animal (As described in the 1992 paper Risk discrimination of eye contact and directness of approach in black iguanas  by Joanna Burger).

Octopuses: Maybe not as Bright as we Think

No, I’m not talking about their intelligence, of course, the octopuses we have are plenty smart, even though they sometimes seem to forget what exactly to do with a crab we give them for food, deciding to instead stare at them for a while. I’m talking about their physical coloring, their chromatophores.

Their coloring is an extremely reliable way to know if you’re coming too close towards them. Even when they’re still in their tank, if you quickly approach the glass they will drastically darken their color, hoping you leave them alone.


When there’s a fair bit of distance between the competitors, they both appear to be a shade of light beige, but once that distance closes and we enter the “danger zone”, the one going on the offensive colors its tentacles a dark brown before entering the active wrestling bout.

In the pictures below we can identify the attacker and defender by their relative colorings, the bottom octopus flaring up with color in its first offensive, and then the top one flaring up in retaliation.

I’m Bored Already, So What and What’s Next?

If we can confidently identify parallels between these octopuses and other non-cephalopod animals when it comes to approaching and commencing a fight, we might be left with a great assay tool to study the physiological and genetic influences on this behavior. Bimacs are quite ubiquitous and easy to care for animals, and so finding such a use for them would help make neuroscience a more accessible topic for audiences outside of research laboratories, since even a high-school student can take good care of a bimac octopus.

I’m now working on a program that uses convex hulls to draw a contour surrounding the octopus, in order to get a bearing its relative size and tell us more about what it’s doing with its tentacles. A tightly curled up octopus will have a very small contour, whereas a more freely spread out one will take up a much larger area with its contour. This might prove to be interesting information when it comes to analyzing the initiation of the wrestling matches where there is a lot of shape changes in the octopuses.

Additionally, I’m hoping to gather enough data in the next couple weeks to show real trends in the octopus behavior and run more general analyses on the full collection of vectors. This will let me say more confident statements on the overall behavior of the bimacs.