The Master Archer

The Master Archer

▶ Lurking under the water surface in the estuaries and mangroves of India and Polynesia, the archer fish Toxotes (from the Greek Τοξοτης for archer) precisely aims a ballistic jet of water that knocks off a hapless insect from the shrubbery above, sending it tumbling into the water where it is promptly devoured. To dislodge prey anchored firmly to the vegetation with forces up to 10 times their body weight, the water jet must achieve a power of 3000 Watts/kg within a fraction of a second. Since this intrepid hunter was first described 250 years ago, scientists have puzzled over this mastery of archery.

Fishy Physics: Biologists first considered a mechanism similar to the chameleon, where energy is stored in coils of collagen inside the tongue (explained in the Chameleon Catapult post But dissection of the archer fish revealed no such specialized structure. Besides, they calculated that muscle power could maximally account for ~15% of the observed force of the water jet. Researchers then resorted to analysis of high speed video recordings of the archer fish in action. What they saw was a thin jet of water with a “head” that becomes increasingly bigger during flight. Surface tension and inertia hold the head together, pushing the tail jet into the head forming hammer-like pellet which strikes with deadly force. A fancy term for this is hydrodynamic amplification, and the physicists among you may enjoy reading about the “Ohnesorge number” and “Rayleigh-Plateu Instability” in the referenced paper. The rest of us will be intrigued by the similarity to Drop on Demand Inkjet Printing which similarly uses an explosively ejected drop of ink, as in Canon’s Bubble Jet printer ( The archer fish achieves all this at a low evolutionary cost by gulping a small amount of air into a gun-barrel shaped groove in its mouth and closing its gills before delivery. Just like Diana the huntress amplified her muscle power with a bow, this little fish also exploits an external hydrodynamic lever to capture its prey.

REF: Vailati et al. (2012)  PloS ONE; open access 

H/T to PJ Rosenberg for inspiring this post with the gif image he shared to the Science on Google+ community (


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44 Responses to The Master Archer

  1. Awesome is such an overused term Rajini Rao but I can’t think of another one to describre this. AMAZING!! And what a pity that humans decided at some point to dare to define the capacities and limits of species . When really there was no need to do so at all, because  mother nature had done all that anyway. With much more wisdom than (wo)man.

  2. Rajini Rao says:

    Agree, Rebecca Rippin . This little fish is only a couple of inches in size and can capture prey  several feet away! According to what I read, the bubble jet printer could well be an example of biomimicry. We have a lot more to learn 🙂

  3. Indeed we do Rajini Rao – and how fabulous that you can make that connection!! I can’t contribute to your scientific advances. But I could make you a nice cake while you stride on 🙂

  4. Rajini Rao says:

    Yum…cakes trump fishy physics any day,Rebecca Rippin! 😀

  5. I love this little fish. I’ve known about him for years, but it’s great to read about the mechanism he uses to create such a powerful water jet.

    Thanks for sharing.

  6. Rajini Rao says:

    Then you’ll also enjoy this cute little tidbit from Wikipedia, Christopher Lamke . Apparently, the adults are so accurate that they get their prey in the first attempt. The younger fish, though, still need practice. So they hunt in “schools” increasing the chances that at least one jet hits the target. This brought to mind a bunch of kids practicing archery with little bows and arrows 🙂

  7. Chad Haney says:

    What is equally amazing about archer fish, is their vision. They have to target with their eyes in water and their prey being in air. Also, they search for prey against the foliage (background) similar to humans yet lack a visual cortex.

    A spitting image: specializations in archerfish eyes for vision at the interface between air and water

    Proc. R. Soc. B 2010

    Visual search in hunting archerfish shares all hallmarks of human performance

  8. Rajini Rao says:

    Thanks so much for the links, Chad Haney . I’m checking them out right now. They must also take the different refractory indices of air and water, and accommodate for the bending of light.

  9. That is so cool, Rajini Rao . I have the same image of little kids practicing with bows and arrows. Thanks for sharing.

  10. Chad Haney says:

    Yes, Rajini Rao parallax is difficult for humans to understand, yet the archer fish has no problem.

  11. Bob Calder says:

    The index of refraction doesn’t change, so when a fish looks up, things are always going to be in the same relative position. I’m more interested in whether the behavior is taught and learned.

  12. Marta Rauch says:

    Rajini Rao fascinating!

  13. Tom Lee says:

    This fish is so cool Rajini Rao

  14. Rajini Rao says:

    Yes, indeed fascinating and cool Tom Lee and Marta Rauch !

    Bob Calder you may enjoy this paper that shows how young fish can be trained: Clearly, they learn by trial and error. I’ve not read the paper in depth to know if they learn from each other (perhaps you can advise us of that).

    Unless their eyes are above water, they will have to deal with the difference in refractive indices. Here’s a pop sci blog that shows it:

    The abstract of Chad Haney ‘s link makes the same comment: “During spitting, their eyes remain below the water’s surface and must adapt to the optical demands of both aquatic and aerial fields of view. These challenges suggest that archerfish eyes may be specially adapted to life at the interface between air and water.” 

  15. Looks homo sapiens are the ones, that are dumb to be relying so much on fossil fuel for energy. Thanks Rajini Rao for giving me the complex.

  16. Rajini Rao says:

    Aww, we may wise up in time, R Prakash Prakash . 

  17. Chad Haney says:

    Rajini Rao I love the path that #sciencesunday leads us down each Sunday.

  18. Bob Calder says:

    “Moreover, all archer fish of a group were able to learn the complex sensomotor skill from watching a performing group member, without having to practice.”

    Obviously not our kind of learning, but definitely transfer.

  19. Bob Calder says:

    I’m reminded of the theory of language acquisition that uses theoretic computational load for humans to take down a rabbit with a stone at increasing distances. From what I recall, the computational load increases mightily at modest increases of distance.

  20. Jim Carver says:

    Bob Calder I would expect that as a stone thrown exhibits a parabolic arc under gravity as the x^2 function. Other factors, such as wind are introduced with increasing distance as well.

    One thing you can say…this creature couldn’t skip a stone across the water. 😉 

  21. John Nahorny says:

    On the bubble jet the printhead element heatst the ink causing it to bu bblec throught a nozzle on to the paper. The size of the nozzle cause,s, the speed of the ink and force.

  22. Rajini Rao says:

    John Nahorny , yes, thanks! It’s interesting that the ink boils, vaporizes, and then re-condenses in the process. Surface tension pulls more ink out of the reservoir. 

  23. those thing made me try the same thing when i was a little kid but with out water…two magnet and i swallowed them but every thing…came…out…fine;)

  24. Rajini Rao says:

    You must have a magnetic personality, finnlinksorajosh light ! 🙂

  25. Rajini Rao says:

    Sagnik Sarkar , they are found in north-east India, coastal areas and mangroves in brackish, shallow and murky water. Perhaps in an aquarium 🙂 Let us know if you get to see one. 

    Here is what they look like:

  26. Amazing! Where in India do you find this. (which state)

  27. Rajini Rao says:

    Able Lawrence , I don’t have specific states but the information I found mentioned mangroves (may be W. Bengal) and coastal areas in the northeast. 

  28. Kumar Susma says:

    i look nice a video 

  29. Rahul Joshi says:

    What a fascinating creature! Not only does it have an effective (and powerful) hydraulic system but also sharp eyes from under water. Who wuda thunk?!

  30. Rajini Rao says:

    There may be some two-legged creatures in our home country, Rahul Joshi , who share this accuracy when it comes to spitting, no? 🙂

  31. Chad Haney says:

    Rajini Rao that was something I learned in grad school. A large percentage of male Indian classmates/post docs like to spit. Whenever I was walking with an Indian colleague who had not been in the US long, they would invariably spit while walking. Is there a cultural explanation? Sorry, I don’t mean to offend.

  32. Rajini Rao says:

    I know, it is an awful habit that comes from chewing tobacco in betel leaves (paan), originally (I believe the stuff burns). I’m sure very few chew betel leaves or tobacco any more yet, culturally it is acceptable to spit. 

  33. Rahul Joshi says:

    Haha.. Rajini Rao , true. I stand to that testimony every day. :X :X

    Once again, who wuda thunk?! :p

  34. Rahul Joshi says:

    Chad Haney it’s the same as cowboys spitting on the chewed end of cigar and tobacco. Wild wild east, I reckon.

    PS: I personally do not know anyone who does that. Just that I see lot of labor class do it.

  35. Chad Haney says:

    In Southeast Asia, it’s the women that chew betel nut.

  36. Rahul Joshi says:

    It seems to help.. erm.. pass time.

  37. Rajini Rao says:

    It is fortunate then, that I have been keeping myself busy 🙂

  38. Rahul Joshi says:

    ROFL!! Don’t know about you, but certainly a relief for those who benefit and will benefit from your research in the days to come 🙂

  39. Vishnu RR says:

    cool nature is our mother pls dedicate to who love  nature very much

  40. That’s something else wow

  41. Kilee Bough says:

    Hahaha gonna get their meal … Too cool

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