Meet Bolbometopon muricatum—the bumphead parrotfish to its friends. It’s not a Pokemon but the world’s largest parrotfish—a fish that chews up coral with a birdlike beak and poops out sand. It can reach 1.5 metres in length and weigh 75 kilos, and it lives in all those places that make fantastic postcards—the reefs along coastlines of the Indo-Pacific and the Red Sea. Or it did, until humans started chasing it away. Bumphead parrotfish can be pretty tasty (apparently), and big specimens would provide a lot of food. Overfishing and degradation of reefs have made this fish’s populations plummet. Spearfishing, in particular, has been a problem for it, and made it wary of divers and snorkellers in many places. Its scarcity and shyness have made observing its behaviour difficult, and besides, who knows if a solitary fish in an area where fishing is common is acting “naturally”?
Four intrepid scientists—Roldan C. Muñoz, Brian J. Zgliczynski, Joseph L. Laughlin, and Bradford Z. Teer, all supported by NOAA, made their way to Wake Island, about halfway between Hawai’i and the Philippines, a protected area where fishing is illegal. This isolated site has a Bolbometopon population that is large, healthy, and, most importantly, unafraid of humans. Here they saw groups of several hundred of these fish looking for mates, and described an extremely unusual and spectacular behaviour. Bumphead parrotfish do indeed have a big bony hump on the front of their head—larger in males than in females. No one was quite sure what it was for: in addition to the obvious sexual selection hypothesis, it was speculated that they might ram coral heads to break them up into easier-to-eat pieces. But in the big breeding schools around Wake, the male parrotfish clearly and repeatedly used their bulging foreheads to ram other males. Like deer, sheep, and possibly pachycephalosaurs, the fish size each other up before rushing straight at each other and meeting with a bang. Check out the supplemental videos to this paper—the head-on collision is loud and painful-sounding.
Muñoz et al.’s findings are more than just a cool natural history story—they’re a reminder that humans can have drastic effects on the environment, not just in terms of numbers of plants and animals but in terms of their behaviour. While it’s important to have areas open to the general public for tourism, education, and fisheries purposes, we need to remember that even healthy, well-managed such areas can be very different from a “pristine” (though I hesitate to use that term) state. Understanding how animal behaviour changes when humans interact with them is hugely important in planning protection and recovery schemes for endangered species. (And if contributing to this knowledge involves diving on coral reefs, allow me to be the first to shamelessly volunteer!)
Muñoz, R., Zgliczynski, B., Laughlin, J., & Teer, B. (2012). Extraordinary Aggressive Behavior from the Giant Coral Reef Fish, Bolbometopon muricatum, in a Remote Marine Reserve PLoS ONE, 7 (6) DOI: 10.1371/journal.pone.0038120
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