The Kingman reef ecosystem is a complex living machine composed of many thousands of species, which are linked by relationships of different natures. Some organisms, such as corals, create habitat for others; others, such as sea cucumbers, work as garbage cleaners processing debris. But nothing characterizes better the struggle for existence than the relationship between predator and prey. Predation is a rather unfair relationship in which there is always a winner-and a loser. So engrained is it in our perception of nature, that students of linkages between species in an ecosystem have consistently worked on food webs and often ignored most other kinds of relationships.

From a naturalist's perspective, this is understandable. It is more exciting to observe lions hunting zebras or orcas killing seals than, say, to painstakingly measure growth rates of corals and calculate what three-dimensional shelter they provide for little fishes. Maybe it is in our genes, from the African times where humans waited patiently for felines to bring down a prey, to then scavenge it.

In Kingman we also observe attentively, but the only things we take are esoteric numbers in a myriad of waterproof paper sheets and images. Despite hundreds of person-dives, we have not observed any killing by sharks, although red snappers have annihilated sea urchins and giant clams in front of our eyes. However, we have witnessed some predation events that are key to the functioning of this ecosystem. For us, they were terribly exciting, although they may seem unglamorous to the layman.

Two days ago we observed a front of 30 crown-of-thorn starfishes eating mound corals. A starfish eats by hanging its stomach out of the lower part of its body and dissolving the thin layer of living coral on the surface of the massive skeleton that has been built by many generations of coral polyps. In front of the starfishes the coral was yellowish and alive; behind them there was nothing but a bleached skeleton.

Under "natural" densities, the starfishes clear space for new corals to join the population. At abnormally large densities, they can wreak havoc and destroy entire coral reefs, as it happened in Australia 20 years ago.

Crown-of-thorn starfishes have a round, compressed body about ten inches wide, surrounded by 15 fat arms. Both body and arms are covered by hundreds of stinging spines that make them look like a dark knight from a Tolkienesque world. Unlike evil knights, however, the starfishes range from gray to bright red.

If they seem so unappetizing, is there any species that eats them? There is, and today we were fortunate to observe an attack. A triton snail 16 inches long had a crown-of-thorns starfish trapped and was eating it patiently. Snails are slow-moving creatures that carry a heavy shell that is a mosaic of brown, ochre, black, and white. When they find a starfish they throw their muscle out of their shell and grab the starfish from below. The spines of the starfish do not deter the triton, which takes a firm hold. The starfish gnarls, impotent, and the snail starts ingesting the soft tissue on the lower side. That is the end of the story; a story that can last many an hour, for ingestion and digestion of such unpalatable creature takes patience.

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