National Geographic : 1972 Apr
reflects its light. Ron, Ben, and I took turns at the helm during the night passage, watching the compass's red glow and the white-topped black masses of the big beam seas rolling in out of the darkness. Although there is no dry land on the Sau marez Reef, it boas s a landmark visible for miles; a U. S. Liberty ship, high and almost dry on the outer coral rampart, rising 80 feet above the white wa er that swirls around it. Blown onto the coral by a cyclone in 1945, the Francis Presto Blair still looks from a distance like a ship under way instead of the forlorn, rust-rotted r in she is. We sighted her at dawn, and by midmorning we swung at anchor behind the reef on which the sad hulk stood. On the ocean side a few hundred yards away, cobalt breakers as big as houses ex ploded in slow frost-white cataclysm and almost palpable thu der. Tiny Head Holds Deadly Peril Beneath the surface we found a marine world different from that of the Swains. Extraordinary visib lity-up to 200 feet, we reckoned-and a smaller fish population gave it an empty look, a sense of ocean and remoteness from th realm of man. But the snakes were there. I spotted a slender tiny headed specimen on the first dive, and added Microcephalophis gracilis-one of the two most venomous sea snakes-to our list. Exploring the reef edge, Ben found a mat ing pair, small dark creatures of a still un named species. The two intertwined for a moment and then rose straight up, still half encircling each other, to separate at the sur face. The male mace a quite understandable lunge at me before heading off over the reef top, as his mate subsided gently to the sandy bottom. We let then go. Other snakes appeared: first an olive snake, which came to inspect our swaying anchor chain with appare tly amorous fascination. We followed it on its rounds, noting again that, like others of ts breed, it passed by lit tle fish without so much as a snap of the jaws. I had noticed this curious behavior before and wondered at it. Unlike M. gracilis and some other small-h aded snakes that live on fish eggs, the olive snake is a fish eater. But how did it stay alive if it never pursued a fish? This time I knew. Hal had explained that this particular species cannot catch fish un less it corners them in crevices. Placed in an aquarium with free swimming fish, the olive snake will starve. 574 A silvery flash near the foot of a coral cliff caught my eye. I swam over and saw, for the first and last time, a snake that had proved itself a successful hunter. It belonged to the dark new species (probably part of the Aipy surus clan), and it held in its mouth a perfect ly motionless fish about 21/2 inches long, gleaming white, with a few liver-colored spots: a crevice dweller, seized by stealth in the Aipysurus tradition. Later I put on an Aqua-Lung to explore the base of a superb bommie (as Australians call a coral head), a 50-foot monolith rising out of pure sand. I eased along the bottom, peer ing into caves and crannies and feeling some thing like an olive snake myself. A glossy little black snake appeared, gentle as a kitten. It made no attempt to bite as I slipped it into a net bag. I showed Hal my new acquisition. "Do you know what you have here?" he asked, peering closely at my little shiny black snake. "Do you know what this is?" he added rhetorically. "This animal is a melanistic variant of Emydocephalus annulatus." He meant a black version of the turtle-headed, ringed sea snake. "That makes five species so far. Not bad," I said. "Happiness is another species of sea snake," said Hal. Even Sharks Shun Sea Snakes The next morning we collected another M. gracilis, which we found with its minute head stuck into a hole in the sand from which it was probably ingesting fish eggs (right). We watched it for 37 minutes, not wishing to interrupt its meal, until cold, boredom, and the arrival of a large shark moved us to unplug it from the bottom. During the entire span of its leisurely meal, M. gracilis protruded blind and unprotected from an open expanse of sand bottom, ex posed to attack from any predator. The proc esses of evolution could not have allowed the species to develop such relaxed eating habits if there had been any danger that they would lead in time to the extinction of the species. Obviously, this and other sea snakes have few enemies. Apart from some Asians, who eat sea snakes and sell their skins, sea eagles are the only creatures proven to feed regularly on these reptiles. They seize them on the surface as they come up to breathe, and drop them on rocks to kill them.