National Geographic : 1976 Jan
(Continuedfrom page 130) white coat for a darker, so-called "beater," pelt. To scientists the pup's white coat has posed a major problem in conducting aerial cen suses. Ordinary films record the dark shapes of adults against white snow and ice, but they fail to register the white-on-white of pups. Since adults are continually in and out of water, it is impossible to count them at any given moment. The only constant factor is the number of pups, which tend to remain on the ice for the first few weeks of life. In 1973 Nils 0ritsland and I sought to solve the problem. After months of research we concluded that ultraviolet photography held the key. For reasons still unknown, the infant harp seal's white coat absorbs much of the ultraviolet spectrum in sunlight. So does the white coat of the polar bear, al though those of the arctic fox and hare tend to reflect ultraviolet light. Snow and ice also reflect the ultraviolet, so by using a special lens and film for ultraviolet rays, one should get a black image-the pup -on a white background. We received valuable support from Profes sor Keith Ronald, Dean of the College of Bi ological Science at the University of Guelph in Ontario, and also Chairman of the Com mittee on Seals and Sealing. Additional help came from the Canada Centre for Remote Sensing and Dr. David Sergeant of the Arctic Biological Station, Environment Canada. Nils and I equipped an aerial survey cam era with a quartz lens and filter that admitted ultraviolet rays but screened out most visible light. Exhaustive laboratory tests and winter flights over the Gulf of St. Lawrence con firmed our theory: With the new technique we could count harp seal pups as accurately from the air (left) as we could on the surface. Our work had other, less welcome, results, for we also discovered that our camera saw right through certain types of arctic military camouflage! Not only were seal pups unveiled, but also installations and equipment carefully concealed beneath particular types of white paint. The discovery added yet another prob lem to arctic military operations. With the new ultraviolet technique we con ducted our first full-scale aerial census of harp seals in the western Atlantic last February and March. Although still in the experimental stage, the survey gives sealers and conserva tionists alike cause for concern. Our pup count came to fewer than 200,000, suggesting a total population-both adults and young-of fewer than a million harp seals in the western Atlantic. The figure supports the view that production of pups has declined steadily in recent years, despite the reduction of hunting quotas and the ban on large seal ing vessels in the Gulf of St. Lawrence. In fact, our pup count was less than a fifth of the estimated figure for 1952, which was made without the advantage of modern equipment. Factory Ships Take a Huge Toll The results of our census may well inspire renewed calls for a total ban on the hunting of harp seals. Yet in any controversy there are few absolutes, and the debate over the harp seal is no exception. Wholesale hunting by large ships equivalent to floating factories is far different from the individual techniques of the local sealer, or landsman, who has borne the brunt of criticism for the hunt. On the Magdalen Islands in the Gulf of St. Lawrence live 14,000 Canadians who KEVINMCVEIGH,FISHERIESANDMARINESERVICE,ENVIRONMENTCANADA Pup's temperature registers on the scale of the author's radiant-heat detector. An assis tant professor of zoology at the University of Guelph, he gathered varied data in the course of his search for a reliable seal census.