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A Survey of Nocturnal Vertebrates in the Kartabo Region of British Guiana

1933; Wiley; Volume: 2; Issue: 2 Linguagem: Inglês

10.2307/964

1365-2656

Stanton C. Crawford,

Species Distribution and Climate Change

THE purpose of this study was to survey the nocturnal activities of a large number of animals, preliminary to a general investigation of the nature of the nocturnal habit. Observations made on invertebrates will be reported separately. This problem would ultimately include a consideration of special adaptations for life in the darkness, and an analysis of the usefulness at night of the several senses, but these discussions are reserved for a later report. Field observations were made in June, July and early August of 1924. Twenty-one night trips were made for the collection of data and specimens, as follows: fourteen near Kartabo Point, at the junction of the Cuyuni and Mazaruni rivers, 45 miles from the coast; one in the vicinity of Upper Camaria, 7 miles above Kartabo on the Cuyuni river; one on an island at Matope, 10 miles farther up the same stream; two from a base 4 miles south-west of Kartabo in the wedge-shaped tract between the Cuyuni and Mazaruni rivers; and three from Hills Estate, on the Mazaruni river near its junction with the Essequibo. Other trips at dusk and dawn (8), overlapping the hours of darkness, bring the total number of periods devoted to observation to thirty-two. Many records made at other times have been useful. All of the places named above are in the low-tide-water area, with the exception of Matope, in the hills, and Upper Camaria, in rolling country at the head of a 4-mile rapid in the Cuyuni river. All of the localities are in the rain-forest area, but represent variously the conditions of deep jungle, open clearing, tide-water shore, and islands in inland rapids. Meteorological data were recorded for each trip. Temperature can probably be disregarded as a possible factor affecting activity of vertebrates, since the gross variation during any one night, or even from one night to another, was never more than 6? F. In these months humidity also is remarkably constant, at about 85 per cent. Allee's (1) observations at Barro Colorado island also showed only small variations in barometric pressure, air temperature, air movement, and other environmental factors on the jungle floor. At Kartabo the chief variables were light (including moonlight), fog (affecting available light), wind, rain and tide (the last three named providing mechanical disturbance). The absence of light looms as the most characteristic factor of the nocturnal environment in the rain forest.