The ecology and life history The ecology and life history of the common frog (Rana temporaria temporaria) ecologylifehisto00sava Year: 1962 138 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG Spawning time. I cannot so easily credit that observers' errors are at work in the phenomenon now under consideration. James (1944) found that the calling of Hyla nigropes, which breeds in Costa Rica in the dry season, occurred regularly at sundown, except when the afternoon had been raining. Evening rain had no effect of this kind. ISOPHENES IN YEAR-DAYS 100 200 30O RAINFALL IN MILLIMETRES Fig. 37. Joint
The ecology and life history The ecology and life history of the common frog (Rana temporaria temporaria) ecologylifehisto00sava Year: 1962 138 ECOLOGY AND LIFE HISTORY OF THE COMMON FROG Spawning time. I cannot so easily credit that observers' errors are at work in the phenomenon now under consideration. James (1944) found that the calling of Hyla nigropes, which breeds in Costa Rica in the dry season, occurred regularly at sundown, except when the afternoon had been raining. Evening rain had no effect of this kind. ISOPHENES IN YEAR-DAYS 100 200 30O RAINFALL IN MILLIMETRES Fig. 37. Joint Functional Regression Diagram, Showing the Relation between Rainfall and Temperature, and Spawn Date for the Month Mo The diagram at rainfalls higher than about 80 mm resembles that for Mi, but is distinguished by a well-marked ridge of lateness almost vertically through the diagram at about this value for rainfall. There is something that determines that frogs should be later when Mo is fairly wet than when its is drier. At high rainfalls the usual relation is observed. This could, of course, be a coincidence, and nothing to do with the phenomenon we are discussing. Forty millimetres for a whole month is light rainfall. That it should fall so often at the exact time when the observers were about to inspect their ponds is rather diificult to believe. I feel fairly certain that this is a real event, and perhaps we should seek for a possible common cause for both phenomena. When we come to consider light it may be possible to suggest a rational explanation.
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