The Burrowing and Emergence of the Spade‐Foot Toad, Pelobates fuscus fuscus Wagler.

SUMMARY.1  The burrowing process has two phases–a simple scraping away of the soil by the hind foot, and at intervals another action which results in the sudden ejection of loosened soil over the back of the retreating animal. 2  The burrows have the openings closed, and are not used a second time. 3  Emergence does not occur on every night. 4  Emergence occurs most often on wet nights, even in terraria not exposed to the rain. 5  Emergence is independent of temperature, temperature changes, light, time elapsing since the last sight of daylight, hunger, defaecation, urination, carbon dioxide changes, humidity, odours of night air. It occurs at the normal time in toads hermetically sealed in darkened jars in a thermostat. 6  Emergence varies with the time of sunset. 7  Emergence in animals transported round one quarter of the circumference of the earth occurs at the local time and not in the evening of the country of origin. It is therefore not a 24‐hour rhythm, but is externally determined. 8  There is plenty of air for the animals in their closed burrows, and respiratory metabolism is not suspended or reduced beyond the normal reduction in resting animals. 9  Even in animals which remain buried there is more C0 2 produced at night than by day. This rhythm is not shown in toads kept long in captivity. 10  The paper records facts but does not postulate hypotheses, and points out that no explanation is at hand of the manner in which environmental changes are conveyed to the buried animals. 11  A classification of animal rhythms is proposed.