Ecology of Cave Use by the Frog, Rana palustris

Abstract

A trogloxene population of the pickerel frog, Rana palustris, was studied at Ralph''s Ford Bluff Shelter (RFBS), a cave on the northern edge of the Ozark Plateau in central Missouri, [USA]. Males were present beginning in July with females first observed in September. Overall numbers began to increase in September with maximum numbers present from late November through early March. Wintering population numbered in the hundreds. Movement of frogs within the cave corresponded to changes in surface and cave temperatures. Frogs became inactive at cave temperatures below 6 C and concentrated in large numbers in a physically and thermally sheltered hibernaculum near the center of the cave. Entry and emergence from hibernation in the cave corresponded with the seasonal reversals of temperature gradient between the cave interior and the surface. Emergence date varied by 6 weeks over 4 years of study. Winter mortality was skewed towards juveniles and concentrated in the latter half of winter (January-March). Feeding was suspended from mid-November through early-March. Rana palustris is an important component of cave ecosystems in the Ozarks. The origin and importance of cave utilization in the species is probably related to historical factors, and dependent upon physiological pre-adaptations and certain ecological advantages of trogloxene habits.