Water Hole Fidelity in the Marine Toad, Bufo marinus

Most anuran amphibians do not possess the hydric independence that has evolved in the amniotes (Carroll, 1982) and therefore may expend more time and energy in the maintenance of proper water relations. Toads of the genus Bufo have been studied extensively in the laboratory in order to determine the limits of their tolerance to desiccation (Krakauer, 1970), the water storage capacity of the bladder (Ruibal, 1962), the hormonal basis for their water balance response (Shoemaker and Waring, 1968) and their ability to absorb water from the environment (Walker and Whitford, 1970; Bentley and Main, 1972; Lillywhite and Licht, 1974). This genus shows an impressive array of physiological adaptations to water loss. However, these characteristics represent only part of the entire adaptive suite (Bartholomew, 1972) and are likely coupled with behavioral mechanisms of hydroregulation such as local movements in response to water availability. Although extensive toad movements have been noted seasonally for reproductive purposes (Turner, 1959), field documentation of movements in the context of water regulation is lacking for Bufo. Studies using the giant toad, Bufo marinus, have contributed a great deal to the body of physiological information on water relations of anurans. Although this toad exhibits a large geographic distribution due to its frequent introduction outside of its native range (Easteal, 1981) and although dehydration appears to be a significant mortality factor in its populations (Zug and Zug, 1979) there have been few behavioral studies conducted in the field. Those that have deal