O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)
Adler, Kr.: Sensory aspects of Amphibian navigation and compass orientation 7-18. o.
oriented (for example, B. americanus , DOLE 1972) and others disoriented ( B. borea s, TRACY & DOLE (1969). Blinded-and-anosmic toads are disoriented ( B. valliceps , GRUBB 1970). It is not clear whether experimental techniques, motivation or species differences account for this variation. One frequent problem for the interpretation of homing experiments is knowing whether displaced animals are beyond the area of their previous familiarity and whether winds are uniformly from the home direction or not. Among Amphibia, salamanders are especially attentive to odors, particularly for social functions (JAEGER 1978a), but al«io for short-distance orientation (for review see MADISON 1972). However, the idea that homing salamanders climb vegetation in order to detect distant odors has been reinterpreted as a foraging strategy, since climbing salamanders ingest more prey than do others on the forest floor (JAEGER 1978b). Light cues which do not require time-compensation, in contrast to polarized light and the sun, can also be used for orientation. Phototactic orientation behavior is well known in amphibians (see ADLER 1976; and JAEGER & HAILMAN 1973, for reviews), but note that phototaxis can persist in frogs lacking both eyes and frontal organs but with the pineal body intact (RALPH 1978). Experiments with Fowler* s toads (Bufonidae: Bufo woodhouse l) under moon or stars suggest that these cues might be used at night (FERGUSON & LANDRETH 1966) although tests with some other species producëd conflicting results (FERGUSON et al. 1965, GORMAN & FERGUSON 1970). These experiments need to be carefully replicated, ideally in a planetarium where the several potential cues can be controlled separately, before we can be certain about the use of these cues. Sounds are known to function in orientation, in addition to their social roles In mate selection, species recognition and territorial defense (JAEGER 1978a). Among amphibians, the importance of sound cues has been demonstrated only for frogs and toads, both in providing a cue towards which the animal can directly orient (FERGUSON & LANDRETH 1966) or a reference cue for compass movements in other directions (LANDRETH & FERGUSON 1966). Whether kinesthetic cues are utilized in long-distance orientation is not certain. A kinesthetic sense, the body's position based on sensory data from the semicircular canals and proprioceptors, theoretically could be utilized to maintain movement along some pre-determined course or, by doubly Integrating the sensory input, to retrace the displacement path. Experiments were performed with migrating newts (Salamandridae: Taricha toro3 a) which were spun on turntables to disrupt sensory Input from the semicircular canals; the animals later showed random movements or merely oriented in the direction of release (ENDLER 1970). The animals had to resume their journey only 3 minutes after being spun, however, and it is not known whether a longer resting period would have permitted them to orient in the original migratory direction. DISCUSSION It is clear from this brief review that a wide variety of cues can be utilized for long-distance orientation, even in a given species of amphibian. Indeed.it is possible that additional sensory modalities useful for orientation will be identified in the future. The problem immediately confronting us is to determine how these cues are integrated, both functionally and developmentally, to yield an appropriately adaptive response. In addition, we need to know how organisms decide which cues to utilize at any given moment when several potentially useful but conflicting cues are available. For example, the hierarchiai value of different cues is demonstrated in experiments with Fowler's toads originally orienting to their breeding pond which instead reorient toward the tape-recorded sounds of a breeding chorus of that species (FERGUSON & LANDRETH 1966). Ontogenetic factors are particularly important for amphibians (FERGUSON 1971) and the influence of motivation, physiological state and seasonal differences (FERGUSON et al. 1968, ADLER & TAYLOR 1981) combine to make the design of critical experiments quite complex. ACKNOWLEDGEMENTS I thank John B. PHILLIPS and CHRIS PELKIE for a review of the manuscript, MICHELLE REIF for adapting several of the figures and KONRAD KLEMMER for correcting my German captions. Our research program is supported by the U.S. National Science Foundation (grant BNS 79-24525) and the U.S. Department of Agriculture (Hatch Act funds).
