O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)
Adler, Kr.: Sensory aspects of Amphibian navigation and compass orientation 7-18. o.
to earth-strength fields, a magnetic map, if it is being used in a bicoordinate manner to determine a position on the earth, would depend on very small gradients in one or more parameters of the field (total intensity, horizontal and vertical intensities, inclination and declination). As a consequence, homing orientation would be expected to be sensitive to small changes in the field. We are currently investigating this possibility. Use of Other Cues for Orientation Amphibians are known or suspected to use a variety of additional cues in long-distance orientation which can be mentioned only briefly here. Several studies (reviewed in FERGUSON 1971) point to the use of landmarks as reference points for orientation, and in fire salamanders (Salamandridae: Salamandra salamandra ) even small differences in visual patterns situated abovegoalboxes permitted discrimination (HIMSTEDT & PLASA 1979). However, when provided with different landmarks under indentlcal conditions green frogs (Ranidae: Rana clamltans ) consistently chose to utilize different cues or combinations of cues to orient but on an individually-consistent basis (ADLER 1980). Odors can also be used for orientation and appear to be particularly, if not exclusively, useful at short range to locate specific sites. A classic demontratlon of the use of odors is the movement of male newts (Salamandridae: Tartcha rlvularis ) upstream to sponges attached underwater to rocks; these sponges, unlike control sponges, had previously been placed In a bucket with reproductlvely-actlve females (TWITTY 1955). Several workers have studied the use of odor cues In homing by cutting the olfactory nerves or by destroying the nerve terminals in the nasal cavities. Such studies with toads (Bufonidae: Buf o sp.) yield varying results with some species (Störung des Erdmagnetfeides) Fig. 7. Orientation performance of cave salamanders ( Eurycea luclfug a) in relation to natural magnetic disturbance. Each data point represents the percentage of salamanders (n = 15 In all Instances except three where n Is Indicated) scoring in the corridor predicted from the eiven magnetic field axis. Disturbance of the earth' s magnetic field is measured as the mean hourly DST values (horizontal component of the earth's field for the 8-hour period prior to each test). Note that the relationship of performance to magnetic disturbance is highly significant, with oriented responses appearing to occur only on magnetically more quiet days (but see text for interpretation). Compiled from data in PHILLIPS & ADLER (1978)
