Thesis

Homing and orientation in hyla regilla baird and girard and bufo boreas baird and girard

Both stream-dwelling and pond-dwelling Hyla regilla home rapidly and accurately after displacement. The majority of returns occurred within 24 hours and the homing rates ranged from a minimum of 37 m/day (overland) for pond-dwelling frogs to a maximum of 125m/hour (aquatic) for stream-dwelling frogs. A very high degree of fidelity to a limited home range was noted as most animals returned to within a few meters of their original capture site. Juvenile and adult Bufo boreas exhibited accurate Y-axis orientation, both in a terrestrial arena and in an aquatic arena, via sun-compass. No evidence was found indicating that these toads can successfully orient utilizing stellar cues, although some evidence indicates that they may mistake a full moon for the sun under certain conditions. The Y-axis orientation of B. boreas was shown to degenerate over a six-day period when the toads were kept in light-tight boxes and thus deprived of their usual celestial, solar and other cues. Attempts to alter the natural Y-axis direction of B. boreas by exposing them to artificial shorelines and an advanced diel cycle resulted in inconclusive data. Both pond-dwelling and stream-dwelling H. regilla oriented successfully in the terrestrial arena using stellar cues, as well as a sun-compass. Their orientation during night was not as accurate as that exhibited when the sun was visible. Hyla regilla oriented towards a recorded chorus in preference to celestial cues. The frogs were also able to distinguish between a recording of their home chorus and that of a foreign chorus; they preferentially moved to their home chorus. Bufo boreas did not respond to tape recorded calls. Larval frogs and toads tested in an aquatic arena did not exhibit Y-axis orientation in response to solar cues. Adult H. regilla and B. boreas tested in a Y-shaped wooden maze did not move toward airborn scents of water from their home area, mud from their home area or a female frog or toad. Thus, no evidence was obtained to show that these animals are capable of utilizing olfactory cues to orient or home.

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