Orientation of the Toad, Bufo japonicus, toward the Breeding Pond

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A variety of orientation cues has been suggested for the migration to the breeding site in adult amphibians. We categorized the cues into the following 3 groups: 1) cues from the breeding pond such as male calling and pond odors, 2) celestial cues such as the sun light and the magnetic field of the earth and 3) cues from the area or route of the migration which compose a local map such as a visual and olfactory maps. To determine which of these is used by the toad, Bufo japonicus, we designed and conducted a displacement experiment in which migrating toads from one direction were transported to the ground in the opposite side of the pond. The displaced toads were completely disoriented and moved to random directions. We conclude that the toad uses a local map) to orient to the breeding pond and cues from celestial bodies and the pond are not used. We also found that adult toads tracked the same route on both trips from and to the pond. This suggests that the local map was memorized by newly metamorphosed toads at their first terrestrial trip from the pond. The next step of our study was to determine what sense is used to receive the cue . We found blind toads, whose upper and lower eye-lids were stitched together, could reach the pond at a similar rate with the sham-operated and intact toads. However, anosmic toads, whose olfactory mucosa were damaged by the treatment with a 5% silver nitrate solution, rarely reached the pond. Tracking experiments with blind toads and toads bearing a bar magnet on their heads revealed that neither blindness nor the magnet had any effect on either the direction or distance of the migration to the pond. In contrast, anosmic toads could not orient properly and moved in random directions. We speculate that newly metamorphosed toadlets remember the route or area of their first terrestrial migration by using the olfactory sense. In the spring, two to three years later, they start their breeding migration to the home pond by using a local olfactory map and reverse tracking of the memorized route.
社団法人日本動物学会の論文
1995-08-15

Orientation of the Toad, Bufo japonicus, toward the Breeding Pond

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