Graduate Thesis Or Dissertation
 

Orientation and navigation in the rough-skinned newt, Taricha granulosa

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/kd17cw25m

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  • In the field of herpetology, most studies of homing have been carried out with anurans and, to a lesser degree, reptiles. Studies of orientation and navigation in urodeles have been limited to a few brief notes and the extensive investigation of Taricha rivularis by Twitty (1959 and 1964). The rough-skinned newt, Taricha granulosa, is abundant and widespread throughout western Oregon. Their regular breeding migrations have been noted by herpetologists for years; however, it has never been established whether or not the newt is capable of returning to the same breeding pond annually. This investigation was started to determine how strong an identification T. granulosa has with a particular breeding pond and what mechanisms might aid it in returning to that pond. Prior research on sensory mechanisms utilized by T. rivularis during its breeding migrations indicated that olfaction was of prime importance to that newt. Between June, 1964 and June, 1966, 4, 577 newts were marked and released at three ponds 11-31 miles apart. Newts exchanged between ponds were blinded, had the olfactory nerves destroyed or were marked and released unharmed as controls. A portion of the newts were released at distances of 100 yards, mile and 1/4 mile from their individual home ponds. Drift fences with funnel traps or drop traps were placed near each pond to intercept homing newts. Only controls were recaptured returning to the home pond during this study. Percentages of returns ranged from 0.7 percent for animals displaced 31 miles to 23.8 percent for those released 1/2 mile from the home pond. The time required to travel a known distance varied from 1/2 mile in five days to 3 1/2 miles in 485 days. A second phase of the study consisted of testing the orientation ability of newts placed in an enclosure wherein only solar or celestial clues were available to them. During 41 separate daylight trials, 1,047 newts were tested. A total of 155 newts were tested during five night trials. Scatter diagrams showed that, during daylight hours, initial headings in the orientation ring were correlated with the general bearing that newts were following when captured at the drift fences (Y-axis orientation). Chi-square tests applied to totals of animals trapped at 16 points around the ring's circumference indicated a probability of less than .02 that newts had made a random choice of direction when released during daylight. Distribution diagrams and chi-square tests of night runs indicated a random distribution in the orientation ring during darkness. A limited sample size made the significance of night tests questionable. Newts returned from distances of up to 3 1/2 miles and were able to orient in an enclosure which was far removed from the influence of any odors emanating from their home pond. Indications are that vision as well as odor may play a significant role in navigation of this species during its breeding migrations.
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file details DarrowThomasD1967.pdf 2017-08-07 Pubblico Scaricare