Course and timing of the homing migration in the newt Taricha rivularis
Proceedings of the National Academy of Sciences, 56 (3):
864-871 (1966)DOI: 10.1073/pnas.56.3.864
Abstract
A previous account has established that the newt Taricha rivularis returns to the
home segment of breeding stream after displacement for major distances.' Of the
questions raised by this finding, the present paper deals with two. One concerns
the route taken by the homing animals, principally whether it is terrestrial or
aquatic; the other pertains to the timing of the homing journey, with primary
reference to its initiation and completion. These and other aspects of our studies
on newt homing have been touched upon in other publications,'-3 especially in a
book on salamander biology,4 but in this and a series of papers to follow, our
findings will be presented in more detailed, definitive form.
Aerial photographs and descriptions of the study area in the coastal mountains of
Sonoma County have already been published;' 5 the streams and topography of
the area are further shown in Figure 1. Pepperwood Creek, especially the portion
("experimental stretch") designated by the numbered segments or "stations," is the
stream within which our most intensive homing studies have been based, but refer-
ence will also be made to important evidence on the course and timing of homing
from interstream displacements.
Intrastream Displacements.-Of the numerous displacements that have been
made within the experimental stretch, three lend themselves most directly to clarifi-
cation of the questions at hand. Figure 2, although published elsewhere,4 is re-
produced here because it serves so well to introduce these questions and also bears
materially on their answers. The histogram shows the locations of stream recaptures
of animals displaced for a straight-line distance of approximately 1 mile. (On
recapture the animals were given a toe marking to avoid recording the same animals
again on subsequent encounters.)
One will note the virtual absence of any animals in the long stretch of stream in-
tervening between the home area and the release site. Most of the animals were
recaptured in the home segment of stream, and almost all of the remainder were at
or near the release site. Rivularis is aquatic only during the breeding period, and
annually throughout this season we patrol the entire experimental stretch regularly
and intensively. We can thus be sure that animals recaptured in the home seg-
ment of stream during the later years following displacement have not re-entered
the stream at points en route home, either to use it as a homing pathway or perhaps
for any navigational cues it might afford them in resuming their terrestrial home-
ward migration. Otherwise, we would have encountered them at intermediate sites
between the displacement and home areas.