Freiburg (_op. cit._: 384) concluded that ant-eating frogs seem to have
no individual home ranges, but wander in any direction where suitable
habitat is present. However, from records covering a much longer span of
time, it became increasingly evident that a frog ordinarily tends to
stay within a small area, familiar to it and providing its habitat
requirements.
Nevertheless, in all but a few instances the marked frogs recaptured
were in new locations a greater or lesser distance from the site of
original capture. The movements made by these frogs were of several
distinct types:
1. Routine day to day movements from shelter to shelter within
the area familiar to the animal, the "home range."
2. Shifts from one home range to another; such shifts may have
been either long or short, and may have occurred abruptly or
by gradual stages.
3. Travel by adults to or from a breeding pond. In most or all
instances these adults were regularly established in permanent
home ranges, and they often moved through areas unsuitable
as habitat to reach the ponds.
4. Movements of dispersal in the young, recently metamorphosed
and not yet settled in a regular home range.
Usually there was uncertainty as to which types of movements had been
made by the recaptured individuals. Some may have made two or three
different types of movements in the interval between captures.
On many occasions individuals were found beneath the same rock on two
consecutive days, or occasionally on several successive days. Rarely,
such continued occupancy of a niche lasted several weeks. In 1949, a
frog was found under the same rock on June 4, 6, 26, 27, and July 1, 3
and 11. This was an immature female, presumably metamorphosed late in
the summer of 1948. During the five weeks period covered by the records,
it grew from 27 mm. to 34 mm. In 1952, another individual was found
under its home rock on June 23 and 30, July 2 and 3, and August 14 and
20. In 1952 a juvenile was found under a rock on May 30, June 4, and
June 17. These three individuals were exceptional in their continued
occupancy of the same niches. Among the hundreds of others recorded,
none was found more than twice in any one place.
Despite the fact that field work was concentrated on small areas which
were worked intensively, only eight per cent of the frogs recorded were
ever recaptured, and most of those were recaptured only once. Only 13
individuals yielded series of records, well spaced, in two or more
different years. These few individuals recaptured frequently may not be
typical of the entire population. The low incidence of recaptures
indicates that relatively few of the frogs present on an area at any one
time have been taken. Because of their secretive and subterranean habits
most of the frogs are missed by a collector who searches by turning
rocks, or trapping with pitfalls. Therefore, even though a marked frog
may survive and remain within a radius of a few hundred feet of one
point for months or even years, the chances of recapture are poor.
One female was caught first as a juvenile on June 8, 1950. On April 24,
1951, when first recaptured, she had grown to small adult size, and was
only 18 feet from the original location. On July 30, 1951, however, she
was recaptured 750 feet away. At a fourth capture on May 21, 1952, she
had shifted 70 feet farther in the same direction. At the final capture
on June 24, 1952, she was approximately 140 feet from both the third and
fourth locations. The sequence of these records suggests that the frog
had already settled in a home range at the time of her first capture in
1950, and that approximately a year later she shifted to a second home
range, which was occupied for the following year, at least.
[Illustration: FIG. 8. Distances between captures in frogs marked, and
recaptured after substantial intervals including one or more
hibernations. Distances are grouped in 25-foot intervals. For longer
distances the trend is toward progressively fewer records, indicating
that typical home ranges are small.]
In several instances, after recaptures as far as 400 feet from the
original location, frogs were again captured near an original location,
suggesting that for some individuals, at least, home ranges may be as
much as 400 feet in diameter.
Figure 8 shows that for movements of up to 400 feet, numbers of
individuals gradually decrease with greater distance. For distances of
more than 400 feet there are comparatively few records. Of the 59
individuals recaptured after one or more hibernations, only nine had
moved more than 400 feet from the original location. Twenty-five were
recaptured at distances of 75 feet or less. The mean distance for
movement for all individuals recaptured was 72 feet. A typical home
range, therefore, seems to average no more than 75 feet in radius. Of
the 59 individuals recaptured after one or more hibernations, 47 were
adults and probably many of these had made round-trip migrations to the
breeding pond. This was not actually demonstrated for any one
individual, but several were captured in each of three or four different
years near the same location.
[Illustration: FIG. 9. Distances between captures and elapsed time in
months in marked frogs recaptured. Few records are for distances more
than 400 feet. There is but little tendency to longer movements in those
caught after relatively long intervals.]
The trend of movements differed in the sexes. Males are more vagile. Of
21 adult males recaptured, none was less than 40 feet from its original
location, whereas six of the 26 adult females were less than 40 feet
away from the original point of capture. Of seven frogs that had
wandered 700 feet or more, five were males.