Hyla robertmertensi has a reverse of this pattern in that the primary note is paired and the secondaries are unpaired. In the sample studied a call-group contains 0-28 secondary notes (generally about 3). The mean duration of the primary is 0.091 (0.07-0.11) second and that of the secondaries is 0.040 (0.025-0.06) second.
Hyla phlebodes and sartori have call-groups composed of a rather short, unpaired primary and several short, unpaired secondaries (0-28 in phlebodes, 0-23 in sartori). The mean duration of the primary of phlebodes is 0.105 (0.07-0.16) second and that of the secondaries is 0.067 (0.035-0.12) second. The mean duration of the primary of sartori is 0.080 (0.07-0.09) second and that of the secondaries is 0.053 (0.035-0.07) second.
The two subspecies of H. microcephala are identical in call pattern and agree closely in duration of notes, although those of the nominate subspecies tend to be slightly longer. Hyla robertmertensi is distinctive in call pattern in that it is the only species having a paired primary; the duration of the primary is completely overlapped by that in the other species, but the secondaries tend to be the shortest in the group. The call patterns of H. phlebodes and H. sartori are identical and the range of duration of notes of phlebodes completely overlaps that of sartori, although both the primary and secondary notes of the latter tend to be somewhat shorter ([Table 5], [Pl. 16]).
Fundamental frequency.—This parameter was analyzed for the primary notes. It was measured for the secondaries as well and was found to differ in magnitude in the same way as the primary note. In a few examples of both subspecies of H. microcephala a high [primary] note, in which the fundamental frequency is exceptionally high, is sometimes emitted (Fouquette, 1960b). None of these notes was used in this analysis; only the fundamental frequencies of normal primary notes are compared ([Table 5], [Fig. 7]).
Table 5.
—Comparison of Normal Mating Calls in the Hyla microcephala Group. (Observed Range Given in Parentheses Below Mean; Unless Otherwise Noted Data Are for Primary Notes.).
| Species | N | Dominant frequency (cps) | Fundamental frequency (cps) | Duration of notes (seconds) | Repetition rate of secondaries (notes/minute) | |
| Primary | Secondary | |||||
| H. m. microcephala | 44 | 5637 | 205 | 0.13 | 0.10 | 268 |
| (5150-5962) | (184-244) | (0.11-0.16) | (0.05-0.14) | (192-353) | ||
| H. m. underwoodi | 47 | 5772 | 220 | 0.11 | 0.09 | 283 |
| (5177-6200) | (192-275) | (0.05-0.15) | (0.06-0.11) | (197-384) | ||
| H. robertmertensi | 25 | 5388 | 162 | 0.09 | 0.04 | 418 |
| (5150-5785) | (140-178) | (0.07-0.11) | (0.03-0.06) | (368-570) | ||
| H. phlebodes | 34 | 3578 | 148 | 0.11 | 0.07 | 284 |
| (3220-4067) | (125-158) | (0.07-0.16) | (0.04-0.12) | (210-350) | ||
| H. sartori | 10 | 3217 | 126 | 0.08 | 0.05 | 434 |
| (2950-3600) | (116-135) | (0.07-0.09) | (0.04-0.07) | (396-477) | ||
The two subspecies of H. microcephala agree closely in fundamental frequency. There is considerable overlap, but the difference between the means is significant at the 0.001 level of probability (t = 4.2406). The call of H. robertmertensi does not overlap that of H. sartori or either subspecies of H. microcephala in this parameter; but it does overlap that of H. phlebodes, although again the difference between the means is significant at the 0.001 level (t = 9.360). Hyla phlebodes and sartori have the lowest fundamental frequencies, and there is some overlap, but here too the difference between the means is significant at the 0.001 level (t = 4.923).