Enforcing insecticide-content water quality standards.

Fig. 2. Captive common dolphins Time intervals between initiatio whistle by one individual and e of a whistle from a second in taken from analyses of whistle group of four. (B) Same; tak analyses of whistles made by a 1 three of the original four; eac hatched area indicates number 4 that one of the two remaining abruptly terminated its norma contoured) whistle. (C) Tin vals between signature whistles by same animal; graph represei whistles that either were repeatec not elicited an intervening respor in 4.1 seconds. was belyzed whistles showed this abrupt nitiation cutoff; all but one occurred when two me most animals responded almost simultaneously to a known outside stimulus. zontours The animal emitting contour 3 acI simulcounted for 61 percent of the cutoffs, nother's while the two highly vocal animals ltaneous emitting contoturs I and 2 accounted for and at only 9 percent each. Thus differences y termiappear in this aspect also of Delphlinuts normal vocal behavior: some individuals tend all anato defer more readily than others. Whistles w\ere frequLently repeated without an intervening response by another animal. A mode is apparent between 1.6 and 1.7 seconds from onset of a whistle to onset of a repeat emisN-805 sion (Fig. 2C). This finding signifies a modal value of abotut 0.8-second delay before a whistle is repeated, because the average duration was abouLt 0.84 second. Seventy-nine percent of all repeat whistles occuLrred within 1.7 seconds of termination of the preceding one. 22-:'9Almost all small toothed whales that ONSET we have investigated emit in addition to contoured whistles a brief pure-tone chirping soutnd, ustLally with a short, sharp upsweep. This sound was emitted N-534 in frequent bouts by the Delphinuiis when first captured: it was usually accompanied by emission of a pulsed sound of a soft. grating quality (Fig. 1 G). At times the chirp was omitted and rapid "barking" bouLts ensued (Fig. 1H). Each "'bark"' was a burst-pulse N'ET sound similar to those made in emotional contexts by other odontocetes (5). All these sotund emissions became most constant prior to feeding and ceased completely after feeding-usuN-461 ally for about 1 hour. Ptulsed souLnds of the click-train type, shown to be used for echolocation by two other species of small odontocetes (1), accompanied feeding. MELBA C. CALDWELL 2 22 A7lait Hancock Founldaitioni, Uniiversity N S7 of Southern Californiiia, Los Anigeles