MEAD ET AL.: OBSERVATIONS ON MASS STRANDING OF SPINNER DOLPHIN 



stranding received a great deal of publicity from 

 the news media, and it would be expected that we 

 would have been notified if any additional animals 

 had turned up on the coast. 



Most of the dolphins bore minor abrasions that 

 were probably incurred while stranding. Only one 

 (504448) exhibited any appreciable physical dam- 

 age. This animal, the largest male of the group, 

 had two large shark bites on the left flank at about 

 midlength and a third which completely removed 

 the left fluke. These bites appeared to have been 

 inflicted after death. 



NECROPSY 



One specimen was necropsied late on the even- 

 ing of 14 July, the others on 15 July. The two 

 animals which were transported to Sea World 

 were necropsied on 16 and 20 July by the Sea 

 World staff. A variety of lesions were observed in 

 the sample necropsied on 15 July. Most were 

 parasitic and not serious enough to account for 

 death. The blubber layer appeared thin, but this 

 was due at least in part to postmortem changes in 

 the hot sun and measurements were not taken. 



The stomachs of all specimens except the three 

 calves were empty. Nicholas Hall (Department of 

 Neuropathology, University of Florida, Gaines- 

 ville, FL 32601) collected the brains from the ani- 

 mals necropsied on 15 July for neuropathological 

 examination. Helminth parasites were collected 

 and forwarded to Donald Forrester (Laboratory of 

 Wildlife Disease Research, University of Florida, 

 Gainesville, FL 32611). Gonad samples were col- 

 lected and later analyzed at the Smithsonian In- 

 stitution by Mead. Teeth were taken from all of the 

 animals except the calves and were sectioned at 

 about 175 /xm in thickness by Odell using a 

 Buehler Isomet Low Speed Saw'', and were read for 

 age determination by Odell and Mead. External 

 measurements were taken by Wells and Scott 

 while the animals were still on the beach, and 

 organ weights were taken during the necropsies. 

 Copies of all the measurements and necropsy data 

 are in the Marine Mammal Program files (Divi- 

 sion of Mammals, Smithsonian Institution, 

 Washington, DC 20560). Skeleton materials from 

 the specimens are being studied by William F. 

 Perrin (Southwest Fisheries Center, NMFS, 

 NOAA, La Jolla, CA 92038). 



REPRODUCTIVE DATA 



The female reproductive tracts were removed, 

 flat diameter of uterine horns measured at their 

 midlength, ovaries collected and fixed, uterus 

 opened and examined for fetuses, and mammary 

 glands checked for gross indications of lactation. 

 The ovaries were examined for externally visible 

 corpora, indications of large maturing follicles, 

 and were weighed. The ovaries were subsequently 

 sectioned by William F. Perrin, providing 

 confirmation of the external examination and an 

 exact count of the corpora albicantia. None of the 

 animals were visibly pregnant and only one 

 (504456) was lactating. For practical purposes, 

 females were considered sexually mature if there 

 were external indications of at least one corpus on 

 the ovaries. There was only one individual 

 (504440) in which there was a discrepancy be- 

 tween the results of the external ovarian exami- 

 nation and the sectioning (Table 1). In this case a 

 large follicle was probably mistaken for a corpus 

 albicans on external examination. 



The smallest sexually mature female was 187 

 cm long, and the largest immature female was 190 

 cm long. A 177 cm female showed no indications of 

 follicular development, while four animals be- 

 tween 180 and 186 cm showed external indications 

 of maturing follicles. The diameter of the larger of 

 the two uterine horns showed a considerable in- 

 crease (about twofold) at sexual maturity. 



The good correspondence between ovarian con- 

 dition and diameter of the uterine horns indicates 

 that the latter may be a useful character for defin- 

 ing sexual maturity, as it is probably the result of 

 pregnancy. 



It seems likely that females begin to mature at 

 about 180 cm and reach sexual maturity at a 

 length of about 188 cm and a weight of about 55 kg. 

 The 188 cm pregnant female reported by Schmid- 

 ley and Shane (see footnote 5) fits this interpreta- 

 tion. 



Considering only those females in which the 

 pulp cavity of the tooth was open and for which an 

 exact count of growth layer groups^ could be made, 

 there were four sexually immature animals, with 

 a mean of 8.25 growth layer groups (7, 8, 8, and 10 

 groups), and three sexually mature animals, with 

 a mean of 10 groups (7, 11, and 12 groups). Al- 



''Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



^Terminology adopted at International Workshop on Deter- 

 mining Age of Odontocete Cetaceans, 8-19 September 1978, 

 Southwest Fisheries Center, NMFS, NOAA, La Jolla, Calif. 



355 



