Hyolingual biomechanics and kinematics in three species of two odontocete genera were investigated to compare adaptations and performance of divergent feeding strategies. Ram and suction feeding are two ends of a continuous spectrum that is poorly-studied in odontocetes. Comparative anatomy identified characters associated with feeding patterns of morphologically dissimilar and evolutionary distant genera. Hyolingual investigations included measurements of hyolingual muscle vectors and hyoid surface area/robustness. ANOVA's revealed Kogia basihyal and thyrohyal surface areas were significantly greater than T. truncatus. However, most predicted muscle tension values were not significantly different between genera. The presence of lateral gape occlusions, broad basihyal and thyrohyals near the caudal oral cavity, and a broad, short tongue were likely responsible for Kogia's effective suction mechanism. These features were absent, or reduced, in T. truncatus. The feeding kinematics of dwarf and pygmy sperm whales (Kogia sima and K. breviceps), and bottlenose dolphins (Tursiops truncatus) were characterized and compared incorporating the Ram-Suction Index (RSI). Mean RSI data support a suction feeding strategy for the phylogenetically basal Kogia (-0.67; S.D.±0.29) and a ram feeding strategy for the more-derived Tursiops (0.94; S.D.±0.11). Tursiops displayed two ram-based feeding behaviors, closed gape approach, where gape increased near food items, and open gape approach, where gape was at least 50% of maximum in the first video field. Four feeding phases were identified in both odontocetes: preparatory, jaw opening, gular depression, and jaw closing. The mean Kogia feeding cycle duration (470 ms; S.D.±139) was significantly shorter (P<0.003) than all Tursiops groups (pooled: 863 ms; S.D.±337, closed gape approach: 662 ms; S.D.±207, open gape approach: 1211 ms; S.D.±207). Kogia mean maximum gape angle (39.8°; S.D.±18.9), mean maximum opening, and closing gape angle velocities (293°/s; S.D.±261 and 223°/s; S.D.±121, respectively) were significantly greater (P<0.005) than pooled Tursiops mean maximum gape angle (24.8°; S.D.±6.6), mean maximum opening and closing gape angle velocities (84°/s; S.D.±56 and 120°/s; S.D.±54, respectively). Negative Kogia RSI values were correlated with increasing maximum hyoid depression and retraction, wide gape angle, and rapid opening gape velocity. Kinematic data support functional hypotheses that odontocetes generate suction by rapid depression of the hyoid and tongue.

Hyolingual biomechanics and kinematics in three species of two odontocete genera were investigated to compare adaptations and performance of divergent feeding strategies. Ram and suction feeding are two ends of a continuous spectrum that is poorly-studied in odontocetes. Comparative anatomy identified characters associated with feeding patterns of morphologically dissimilar and evolutionary distant genera. Hyolingual investigations included measurements of hyolingual muscle vectors and hyoid surface area/robustness. ANOVA's revealed Kogia basihyal and thyrohyal surface areas were significantly greater than T. truncatus. However, most predicted muscle tension values were not significantly different between genera. The presence of lateral gape occlusions, broad basihyal and thyrohyals near the caudal oral cavity, and a broad, short tongue were likely responsible for Kogia's effective suction mechanism. These features were absent, or reduced, in T. truncatus. The feeding kinematics of dwarf and pygmy sperm whales (Kogia sima and K. breviceps), and bottlenose dolphins (Tursiops truncatus) were characterized and compared incorporating the Ram-Suction Index (RSI). Mean RSI data support a suction feeding strategy for the phylogenetically basal Kogia (-0.67; S.D.±0.29) and a ram feeding strategy for the more-derived Tursiops (0.94; S.D.±0.11). Tursiops displayed two ram-based feeding behaviors, closed gape approach, where gape increased near food items, and open gape approach, where gape was at least 50% of maximum in the first video field. Four feeding phases were identified in both odontocetes: preparatory, jaw opening, gular depression, and jaw closing. The mean Kogia feeding cycle duration (470 ms; S.D.±139) was significantly shorter (P<0.003) than all Tursiops groups (pooled: 863 ms; S.D.±337, closed gape approach: 662 ms; S.D.±207, open gape approach: 1211 ms; S.D.±207). Kogia mean maximum gape angle (39.8°; S.D.±18.9), mean maximum opening, and closing gape angle velocities (293°/s; S.D.±261 and 223°/s; S.D.±121, respectively) were significantly greater (P<0.005) than pooled Tursiops mean maximum gape angle (24.8°; S.D.±6.6), mean maximum opening and closing gape angle velocities (84°/s; S.D.±56 and 120°/s; S.D.±54, respectively). Negative Kogia RSI values were correlated with increasing maximum hyoid depression and retraction, wide gape angle, and rapid opening gape velocity. Kinematic data support functional hypotheses that odontocetes generate suction by rapid depression of the hyoid and tongue.

It has been demonstrated that certain environmental fluctuations correlate with cetacean strandings in many parts of the world. I examined the correlations between three environmental variables (upwelling coefficient, temperature, and chlorophyll a concentration) and Kogia strandings in Florida from 1998 – 2007. In addition I examined the correlations between El Niño Southern Oscillation (ENSO) events and Kogia strandings in Florida and the southeastern United States (SEUS) from 1977-2007. Florida was divided into four regions and strandings were segregated by region with 76% of the strandings occurring on the east coast of Florida. AVHRR Pathfinder satellite temperature data, and MODIS Aqua and SeaWiFS satellite chlorophyll a data were downloaded from NASA websites; NOAA Fisheries Southwest Fisheries Science Center upwelling data were downloaded from the ERD Live Access Server, and ENSO data were also downloaded from a NOAA website. Upwelling was examined on a per stranding basis. For each stranding, a square region (16 km x 16 km) of ocean adjacent to the stranding was examined for upwelling index values for the two weeks prior to the stranding (in increments of six hours). Each region was divided into 16 sub-regions (4 km x 4 km). For each increment of time the data were averaged over all 16 sub-regions. A significant change in upwelling index was defined as a change of absolute value greater than or equal to 200 m3/s/100 m of coastline. Of the 174 strandings, 91 (52%) were correlated to at least one significant upwelling event within 14 days prior to stranding. I examined upwelling, temperature, and chlorophyll a concentration on a seasonal basis. The Florida coastline was divided into 16 regions. Each region was examined, for all three variables, out to approximately 32 km from shore. For each region the data were averaged for each month over the entire ten year study and compared to the number of strandings in each region each month. Data covering the regions of Florida were merged into four large regions (the east coast, the Keys, the west coast, and the Panhandle). I found an inverse correlation between chlorophyll concentration and strandings in Florida. In addition I found an inverse correlation between upwelling and strandings on the west coast of Florida. I examined the ENSO record from 1977 to 2007. I found a direct correlation between ENSO events and strandings in Florida (R2 = 0.1626) and the SEUS (R2 = 0.2236).

Pygmy sperm whales (Kogia breviceps) and dwarf sperm whales (Kogia sima) strand frequently in the southeastern United States (SEUS). To detect seasonal trends in Kogia sp. strandings across the SEUS, all 979 stranding events from 1977 through 2005 were segregated by month. A peak in strandings occurred in the late summer and early fall (July – October). The entire SEUS was divided into segments of similar coastline orientation, 1) North and South Carolina, 2) Georgia and the east coast of Florida, 3) Florida Keys, 4) west coast of Florida, 5) Florida panhandle, Alabama and Mississippi, 6) Louisiana and 6) Texas. Most areas displayed a significant peak in strandings in summer and a smaller significant peak in winter. A seasonal index analysis of the strandings revealed the same pattern as the general seasonal analysis. Analysis of wind direction changes preceding stranding events revealed six patterns. The most common pattern was when winds shifted from downwelling-favorable to upwelling-favorable during the week prior to a stranding. Analysis of sea level confirmed that when wind was upwelling-favorable, sea level decreased and when wind was downwelling-favorable, sea level increased. Seasonal upwelling along central Florida’s Atlantic coast observed in the summer correlates with upwelling-favorable wind patterns during summer months, and increased Kogia sp. strandings. A smaller peak in strandings that occurs in the winter months appears to occur when there is a shift from the ‘normal’ downwelling-favorable conditions into a brief period of upwelling-favorable conditions. Along Florida’s Atlantic coast, distances to isobaths from stranding sites were not significantly different from distances of randomly selected sites to isobaths; however, there is a tendency towards shorter distances to isobaths. Along the Georgia, South Carolina and North Carolina coast, distances to isobaths from strandings sites are significantly different from distances of randomly selected sites to isobaths. The distinctive bathymetry of the SEUS Atlantic coast may contribute to strandings across the entire SEUS Atlantic coast. Analysis of the frequency of Kogia sp. strandings during the lunar cycle revealed no significant correlation between strandings and lunar day. Both wind direction and bathymetry may influence frontal structures and water movements, and thus abiotic environmental factors may be significant factors in determining the locations and timing of Kogia sp. stranding events.