BLOODWORTH, B.E.*; MARSHALL, C.D.; Texas A&M Univ., Galveston; Texas A&M Univ., Galveston: Behavioral Performance of Feeding in Kogia and Tursiops (Odontoceti: Cetacea): Ram vs. Suction Feeding Strategies

The feeding performance of two bottlenose dolphins (Tursiops truncatus) and one juvenile pygmy and dwarf sperm whale (Kogia breviceps and K. sima) was compared during controlled feeding trials. Feeding behavior was characterized and a Ram-Suction Index (RSI) measured. The feeding behavior of both genera was composed of four phases: preparatory (Phase I), jaw opening (Phase II), gular depression (Phase III) and jaw closing (Phase IV). The mean Kogia total feeding cycle duration (533 ms; SD�150) was shorter than the mean for Tursiops (847 ms; SD�349). The mean maximum gape angle was greater for Kogia (56.6° SD�3.3) than for Tursiops (25.5° SD�8.5). The mean Kogia RSI (-0.04; SD�0.378) was significantly less (p<0.001) than the mean Tursiops RSI (0.71; SD�0.14), indicating a suction and ram-based strategy for Kogia and Tursiops, respectively. The significantly shorter (p<0.05) Kogia jaw opening phase (172 ms; SD�75) supports the RSI results. Tursiops displayed two feeding behaviors, a Type I in which the mandibles open near to a food item and a Type II in which gape was near maximum while the subject was greater than one meter away from food. Total feeding cycle duration and RSI of Type I behavior (693 ms; SD�273 and 0.65; SD�0.15) were significantly different (p<0.001) from Type II behavior (1135 ms; SD�297 and 0.79; SD�0.05). Significant differences in RSI also existed between Kogia (-0.04; SD�0.378), Type I (0.65; SD�0.15) and Type II (0.79; SD�0.05) feeding behaviors. The results suggest odontocetes demonstrate a wide range of feeding strategies along the ram-suction continuum not previously characterized. Variability among individuals can be high and multiple feeding behaviors are possible even within a single genus (i.e., Tursiops).