. The Canadian field-naturalist. 1987 DOLPHIN: Humpback Whale ^ Killer Whale Interactions 73. Figure 1. Killer Whale jumping over sea lion (visible directly beneath flukes of Killer Whale) after striking it with its tail. The ventral surface of the abdomen and flukes of the Killer Whale are pictured. Note the severed tip of right fluke. Photo by author. Discussion Interactions of Class I nature, described in Observation I, viz., each species apparently ignoring the other, appear to be the most typical situation, comprising 14 (80%) of 18 encounters which I observed. Interactions, or non-intera
. The Canadian field-naturalist. 1987 DOLPHIN: Humpback Whale ^ Killer Whale Interactions 73. Figure 1. Killer Whale jumping over sea lion (visible directly beneath flukes of Killer Whale) after striking it with its tail. The ventral surface of the abdomen and flukes of the Killer Whale are pictured. Note the severed tip of right fluke. Photo by author. Discussion Interactions of Class I nature, described in Observation I, viz., each species apparently ignoring the other, appear to be the most typical situation, comprising 14 (80%) of 18 encounters which I observed. Interactions, or non-interactions, of this sort are also the most common among the terrestrial species, for potential predators are within perceptual distance of prey species during a significant proportion of the time. It may be that in these situations neither predator nor prey is aware of the presence of the other (unlikely), or the behavioral response may be so subtle as to be imperceptible to human observers; however, in either case no overt response ensues. In Class II Interactions, frequently reported for open savanna ungulates, the predator(s) slowly approach the prey with no attempt at attack (, no "rushes", etc.). While exhibiting signs of increased alertness, the potential prey may warily watch the predator move through their midst, often continuing to graze and making no attempt to move off, nor displaying any overt behavioral changes. The animals in these situations are certainly keying on subtle behavioral cues of the predator and these cues allow them to accurately assess the predator's intention and to determine the risk posed by their presence. Observations of the Class //type occurred in 3 (17%) of the 18 documented encounters. In Observation II, typifying Class II Interactions, the Killer Whales changed course and approached the feeding cow and calf Humpback Whales. There was no evidence that the humpbacks responded in any way to the Killer Whales. It seemed unlikely that
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