![]() ![]() Likewise, the dolphins’ acoustic behaviors rise and fall synchronously with the zig-zag swimming patterns. This back-and-forth swimming repeats a zig-zag formation over most of the area, possibly functioning as a social cue for the entire group to coordinate their movement into the deeper seas. They swam toward the open waters and then doubled back into shallower waters. In 1994, researchers described spinner dolphins swimming in a “zig-zag” pattern following their rest period. Group movements during rest are typically in open, sandy-bottom areas where predators are more visible.Īt the end of their rest period, spinner dolphins usually abruptly increase their activity level, including their swim speeds, aerial behaviors, vocalizations, and make shorter dives than when resting. During rest, spinner dolphins rely on vision rather than echolocation for scanning their environment. This behavior may vary seasonally, coinciding with the shifts in day length. They may engage in resting behaviors for about four to five hours daily. When resting, spinner dolphins move back and forth slowly as a single unit, with the animals in tight formation but spaced just out of contact with one another. Spinner dolphins take advantage of the nightly migration that brings their prey species to shallower depths and closer to shore by feeding throughout the night. Spinner dolphin prey species follow a vertical and horizontal migration pattern, staying in deep waters in the ocean during the day, and then moving up in the water column (vertical migration) and inshore (horizontal migration) at night. Spinner dolphins feed at night on species including small fish, shrimp, and squid that are found about 650 to 1,000 feet below the surface of the water. Researchers take photographs of the dolphins' dorsal fins and then match the shape, nicks, and notches in each fin to a catalog of known individuals to obtain life history information for each animal. Individual dolphins are identified by their unique dorsal fins. The three-part color region consists of a dark gray dorsal/back cape, a light gray side, and a white belly. Gray’s spinner dolphins exhibit a tripartite color pattern with counter shading from dark to light. There is a great deal of color variation in spinner dolphins across the globe, depending on the region and subspecies of dolphin. They reach weights of at least 181 pounds. Among Gray’s spinner dolphins (the subspecies that includes Hawaiian spinner dolphins), adult females are 4.6 to 6.7 feet long and adult males are 5.2 to 6.8 feet long. They are slender, with thin, recurved flippers, and dorsal fins that usually range from slightly curved to erect and triangular. Spinner dolphins are relatively small compared with other species of oceanic dolphins. ![]()
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