The species' occurrence in the more northerly portions of this range during the summer and early fall months appears to coincide with the intrusion of warm waters into those areas. They are not uncommon off Nova Scotia in summer and fall and are casual members of the marine mammalian fauna of the remaining Maritime Provinces during that period.
In previous years, saddleback dolphins were not uncommonly encountered by collectors of Marineland of Florida working the northeast coast of Florida, but the species has been conspicuously absent since about 1960. Reasons for this apparent shift of range are unknown.
Saddleback dolphins have from 40 to 50 small, sharply pointed teeth in each side of both the upper and lower jaws. These numbers overlap with only those of the striped and spinner dolphins (with 43-50 and 46-65, respectively). Saddleback dolphins should be readily distinguishable from both these species by the features outlined under the descriptions of living animals and distinguishable from the bridled dolphins by the distinctive markings on the head of the two species (see Figs. 121 and 134).
[Illustration: Figure 130.--Saddleback dolphins captured off St. Augustine, Fla., shown in the tank at Marineland of Florida. The highly distinctive crisscross or hourglass pattern of tan or yellowish tan on the sides is clearly visible. Note also the light tip of the snout and the dark line from the center of the lower jaw to the flipper. This last characteristic readily distinguishes the saddleback dolphin from the striped dolphin, in which the black stripe begins at the corner of the mouth rather than near the center of the lower jaw. (_Photos courtesy of Marineland of Florida._)]
[Illustration: Figure 131.--Saddleback dolphins on the bow of a ship off Massachusetts in 1966. The color pattern, including the dark brownish-gray back, the crisscross pattern on the sides, and the white belly, are clearly visible. The light tip of the snout helps distinguish this species from the spinner dolphins, which have a black-tipped snout. (_Photo by E. Wheeler._)]
[Illustration: Figure 132.--The distinctive crisscross pattern of the sides of the saddleback dolphins is clearly visible even when comparatively little of the animal is seen. Note the falcate dorsal fin, which often, as here, is dark on the border, lighter near the center. (_Photo by R. K. Brigham, courtesy of National Marine Fisheries Service._)]