Spotted dolphins mainly eat small fish and squid. They have also been known to eat pteropods and isopods, which are free-swimming sea slugs. They use echolocation to help them find their prey.
Spotted dolphins form schools that can include less than 100 individuals but may include thousands. They are known to associate with schools of yellowfin tuna, possibly due to their similar diet. The association could also be for protection, however. This association can also lead to spotted dolphins being killed in fishing nets meant to catch yellowfin tuna.
The feeding habits of female spotted dolphins often changes when lactating. Lactating spotted dolphins eat more fish than other spotted dolphins, including those that are pregnant. This is probably because the lactating dolphin needs more energy than others. At equal amounts, fish provides more protein and more energy than squid. A fish diet also assists with lactation by providing phosphorous and calcium. Because fish are hypotonic with sea water, eating them helps reduce the amount of water the lactating female loses.
Spotted dolphins live in tropical and subtropical areas of the Atlantic Ocean, Pacific Ocean and Indian Ocean and are the most commonly found cetaceans in the Gulf of Mexico. Some of them live inshore, but most live offshore because the deeper water has a more consistent temperature.