Are dolphins cold blooded

It depends on which kind of dolphin you are referring to.

The marine mammals are from the families Delphinida(oceanic dolphins - 30 species), Iniida (South American River Dolphins - 3 species), Lipotidae (Yangtze River dolphin - probably now extinct), Platanistidae (South Asian River Dolphins - 2 subspecies), and Pontoporiidae (La Plata Dolphin). Like all mammals they are warm-blooded.

The Coryphaena hippurus, aka Dolphin, common dolphinfish, Mahi-mahi, dorade coryphène, dorado, lampuga, llampuga, lampuka, lampuki, rakingo, calitos, ti-rone or maverikos - is a fish and cold-blooded.