On the other hand, there are five differences between these mythical animals. The first major difference is weight. HydrasThe Hydra's weight is 1800 kg is, a lot heavier than Dragonsthe Dragon's weight isof 450 kg . In contrast, Dragons can live a longlonger time than hydras . Whereas Dragonsthe Dragon's lifespan is 40-80 years, but Hydrasthe Hydra's is only 20 years . Further more, the diet of dragons is fair maldensmaidens, but the hydrashydra's diet is greekGreek warriors. . DragonsThe Dragon population of 6000 is a lot bigger than hydrasthe hydra population of 4 . The last difference is that of the heads. , hydrasThe hydra's head is 6-9 bigger than dragonsthe dragon's, which is 1.