By Helen Briggs BBC News
Its stripy back makes it one of the most recognisable of rodents - but until now it has been unclear exactly how the chipmunk earned its stripes.
Now, scientists have found the evolutionary gene change responsible for the distinctive markings of both the chipmunk and an African mouse.
The gene normally makes the bellies of many rodents light in colour.
The stripes may have helped the animals hide from daytime predators with keen eye sight, such as birds, they say.
Prof Hopi Hoekstra, of Harvard University, US, who led the research, said: "What these two rodents have in common is that they are both diurnal [active during daylight], when one could imagine stripes could be more valuable than if they were nocturnal.
"It is notable that of the rodents that are striped, most are diurnal - again consistent with them being important for evading visual predators (for example, raptors and mammalian carnivores)."