some species of migratory birds are able to sense the allignment of the earths gravitational field. it can also be argued that we in fact have more than 5 senses. for example, what we see is actually a composite image using 2 different sources of information. our retinas contain 2 types of cells, rods and cones. rods function mainly in dim light and provide black-and-white vision, basically measuring light intensity, while cones support daytime vision and the perception of colour, receiving data on wavelength. taste is also made up from data from 2 sources, tastebuds on our toungue and olfactory receptors in the nose. we also have other senses often left unconsidered. for a full list of these take a look at the wikipedia page on senses
http://en.wikipedia.org/wiki/Sense
