they have a very unique relationship with pathogens generally. they have a unique biology and it allows them to co-exist in different ways. >> there are various theories about why that is. it might have to do with how long bats have been around. >> bats are an ancient species. they have been on planet earth a long time and that means they've had a long history of being exposed and adapting to viruses in nature. >> another theory involves their body temperatures. >> a lot of people have come up with these sort of armchair solutions. like maybe it is because they fly and when they fly, their body temperature gets higher and that's like a fever and that gives them the ability to handle viruses more than other animals would. >> he is a biologist and tv host who did his ph.d. work on bats. >> when a virus gets into a