the masai tell us that there is less water in the river now than at any time they can remember.nd if the mara river went away, what impact would it have on all this? >> reid: we're not absolutely sure. but in the dry season, it's the only thing that flows. and so if that water went away, then the wildebeest population would collapse. >> pelley: collapse? >> reid: yes. >> pelley: what do you mean by collapse? >> reid: you know, i don't actually know if there would be very many left, actually. not just the wildebeest-- it would be many of the other species that require water. >> pelley: you would lose hundreds of thousands of these animals? >> reid: oh, yes, absolutely, absolutely. in fact, the estimates are-- and you know, this is a guess-- is that if the river were to dry up completely, okay, in the very first week after it dried up, we'd lose about 400,000 animals that would die. >> pelley: in a week? >> reid: in a week, yes. and, you know, maybe that's an overestimate, but even if it's in a month, that's a lot. >> pelley: we wanted to find out why the mara river seems to be dr