Is there any advantage to fluorescent sheep?

There's been a lot of talk about how dangerous relying on using Cairns to navigate mountain routes can be, but imagine how much more dangerous it would be if you used sheep.

Sheeps' glow-in-the-dark properties make them perfect beacons at dusk. As the levels of ambient light from the sun drop, sheeps' coats re-radiate wavelengths from scattered ultraviolet, violet and blue light in the atmosphere, giving them the appearance of glowing.

Of course these aren't our words, we know absolutely nothing about fluorescent sheep. But two people that do can be found on the New Scientist website. This fluorescent effect, they say, occurs in flowers in order to attract insects, but they haven't been able to answer the crucial question - WHY would sheep want to glow?

Any bright ideas from the OUTDOORSmagic crowd?