So what do they mean, what can they use them for and why do they disappear?
The European Red Squirrels has a wide range of utilities for their eartufts. First and foremost are they used for temperature control. In the high summer, when it get really hot they will loose their eartufts to better rid their bodies of heat, as their primary sweat glands are located in the ears. In the contrary, in the winter, they will become large, lush and fluffy to keep those thin ear lobes warm.
They also serve as a visual indicator, of the squirrels overall health and virility. A good indicator when you're looking for a mate.
It's also believed that they are being used to pick up the slightest change in wind direction, which is highly useful, when you running, playing chase, sprinting and jumping around, more than 4 human house floors up in the air.