A deer’s tail serves multiple survival functions.
QUESTION: It’s obvious how the white-tailed deer got its name, but what is the purpose of this tail? It seems like flagging would only attract predators.
ANSWER: Deer generally live in a forest environment where visibility is often obscured by vegetation. It’s likely the flag acts as a visual signal to other deer.
An upright tail on a stationary deer might be a signal to be alert for danger. When fleeing, it makes it easier for one deer to follow another deer, thus moving away from the danger they may not be aware of.
That white flag may, indeed, also make it easier for predators to follow, but as deer and predators have both been around a long time, it’s obviously more of an advantage than a disadvantage. It’s also worth noting those long white hairs collect and hold scent from urine and other excreted solutions, acting as pheremone flags by more slowly dispersing that scent.
— Recent Ask the Biologist Question: How Low Can You Go? Strike a balance when compensating for ducking the string. Find Out The Answer!