As we lazily floated down the Yellowstone River last week we spotted a young whitetail deer fawn along the bank. Its fur coat had hundreds of white spots.
Whitetail fawns have these spots to help hide them from other animals, like a coyote or bear, that would like to eat them. When they are first born, typically sometime in June, the fawns will hide in the brush or tall grass and not move to avoid being found. They also have very little smell, helping them to hide.
People who are hiking or fishing and come across a fawn like this should leave the small animal alone. Even though it may look like it has been abandoned by its mother, the doe deer is often feeding close by.
It takes about seven months for the fawn to grow inside its mother, or about 200 days. The breeding season for whitetail deer in Montana usually runs from mid-November until the end of the month, although that breeding season is a bit later in Western Montana.
After being born, a deer fawn will have its white spots for about three to four months. So if you see a fawn with spots in late October, it must have been born very late.
When the deer breed, when the fawns are born and when the fawns lose their spots is all meant to ensure that the animals survive winter, when there is less food to eat and the cold weather makes it harder for many wild animals to survive. By being born in the spring, when plants are growing and can provide lots of nutrition and hiding cover, a deer fawn has a better chance of eating healthy food to grow stronger and survive the winter ahead.
When they are only just over a year old, about 16 to 17 months old, a female deer will start the cycle again by breeding and giving birth to its own fawn. After that first fawn, whitetails will often give birth to twins in following years. That means more of the long-legged, white-spotted deer like we saw on the riverbank.
— Brett French, Billings Gazette