Why do deer have antlers, and how do they grow so fast? Can you imagine having to walk around with a set of antlers on your head? I get a headache just thinking about it.
Last year in late May, we saw a Sitka black-tailed deer doe with two newborn fawns in our yard. They took up residence nearby, and we still see the trio nearly every day as they graze on our sprouting grass. The fawns are now almost the same size as the doe, and I wonder when they will wander off on their own. Will the doe have a new set of fawns this year? She doesn’t look pregnant, but we will know for certain in a few weeks.
Does between the ages of five and ten are in their prime and usually produce two fawns a year. Mating season on Kodiak occurs between mid-October and late November. The gestation period is six to seven months, so fawns are born from late May through June. Twins are the most common, although many young does only produce a single fawn, and triplets do sometimes occur. Newborn fawns weigh between 6.0 and 8.8 lbs. (2.7 to 4.0 kgs.). For the first week, a newborn fawn has no scent, allowing the mother to leave the fawn hidden as she browses for food to rebuild her energy reserves after giving birth.
The two young deer we often see in our yard are bucks, and they have little nubs on their heads. Bucks begin to grow a new set of antlers in the late spring because the increased daylight in the spring stimulates the hormones that regulate antler growth. During the spring and summer, antlers receive a rich supply of blood and are covered by a fine membrane called “velvet.” At this time, the antlers are fragile and vulnerable to cuts and bruises. By August, antler growth slows, and they begin to harden. A few weeks later, antler growth ceases, blood flow to the antlers stops, and the velvet dries up and falls off. Bucks then retain these hard, polished antlers throughout the mating season. After the mating season, cells start to de-mineralize the bone between the pedicle and the antler, weakening the connection between the skull and the antler, and the antler falls off. On Kodiak, deer normally begin dropping their antlers from mid-to-late December.
Sitka black-tailed deer antlers are fairly small compared to other species of deer and typically have three or four points on either side, including the eye guards. A very large buck might have five points on each side, including the eye guards.
Deer antlers grow at an amazing rate. Biologists have determined white-tailed deer antlers can grow as much as one-half an inch (1.27 cm) per day during their peak growth. Antler size is dependent on age, nutrition, and genetics. Antlers are made from bone, and they develop from the pedicle on the frontal bone of the skull. Male fawns produce “button” antlers at the age of four to five months, and they begin growing their first noticeable antlers the following year. A young buck’s first antlers may be only single spikes, but antler size usually increases with age until they reach a maximum size. Antler growth requires a great deal of energy, so antler size is dependent on good nutrition and environmental conditions. A buck may produce smaller antlers the year following an extremely harsh winter.
While biologists don’t know why bucks grow antlers, several theories have been proposed:
(1) A buck with large antlers may signal to a potential mate that he is healthy and possess good genes.
(2) Antlers may be used as a weapon during the breeding season to establish dominance between males.
(3) The size of the antlers alone may display age-related dominance without the males having to fight. Although, current research does not support this theory.
(4) Deer may use antlers
to defend themselves against predators. Although, this would only be beneficial for bucks since does don’t have antlers.
It is likely a combination of two or more of these theories point to the true purpose of antlers.
The Kodiak winter of 2016/2017 was very harsh, and biologists estimated as much as 80% of the deer population on the island died. We saw deer carcasses everywhere we hiked in the late winter of 2017. The 2017/2018 winter was mild, and the deer fared much better. The deer wandering through our yard this spring look fat and healthy, and I suspect we will see a bumper crop of fawns this summer.
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Next week, I’ll cover some interesting facts about deer.
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Robin Barefield is the author of three Alaska wilderness mystery novels, Big Game, Murder Over Kodiak, and The Fisherman’s Daughter. To download a free copy of one of her novels, watch her webinar about how she became an author and why she writes Alaska wilderness mysteries. If you like audiobooks, check out her audiobook version of Murder Over Kodiak. Also, sign up below to subscribe to her free, monthly newsletter on true murder and mystery in Alaska.