The best way to estimate the age of a deer – like this 10-point buck from 2015 – is the information you can get from the antlers. Obviously, determining the age of a doe is more difficult. Robert F. Bukaty/Associated Press

“How old do you think this deer is?”

It’s a common question on social media posts, usually accompanied with a trail camera image, or a trophy shot. Responses run the gamut from right on to way off. By following some basic guidelines it is possible to at least come close with a certain degree of confidence.

Let’s start with the low-hanging fruit. In the field, a fawn’s body is smaller and squarer than an older deer, which is rectangular; think of a fawn’s body as a briefcase and a doe’s as a suitcase. Fawns have a smaller head compared to their body size, and a shorter nose. Obviously it’s easier when there are adult deer present to compare with. On the game pole, a fawn will weigh around 40-60 pounds (dressed).

A yearling does have the longer body and nose of an adult, but will be slighter than a mature doe and often alone, or with older, larger does. Dressed weight is probably in the 60-90-pound range.

Yearling bucks are slim-bodied, looking much like a doe with antlers. Those antlers are most often spikes and forks, but some precocious yearling bucks may sport six and sometimes even eight points. Antler beam diameter is one metric biologists use to assess herd health and a yearling’s should be around 15-17 millimeters (between a half-inch and three-quarters of an inch) at the base.

Body weight ranges from 100-140 pounds, but averages around 120. Location and preceding winter conditions sometimes factor in. After a severe winter, sometimes only the larger fawns survive. This is especially true for northern and eastern Maine, where a yearling buck might weigh as much as 140 or even 150 pounds, making the lines of distinction continue even dimmer.

From 2 years old on, does look very similar but there are a couple ways to reliably age them, both of which require a carcass. One is tooth wear and replacement, and there are charts available online. The other is by making a cross-section cut of a tooth and counting cementum annuli, like growth rings in a tree, which is done in the lab. This applies to bucks as well, but antlers and body weight and shape can get you in the ballpark.

At 2-years-old, a buck should sport a rack of at least six and more often eight points that will score up to 120-130 inches (A deer is scored by adding up specific measurements of a buck’s rack, including width, length of beams and individual antler points). Their body is sometimes described as being like a racehorse, thicker in the neck and shoulders than a yearling, but often showing a distinct upward curve where the belly meets the hind legs. Average weight is around 150 pounds but could be 180 or more.

The waters get muddier still when we jump to 3-year-olds. Average body weight is around 170 but could nudge the 200 mark. Antlers and body sport more mass, especially in the neck and shoulders. These are the bucks that make up a large portion of the local taxidermist’s business nowadays. They may not get you in the Biggest Bucks of Maine Club but many will make Maine Antler & Skull Trophy Club.

At age 4, whitetails reach maturity, which means skeletal growth has stopped so excess minerals can now go toward antler growth. The biggest difference will be in the bases of the main beam, which should have a circumference of at least 4 inches, or be as big around as a deer’s eye. Body weights still vary considerably, averaging 190 but quite often in the low but in 200s.

At 5, 6 and if they make it, 7, a buck should be in his prime, sporting the largest rack he ever will and with the most body weight. He’ll be well over 200 pounds and should sport a rack of antlers that will make the record books; there are always exceptions.

Beyond that, and some deer do make it, they start to decline. Bucks and does will still have big bodies but the buck’s rack may diminish. It should still have wide bases but mass and points will decline. As for does, anything over 140 pounds is a mature deer, and you’ll have to look at the teeth to guesstimate how old it really is.

Bob Humphrey is a freelance writer and Registered Maine Guide who lives in Pownal. He can be reached at: bob@bobhumphrey.com