Ask The Biologist

Fawn Shortage

Fawn Shortage

By Bob Humphrey

Is it getting more common to see adult does with only one fawn?

QUESTION: It seems like does in my area have been having fewer fawns over the past few years. We used to see them mostly with twins, but now they just have one, and sometimes none. Can you tell me why? — Will W.

ANSWER: I can’t say for sure, but I can offer a few possibilities. Does most often don’t breed until their second fall, and they typically give birth to a single fawn the following spring.

In areas with optimum habitat some (perhaps as many as half) of the doe fawns will be bred and also have a single fawn as yearlings. An abundance of does with single fawns could be an indication of a young and growing population. However, you noted this was a recent phenomenon, so that’s not likely the case. Plus, there should still be a sizeable proportion of older female deer in the herd.

From age two on, most adult does give birth to twin fawns, and occasionally triplets. However, only a portion of those fawns ever see their first autumn. The rest succumb to disease, accidents and predation.

The latter is often the leading cause of fawn mortality. You didn’t mention where you live, but a number of recent studies, particularly in the Southeast, have shown a significant increase in fawn mortality that is largely attributable to coyotes. The effect is no less severe in the northeast, it’s just been going on a lot longer.

Where I live in southern Maine, most of the mature does we observed 25 years ago had twins fawns. Now it’s far more common to see only one fawn, and as many as 50 percent of mature does have no fawns with them in the fall.

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