the brothers

Actually, I don’t know if they really are brothers, but they are roughly the same size and look to be similar in age judging by the size of their antlers, and seem to like to hang out together as they roam the back yard.

possible fraternal twin bucks

These two medium-sized bucks follow a small herd of does and past year’s fawns through the wetland behind our backyard. The fact that they travel around together seems to indicate some kind of social bond.

So, that got me to wondering if they were, in fact, brothers — twins that grew up together and have stayed together, even during and after the rut when they should have been competitive for the same does.

bucks play-fighting

Like most brothers, they engage in a little play-fighting — mostly shoving matches — but there isn’t any real physicality to their play and it is short-lasting.

And then I began to wonder if they could be identical twins, the product of a single, fertilized egg, or do white-tailed deer even have identical twins?  Are all twin fawns fraternal twins?

possible fraternal twin bucks-

Easy enough to check on whether they are identical or not by inspecting the pattern of the antlers growth.  They each have four times on each side, but the pattern looks different, with the buck in front showing tines that are closer together than the buck in back.

Antler growth is strongly influenced by nutrition, however, which could account for the difference in their pattern.  If they truly are brothers, what is the likelihood that they are identical, or are all twin fawns fraternal?

Unlike humans, deer have a two-horned uterus, and typically, each ovary contributes an egg which is fertilized in one of the horns, giving rise to an embryo that develops in that horn — thus, most twin fawns are likely fraternal. The incidence of identical twins is very small, as it is in humans.

However, that doesn’t mean that they are full brothers, the result of eggs fertilized by the same sperm.  Using a molecular genetic analysis, studies on deer herds in Michigan found that 22-26% of twin fawns actually had different fathers (the percentage is higher in penned deer herds than free-ranging), and that the largest, oldest bucks in the herd do not always father all of the offspring.  In these herds, 18% of yearlings, and 50% of 2 year-old bucks were also successful in fathering offspring.

possible fraternal twin bucks-

So, are they brothers or half-brothers, or just best friends??

2 thoughts on “the brothers

  1. Pingback: Lost and found | Back Yard Biology

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