If White-tailed deer are more adaptable and numbers are flourishing in Idaho, do biologists fear the extinction of mule deer in Idaho? Also, do White-tail and Mule deer ever crossbreed?

Question Asked by Mrs. Kress’ Class at Tigert Middle School in Soda Springs

Question Answered by Paul Atwood Senior Wildlife Researcher for Idaho Dept. of Fish & Game

Mule Deer Photo by G. Losinski

Mule deer are better adapted to live in dry, open areas and white-tailed deer are better living in forests that get more rain. Idaho is a large state with plenty of both of those types of habitats. Northern Idaho is wetter and has more trees than southern Idaho so there are more white-tailed deer than mule deer there. Here in southern Idaho we have more dry and open areas so we have more mule deer. There are some areas of southern Idaho where white-tailed deer are increasing and may be considered more successful than mule deer. A good example of this would be the deer found in the river bottoms among houses, farms, and ranches and it does appear that white-tailed deer might be better at adjusting to all of the roads, traffic, and household pets that are also found there. Deer that live in these areas are also non-migratory, which means they live there year round. However, most of the mule deer in southern Idaho do not live in these areas. Most of the mule deer in southern Idaho are migratory and they spend their summers up high in the forests and spend the winter in the foothills and desert areas. In these dry, open areas there is isn’t any reason to think that white-tailed deer are outcompeting mule deer. Wildlife managers are concerned about the future of mule deer populations but that concern is focused on the loss of winter ranges and loss of migration routes that are essential to mule deer.

White-tailed Photo (BY-SA 3.0) Averette on Wikimedia Commons

There are areas where mule deer winter ranges overlap with white-tailed deer in southern Idaho. If there are a lot of deer in these areas of overlap then wildlife managers might want to keep the numbers of white-tailed deer lower to prevent the two species from competing for food. These areas of overlap are also where it is most likely to find crossbreeding between mule deer and white-tailed deer, which is also known as hybridization. When a deer fawn is born to one mule deer parent and one white-tailed parent it is a hybrid. Even though there are many areas where the two species overlap, hybrids are fairly rare. That is because the two species don’t interbreed often and even when they do their young have lower chances of survival than deer that are not hybrids.

How to tell if it is a hybrid

  1. The metatarsal gland

This is the easiest way to positively identify a whitetail-mule deer hybrid. Located towards the bottom of the animal’s rear legs, like most of their features, hybrid deer fall somewhere in the middle. They have a metatarsal gland between two to four inches long and sometimes surrounded by just a little patch of white hair.

Hybrid Source unknown
  1. Antlers

Experts agree that antlers are just about the worst way to differentiate hybrids from their parent species,. Whitetail antlers are marked by a number of tines splitting off a main beam whereas mule deer antlers are generally taller and broader, but bifurcated with very small tines.

  1. Tails

Whitetails, like their name suggests, have tails with white undersides that they flare when threatened. Mule deer have white tails with black tips and it is generally more uniform in size all the way around. Hybrid deer usually have a dark brown tail similar to whitetails, but much darker.

  1. Ears

Mule deer can sport ears over 10 inches long, while whitetails only measure about 7 inches,. Hybrid deer measure somewhere in the middle.

  1. Preorbital glands

The little slit in the corner of the animal’s eye. Whitetail preorbitals are tiny slits that are also relatively shallow. Mule deer on the other hand, have comparatively wider and deeper preorbitals, with some going as deep as an inch compared to the whitetail’s half-inch. Hybrids have something in between their parent species.

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