Billy or Nanny? — How to Identify Mountain Goats

Billy or Nanny? — How to Identify Mountain Goats

Photo by Danny Coyne Photography

Judging mountain goats in the wild requires knowledge, experience, and patience. Both male mountain goats (Billies) and females (Nannies) have horns of similar shapes, sizes, and characteristics. At first glance, or to the uneducated, mountain goats of both sexes may look alike. But knowing how to differentiate between billies and nannies is important for anyone that wants to hunt mountain goats. In fact, many hunting opportunities require that the hunter pass a mountain goat identification quiz before being allowed to participate. (We'll talk more about that later in this article...)

Whether you are considering a hunting opportunity that requires the proper identification of goats, or you are simply interested in learning more about these fascinating creatures, let's talk about the differences between billies and nannies...


The Rocky Mountain Goat Alliance (RMGA) video above is a great primer on the differences between billies and nannies.

It seems that most of the focus on differentiating between billies and nannies is on their horns. That's fine, but it can often be difficult to judge horns when you're looking through optics on the mountain. It is helpful to remember that you may be able to tell a billy apart from a nanny before looking at their horns. You can begin to do so by assessing...

  • Sexual Organs: Don't forget the obvious! You may have an opportunity to see the presence of the most defining evidence of all.
  • Proximity: Outside of the rut, a billy is often solitary or in small groups of 2-3. However, a nanny is often in larger groups, and especially in groups (no matter the size) with kids.
  • Posture: A billy will stand and stretch to urinate, whereas a nanny will squat with their rump near the ground.
  • Stature: A billy will have a stockier build and may have a pronounced shoulder hump. Billy's also tend to have more pronounced pantaloons.

After considering the above, you can now further analyze or confirm the identification of a mountain goat by judging these characteristics of the goat's horns and facial structure...

  • Horn Curve: A billy's horns will have a more uniform and consistently gradual curve. A nanny's horns extend more vertically from the base and then have a more distinct curve near the tip.
  • Horn Mass: A billy's horns tend to carry more mass, while a nanny's horns are generally thinner. If you compare the mass of the horns at the base to the width of the goat's eye, an adult billy's horns are typically wider than their eye. Even a mature nanny may have bases that are no wider than the eye.
  • Horn Bases: The base of a billy's horns will appear closer together, whereas a nanny's horn bases will have a more prevalent gap between them. Additionally, it is common for a billy to have large glands visible behind the base of their horns.
  • Facial Structure: A bill will have a longer, more "horse"-like nose. And a mature billy may have a noticeable "roman bulge" on their nose.

When attempting to make a determination between a billy or a nanny, use as many of these criteria as possible. Do not get fixated on one aspect, such as horn mass at the base, and forget to assess other criteria that will challenge or confirm your judgment.

Nanny Mountain Goat

Horn bases no wider than the eye. Thinner mass throughout the horn. A distinct "kink" or horn curve near the tip. A shorter nose with no bulge. The goat in this photo by @kevink_photo is a Nanny.


With this information and some practice spent looking at goats online, I was able to get a perfect score on Alaska's goat identification quiz on my very first attempt. But remember, that doesn't mean that judging goats on the mountain will be easy!

If you want to quiz yourself, here are two great online quizzes in PDF form that you can take...

Finally, the Rocky Mountain Goat Alliance regularly has "Billy or Nanny?" posts on their Instagram account, @GoatAlliance. The comments on those posts are also great ways to "see" how other people think through their logic as they choose Billy or Nanny for the goat in the photo.


In different states, or for different hunting opportunities within a state, some regulations may restrict the harvest of a nanny or a billy. There are both billy-only and nanny-only hunting opportunities out there. For other hunting opportunities, the harvest may not be restricted to a specific sex, but the harvest of billies may be strongly encouraged.

The area that I will be hunting in Alaska this fall is a Registration Hunt. While the tags available for registration hunts in Alaska are not limited, the harvest of mountain goats is limited. The hunting unit is divided into several smaller zones — each zone having a specific harvest quota based on a point system.

The harvest quota is established with a point limit that equates to roughly 6% of the estimated goat population in that specific area. So if there is an estimated population of 100 goats, 6 "points" are allowed for harvest in that area. The harvest of a billy is 1 point, but the harvest of a nanny is 2 points. Therefore, an area with 6 points allows for the harvest of 6 billies, or 3 nannies — or a combination of billies and nannies that reaches the 6 point quota.

Hunters participating in this registration hunt are required to pass a goat identification quiz before they begin their hunt. This ensures that all hunters have a basic understanding of how to tell the difference between billies and nannies. Of course, as we discussed above, judging goats on the mountain in real-world conditions is more difficult than looking at photos or diagrams of goats. It is important that hunters have good optics, stay patient, and also get as close as possible to accurately judge goats in the field.

As discussed in the video from the Goat Alliance (above), harvesting nannies impacts the future goat numbers in a herd more than the harvest of billies. It is important that hunters seek to understand the unique population dynamics of the area they will be hunting and align their harvest goals with the wildlife biologists' recommendation for that specific area.

Mark Huelsing is the host of the Hunt Backcountry Podcast and works at Exo Mtn Gear — though he's never been able to figure out his job title. Connect with Mark by sending him an email (mark at or DM @MarkTheFark on Instagram.

To follow along and receive future articles in this series, sign-up to receive email notifications from Exo Mtn Gear. You can also view all articles in this series at the SEAK Adventure series archive.

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