Nasal Bots in White-tailed Deer


Most hunters that have harvested any number of white-tailed deer have unfortunately found nasal bots. At first glance, what a hunter encounters looks like a large maggot. And it basically is, and they live in the cavities of the nose and mouth. Nasal bots are the larvae of a specific kind of fly that belongs in the genus Cephenemyia. Deer biologists actually find them in a high percentage of whitetail deer, particularly when a thorough examination of the head is conducted. From my experience, white-tailed deer in Texas are much more likely to have nasals bots than not.

These bots are specific to members of the deer family, which also includes elk and mule deer in the United States. Nasal bots begin life when the adult fly lays a group of eggs around the nose or mouth of a deer. The small larvae within these eggs are then released when the deer licks the eggs. The warm, wet saliva creates an environment that permits the “hatching” of the immature bots. These larvae then migrate to the nasal passages and occasionally into the sinuses where they molt into larger stages of the maturing larvae.

White-tailed deer often have nasal bots

The mature larvae then move to the deep cavities in the deer’s mouth called the retropharyngeal pouches. The fully matured bots then exit and pupate in the ground until emerging as adult flies that begin the life cycle all over again.

To a white-tailed deer, for example, these bots are typically only a minor nuisance as they do irritate the lining of the nasal passages and move about in the retropharyngeal pouches. In fact, most sneezing and coughing of deer is assumed to be the result of nasal bots. From a clinical perspective, the bots do not cause deer any harm. No sores, infection, nor other problems have been reported even when the parasites are present in large numbers.

Hunters normally encounter nasal bots after the deer they harvested has begun to cool. After the deer dies, the body temperature falls and the bots begin to leave the nasal passages and oral pouches in search of a more suitable environment. These bots then exit through either the nose or mouth. Bots can also move in the wrong direction, or down the trachea (where it is usually warmer), and may appear to be in the body cavity of the deer even though they are not.

Lastly, nasal bots pose no disease threat to deer hunters and do not harm the venison. Remember, nasal bots are only found in nasal passages and around the mouth of deer. Deer “infected” with these harmless parasites are safe for human consumption, although I suspect many unknowing hunters have discarded carcasses after observing¬†an ugly larvae crawl out of a deer’s nose.


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11 Replies to “Nasal Bots in White-tailed Deer”

  1. I was “fortunate” to witness one crawling out of the nose of the first deer I ever killed when I was a kid back in the day. What did my dad tell me after seeing this?…”Don’t tell your mother.” Good to know they’re harmless parasites.

  2. Blake, you very well could have. The small larvae have to work their way up into a deer’s nasal passages, so you would imagine the “infected” deer must feel something, no matte how small.

  3. Found one after boiling cleaning and bleaching a 9 point for a euro mount. The head was ready for mounting totally prepared. We were admiring it a day after taking out of peroxide and my son noticed something in the nasal cavity. We pulled it out with hemostats. My son still thinks its a cocoon from leaving it on the back porch in the solution. Wait till I show him this!!!

  4. Tim, nasal bots are widespread and I think just about every deer has them at lower latitudes. They are found in the nasal passages (technically) but we know what you mean.

  5. Just went out to the barn to check a doe I shot, field dressed then hung up in the barn to cool/age. The deer has been hanging for three days in 30′ weather. It was horrific, odd to find a large larvae hanging dead out of the nostril. Luckily, I googled and found this page.Thanks.

  6. In bucks that I have shot there are bot fly holes in the main beam of each antler. I heard the moved there during the velvet stage because of a greater blood flow, then the fly exits before antler hardens leaving a cool looking 1/4′ hole.

  7. I had put a buck head in the freezer for a few days to later thaw it and prepare it for a skull mount. While skinning the head and removing the jaw, I noticed more than 20 of these disgusting parasites congregated in the nasal passages and in the back of the deer’s throat I’ve shot many a deer but I’ve never noticed anything like this before. Nice to learn they are harmless to the venison. They had to have been driving the buck crazy. I don’t see how the deer could have breathed through its nose!

  8. Shot a small, but legal FL buck today and was going to hacksaw the top of the skull, but nobody had a hacksaw. I proceeded to skin back the skull and cut the head off close to the jaws, exposing the sinus cavity. That’s when I immediately saw ~15-20 of these large larvae in that area. First time I ever saw this, but I normally don’t poke around in that area. I assumed they were a bot fly and after reading this article I was convinced I was right. The buck was perfectly healthy otherwise.

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