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A Bear’s Sense of Smell

If someone were to ask you, “how does a bear smell,” you could answer in two ways. Bears smell real bad – or so I’m told – or bears smell exceptionally well, as I discuss below.

Big Black Bear

Bears are thought to have the best sense of smell of any animal on earth. For example, the average dog’s sense of smell is 100 times better than a humans. A blood hound’s is 300 times better. A bear’s sense of smell is 7 times better than a blood hound’s or 2,100 times better than a human.

Bears acute sense of smell evolved in order to help them find food, mates, keep track of their cubs and avoid danger, particularly between competing individuals. Except for mother bears, bears are territorial animals that need to range widely to find enough food to sustain themselves. A bear’s sense of smell is so acute that they can detect animal carcases upwind and from a distance of 20 miles away. You should just assume that they can smell the food in your food bag too.

Bears have an incredible sense of smell because the area of their brain that manages the sense of smell, called the olefactory bulb, is at least 5 times larger than the same area in human brains even though a bear’s brain is one third the size.

Bears also have highly developed noses that contain hundred of tiny muscles and let them manipulate them with the same dexterity as people’s fingers. The surface area inside their 9 inch noses also has hundreds of times more surface area and receptors than a human’s.

So the next time you make camp in bear country, make sure you hang a bear bag or store your food in a bear-resistant bag or cannister at least 100 yards away from your shelter. You should also seriously consider lining your food bag with an OPSACK 100% odor-proof plastic bag. These plastic bags are 17,000 times more odor-proof than normal ziploc bags and can significantly reduce the chance of a human bear encounter.


  1. Awesome post! I've been experiencing an unfounded fear of black bears in the northwest in my travels this year. People are terrified of the black bears, so much, that they make decisions that actually antagonize the situation. I'm hoping to put a post up about just that in the coming months. Keep up the great work!

    One of the reasons I like backpacking so much is that you typically don't encounter 'trash' bears or other animals in wilderness – these unfortunate creatures usually hangout at the popular campgrounds and easy/popular hikes.

    • Where in the Oregon area might I find a black bear. I do wildlife photography and have yet to see a wild bear!

    • In Canada too, urbanites and even “outdoorsy” people have an unwarranted fear of bears. In the area I lived most of my life, I’d run into bears perhaps once every 2 weeks on my training hikes. I don’t carry bears spray and I don’t feel the need too. I’m in more danger driving to the hike than I am from bears. A bear may kill you- but it’s very rare.

      • We had cabins on the border in International Falls and were used to seeing bears, chasing them away when necessary, but it was funny to see people not used to them go ballistic at seeing one. I was at the end of the lane getting the mail and a guy came running down the road and it seemed weird. A couple minutes later a black bear came ambling nonchalantly down the road and I figured it out.

    • like i didn’t know that

  2. Researching this article was really interesting. I have yet to meet a black bear face-to-face, but knowing that they can smell way in advance makes me doubt that I ever will.

    • Never say never. Last Monday night in the campground in stay at. I was coming out of the bathroom and came across a 300 lb. bear he was less than 2 feet away from . We both ran in opposite directions. It was

  3. If they use red pepper in bear-spray containers,

    then why not grind some fresh red pepper cyan in

    a prosser,or coffee grinder. Just set it to a fine setting then fill an empty seasoning container. Before you hoist the the Bear-Bag up

    into the air, shake some of this pepper in the

    bag,…and on the bag too ! Just becarefull not

    to be down wind or breath to heavy around the

    food bag,…wear protective eyeglass's too.

    If the Bears sence of smell is that keen,…it

    will know that it is something to avoid.

    If you hear somthing …sneezing at 2AM its probly a Racoon or some FisherCat ??

    • You are a danger to everyone else out there

      • I’ll second that one. The “repellent” nature of red pepper is that it in an aerosol form and will irritate the eyes and upper respiratory system of the bear just long enough to get away. Putting red pepper in your food bag would just make it seasoned that much better.

  4. Sounds like a great way to self-inflict pain. I prefer to just hang the bag out of reach.

    • We are in the Smokies in Tennessee , And have been for almost a week and we have yet to see a bear.

    • We are in the Smokies in Tennessee , And have been for almost a week and we have yet to see a bear. We are pretty disappointed.

  5. I have yet to see anyone effectively hang food out of reach of a bear. For this reason, hanging food in places such as Yosemite, is actually illegal. A bear proof container is really the only way to go in bear country.

    Secondly, I don't believe those "odor proof" bags really do anything. If a police drug dog can sniff drug residue from a now empty ziploc, placed in the trunk of a locked car, I'm wondering how effective these bags will be once you touch the outside of them with food on your hands?

  6. Great post!

    As a side note, you might want to avoid trying to bear-proof any food containers with anything like the bear pepper sprays. Apparently the residue from those sprays have been known to actually attract bears, at least those with capsaicin as the active ingredient.

    I think it's more about the stinging sensation when sprayed than the pepper smell.

    If you love bears, or are interested in them, you all should check out Bear Attacks: Their Causes and Avoidance<img src="; width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /> It's a great book with a lot of valuable information about grizzly bears and black bears.

    That last part wasn't meant to sound like an advertisement. hehe

    Safe travels.

  7. What a fascinating read! My family and I have been so lucky in all our years of camping never to have had a bad experience with bears. I'm thinking now we might take more precautions than we have in the past, though, because I'm writing our positive experiences off to luck after this read!

  8. Funny that I noticed this post this morning–just this weekend I went on a short camping trip to a state park just outside of Minneapolis, where there were not "supposed" to be any bears. I was in a backpacker site and had my food in an OP Sack. I was planning on hanging it, mainly to practice for an upcoming solo hike in the northwoods. It was late when I got in to camp (and I was lazy) and I ended up just putting the OP Sack in my tent (around here I mainly worry about smaller critters getting into my food rather than bears).

    To make a long story short I was woken up on Saturday morning by some rather noisy shuffling through the brush next to my tent. I expected to peek out and see a few deer grazing nearby. I was shocked when I stuck my head out the fly and found a huge black bear about 10 feet from my tent (and a small bear cub!). It didn't see me, and didn't even take notice of my tent or come any nearer, it just shuffled on through after about 5 minutes. I have to assume it couldn't smell the rather "stinky" contents of my food bag in the OP Sack. Obviously I was lucky considering my laziness in not hanging my food! But I was also impressed with the OP Sack.

    I later spoke to the ranger and it appears that this year given our spring drought the bears have vastly increased their range for foraging and so have moved into the public areas of the park, but so far have not caused any problems for campers. I was pretty scared when I saw the bear, so I did a little more research into what to do in a future encounter (other than hide in my tent!). I found a very interesting site with research-based information: It definitely cleared up a lot of misinformation I had about black bears, and thought it might be of interest to others related to this post. I especially liked the numerous videos of bear interactions and also what their "bluff" aggression looks like and means. I'll still probably be scared if I am lucky enough to see a bear again, but hopefully I'll appreciate it more!

    • The bear could smell the food, but it likely didn’t bother BECAUSE it smelled and heard you looooong before you even woke up. A mother bear is always on the defense when she has cubs with her. She has to defend them from any possible threat, because there are SO many and they are 100% dependent on her. Investigating a small amount of food *they have amazing sense of smell, so she’d know vaguely how much of a meal she’d find by what she could smell* while a potential threat is guarding it in an object (tent) she can’t identify was probably more than she was comfortable with.

  9. You were very lucky. The first thing I always do when I reach camp is to hang a bear bag. Doesn't matter how early or late I arrive. It gets my food out of the way during camp preparations and helps avoid trying to hang it in the dark. Plus I always use an OP sack as a liner.

  10. Please share your sources with me. Where did you find the size of the bear's olfactory bulb? And how keen it's sense of smell is in comparison to our own? Thanks!

  11. I wrote that post a long time ago and had to do some digging to get those facts. But I can't remember where I found the info you want. I think I had to read some academic papers to find it – believe it or not, I actually know a lot about brain anatomy. I found everything via google however, so you should be able to too.

  12. I didn't mean to imply that I didn't beleive you; you probably do know more about brain anatomy than I do. I've seen similar figures scattered accross the web, but I haven't been able to find the research to back it up, and I need that in order to use it myself. I was just hoping that you had kept your sources. Thanks anyway. And thanks for encouraging people to keep bears wild!

  13. The OpSack works. Our group witnessed a black bear walking right by a full OpSack while checking out our camp, obviously looking for food. He was interested in various human smells on tents, etc., but didn't notice the food bag lying right there on the ground.

  14. Regarding those scent proof Opsacks: I meticulously, carefully sealed an open can of cat food in a ziplock, washed my hands, put on nitrile gloves and sealed that in an Opsack. Then I hid it under one of several clean towels on the tile floor of our family room. Our year-old beagle entered the room, stood still wiggling her nose about 5 seconds, turned to the correct towel and began sniffing directly over the cat food. She had the prize in under 20 seconds. I passed this along to the manufacturer, but no reply.

  15. Is there an offensive smell that bears do not like?

    • I wouldn’t venture a serious reply, but I can say that as a young teen I was sleeping out in the open in Sequoia National Park. That night a bear walked all around me, pooped nearby and left without waking me. Possibly teenage boys emit such an odor.

  16. How about human urine, does that repel them?… or possibly attract them? I’ve read stories about people peeing around their campsite hoping that will keep bears away. Don’t know if it’s affective. I’ve also read that fabric softener cloths work. Bears apparently hate that smell.

    • If you intend to sleep in grizzly or polar bear country, an electrified fence and armed sentries. Or just take your chances that you will awaken in time to use bear spray, and pray that it works. You might sniff around to see if a bear might peed around where you want to sleep to mark his territory. Yours might piss ‘m off.

  17. i live in the adirondacks and have found out that a cap full of bleech or ammonia will keep them away..if you dont bother them ,,they wont bother you,,hunting season is worse time,,if someone wounds one ,,he is ugly,,also dont get between cubs and momma,,happy camping and hicking

  18. Unfortunately, the amount of conjecture continues to grow on the subject of sense of smell among mammals, especially bears.

    When comparing the “sense” of smell among mammals, it is better to compare olfactory receptors AND the size
    of the part of the brain that processes smell. 40 Times better is completely unreliable.

    Human: 6 Million Olfactory Receptors

    Dog: Up to 300 Million Olfactory Receptors. The portion of the brain that processes smell is 40 times larger (relative to overall brain size) than a human brain). The number of olfactory receptors varies among dog breeds with the bloodhound having a great
    deal more than other breeds.

    Black Bear: Ah, and let the conjecture flourish! Some say a bear can smell up to 1 mile away. And some say 20 miles. Another source said 18 miles. So which is it?
    How many olfactory receptors does a black bear have? I sure don’t know and didn’t find consistency among those who claim to know.

    The numbers used here, 100 times better, 7 times better, and 2100 times better are interesting in that there are several bear articles on line that use the same numbers. Comparing the dates of the earliest comment for this article to the dates on the other articles indicates that many people have simply copied these numbers to their own articles (without fact checking).

    I know from experience that an animal’s sense of smell appears to be much greater than my own. Comparing a dog
    and a bear, i don’t know because of so much vagueness and lack of facts sited in articles that are at the top of the “Popularity” search lists.

    A zoologist and a veterinarian would probably be a more reliable source.

  19. In 1990 i was a freshman at the University of Wyoming, and spent that summer working in Yellowstone. Made srveral hikes in bear country. The Grizzly’s acute sense of smell was reinforced by the DNR officers who patrolled the park. To basic rules: Dont hike alone and make sufficient noise so any bear is not surprised by your approach. Saw Grizzlies, but always at a distance.

  20. Sources, please?

  21. I don’t know about Grizzly’s, but the Black bears are not as bad as their reputation. They are very scared of people and would rather run away when they see you than attack you for your food in your back pack. We live in the northwest corner of CT and see plenty of them. They come to eat from the bird feeders and usually run away when we go outside. Some of them are so used to us that they just continue eating when seeing us, but never tried to attack. When they smell food in the garbage or your cooler, they steal it when you are not too close to it, but not going after you. Usually you just have to clap your hands and they run, or just buy an airhorn and you can use that to scare them away. It works on telemarketers also. :-)

  22. I think that you should just not camp in a bear sighted area you could get hurt if a bear broke in to your tent nut you can play the most annoying noise you know to scare it away

  23. I would not put bear spray on your items to deter bears. It has been pointed out in several articles, that bear spray sprayed at a bear deters them, however……the dried spray mellows into a smell that then attracts bears and can do so for several weeks.

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