True Facts: Proboscis Monkey

True Facts: Proboscis Monkey

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Research cited:

Dixson A, F: Copulatory and Postcopulatory Sexual Selection in Primates. Folia Primatol 2018;89:258-286. doi: 10.1159/000488105

Lucia F. Jacobs, Basil el Jundi, Almut Kelber, Barbara Webb; The navigational nose: a new hypothesis for the function of the human external pyramid. J Exp Biol 6 February 2019; 222 (Suppl_1): jeb186924. doi:

Nishimura T, Mori F, Hanida S, Kumahata K, Ishikawa S, Samarat K, et al. (2016) Impaired Air Conditioning within the Nasal Cavity in Flat-Faced Homo. PLoS Comput Biol 12(3): e1004807. doi:10.1371/journal.pcbi.1004807

Ikegaya, H., Suzuki, M., Kondou, H. et al. Nose size indicates maximum penile length. Basic Clin. Androl. 31, 3 (2021).

Hiroki Koda, Tadahiro Murai, Augustine Tuuga, Benoit Goossens, Senthilvel K.S.S. Nathan, Danica J. Stark, Diana A. R. Ramirez, John C. M. Sha, Ismon Osman, Rosa Sipangkui, Satoru Seino, Ikki Matsuda (2018) Nasalization by Nasalis larvatus: Larger noses audiovisually advertise conspecifics in proboscis monkeys.
Science Advances 4(2): eaaq0250. doi:10.1126/sciadv.aaq0250

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36 Responses

  1. zefrank1 says:

    Happy to have Curiosity Stream as a sponsor. Go to and use code ZEFRANK to get Curiosity Stream for only $14.99 for the whole year.

    • 🌟 Don't Lose Your Spanish says:

      1:04 Those lips though. xD 😀

    • Shala Carter says:

      Oh, good! Something I want to watch.

    • ScriptKeeper says:

      I was hoping they peacock would appear when you brought up the beeirds, and was not disappointed!!!! Still want a True Facts: Peacock episode, because it’s a humor goldmine

      Also the vomiting monkey statue made me cackle out loud, glorious!

    • Xitaris says:

      I’m a little surprised curiosity stream has been such a consistent sponsor since you have pretty risque content. Is there any push back from them, tell you to tone it down? (please don’t, I love your content)

    • cypher says:

      … for just the cost of something else that cost $14.99 … 😄😆😂😅

  2. A Laughing Wolf says:

    I’ve always loved Zefrank’s humor so much, because it’s like a Nat Geo documentary where the narrator can say LITERALLY anything without being fired while still sounding so professional. I don’t know how to better describe it, it’s just so damn funny to me with the way he talks

  3. Conmara says:

    When I lived in Brunei as a kid, I’d often see Proboscis Monkeys while on safari through the mangroves, but the funnier story comes from when I visited a zoo in Malaysia. Essentially, i brought a toy jaguar with me as I wandered around the place, and when I got to the Proboscis Monkey enclosure and propped myself up on the viewing platform, they caught sight of the jaguar and quite literally went ape shit, the males roaring and flopping their red chillies towards the jaguars direction. In hindsight, probably wasn’t that funny for them, but its hard to take them seriously when they were doing that.

  4. Edward Haas says:

    I would beg for more frequent True Facts, but I think the product quality is well worth waiting patiently for.

  5. FlyntofRWBY says:

    I’m so glad I found your channel all those months ago, cause whenever I need a good laugh, I just pull up your channel.

  6. Korey Hayden says:

    “True facts is not for children, nor is it for adults who don’t act like children”

    🤣🤣🤣 I love it!

  7. Irrazzo says:

    One question about the extremely snub-nosed monkeys: What do they do when it rains?
    Short Google answer: Apparently some species hide their face between their knees when it rains, locals say (see Rhinopithecus strykeri), or they have to sneeze.

  8. Heather _ says:

    So many quirky one-liners its hard to pick a favorite. Always a good day when Zefrank uploads.

  9. LBN & BN says:

    Been tapping on YouTube videos a lot today. News, history, commentary. philosophy, and finally it’s Paid Off- big time. Zefrank giving us biology as only he can .Yay!!!

  10. Hannah Esquenazi says:

    I love your videos! I study primates and I adore the primate videos you’ve made! I don’t know if you know this, but your videos are used in university classes because your videos are accurate, funny and incredibly useful! My teacher showed many of yours because of how good they are! I’m so happy you made another primate one! I can’t wait for the next one!

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