11年後のレッドリスト｜カッショクハイエナ：迫害は続き、希望も芽吹く【IUCNレッドリスト比較】

Hey everyone, Keijin here.

Today, I want to share a thought with you: what if the brown hyena (Parahyaena brunnea) is actually the “ultimate medical data bank,” evolved to survive the harshest environments on Earth?

Back in a 2014 encyclopedia, the brown hyena was listed as “NT: Near Threatened”—mostly because they were constantly being shot, poisoned, caught in traps, or hunted down by dogs.

Fast forward to the IUCN Red List as of 2026, and their status remains unchanged at “NT: Near Threatened.” However, recently in major habitats like Namibia, we’re seeing some promising steps: farmers and conservation groups are starting to form more advanced, cooperative agreements.

So right now, I feel like the brown hyena exists in this fragile balance—a state where “persecution continues, but hope is starting to take root.”

This is a quick read, taking about 5 minutes. I hope you’ll stick around to the end.

特徴

• 見た目：長くて粗い体毛（暗褐色〜こげ茶）と、立ち耳・背中のたてがみ状の毛が目立つ。脚には淡い縞が入ることがある
• 暮らし方：夜行性で、人目につきにくい（調査・個体数把握が難しい種とされる）
• 食性：腐肉食（スカベンジャー）的な比重が高く、獲物を「狩る」より“見つけて食べる”場面が多い。小動物や昆虫、果実なども利用する
• 社会性：単独で動く時間が多い一方、血縁中心のクラン（群れ）と共同のねぐら（デン）をもつ社会構造が知られる
• 希少性：現生ハイエナ類の中では希少とされ、世界個体群は「成熟個体で1万未満」といった推定が引用されることが多い

生態など

• 生息環境：乾燥地〜半乾燥地に適応し、降水が少ない地域でも行動できる（広い行動圏を使う例も報告される）
• ふえ方（繁殖）：哺乳類なので胎生。子は巣穴（デン）で育つ。地域によって繁殖成功や子の生残は環境条件の影響を受ける
• 役割：死骸を処理することで環境を“掃除”する側面があり、生態系の物質循環に関わる
• 脅威：家畜被害の誤解・報復による殺傷（罠・銃・毒餌など）、生息地の改変、道路での死亡、餌資源の変化（獣害対策や衛生管理の影響）などが複合的に効く
• 保全の方向性：農地・牧場地帯での共存（被害実態の可視化、誤解の低減、毒餌や罠の抑制）、保護区ネットワークと土地利用に応じた地域別の対策、個体群モニタリングの改善が重要テーマとして挙げられる

出典

• 学術論文（保全・分布の整理：Koedoe 2017）
• Mammal Diversity Database（分類・タクソン情報）
• IUCN評価（2015）の引用を含むPDF（米国規制文書添付）
• Animal Diversity Web（Brown hyena / Hyaena brunnea の解説）
• 学術論文（個体数推定・IUCN区分への言及：Westbury et al. 2018, PMC）

出典

• IUCN Species of the Day（Brown Hyaena の概説PDF）
• Carnivore Red Data Book（Brown Hyaena 種アカウントPDF）
• SANBI Species Status（Parahyaena brunnea 地域評価ページ）
• IUCN Red List of Threatened Species（Parahyaena brunnea 抜粋PDFとして流通）
• South African Journal of Science（brown hyena の個体数推定と IUCN 分類の記述を含む）

出典

• Namibia Carnivore Red Data Book（カッショクハイエナ種アカウントPDF）
• Koedoe (2017) Winterbach et al.（ボツワナの分布・農地での保全と連結性）
• SANBI Species Status: Brown Hyaena assessment（南ア評価・脅威と保全提案）
• U.S. Federal Register (2001-05-18)（CITES附属書IIからの削除が採択された記録）
• IUCN/SSC Hyaena Specialist Group Action Plan (1998)（ハイエナ類の保全行動計画PDF）

Me: So, what did you think after reading this?

Questioner: It says here that “by quickly cleaning up animal carcasses, they prevent the spread of infectious diseases (like viral outbreaks) in the savanna and keep the ecosystem balanced.” But that made me wonder—are brown hyenas themselves safe from those diseases? And don’t they get sick from eating rotten meat?

Me: That’s a great point. Now that you mention it, I’m curious too. Let me look into it.

出典

• Development of a hyena immunology toolbox（炭疽・狂犬病などへの耐性言及、免疫研究）
• The Intestinal Eukaryotic and Bacterial Biome of Spotted Hyenas（腸内生物叢の多様性・要因）
• Human bone marrow as a tissue in post-mortem microbiology（骨髄が骨により保護されやすいという整理）
• Markedly Elevated Antibody Responses in Wild versus Captive Spotted Hyenas（野生個体の抗体指標など）
• A neo-taphonomic approach to human campsites modified by scavengers（スカベンジャーの骨髄選好の記述）
• Mucosal immune responses and intestinal microbiome associations in wild spotted hyenas（粘膜免疫と腸内細菌叢の関連）
• Regular exposure to rabies virus and lack of symptomatic disease in Serengeti spotted hyenas（狂犬病曝露と症候性の欠如）
• First bone-cracking dog coprolites provide new insight into bone consumption（ハイエナ類の骨摂取・消化と排泄物の炭酸塩言及）
• The giant hyena Pachycrocuta brevirostris: Modelling the bone-cracking behavior of an extinct carnivore（骨髄量の多い骨の優先破砕）
• The Evolution of Stomach Acidity and Its Relevance to the Human Microbiome（胃内pHデータ整理、ハイエナの直接pHデータが乏しい旨）
• Bacterial Community Succession, Transmigration, and Differential Gene Transcription in a Controlled Vertebrate Decomposition Model（分解過程で骨髄も微生物により変化し得る枠組み）

Questioner: So their stomach acid is like the xenomorph blood from the Alien movies—it just dissolves absolutely everything! But if we put it like that, do you think people will start picking on them again, labeling them as “alien monsters”?

Me: Yeah, I can definitely see that happening. Even in human society, childhood nicknames and reputations are notoriously hard to shake off. You could move away, completely change your surroundings, and yet the second you go back to your hometown and run into old friends, they see you exactly the same way they used to.

But putting that aside for a moment, what really caught my attention was this whole idea of an “ecological barrier” operating inside the stomachs and intestines of brown hyenas. It sounds like the scientific community is still debating the exact mechanics, but I’m going to dig around and see if there’s any research looking into whether this kind of barrier could actually be useful for humans in the future.

出典

• 狂犬病曝露と症状・生存（PNAS 2001）
• 斑点ハイエナTLR1–10（Vet Res Commun 2014）
• 斑点ハイエナの粘膜免疫と腸内細菌叢（Communications Biology 2025）
• 抗菌ペプチド総説（Cathelicidins: family of antimicrobial peptides. A review）
• 斑点ハイエナ免疫ツール整備（Development of a hyena immunology toolbox）
• ハイエナ科ゲノムと抗菌ペプチド候補（Genome-Wide Analyses… Striped hyena）
• IUCN/創薬背景（抗菌ペプチド総説：Cathelicidins— a rich seam of antimicrobial peptides…）

Questioner: So hyenas aren’t just the savanna’s cleanup crew; they’re more like the “ultimate medical data bank that evolved to survive the harshest environments on Earth.” That means persecuting them to the point of extinction is basically as serious as humanity throwing away our future miracle cures, right?

Me: Speaking of which, the giant panda is super interesting too, though they went in the exact opposite direction of the brown hyena by specializing in a very unique herbivore diet.

People say a panda’s gut isn’t actually optimized for breaking down cellulose like typical herbivores. Overall, their microbiome is much closer to that of a bear (leaning toward carnivore, just like the hyena).

So instead of efficiently breaking things down to extract nutrients, they just accept their poor digestion, pick bamboo, and eat an absolutely ridiculous amount of it.

Although, researchers are still piecing together exactly how much their gut bacteria helps them compensate for this massive inefficiency.

Anyway, whether hyenas and pandas are willingly hopping onto the examination table for the sake of human research is another story, but hopefully, this gives the brown hyena a bit of a PR boost.

When you really think about it, every creature on Earth has some kind of role to play. There’s no such thing as a useless species. The world keeps turning by maintaining this razor-thin, yet incredibly miraculous balance.

But right now, for the convenience of just one single species, we’re impacting the planet so much that we’re actually altering the climate. The Earth keeps spinning, sure, but we’re driving one precious species after another to the brink of extinction.

So what’s the root cause of all this? I think about it every single day, and I always come back to the idea that it’s the result of us constantly viewing things through the lens of “winning and losing” or “good and evil.”

That’s why I feel like the closest thing we have to a solution moving forward is to focus on “co-prosperity”—living alongside all forms of life, whether it’s microbes, animals, or trees.

Also, and this is something I’ve started feeling recently: maybe the very idea of trying to replace the massive energy output of fossil fuels with an equal amount of alternative energy is fundamentally flawed.

So rather than just “saving energy,” maybe we need to dig deeper, remember what life was like before the Industrial Revolution, and rebuild from there… I’ve toyed with that idea, but then you immediately hit a wall: “What are we going to do with 8 billion people?”

Modern agriculture is practically built on chemical fertilizers made from fossil fuels and tractors that run on diesel. If we just ditch fossil fuels and revert to old-school farming, we’re talking about billions of people starving to death starting tomorrow.

But even knowing that, I just can’t bring myself to completely throw away that line of thinking.

How did you feel reading this?
I would be incredibly happy to hear your thoughts in the comments.

Thank you so much for your valuable 5 minutes. I pray that those 5 minutes will reach the Brown Hyaena.

Keijin