Risso's Dolphinハナゴンドウ

Grampus griseusLC— Least Concern

Risso's dolphin is a large, robust dolphin found in temperate and tropical waters worldwide, easily recognized by its blunt, bulbous head and body covered in white scars accumulated over a lifetime of social interactions and squid hunting. A specialized squid eater that dives up to 600 m and forages mainly at night, it is classified as Least Concern by the IUCN despite localized threats from fishing bycatch and pollution.

Risso's Dolphin (reference photo)
Photo: OpenCage (Wikimedia Commons) / CC BY-SA 2.5 / Source / cropped

Species Data

Classification
Artiodactyla / Delphinidae Source
Distribution
Found nearly worldwide across the Indian, Pacific, and Atlantic Oceans, as well as the Mediterranean, North, Red, and Baltic Seas, but absent from the Black Sea. Source

Did You Know?

  • Linear scars from social interactions and squid battles accumulate over a lifetime and turn white, eventually covering much of the body and making older individuals appear almost entirely white. Source
  • Risso's dolphins have only two to seven pairs of teeth, all in the lower jaw, which are thought to function mainly as display weapons in social interactions rather than for feeding. Source
  • They have been recorded diving to depths of 600 m in pursuit of squid, and their tall dorsal fin can lead to them being mistaken for young or female orcas. Source

Where to See This Species

8 facilities · 0 individuals

アドベンチャーワールド (Adobencha World)WakayamaOpened in 1978

アドベンチャーワールドのWikipedia記事に飼育種として記載 Source

マリンワールド海の中道 (Marin World Uminonakamichi)FukuokaJR博多駅から鹿児島本線で香椎駅まで11分、JR香椎線（西戸崎行き）に乗り換え「海ノ中道駅」まで20分。

マリンワールド海の中道のWikipedia記事に飼育種として記載 Source

下田海中水族館 (Shimodakaichuu Suizokukan)ShizuokaOpened in 1967

下田海中水族館のWikipedia記事に飼育種として記載 Source

江の島水族館 (Enoshima Suizokukan)KanagawaOpened in 1954

江の島水族館のWikipedia記事に飼育種として記載 Source

新江ノ島水族館 (Shinenoshima Suizokukan)KanagawaOpened in 2004

新江ノ島水族館のWikipedia記事に飼育種として記載 Source

南知多ビーチランド (Minamichitabichi Land)AichiOpened in 1980

南知多ビーチランドのWikipedia記事に飼育種として記載 Source

箱根園水族館 (Hakoneen Suizokukan)Kanagawa

箱根園水族館のWikipedia記事に飼育種として記載 Source

Kamogawa Sea WorldChiba東京駅から特急わかしおで約2時間、JR「安房鴨川」駅下車後、無料送迎バス（西口バス停発）で約10分。

ハナゴンドウのWikipedia記事に飼育施設として記載 Source

Conservation Story

Conservation Status

IUCNではLC（低懸念）です。広域に分布しますが、海洋環境の変化と混獲への注意が必要です。

Habitat

世界の温帯・熱帯の沖合、とくに深い海域。

Threats

  • 漁網への混獲
  • 海洋汚染
  • 海中騒音

Conservation & Breeding Efforts

  • 分布と個体群の調査
  • 混獲の記録と低減
  • 鯨類の生態を伝える教育展示

Sources

ja.wikipedia.org

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FAQ

Why are Risso's dolphins so scarred and pale?
Linear scars from social interactions with other dolphins and from grappling with squid accumulate over a lifetime and turn white, so older individuals often appear almost entirely white. Source
What do Risso's dolphins eat?
They feed almost exclusively on squid, hunting mostly at night and diving as deep as 600 m in pursuit of prey, with some populations also taking octopus. Source
How many teeth do Risso's dolphins have?
Just two to seven pairs, and all of them are in the lower jaw only. These teeth appear to function mainly as display weapons for social interactions rather than for capturing food. Source

Source: ja.wikipedia.org