Duckbill sleeper
Butis butis
- Usual depth0–3 m
- Water temperature22–30 °C
- Best monthsAugust, September, and October
- How commonOccasional
Photo credit: (c) coenobita, some rights reserved (CC BY), uploaded by coenobita · CC BY · iNaturalist
About this species
Butis butis, the crazy fish, duckbill sleeper, or upside-down sleeper, Ikan Ubi is a species of sleeper goby that are native to brackish and freshwater coastal habitats of the Indian Ocean and the western Pacific Ocean from the African coast to the islands of Fiji. They prefer well-vegetated waters and can frequently be found in mangrove swamps. They are small, drably-colored fish, reaching a maximum length of only 15 cm (5.9 in). They are predatory and are known for their behavior of swimming vertically – or even upside down – while hunting.
Text from the Wikipedia article “Crazy fish”, licensed CC BY-SA 4.0. Read the article
Where and when
Where it has been recorded
Worldwide
Loading the map
Best months
Worldwide (open data)
- January: 18 records
- February: 19 records
- March: 28 records
- April: 29 records
- May: 30 records
- June: 34 records
- July: 38 records
- August: 51 records
- September: 64 records
- October: 50 records
- November: 24 records
- December: 21 records
Depth and water temperature
Depth
Mostly recorded at 0–3 m · Deepest record: 10 m
Water temperature
Recorded in surface water of 22–30 °C
Photos
(c) coenobita, some rights reserved (CC BY), uploaded by coenobita · CC BY · iNaturalist 
(c) BEDO (Thailand), some rights reserved (CC BY-SA) · CC BY-SA · iNaturalist 
(c) BEDO (Thailand), some rights reserved (CC BY-SA) · CC BY-SA · iNaturalist 
(c) coenobita, some rights reserved (CC BY) · CC BY · iNaturalist 
(c) coenobita, some rights reserved (CC BY) · CC BY · iNaturalist 
(c) Nicola Crockford, some rights reserved (CC BY) · CC BY · iNaturalist
Names and classification
- English
- Duckbill sleeper, Crazy Fish, Crimsontip Gudgeon, Crimson-tipped Flathead-gudgeon, Crimson-tipped Flathead Gudgeon, Crimson-tipped Flathead-sleeper, Crimson-tipped flathead-sleeper, Duckbill sleeper, Crimson-tipped Gudgeon, duckbill sleeper, Flat-headed Gudgeon, Flat-head Gudgeon, Pointed Head Gudgeon, Upside Down Sleeper
Names in 3 more languages
- French
- Butis à épaulette noire, Cabot noir
- Japanese
- ノコギリハゼ
- Thai
- ปลาบู่เกล็ดแข็ง, ปลาบู่จาก
Other scientific names: Cheilodipterus butis, Eleotris butis, Elestris butis
Similar species
- Ambon Gudgeon
Butis amboinensis
Mud sleeperButis koilomatodon
- Northern mud gudgeon
Ophiocara porocephala
Chinese GudgeonBostrychus sinensis
Sources and credits
Names and taxonomy: WoRMS (CC BY 4.0) and the GBIF Backbone (CC BY 4.0). Photos: iNaturalist observers, each under the licence shown (CC0, CC BY or CC BY-SA).
- Depth, temperature, months and maps: records from OBIS and GBIF under CC0 or CC BY.
- Descriptions: Wikipedia, licensed CC BY-SA, each linked to its article.
- Conservation status as published by GBIF (IUCN Red List).
- 571 open-data records from 1922 to 2023.
- Species data updated October 26, 2026.
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