Ammonite / Earthworm (Lumbricus terrestris) moving through leaf litter, footage taken using an endoscopic camera in controlled conditions, Bristol, England, UK, June.
Tony Wu / Korean sandlance (Hypoptychus dybowskii) egg clusters on Sargassum (Sargassum horneri). Fish produce sticky secretion in kidneys that adheres eggs to Sargassum. Hokkaido, Japan. May.
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Eric Baccega / Common hippopotamus (Hippopotamus amphibius). Skin with secretion of blood sweat, a red substance that acts as natural sunscreen. Beauval Zoo Parc, France. Captive.
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Eric Baccega / Common hippopotamus (Hippopotamus amphibius). Skin with secretion of blood sweat, a red substance that acts as natural sunscreen. Beauval Zoo Parc, France. Captive.
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Eric Baccega / Common hippopotamus (Hippopotamus amphibius), close up of eye. Skin spotted with secretion of blood sweat, a red substance that acts as natural sunscreen. Beauval Zoo Parc, France. Captive.
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Eric Baccega / Common hippopotamus (Hippopotamus amphibius), close up of eye. Skin spotted with secretion of blood sweat, a red substance that acts as natural sunscreen. Beauval Zoo Parc, France. Captive.
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Yashpal Rathore / Asiatic elephant (Elephas maximus) male in musth grazing, with secretion of musth from temporal gland near ear visible. Jim Corbett National Park, India.
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Yashpal Rathore / Asiatic elephant (Elephas maximus), male with musth secretion from temporal gland near ear visible. Jim Corbett National Park, India.
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Ammonite / Earthworm (Lumbricus terrestris) secreting lubricating mucus before moving away from camera, footage taken using an endoscopic camera in controlled conditions, Bristol, England, UK, June.
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Charlie Summers / African elephant (Loxodonta africana), close up of face showing patch of secreted hormone, a sign that the animal is in musth, Ngorongoro Crater, Tanzania, East Africa
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Charlie Summers / African elephant (Loxodonta africana) close up of face showing a patch of secreted hormone, a sign that the animal is in musth, Ngorongoro Crater, Tanzania