Will Burrard-Lucas / Black and white image of African elephant (Loxodonta africana) bull with extremely long tusks, Tsavo Conservation Area, Kenya. Editorial use only.
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Sebastian Kennerknecht / African Elephant (Loxodonta africana) bulls fighting, Kruger National Park, South Africa
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Sebastian Kennerknecht / American Bison (Bison bison) bull browsing in winter, Yellowstone National Park, Wyoming
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Mark Raycroft / Elk (Cervus elaphus) bull in river in mist, North America
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Mark Raycroft / Elk (Cervus elaphus) bulls fighting, North America
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Donald M. Jones / Elk (Cervus elaphus) bulls fighting, western Canada
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Donald M. Jones / Elk (Cervus elaphus) bull bugling, western Canada
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Donald M. Jones / Caribou (Rangifer tarandus) bull in tundra, Denali National Park, Alaska
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Donald M. Jones / American Bison (Bison bison) bull, National Bison Range, Montana
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Donald M. Jones / American Bison (Bison bison) bull, National Bison Range, Montana
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Donald M. Jones / American Bison (Bison bison) bull, National Bison Range, Montana
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Jack Dykinga / Ponderosa pine (Pinus ponderosa) growing in Grand Staircase-Escalante National Monument, Utah, October 2014.
