Tony Wu / Humpback whale calf (Megaptera novaeangliae australis) female nudging her mother's mammary gland whilst trying to feed. Vava;u, Tonga, South Pacific.

Steve Downer / Male Three spined stickleback (Gasterosteus aculeatus) nudging female into nest to encourage egg laying, female exits and male enters nest to fertilise eggs, April. Captive.

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams, western Montana

Christophe Courteau / Male Burchell's zebra (Equus quagga burchellii) nudging the head of a dead pregnant female that died due to complications whilst giving birth, trying to wake her up. Etosha National Park, Namibia.

Denis-Huot / Masai Giraffe (Giraffa camelopardalis tippelskirchi) mother nudging newborn baby giraffe in rain. Masai-Mara game reserve, Kenya.

Jane Burton / Cavalier x Spitz puppy nudging blue tabby kitten and stepping on its paw, both 8 weeks old

Jane Burton / Brittany Spaniel pups, 6 weeks old, one nudging the other while it yawns

Tui De Roy / Gray Whale (Eschrichtius robustus) calf playfully nudging its mother's head, Baja California, Mexico

Suzi Eszterhas / Hippopotamus mother nudging young {Hippopotamus amphibius} Masai Mara Reserve, Kenya

Carol Walker / Mustang / Wild horse - stallion nudging colt, mare grazing, Wyoming, USA. Adobe

Konrad Wothe / African bush elephant (Loxodonta africana) mother and calf drinking and playing at small waterhole. The juvenile goes head-to-head with the adult, nudging and pushing against the its trunk. Then the a...

Tony Wu / Male Roundbelly cowfish (Lactoria diaphana) nipping and nudging female upward just prior to spawning. East China Sea, Kagoshima Prefecture, Japan.