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

Doug Wechsler / Giant toad showing paratoid gland behind eye {Bufo marinus} Costa Rica Guanacaste NP,

Konrad Wothe / Red Wood Ant (Formica rufa) colony reacting in defensive behavior by spraying formic acid from a gland in rear of their abdomens, Sweden

Melvin Grey / Dik-dik (Madoqua saltiana) male with scent gland below eye, portrait. Manyara, Tanzania.

Charlie Summers / Pronghorn antelope (Antilocapra americana) rubbing his preorbital scent gland on a pine sapling, Custer State Park, South Dakota, USA.

Phil Savoie / European honey bee (Apis mellifera) worker at hive entrance emitting Nasonov pheromone from abdominal gland and fanning wings to spread the scent to returning workers, Monmouthshire, Wales, UK. Septem...

Milan Radisics / European beewolf (Philanthus triangulum) female grooming antennae. The antennae of these species has symbiotic bacteria living in the antennae gland. In females, these glands are involved in the prese...

Milan Radisics / European beewolf (Philanthus triangulum) grooming antennae. The antennae of these species has symbiotic bacteria living in the antennae gland. In females, these glands are involved in the preservation...

Chris Mattison / Cane toad (Rhinella marina) showing the massive parotoid (poison) gland behind its eye. Costa Rica. (Formerly Bufo marinus)

Tui De Roy / Little blue (White-flippered) penguin (Eudyptula minor albosignata) showing uropygial gland in tail, which produces oils for keeping feathers in good condition. Flea Bay, Banks Peninsula, South Island...

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.

Yashpal Rathore / Asiatic elephant (Elephas maximus), male with musth secretion from temporal gland near ear visible. Jim Corbett National Park, India.