Richard Du Toit / Two Blackbacked jackals (Canis mesomelas) staring at each other, Addo Elephant National Park, Eastern Cape Province, South Africa.

Richard Du Toit / Two Gemsbok (Oryx gazella) running in dry grassland, Kgalagadi Transfrontier Park, Northern Cape Province, South Africa.

Richard Du Toit / Two Amethyst sunbirds (Chalcomitra amethystina) perched face to face on flower stem, Garden Route, Western Cape Province, South Africa.

Richard Du Toit / Kori bustard (Ardeotis kori) with two chicks in grassland, Kgalagadi Transfrontier Park, Northern Cape Province, South Africa.

Roman Willi / Mason bees (Osmia bicornis) pair mating, Lucerne, Switzerland. April. Focus stacked Image.

Roman Willi / House sparrow (Passer domesticus) fledgling begging for food from adult male, Lucerne, Switzerland. May.

Roman Willi / Hourglass tree frogs (Dendropsophus ebraccatuus) pair in amplexus, Limon, Costa Rica. Focus stacked image.

Roman Willi / Midwife toads (Alytes obstetricans) pair, female transferring eggs to the male, Lucerne, Switzerland. April.

Roman Willi / Midwife toads (Alytes obstetricans) pair, female transferring eggs to the male, Lucerne, Switzerland. April.

Roman Willi / Common grassfrogs (Rana temporaria) pair in amplexus, Lucerne, Switzerland. March.

Roman Willi / Red-eyed tree frogs (Agalychnis callidryas) pair in amplexus, Limon, Costa Rica. Focus stacked image.

Joel Sartore / Photo Ark / Variegate darters (Etheostoma variatum) pair, portrait, from the Lavisa Fork River, Virginia. Female, top. Photographed at the Aquatic Wildlife Conservation Center, Virginia, USA. Captive.