Closeup shot of baby ducks swimming in the lake

Closeup shot of baby ducks swimming in the lake

Group of ducklings in a pond

Group of ducklings in a pond

Two baby ducks are swimming in the water

Two baby ducks are swimming in the water.

Two ducks are sitting in a pond

Two ducks are sitting in a pond, one of which is the only one that is the duck.

Cute ducklings sitting in the grass

Cute yellow ducklings sitting in the grass

Duckings in a wooden basket on a background of green grass

Yellow ducklings in a wooden basket on a background of green grass

Two ducks are sitting in a pond

Two ducks are sitting in a pond, one of which is the only one that is the duck.

The Pit Organs of Two Different Snakes

A python (top) and rattlesnake illustrating the positions of the pit organs. Arrows pointing to the pit organs are red; a black arrow points to the nostril.

The ability to sense infrared thermal radiation  evolved independently in three different groups of snakes, consisting of the families of Boidae (boas), Pythonidae (pythons), and the subfamily Crotalinae (pit vipers). What is commonly called a pit organ allows these animals to essentially "see" radiant heat at wavelengths between 5 and 30 μm. The more advanced infrared sense of pit vipers allows these animals to strike prey accurately even in the absence of light, and detect warm objects from several meters away. It was previously thought that the organs evolved primarily as prey detectors, but recent evidence suggests that it may also be used in thermoregulation and predator detection, making it a more general-purpose sensory organ than was supposed.

Two ducks are sitting in a pond

Two ducks are sitting in a pond, one of which is the only one that is the duck.

Canvasback two ducks in water

Notes: Red heads and black breast, with back and flanks of canvas white. Pretty straightforward. Females echo the pattern more palely.