This week's dirt: New study suggests birds with high color variation evolve more quickly, fossils belonging to giant panda ancestor found in Europe, scientists say lizard spit may curb our appetite, and a recent court ruling that pit bulls are “inherently dangerous” sparks debate.

Watch the full episode of the PBS Nature film which examines koala communication, vocalization, and social structure.

Watch the full episode of PBS Nature's Silence of the Bees, which looks at a recent phenomenon dubbed Colony Collapse Disorder (CCD).

This week's dirt: Scientists say dinosaur flatulence helped warm Earth, Orangutans get into iPads, DNA traces gray whale population decline back to whaling era, Cypress family of trees tells us quite a bit about evolution, Brazilian rainforest fungus takes over ant brains, and more.

An interview about koala communication, vocalization, and social structure with Dr. Bill Ellis, head of The University of Queensland's Koala Ecology Group.

Information about the eucalyptus leaf-eating marsupial Phascolarctos cinereus.

A fight erupts between two koalas after one of the males invades the other's territory.

A male koala roams the Australian suburbs in search of a mate to produce offspring.

A baby koala consumes his mother's pap, a secretion that will give the joey the bacteria needed to digest eucalyptus leaves.

Watch the full episode of the PBS Nature film, The White Lions— the story of two remarkable and extremely rare white lion cubs on their journey to adulthood.