Tusks are elongated incisor teeth that continue to grow. Although tusks are present at birth, the "baby tusks" fall out after a year, and permanent ones replace them. This image is from Mind of a Giant.
Australia: Male red kangaroos (Macropus rufus) fighting. Male reproductive success can be linked to fighting ability. Fighting helps establish dominancy in the mob and thus gain access to the females (and pass on their genes). This image is from Moody Beasts.
America: Butterfly emerging from its cocoon. Monarch butterflies (Danaus plexippus) migrate to warmer climates and due to their short life cycle, they rely on a hormone to suspend its life in a state of youth â until it arrives at its destination. This image is from Moody Beasts.
Australia: A close shot of a rattle snake (crotalus) and jointed rattles on the tail. During a stressful situation, the snake's corticosterone levels (stress hormone) elevate resulting in a reductions in testosterone. This can lead to a reduction in aggressive behaviour. The rattle snake will rattle his tail when threatened and scare away any possible danger. This image is from Moody Beasts.