This is another great nature game. Have all the girls face you in a circle. Talk and snap your fingers rapidly while facing them. Have them cup their hands behind their ears, which effectively triples the surface of their ears.
They will notice a drop in pitch (that is the sounds will get deeper) in the sounds of both your voice and the snapping of your fingers.
Give a blindfold to each pair of girls. Have one girl tie on the blindfold and have her turn around three times or so, so that she isn't aware of whether she is facing towards or away from her partner.
Then she cups her hands behind her ears - "deer's ears'.
Her partner - the 'predator' - is to sneak up on her through the leaves on the forest floor. To do this quietly, she needs to concentrate on balancing on her right foot while she lifts her left foot up, so that she doesn't scuff her heel through the leaves and rustle them. Then she puts the ball of her foot down, slowly and lets her weight settle. Then she slowly puts her heel down.
If the 'deer' is facing away from her, the 'predator' has a much better chance of sneaking up and touching her. If the 'deer' happens to be facing her, the 'predator' is going to have a much tougher time of catching her unawares.
In the wild, predators don't tend to hunt in the rain, they can't hear over the sound of the rain itself. But while the leaves are wet, everyone is out there. The prey can move silently and so can the predators.
Do watch your tendency to call all the animals 'he'. Red squirrels for instance are more like 70% female than even 50%. Gender bias shows up in the oddest spots!!!! (Cows are she!! Bulls are he.)