The pressure to keep billions of humans fed can have a transformative impact on amimal populations. Overharvesting that targets the largest animals can result in reduction of the average size of species, as seen in Caribbean conch snails. And sport-fishing pressure on large mouth bass can winnow out the most agressive in the gene pool, resulting in a "lazier," more passive remnant population. Martha Foley and Curt Stager talk about the human factor in animal evolution.

Keratin, the substance wool, hair, and feathers are made from, makes a pretty thin diet, but the clothes moth has been dogging humanity's closets and drawers for hundreds of years, unravelling the work of generations of knitters and weavers to feed its larvae.

Of all the places a cat can hang out, why do do many of them want to hang out in boxes? According to researchers, cats that spend time in close confines are measurably less stressed than those remaining in the open. As Curt Stager tells Martha Foley, it's not just house cats who feel this way.

Martha Foley has never succeeded in keeping a nature journal long-term, but Curt Stager finds them invaluable in his work. He records his observations on paper, but also finds great data through researching the journals of past observers, from Samuel de Champlain to Thomas Jefferson, to ordinary little-known North Country folk. His hint - always put it on paper. Whatever became of all that stuff on your floppy diskettes?

Humans, birds, and whales are not the only creatures who can sing. Martha Foley and Dr. Curt Stager discuss recent research that uncovered bats also use learned songs to communicate.

We tend to think that dogs do this, and that cats do that. We think animal species have a recognizable set of behaviors that define the nature of their kind. But what about individual animals? Does each have something we could understand as a unique personality?

The complex web of species interaction is full of odd associations. Stocking a lake with fish cuts down on dragonflies, which helps pollinators, which helps the flowers bloom. Or it can cut down on amphibians such as newts, which is bad for garter snakes. Invasive flowering purple loosestrife is good for insects and birds that feed on them, but hard on plankton, which is at the bottom of the food chain for everything. Martha Foley and Curt Stager look an unintended consequences of human actions in nature.

Martha Foley? - not a fan of bugs. And Curt Stager took a course on them to steady his own reactions. The Natural Selections team looks at the outliers on the spectrum, the largest and smallest of critters with too many legs. New Zealand's weta makes a real handful. The fairy fly is nearly invisible. Some prehistoric dragonflies were big enough to make off with the cat.

All creatures breathe in some fashion, but how the job gets done has changed from fish to amphibian to reptile to mammal. Curt Stager and Martha Foley chart the evolution of animal respiration.

The ubiquitous bird of cities and towns was designed for a different environment. The pigeon's distinctive style of flight is adapted for maneuverability in tight places - near vertical takeoffs and quick changes of direction. This adaptation to cliff and mountainside environments serves them well among our urban cliff dwellings. Curt Stager and Martha Foley discuss.