music: 50's Chart Toppers: Name The Artist: South of the Border (Down Mexico Way)?

Questions

There are ---------- that nest in trees. These creatures may spend their whole life without ever touching the ground.?

The mudskipper is a fish that can actually ----------?

The domestic cat is the only species able to hold its tail vertically while walking. Wild cats hold their tail horizontally, or tucked between their legs while ----------?

Sharks and rays are the only animals known to man that cannot succumb to cancer. Scientists believe this is related to the fact that they have no bone - only ----------?

There are more than 100 million ----------?