I read this old book when I was about 12 about a man who was least likely to survive but was stranded on an alien planet and had to copy the aliens who lived there to figure it out. The aliens were humanoid with large pot bellies and skinny legs I believe. He couldn't find water and watched them dig a little in the dirt and pull out plants that were full of water.
He also figured out that the aliens had sex to create anything they wanted, they just had to visualize it very detailed while it gestated. He ended up using that technique to get off the planet I think.
It was a long time ago that I read this, so I don't remember the details, but I think it was called something like "Panic Signal" or something like that. Amazon didn't turn up anything.