I remember having a short exchange with one of my editors early in the drafting process of Without Warning, a brief conversation about exactly who got zapped. It was important, because there does exist a brief one par explanation of the Wave, locked away in a secure and secret location, written before the book was composed, explaining what the Wave is, what it does, and why.
The book, however, remains deliberately vague, because most of it is concerned with the character's immediate reaction to the Disappearance. WW is much less about the Wave than about crisis management. Investigating the phenomenon comes later. And directly investigating the affected areas has to wait until the Wave was gone.
So, allow me to confirm a small spoiler from After America, by way of explanation. And this is Canon.
The Wave took primates.
It killed or temporarily incapacitated vast numbers of verterbrates, but only the primates were Taken.
Birds, btw, instinctively fly away from the Wave, unless they are in it, in which case they get knocked out of the sky, either dead or unconscious.
There is a character in WW, Stavros, who says he can't see any animals moving around in the drove feed from Cuba. But that's just Stavros thinking aloud under pressure. In these books, just because someone says something, that don't make it so.
“No." said Melton. "This is nothing to do with them (al Qaeda). Unless it was merciful fucking Allah, of course, like Saddam is telling everyone. But nobody knows. Some kinda weird energy bubble or something. Seems to have zapped all the primates inside its boundary. Some of them gone. Some of them just sort turned into mush.”
“Primates?” Euler looked aghast. “And mush?”
“Just before I took off, that was the latest on CNN. Some Japanese blogger checking web cams of the San Diego zoo noticed all the monkeys were gone. Didn’t take long to work out from there.”
There is some later discussion of the 'spinal chord' effect. But it's specualtion.
So, a new topic.
To federate with what's left of Canada or not?