Did Newt Scamander capture his creatures against their will?

Question

If they liked being with him, then why would they try to escape all the time?

So you've never had a cat that loved you but wanted to poke your eyes out when you don't let it go play outside? — Gallifreyan, Commented Mar 17, 2017 at 16:25
I imagine they were for the most part captured against their will before Newt then tamed them. Humans help animals throughout the wild in reality but that still doesn't mean the animals go "Oh yes please I'd love to climb into your vehicle," etc. — ThruGog, Commented Mar 18, 2017 at 17:26
They're mostly wild animals that are unable to understand that he's captured them for their protection and survival. It doesn't imply he was mistreating them. — TheMathemagician, Commented Apr 4, 2017 at 10:37

SQB · Accepted Answer · 2017-07-02 07:37:09Z

The only beasts that escaped had a specific reason for leaving the suitcase.

(Almost) all of the beasts had a specific reason for leaving. Let's go through the list:

Niffler

This animal loves shiny things, and can't get enough of them. We see what Hagrid says:

"These're nifflers," said Hagrid, when the class had gathered around. "Yeh find 'em down mines mostly. They like sparkly stuff... There yeh go, look."
_{Harry Potter and the Goblet of Fire, chapter 28}

He only went out to collect more shiny stuff.

The Murtlap

This beast jumps out and attacks Jacob when he opens Newt's monstrous suitcase. It's only defending itself!

Erumpent

This is the rhino-like thingy. It was in heat - it was looking for a mate. That's why Jacob got in such big trouble when he gets doused with the pheromones.

Occamy

This is the blue snake-like animal.

You'll recall that the egg fell out of Newt's pocket - apparently this hatched out of it, so technically this was never in the suitcase.

Demiguise

This is the invisible creature, whose hair can be woven into Invisibility Cloaks.

Newt states why this one escaped - he learned from Newt, and was looking after the Occamy.

Billywig

This the blue bug. I'm not quite sure why it escaped. But it's a bug, and you know that bugs go everywhere...

Bowtruckle

This was just following Newt around, as he really really liked him :P. It wasn't trying to get away.

So:

_{All images taken from the Harry Potter Wiki.}