We have blackberry bushes here probably the same stuff as rasberry. Seattle is very wet. The stuff grows so thick that only rabbits and rats are able to penetrate inplaces. I shot a pheasant last November and it dropped in that stuff. My dog couldn't get it. She was actuallystepping on the bushes climbing trying to reach it.

I've seen small springers slip in there when they can. The holes are usually the size of a football.

Now, Hawai'i had some Keawi trees (related to Mesque). Dogs can go in but I wouldn't try it. Thornstypically grow up to an inch long. There's been times when stepping on them, they drew blood thru the soles of my boots.