Yes - along with around 52% of other plants in the average British garden. Mostly they need to eat them though for them to be toxic, and 'toxic' covers anything from mild stomach upset or sore mouth right through to death and everything in between.

Only if they eat them, Eustace, which is generally unlikely to happen.

Especially with Cordyline, the leaves are pretty tough, can't imagine any animal chewing them for long, never mind eating them.