The credits always state- 'no animal was harmed in this re-construction' so perhaps a tad over-sensitive?...
Doc Martin - 'The GP Always Rings Twice' Page 3
Dolphins.....I believe the Doc should befriend at least one pet dolphin and perhaps a Border Collie. Maybe he could even give the dog some sort of Scottish or Cornish doggy name like Scotty or Laddy....and perhaps he could call the dolphin something like Fin or Flippy... 
One of his own dogs was in the show -- I forget which one, seems he said it was a cocker spaniel. He's also said the scenes where he's mean to the dogs are hard to play. (Check You Tube.)
Anyway, it would be a lot trickier to actually run over a dog <shudder> than to use an elementary camera simulation.
Imagine how many takes the scene could have required. They'd need more dogs than they do babies playing James.