It's extremely difficult to "wack" an injured animal on the head if they aren't near dead already. They are over flowing with adrenaline and trying to escape if they can, once they see some crazy human coming at them with an axe they go bezerk if they can. They may seem dormant but they'll give it all they have - usually at the last moment. Not to mention the huge traumatic event it is to actually kill some large creature with your own hands, and watch them die, most people would be haunted with guilt ridden memories. Then there's the real possibility of an injury - either getting kicked, gored or bitten by the animal. Or even worse stabbing yourself or hitting yourself with the axe if the animal flinches just before you make contact. Some guys may be able to dispatch an animal with a knife or axe but I would say most people couldn't. If you see an injured animal on the road the only option for a quick humane kill is with a firearm. The RCMP will do it but when they discharge their sidearm they must go through a $hitload of paperwork, the CO's are usually unavailable for a timely visit to each roadway episode. I spent too many years traveling the roads of BC late at night and early in the morning, I've had the unfortunate luck of hitting deer and one horse and been at the site of countless other one-sided collisions, I carry a 30-30 or a 410 with slugs in my vehicle for the exact purpose of roadside assistance ( I find a 22 is often too small to do the job on a large freaked out animal). I avoided witnesses when possible or ask the bystanders to walk away while I do what must be done, and I've never reported these incidents unless the authorities were already involved. I've never myself collected the meat but there have been times when others have. In my experience more animals are wounded and leave the roadside to suffer than actually stay at the scene. In most cases these collisions are/were unavoidable, but the advice of slowing down and being attentive at dawn and dusk is your best defense.