By that, i mean what would you consider the most difficult based on the animals intelligence? I have only hunted whitetails for 25 years, so I have no input. I have always read that a mature whitetail is the hardest to kill, I have killed them, but I have nothing to measure it against. Are things like moose, elk, bear,sheep etc, just as witty and difficult to kill? What is your experience on this? I don't mean difficult as in the terrain or accessibility, just based purely on the animals' smarts.

Well, they're not really big game, but for me it's the coyote. I rifle hunt them and feel they are about the smartest thing in the woods.

A good wife! Finally found one!

I would have to say that yotes are very clever. All the years and hours in the woods I have only seen one. I missed it. And I hunt in some very heavily populated areas....darn things are just flat slick, but i have never "hunted" for them.

MATURE whitetail on how tough it is to get close.
Coyotes also, since I have not got one with the trad bow.
Other big game as you say, tough due to terrain, etc....but a big whitetail is like a ghost.
No experience with mule deer yet.

Mature mule deer will give you a run for your money.  Yotes are tough as well.  White tails can be tough, or not, depending on where and how you hunt them.

Coyotes & Bobcats are very difficult to get a shot at, and by far the most difficult I have ever hunted.

Decoys are real handy. Not necessarily to draw them in, but to hold their attention while you draw & take the shot.

I would imagine that any mature animal is tough, else they wouldn't be mature huh? I know for me, whitetails are not that difficult most times, but a mature whitetail, doe or buck, seems to be a different ball game. Those old nanny does can be a legit challenge.

Perfect arrow flight

Mature whitetail, bobcat, and coyote. I've taken all three. Bobcat senses are unbelievable. Coyote are usually fast pace, and mature whitetail all I can say is, WELL! They are an intense chess match at times.

atatarpm, I agree!

Whitetail
Coyotes
Hogs
Mule deer
Elk

I'd rate coyotes toughest if not calling.  

I have not hunted big horns or goats, but have spent a lot of time around them, stalking and observing.  So far my experience would put them well below elk.  But, ask me again when I finally (if ever) draw a sheep tag!  

Turkeys

Basing my answer solely on mature animals of 5-6 years or older and strictly from an intelligence perspective.  

#1 Boar Hog
#2 Boar Hog (not a typo)
#3 Zebra
#4 Coyote

If you take away the age factor, a young hog or coyote don't make my top 10.  If you add environment, big prairie mule deer are way up there in my rankings.
 
Interesting thread here.

A big old mature whitetail doe.

The black bear is the most intelligent animal in north america.  That may not make them so hard to hunt but they surely are.  

I don't think there is any real answer to this question.  Coyotes are really tough to call in and kill with a trad bow.  As are turkeys but with a gun, there isn't much to either of them.  Mature bucks are way up there because they are so nocturnal.  Bears that have been hunted a lot are pretty well unkillable.  Sheep and Goats are super tough to hunt simply because of their environment.  

I don't have much respect for feral hogs but I'm sure that older ones become almost completely nocturnal.  Every critter has it's difficulties and I love all of em.

If a mature doe had the eyes of a turkey, and a turkey had the nose of a doe.. We'd all be starving

Trophy Blacktails, They don't pattern as easily as whitetails do and don't spot and stalk like you can a mulie. Don't call like elk or coyotes but in early rut you can rattle them. I have killed a couple of real nice ones but over the last twenty years made hunting them secondary to elk which are my favorite animal to hunt.

God bless, Steve

I forgot Coues deer.  I had my first experience with them this year.  I think if there were no such thing as water holes, nobody would ever kill one with trad gear.