Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Early game blue READ THIS
As you probably noticed this build doesn't include smite and it is a jungle udyr build. Smite becomes completely obsolete late game and therefor I don't get it as a summoner skill. Therefor i prefer flash to opt into a blinking bear stance stun. Now if you have this full rune page the golem will die. However, many people will not have this rune page so I suggest having one of your team mates hit the golem 2-3 times for you.
This build does not include any defensive items (depending on the flow of the game you may opt out the bloodthirster and madreds into an early lantern and get a frozen heart) Getting regular boots and a vampiric scepter allows you to jungle much more efficiently but also be fast enough to gank without having to have ghost up. Frozen mallet makes udyr run and every good udyr should have it. Aside from all of that the rest is fairly self explanitory.
I go down the defensive tree a little differently than most Udyrs. I dip into the mana health regeneration because of the copious amounts of mana he gets late game. Ardor is uselss and there is nothing else that he really needs in any of the other trees.