It's a good idea to have a long range telephoto or telephoto zoom for wildlife that extends into the 200-400 range, especially on the boat portion of the tour. VR (Vibration Reduction) is handy, as is a fast lens (i.e. - Anything wider than f/4 - recommended f/2.8), as you want to be equipped to get sharp shots on cloudy days. As for your time on the trail at the glacier be sure to bring your macro if you like shooting close up, or your wide angle if you enjoy taking landscape photos. If all you have is a single, all in one lens (i.e. - 28mm -300mm), you'll be just fine with that. Remember it's how you use what you've got!