There's the option of an external battery pack that can be kept warm while connected by wire to the camera; some cameras have this as an optional accessory, plus there are some independent brands of external power packs. This is what I was able to use while mushing. It allowed me to keep the battery pack close to my body for warmth, which allowed for more shooting time.
It's important to remember that you want to pay careful attention to your battery charge level while taking pictures. One way to corrupt the file system on a memory card is losing power while writing to it. While camera manufacturers try to safeguard writing to media, all bets are off when a battery is at its lowest charge level. If the camera runs out of juice at the critical time when the media card's file directory table is being written to, you could lose or damage some of the data on the card. So replace the battery when the camera warns you, and in cold weather, don't think you can take one more shot before swapping because the battery's power can diminish quite quickly.
Another suggestion is to practice limiting the use of the LCD. This can help reduce battery drain.
And while I'm on the subject of practicing, there are some other things to think about when you're heading out into cold weather.
Have you ever operated your camera while wearing heavy gloves or mittens? Go to an outdoor clothing store and bring along your camera. It also helps to try using your camera while wearing those gloves. If you practice in Florida where it's warm, you'll have a better chance for success in Yellowstone.
You might also want to make sure that you're familiar with your camera's exposure override settings. You'll be around a lot of snow, which can drive the metering system in any camera crazy. If you have the time, when you arrive at Yellowstone, try taking pictures outside right away before you head out on the trails, and see how the images look. You might want to adjust the exposure settings accordingly.
Be very careful of moving a cold camera into warm conditions. This can cause major problems because of condensation, both on the outside and inside of the camera. Keep the camera in a zipped camera case or put it in a plastic bag until it warms up.
Also, with any outdoor conditions, make sure you bring something you can use to clean your lens.