Bighorners of the Eastern Virgin

Bighorners of the Eastern Virgin is a side quest in the Fallout: New Vegas add-on, Honest Hearts.

Quick walkthrough
Talk to Follows-Chalk about local wildlife. After this he tells the Courier about a lost calf. The player must move through the canyons above the Dead Horses Camp and bring the lost calf back to its mother. This is done by feeding it banana yucca fruit, and leading it back to the mother bighorner, optionally not killing any other bighorners along the way. Speaking to Follows-Chalk again completes this quest.

Detailed walkthrough
Talking to Follows-Chalk about interesting wildlife in Zion will initiate this quest. After receiving it, head to Angel Cave and go up the slope to left of the camp as you look at it from the island. After maneuvering across the river over the three rock bridges, you will find the lost bighorner calf at the end of a narrow passage opposite the end of the last bridge.

Once you have found the lost calf, you may want to save your game. There are a number of random ways this quest (or just the optional part) can fail, so you may need to reload and try again. In order to complete the optional part of the quest just don't get too close to any of the other bighorners on your way there and they won't attack you. If you do get close, make sure you back away as soon as you can, as they won't attack if you move quickly. If the player, a companion, or any other NPC kills a bighorner, the optional part of the quest fails.

You will have to feed the lost calf a banana yucca fruit to get it to follow you. Be sure to have 3-4 banana yucca fruits on you (there are 3 banana yucca fruit plants along the route) as once the calf follows you a little ways he will get scared and you will have to feed him another to get him to follow you again. It can take 5-10 seconds after feeding for the calf to start following you again.

Return back across the rock bridges to the mountain bighorner mother. Choose to either return the calf or keep it and if the former, speak to Follows-Chalk to complete the quest and receive the reward. If you have had to kill one or two bighorners in the process of completing the quest, Follows-Chalk will still give the reward. He indicates that he understands but wishes they had not been killed.

Leave Follows-Chalk or Waking Cloud waiting near the Angel Cave as they can spook and start killing bighorners, which is 'blamed' on you.

Bugs

 * Sometimes the calf will become stuck in the last rock bridge you have to cross before reaching the bighorner mother. Reloading an old save and trying again has worked to circumvent this. Although if the calf gets stuck in the rock you can still return it to the bighorner mother.
 * When you walk past the first bighorner, the game may crash.
 * When you walk across the rock bridge, the game might crash.