In the case of wolves hunting elk, they will often target the oldest, sickest, or youngest animals in the herd. These animals are typically slower and weaker than the rest of the herd, making them easier for the wolves to catch. Additionally, these animals may be more likely to be carrying diseases or injuries, which can make them even more vulnerable to predation.
In some cases, wolves may also target the strongest or healthiest animals in a herd, particularly if the wolves are in a large pack and are able to take down a larger animal. However, this is less common, as the strongest animals are often more difficult to catch and kill.