Final answer:
The sight of male mule deer apparently caring for a fawn is unusual and there isn't well-known evidence of such behavior. Female mule deer typically raise the fawns, which are weaned around 3-4 months old and reach sexual maturity at about 18 months.
Step-by-step explanation:
The observation of male mule deer seemingly guarding a fawn without the presence of a female is indeed an unusual behavior, as typically, mule deer bucks do not play a role in the rearing of offspring. While there is no widely documented evidence to suggest that male deer take care of the offspring in the absence of a mother, occasional instances of such behavior may occur, especially if the bucks are related to the fawn and are providing temporary protection. The more common scenario is that mother deer is likely nearby but not visible at the time of observation.
According to National Deer Association, fawns are generally weaned by 3-4 months, which aligns with the age of the observed fawn, allowing it to potentially survive without nursing. This also indicates that the fawns are entering a more independent stage before reaching sexual maturity at around 18 months, as per the National Wildlife Federation. However, the presence of three male bucks with a fawn, without a visible female, remains an uncommon sight and possibly a specific case rather than a regular behavior in deer populations.