What don’t you already know about our local white-tailed deer? They spend their lunch time browsing on your decorative ornamentals and threaten to run impulsively in front of your car at night. Of course they are noble looking and as we come upon them on a trail they may first stare at our curious two legs but then the deer eventually turn and flee. The most conspicuous part of that act is the raised tail as the deer bound off and leave the scene. What is going on here? A common interpretation is that the raised white underside of the tail might serve as an alarm signal to alert other members of the herd and when disturbed, the signal helps to coordinate the group’s escape.  That may be true, but an alternative explanation is that the signal is not just for other deer but is directed to the predators as well.   In that latter case, the meaning of the signal could be “You’ve been detected and I’m fast and elusive and any effort to catch me would be unprofitable”.  If alerted deer are difficult to capture then it would be in the predator’s interest to ignore tail-flagging prey.  This is particularly useful for the deer in defense against ambush predators (mountain lions) that rely upon surprise rather than against other predators (such as wolves) that have the stamina to chase and run down prey.  

Of course, I doubt mountain lions have ever been on Long Island and we haven’t had a healthy supply of wolves here for about 300 years, but white-tailed deer are broadly and densely distributed throughout the United States (and my backyard)  and so the deer continue to find that adaptive white accessory very useful for whatever purposes it serves.