Puddling Behavior of Butterflies

During the first 2 ½ days of our spring Great Smoky Mountains trip, I was perplexed to see Tiger Swallowtails and Spicebush Swallowtails flying down the Newfound Gap Road, the main road through the Park.  Every 5 minutes or so, one of these large butterflies would sail by. I simply could not figure out the attraction of all that pavement.   There was a hint two days into the trip when I spotted a Tiger Swallowtail flapping its way along the course of one of the many mountain streams common in the Smokies. 

The problem of the pavement-seeking butterflies was solved in our third day when we stopped at a stream at the base of the mountains so that Michael could photograph it.  Some fifty Tiger and Spicebush Swallowtails were roosting on the ground, crammed into a wet area by the side of the stream, all in the space of about a square foot.  What were they doing there?  It’s called “puddling,”and is a behavior observed in butterflies all over the world (we’ve also seen it on a trip to Vietnam years ago).  Just taking their usual diet of nectar, butterflies can’t get enough sodium and minerals to reproduce.  So in many butterflies the males flock to shallow puddles or moist soil and sip the nutrient-infused water they find there through their long, tubular proboscis.  They seem to like to do this in groups, and the sight of butterflies already puddling may attract other individuals.  And indeed, every few minutes, another butterfly would flap its way down the stream and land in the puddling area. Of course, this was quite a photo opportunity, and Michael took advantage of it immediately.  The butterflies must have been quite concentrated on their drinks, because we came quite close to them without scaring any off.

Further up the trail we came to a very shallow streamlet crossing the gravel, with a few individuals puddling.  There were lots of puddles and streams along the Newfound Gap Road, so I guess that was what all those road-hugging butterflies we saw were looking for.  Perhaps the road itself resembles a stream course for the butterflies, and cues them to search along it for puddles, as they certainly were doing along the stream where Michael photographed them.

Charlotte