By sundown the towering cumulus were clouding the southwestern sky. Only a few minutes later the clouds were nearer, thunder was rumbling incessantly and bolts of lightning were spearing the heavens. We started eastward then decided to leave the pavement and drive along a sandy desert road. Good choice. A big boa, Boa constrictor ssp., had started to cross.



Although small for a boa (5 to 7 feet) and of dark coloration, this heavy-bodied snake was among our target species on this trip.

Brad and I were in southern Sonora, Mexico. The last time I had been there, about 4 years earlier, this northwestern Mexican state was in the midst of a several year drought and herp movement had been at a minimum. At that time, after seeing only a few leopard frogs and spiny-tailed iguanas, I quickly headed straight back to the border and spent a few days in Arizona before heading home.

But this time, not only was there promise of rain, there was ample evidence that the seasonal monsoons had arrived in the form of dampened earth, replete roadside ponds, chorusing anurans and the boa then on the road before us.

That evening it had poured for well over an hour and the herp activity was spectacular. Before returning to our motel we had seen and photographed more than 20 species. Among these were 4 boas of fair size.

What a difference the rains made.