The Bullhorn Acacia

The Bullhorn Acacia is probably the last tree you’d want to meet in a dark alley. Growing up to 15 meters tall, it wields long, sharp, bullhorn-shaped thorns that serve up a nasty scratch if you venture too close. And if you think this plant sounds mean, you should meet its friends.  The leaves of the Bullhorn Acacia lack the bitter alkaloids that normally act as a deterrent to predators, so the tree enlists an army of aggressive Acacia Ants to serve as its defense system.  When the leaves are damaged, a chemical alarm is released, and the offending hungry insect or curious mammal is greeted by a rush of biting, stinging, and altogether angry ants.  Even sneaky vines and nearby plants that threaten their host’s access to light and water are systematically destroyed by these vigilant little creatures.  In return, the Bullhorn Acacia shelters its defenders in its large hollow thorns, and provides them with food in the form of carbohydrate-rich nectar and protein lipids, visible as orange-yellow granules on the leaf tips. This fierce looking and rather inhospitable tree turns out to be in a beautifully evolved, long-term symbiotic relationship: a good reminder to never judge a plant by its thorns.

Photo: Doug Taron

This entry was posted on Thursday, March 6th, 2014 at 8:00 am. It is filed under Costa Rica, Harmony Hotel, Nature. You can follow any responses to this entry through the RSS 2.0 feed.