There are nearly 800 species of acacia trees in the world, and most don’t have thorns. The famous "whistling thorn tree" and the Umbrella Thorn tree of Kenya are species of acacia that do have thorns, or spines.
Giraffes and other herbivores normally eat thorny acacia foliage, but leave the whistling thorn alone. Usually spines are no deterrent to giraffes. Their long tongues are adapted to strip the leaves from the branches despite the thorns.
The thorny acacia like dry and hot conditions. The thorns typically occur in pairs and are 5-8 centimetres (2-3 inches) long. Spines can be straight or curved depending on the species.
MARTINA NICOLLS is an international aid and development consultant, and the author of:- Similar But Different in the Animal Kingdom (2017), The Shortness of Life: A Mongolian Lament (2015), Liberia’s Deadest Ends (2012), Bardot’s Comet (2011), Kashmir on a Knife-Edge (2010) and The Sudan Curse (2009).