Whistling Thorn

Whistling thorn acacias are defended by ants, but the relationship is more complex than simple mutualism. Four different ant species compete for occupancy, and each provides different defense quality. Crematogaster mimosae is the most aggressive defender. Crematogaster sjostedti is a poor defender that castrates the tree by destroying flowers. The tree doesn't choose its partner - ant competition determines which species occupies each tree.

The 'whistle' comes from holes that ants chew in swollen thorn bases. Wind blowing over these holes produces an eerie whistling sound audible across the savanna. The sound might deter browsers, but it's primarily a byproduct of ant architecture. The ants modify their housing in ways that accidentally affect tree defense.

Research shows that when large herbivores (elephants, giraffes) are excluded, trees reduce their investment in ant housing and food rewards. With herbivory pressure removed, maintaining the ant army becomes all cost and no benefit. Trees can dial up or down their investment in defense based on actual threat levels - the mutualism is conditional, not obligate.

The business insight is that defense partnerships require ongoing justification. When threats decrease, maintaining expensive defensive partnerships becomes waste. Whistling thorn teaches that the right level of defense investment depends on actual threat environment - and that monitoring threats should drive defense budgets, not legacy commitments or worst-case scenarios.