Giant tortoise migration in the Galápagos may be stymied by invasive trees

Spanish cedar trees create dense, brambly forests that tortoises avoid by shambling around them

A giant tortoise stands on soil in front of some trees.

Many Western Santa Cruz tortoises (one shown) in the Galápagos travel for weeks uphill during the dry season to feed on the vegetation that flourishes at higher elevations.

Rashid Cruz

After trudging upslope for weeks, a giant tortoise slows its hundreds of cumbersome kilograms to a stop. Dense woods defended by barbed wire–like blackberry bushes block its path.