In a new study published this week in the Biotropica, researchers say that after a four year study, tracking the movement and foraging behavior of giant tortoises on the Galápagos Islands, it appears that they are seeking out sweeter treats of invasive flora and fruits instead of their local fare.

According to an April 7 edition of the Science Times, when researching a pair of the tortoises on the island of Santa Cruz, researchers were stunned to find that the tortoises there would trek up and down an extinct volcano now populated with humans in search of vegetation. And the question that arose was: why? If the species could live without food for such a long time, then why would they be seeking out food year-round.

“Why would a 500-pound animal that can fast for a year and that carries a heavy shell, haul itself up and down a volcano in search of food?” lead author of the study, Stephen Blake says. “Couldn’t it just wait out the dry season until better times came with the rains?”

Together with Blake, a researcher with Washington University, the pair of tortoises were followed and studied by Fredy Cabrera of the Charles Darwin Foundation in the Galápagos. The researchers outfitted the giant tortoises with GPS tracking devices to track their movements throughout the year, and after four years in search of an answer, they finally came to the conclusion that the slow-moving tortoises spent more time foraging non-native plant species which forced them to change their travel plans quite a bit.

With their diets now being comprised of more than half non-native flora, the tortoises are making an advantageous choice in seeking out fruits and greens that are higher in sugar content in that they will give the tortoises a richer diet, packed with more energy.