Scientists have found that invasive species make up approximately half of a Galapagos Tortoise’s diet – with the tortoises going out of the way to forage for foreign plants.
Giant tortoises thrive on tastier invasive plant species
Stephen Blake from the Washington University in St Louis and Fredy Cabrera from the Charles Darwin Foundation published the results of their research in the March edition of journal Biotropica. By studying the eating patterns of giant tortoises on Santa Cruz Island, they found that the tortoises migrate from arid lowlands to the island’s humid highlands in search of food, spending prolonged periods of time in the agricultural highlands where invasive species are widespread. The reason? Foreign plants are tastier and more nutritious: Blake explains that an endemic guava plant “produces small fruits, containing large seeds and a small amount of relatively bitter pulp in a thick exocarp. By contrast, the introduced guava, Psidium guajava, is large, containing abundant sweet pulp in a thin pliable exocarp.” The study also found that the consumption of invasive plants had no negative effect on the tortoises and could even improve their health.
The findings are unusual, given that the effects of invasive species on Galapagos wildlife are largely negative. Though the number of tortoises is not great enough for this feeding pattern to have a significant impact on the spread of invasive plant species, Blake explains that it is fortunate that “tortoise conservation seems to be compatible with the presence of some introduced species”.
Photo Credit: Flickr – Amaury Laporte