Endangered Galapagos Tortoises Thrive on Invasive Plants

It turns out that invasive plants may be helping endangered tortoises. Scientists have discovered that two subspecies of endangered tortoise have diets that are halfway made up of introduced species of plants.

The iconic giant tortoises of the Galapagos Islands are endangered. In fact, giant tortoises only thrive in two locations: the Aldabra Atoll in the Indian Ocean and the Galapagos Archipelago.

Since the 1930s, invasive plants have increased on the Galapagos Islands. Introduced plants increased as native highland vegetation was cleared for agriculture. But it seems as if the tortoises prefer this introduced vegetation over native plants.

"Biodiversity conservation is a huge problem confronting managers on the Galapagos Islands," said Stephen Blake, one of the researchers, in a news release. "Eradicating the more than 750 species of invasive plants is all but impossible, and even control is difficult. Fortunately, tortoise conservation seems to be compatible with the presence of some introduced species."

In fact, the researchers found that the tortoises spent more time browsing on introduced species of plants than on native ones."

We really weren't that surprised," said Blake. "Consider it from a tortoise's point of view. The native guava, for example, produces small fruits containing large seeds and a small amount of relatively bitter pulp in a thick skin. The introduced guava is large and contains abundant sweet pulp in a thin, pliable skin."

The findings show that invasive species of plants aren't always bad-at least in this case. Instead, the plants are helping feed these endangered tortoises.

The findings are published in the journal Biotropica.

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