Galápagos tortoises have a unique, mutualistic relationship with a particular bird in their native land called the Darwin’s finch. The Galápagos tortoise solicits itself to the finches by displaying a particular posture when in the presence of these birds. During this interaction, the tortoise rises up as high as it can, extending its neck way up into the air, which then signals to the finch that it is safe to land on the tortoise and pick off ectoparasites. The tortoise holds this statuesque posture, termed the “finch response,” for a long time while the finch is hard at work. This outstretched position enables the birds to reach otherwise inaccessible spots on the tortoise’s body such as the neck, rear legs, and skin between plastron and carapace. We refer to this interaction as “symbiosis,” because the tortoise benefits from having the parasites removed, and the finch benefits by receiving a meal.
Galápagos tortoises at the San Diego Zoo also show this natural behavior, despite the lack of Darwin finches in San Diego. When a Galápagos tortoise notices a keeper approaching, it often stands up as high as possible and stretches its neck up in the air, standing perfectly still, appearing to be in a trance. In this case, the tortoise is trying to solicit a neck scratch from the keeper rather than parasite removal. Many of the tortoises will remain perfectly still while they are receiving a neck scratch and even continue their statuesque posture minutes after the keeper has left. We interpret the neck scratch as something desired, as several of the tortoises even seek out the keepers and follow us around until we agree to offer a satisfying scratch.
It is very tempting to Zoo visitors to also want to reach over and pet the Galápagos tortoises at the exhibit, especially when they witness this special bond the tortoises share with the keepers. At the new Fetter Family Galápagos Tortoise Exhibit, we have incorporated a “contact zone” in the upper yard of the enclosure. Within this contact zone, our guests get the unique opportunity to interact more closely with the tortoises when a keeper is present, including giving a neck rub to a tortoise, provided the animal is standing close enough to reach! We are also lucky to have a group of wonderful and dedicated volunteers who are happy to demonstrate to our guests how to safely pet the tortoises and can share other fun facts about the animals as well.
Jenna Ramsey is a senior keeper at the San Diego Zoo. Read her previous post, The Zoo’s Oldest Animal.