Aug 17, 2019 | Updated: 07:24 AM EDT

Scientists Look Into Impacts of Mismatched Migration Route on Tortoises

Apr 20, 2019 02:21 PM EDT

dome-shelled Galápagos giant tortoise
(Photo : Mfield, Matthew Field)
A dome-shelled Galápagos giant tortoise, Chelonoidis nigra

Almost all wildlife are creatures of habit. In the case of the Gardeners of the Galapagos, adult tortoises spend the dry season in the higher regions that are engulfed in clouds allowing vegetation to grow.

The creatures would later trek back to the lower and relatively warm areas when the rainy season begins. By that time they return, there is already an abundance of nutritious vegetation that the tortoise can live on.

For so many years, in order to find the optimal food quality and temperatures, the tortoise has been taking the same migration route. To keep their energy levels high, the timing of their migration is essential. However, a tortoise's ability to migrate at the right time could be disrupted by climate change.

The journal Ecology of the Ecological Society of America published the research, where GPS was used to check the timing and patterns of the migration of tortoise over a number of years.

Guillaume Bastille-Rousseau, the lead author of the study explains that they have three main goals with their research. First was to determine if the tortoises adjusted their timing of migration to the current conditions of the environment. Second, if they did adjust, what are the clues that they used as a signal to adjust the timing of migration? Lastly, what are the implications to the energy of the tortoises as affected by the mistiming of migration?

Since many other migratory species operate the same way, the researchers are expecting the migrations to be tied with the current conditions of food and temperature.

Bastille-Rousseau explained that many animals such as ungulates would "surf the green wave" which means that they can track the current environmental conditions and migrate to this accordingly.

However, after much research, the scientists' expectations were not met and the tortoise was observed to migrate but not with the current environment the conditions.

The lead author explains that over the years, there is a mismatch in tortoise migration, where there is a fluctuation in the activity often by over two months.

This means that some tortoises may not be migrating just to forage. Female tortoises will have to make decisions to migrate related to nesting.

On the positive side, the mismatched timing of migration does not have any critical impact on the tortoises' health just yet. This might be because a tortoise can potentially live up to 100 years old. Giant tortoises are so resilient that they can live a year without eating while other species have to eat regularly just to survive.

Giant tortoises in the Galapagos are called Gardeners for a good reason. The creatures are responsible for seed dispersal for very long distances. Their migration has been key to the survival of many trees and plant species.

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