Why do giant tortoises migrate? We spoke to Courtney Pike at the Charles Darwin Foundation about her work to understand and protect the ancient tortoise highways of Galapagos.
Communications and Education Officer
Galapagos giant tortoises embark on seasonal migrations between the humid highlands and arid lowlands. But these routes aren’t random, they are caved out over many years, making them vital for tortoise conservation.
We spoke to Courtney Pike, senior researcher at the Charles Darwin Foundation and leader of the Galapagos Tortoise Movement Ecology Programme, about their work, partly funded by GCT, to learn everything there is to know about the movements of these gentle giants.
Why do tortoises need to migrate?
Well, actually, not all giant tortoises migrate – but those that do generally migrate to access seasonal food resources. As vegetation in the arid lowlands becomes less abundant during the drier season, many giant tortoises move up to the highlands, where vegetation remains available to forage all year round.
The return of heavy rains during the wet season promotes the growth of more nutritious vegetation in the lowlands, so many migrating tortoises return to forage on this new growth. Additionally, reproductive females that migrate to the highlands to forage then return to the arid lowlands to lay their eggs.
For over a decade we have been supporting work to map the migration routes of Galapagos giant tortoises.
How do tortoises establish their migration routes?
That is one of the biggest questions that we are still trying to answer. Based on our studies, we know that tortoises move between the highlands and lowlands for food resources. However, we still don’t know how each individual first establishes their migratory route. For example, it is unclear if females that hatched at one nesting site return to that same site once they reach reproductive age, more than 20 years later.
Giant tortoises have most likely been migrating for thousands of years in Galapagos. Once their migratory routes are established, they may use spatial memory to retrace similar routes each year. Their migratory patterns are also shaped by climate, food availability, and the presence of open pathways or less dense vegetation that they can move through.
Why is it important to tag and track giant tortoises as they migrate across the Islands?
Long-term tracking of giant tortoises in Galapagos allows us to better understand their movements and migratory patterns. These data also help us identify potential threats to tortoises’ migratory routes and their overall health. Disturbances to their habitats on inhabited islands can disrupt their migratory routes due to fences, invasive plants, roads, and changes in land use.
Continued monitoring of their movements also helps us understand how giant tortoises are responding to climate change. Together, these data help guide conservation and management actions that protect giant tortoises’ migration routes, habitats, and health.
We have lots of free educational materials all about the giant tortoises of Galapagos!
What are some of the risks pollution, including plastic pollution, poses for giant tortoises along their migration routes?
Giant tortoises can be exposed to a wide range of pollutants along their migration routes, from chemical contaminants to trash and plastic waste in areas with greater human activity. As they have not evolved in environments with human-made waste, some individuals may ingest trash and plastic debris they encounter in their habitat.
Our research group has recently documented plastic ingestion by giant tortoises on Santa Cruz island, showing that this already takes place in shared landscapes. Although the effects of pollution and plastic ingestion on giant tortoise health are still being studied, plastic ingestion may cause digestive problems, increase exposure to chemicals associated with plastics, negatively affect overall health, and, in severe cases, lead to death. These findings highlight why reducing pollution, including plastic waste, along giant tortoise migration routes is important for protecting the health of giant tortoises and other wildlife that share their habitats.
Why is it important for local communities to play a leading role in helping to protect tortoise migration routes from pollution?
Local communities have a shared responsibility to help protect the environment in which they live and the unique wildlife of Galapagos, including giant tortoises. While much of Galapagos is protected, tortoises also migrate through agricultural and privately owned land, and some of their migration routes overlap with human activities in highly populated areas. Therefore, local communities play a central role in protecting tortoise migration routes from pollution. Management of trash, plastic waste, and other pollutants is key to protecting the health of giant tortoises, other native and endemic wildlife, and people who live in Galapagos.
A study published in the journal Environmental Pollution has found that giant tortoises on Santa Cruz island are ingesting items including medical face masks, glass and plastic bags.
Adopt a Galapagos giant tortoise today and help to protect this species, their habitats and other Galapagos wildlife.
