Invasive rats on islands harm native species and ecosystems. Removing rats can help restore the balance, but it also changes what other animals eat. A study looked at how rat eradication affected land crabs. They found that after rats were gone, the crabs started eating different things. This led to a wider variety of foods being eaten by the crabs. This change in diet could have big effects on the whole island ecosystem. The study used a method called stable isotope analysis to figure this out, showing that it can be a useful tool for monitoring ecosystem changes.