1. Flying foxes in Guam were found to have significantly higher levels of the neurotoxin BMAA than the cycad seeds they eat, confirming that cycad neurotoxins biomagnify within the Guam ecosystem. 2. Consuming a single flying fox could result in a BMAA dose equivalent to eating over 1,000 kg of processed cycad flour. 3. Traditional feasting on flying foxes by the Chamorro people of Guam may be related to the high prevalence of neurodegenerative diseases like ALS-PDC in Guam.