During the mobula ray’s migration season, which runs from late April to July, the marine animals form massive aggregations called fevers. The image above was captured by Mongabay founder and CEO Rhett A. Butler in Baja California, a northwestern state of Mexico. The region is home to at least five species of mobula rays. Mobula munkiana, commonly known as Munk’s devil ray or Munk’s pygmy devil ray, is the most common, and is listed as vulnerable on the IUCN Red List. The other four species are much scarcer due to slow reproductive rates and population decline due to fishing bycatch. The bentfin devil ray (Mobula thurstoni), spinetail devil ray (Mobula mobular) and sicklefin devil ray (Mobula tarapacana) are all critically endangered. The oceanic manta ray (Mobula birostris) is listed as endangered. Banner image: A fever of mobula rays photographed underwater in June 2025. Images by Rhett A. Butler/Mongabay.This article was originally published on Mongabay