Manta Rays Dive to Extreme Depths: 1250 Meters for Precise Migration

Groundbreaking scientific findings, unveiled in 2025, are fundamentally reshaping our understanding of the behavior of oceanic manta rays (Mobula birostris). It has been discovered that immediately preceding extended migratory journeys—those spanning over 200 kilometers—these massive rays undertake extreme deep dives, reaching depths of up to 1250 meters. Previously, the scientific consensus held that mantas rarely ventured below 120 meters, a depth marking the boundary of sunlight penetration in the ocean.

As the largest rays on the planet, oceanic mantas can boast a wingspan reaching seven meters and weigh in excess of two tons. While their graceful movements near the surface have long been familiar to researchers, these sudden descents into the perpetual darkness of the midnight zone reveal an entirely new facet of their biology.

This comprehensive investigation was conducted by an international consortium of scientists, including experts from Murdoch University in Australia. The research spanned a decade, running from 2012 through 2022. Utilizing satellite transmitters, the team amassed over 2700 days of tracking data across 24 individual mantas, meticulously recording their migratory paths, precise depths, and water temperatures encountered. During this period, 79 instances of these extreme deep dives were documented. Notably, 71 of these events occurred specifically within the waters off the coast of Aotearoa (New Zealand).

This concentration of deep diving activity strongly suggests that these vertical excursions are not related to foraging but are instead an integral component of their navigational strategy. The unique underwater topography of the New Zealand shelf, characterized by abrupt transitions into deep-sea environments, appears to facilitate the use of what researchers term 'vertical corridors' just before the mantas embark on their northward migrations. In contrast, regions like Indonesia or Peru, which lack these dramatic depth gradients, show fewer instances of this behavior, accounting for observed regional differences.

The scientists observed that mantas do not linger at their maximum recorded depths; rather, their descent and ascent patterns are characterized by a series of short, step-like movements. This specific pattern bolsters the leading hypothesis: the animals are actively gathering critical environmental data. They are likely sampling stable oceanic parameters—such as temperature, water density layers, and magnetic signatures—to establish a reliable reference point for orientation once they are navigating the open sea where visual cues are absent. In essence, the deep zone functions as an 'oceanic GPS' system for these creatures.

The implications of this decade-long study are significant for marine conservation efforts. The findings underscore that the survival of manta rays is intrinsically linked not only to the health of coastal feeding grounds but also to the integrity of deep-sea ecosystems. These deeper environments are increasingly threatened by the pressures of industrial fishing operations. Therefore, effective species preservation strategies must now incorporate the protection of these vital deep-dive routes, as successful long-distance migration hinges directly upon them.