Young giant manta rays in Central America appear to spend their early years in shallow coastal waters, using nearshore habitat as a refuge before moving into the more hazardous open ocean. The finding comes from a study that combined acoustic tracking, satellite tracking and photo identification across five locations between 2018 and 2025.
Giant manta rays can reach extraordinary sizes as adults: up to nine meters long, with a disk width of about seven meters and a weight of up to 2,000 kilograms. That scale gives mature animals few natural enemies. Their pups, however, lack that protection and may be vulnerable to predators in offshore waters, including several shark species and orcas.
A sharp change with age
The researchers report that the species’ movements change substantially as mantas mature. Individuals with disk widths of roughly three meters or less remained in shallow, nearshore waters. Most tracked adults, by contrast, made long-distance movements along the continental shelf break and crossed national boundaries in Central America.
Lead author Jeffry Madrigal-Mesén, a researcher and project leader at Mantas Costa Rica, described the result as evidence that manta behavior cannot be treated as a single, uniform pattern throughout life. In the study’s interpretation, coastal areas provide younger rays both access to food and relative safety while they grow.
Three tools, one movement record
The research team used acoustic telemetry to monitor fine-scale movements of 59 individuals at coastal aggregation sites, including cleaning stations. Satellite telemetry followed large-scale movements of 12 animals, while photo identification helped distinguish individual rays over time.
Together, the methods produced more than 12,000 detections. The authors argue that using several approaches was necessary because each tool captures a different part of the animals’ lives. Acoustic tags can reveal repeated local use of particular coastal areas, while satellite tags can show broad routes that extend far beyond a single observation site.
The resulting record suggests that conservation planning needs to account for both life stages. Protecting only offshore migration corridors may overlook habitat that juvenile mantas rely on, while protecting coastal aggregations alone would not address the long movements made by adults.
Why coastal habitat matters
The study frames shallow coastal waters as more than temporary stops. For immature giant manta rays, they may function as developmental habitat: places where young animals can remain until they are large enough to face the risks associated with open-ocean travel.
That distinction is important for a species whose adults can range across borders. If juveniles consistently depend on particular coastal areas, local pressures on those places could have consequences that are not visible from adult migration data alone. The findings also underline the value of connecting management across jurisdictions, since adult movements in the research crossed national boundaries.
What the research adds
According to the researchers, this is the first study focused on giant manta ray movement in Central America. Its central contribution is a clearer picture of how habitat use differs between younger and mature animals: juveniles stayed close to shore, while most adults traveled long distances near the continental shelf break.
The work does not erase the need for further observation. The satellite sample was limited to 12 rays, and the study reflects tracking at five locations over several years. Still, the convergence of the acoustic, satellite and photo-identification data gives the team confidence that the age-linked shift is real.
For coastal planners and marine conservation groups, the practical message is straightforward. Giant manta rays may require a connected protection strategy that recognizes juvenile refuges near shore as well as the offshore routes used later in life. The places where a manta begins its life and the waters it uses as an adult are part of the same conservation problem.
This article is based on reporting by Phys.org. Read the original article.
Originally published on phys.org
