On today’s episode of Species Tuesday, we highlight the giant oceanic manta ray (Manta birostris). Found throughout temperate and tropical waters, these gentle giants are close relatives of sharks and skates. They are classified under the family Mobulidae, and are one of two species within the genus Manta. Giant manta rays are aptly named, as they can reach up to 7 meters from wingtip to wingtip and can weight up to two tons. There’s no reason, however, to fear these eagles of the sea. Giant manta rays are filter feeders, meaning they consume tiny zooplankton found drifting through the open ocean.
Giant manta rays are a highly migratory marine species, traveling with the currents to find productive areas that are rich in plankton. Though commonly associated with offshore islands, they’ve been recorded as far north as California and New Jersey and as far south as Peru, South Africa, and New Zealand. It’s thought that these rays can live between 50-100 years in their natural habitat, though so little is known about this species that it’s difficult to estimate their age accurately. They are slow reproducers, giving birth to just one pup every 2-5 years.
Unfortunately, giant manta rays face a variety of threats aside from natural predation. Though sharks and killer whales have been known to prey on giant mantas from time to time, humans cause the majority of giant manta ray deaths. The IUCN lists giant manta rays as vulnerable, though again more population data is needed to accurately estimate their abundance worldwide. This species is hunted for its meat, which in eastern cultures is an alternative to shark fin, and its gill plates, which are used in traditional Chinese medicine. Many nations have stepped up to protect these gentle giants though, as we discussed in yesterday’s episode. Organizations like the Manta Trust and Manta Watch seek to bring awareness to the issue of giant manta ray hunting, hoping to end this brutal practice.
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