Does a Viral Video Depict a Crab Eating Her Babies?
On February 20 2019, UNILAD shared a video to Facebook titled “Red Crab Eats Her Newborn Babies.” The clip was wildly popular, racking up millions of views and shares in under 24 hours (the video itself can be viewed here.) It was captioned:
Red Crab Eats Her Newborn Babies
Just a momma red crab snacking on a few of her newborn kids… Nature can be terrifying 😳🦀
Clocking in at 47 seconds, the quickly-spreading video was not accompanied by any additional contextual information. But similar entity ViralHog shared the same video to YouTube one day earlier. That iteration had a longer description, and was titled “Female Crab Eats Young on the Run.” As the description noted, the crab shown was purportedly eating zoea larvae — but originally, the accompanying blurb clarified that the meal was the spawn of different crabs, not her own:
Occurred on December 31, 2018 / Christmas Island, Australia
“Every year, 50 million Christmas Island red crabs migrate from their jungle homes out to the coast to spawn their eggs into the sea in a spectacular event, timed with the tides and a special phase of the moon. The baby crabs drift around out at sea for the first month of their life and if they are lucky, the currents bring them back to Christmas Island. If some spawning crabs decide to migrate a month late, aiming for the same tide a month later, occasionally you’ll have this remarkable situation of pregnant female crabs coming down to the coast to spawn at the same time as last months baby crabs are coming back out of the water in a living red carpet heading into the jungle. Amazingly, filming this crab on her way down to spawn, she was stopping along the way to feast on the tiny returning crabs, popping them into her mouth like popcorn! Incredible! The dark side of nature!”
But even that wasn’t the entire story. According to the initial description, the red crab was eating plankton, specifically zooplankton, and even more specifically meroplankton:
The name plankton is derived from the Greek word planktos meaning to wander, and refers to the weak swimming movements of organisms in this category. Plankton can be subdivided into animals, or zooplankton, and plants, or phytoplankton.
Zooplankton can be further subdivided into holoplankton, i.e. permanent members of the plankton, and meroplankton, i.e. temporary members of this category.
Meroplankton consist of larval and young stages of animals that will adopt a different lifestyle once they mature. For example bottom-living animals such as crabs and lobsters enter the plankton as larvae for the purpose of dispersion. Also many fish are planktonic in the early stages of their development.
Forms of plankton eating plankton itself is not [PDF] entirely unheard of, although crabs largely consume algae and plankton only in small part:
Microzooplankton are themselves grazed on by larger zooplankton such as small crustaceans, typically copepods, krill, and even larval fish.
The video became popular at least in part because of the claim that it shows “a momma red crab snacking on a few of her newborn kids.” Although the description makes for a virally popular Facebook post, it is not accurate. The original description noted that the crab was feasting on larval crabs on her way to spawn; red crabs lay eggs and do not give live birth.