Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world
Species: Dendrochirus zebra
Habitat: Hanging out in the Great Barrier Reef and Indonesia; waging war in Caribbean reefs
It is night-time on the reef. With its Fu Manchu moustache and weed-like fins a lionfish blends into the swaying seaweed.
Spotting a school of little fish swimming slowly through the coral, the lionfish quickly scans around for hungry accomplices. Swimming to them one-by-one it gives a quick wiggle of its tail fin and then a slow undulating wave of its pectoral fins. The accomplices respond with a simple wave of their pectoral fins. The hunt is on.
Together the gang approach the fish, which don't seem to see the lionfish even from up close. Using their fan-like fins they herd the prey into a corner before taking it in turns to dart into the school, each time swallowing their meal whole. Their bellies full, the conspirators part ways into the tropical night.
Native to coral reefs around eastern Australia and Indonesia, lionfish have invaded the Caribbean after well-meaning aquarium owners set their captives free. By feeding on the unsuspecting prey species they have destroyed local ecosystems.
Invisible fish
Lionfish are venemous, and have few natural predators. They are also so adept at camouflage that Oona Lönnstedt at James Cook University in Townsville, Australia, and colleagues recently showed that they seem to be invisible to their prey. In fact, when hunting alone, they convince their prey to swim into their mouths by blowing a stream of water towards them.
But it turns out that they have another trick up their sleeves: very good communication skills.
Studying lionfish both in the lab and on the Great Barrier Reef, Lönnstedt and colleagues found that the fish sometimes conducted a distinctive fin display. Whenever there was another lionfish nearby, the fish that spotted the prey used this signal and up to four other lionfish responded and joined in the hunt.
The signal was only seen prior to a group hunt, which suggests it is a method of communication – a kind of special operations signalling with their fins. "As an intentional signal, it's very rare. It implies that there's a complex cognitive ability in fish," Lönnstedt says.
All fish are equal
Lönnstedt also found that group hunts were more fruitful than solo efforts, which may explain why lionfish are such a successful invasive species.
That's not all. The lionfish also shared the food completely evenly. "That blew our minds," she says. "That's the first time that's been proven in animals. Usually lions or hyenas will catch prey and share it hierarchically. The top animal takes the lion's share, so to speak."
Group foraging and hunting have been seen in all sorts of animals, from chimpanzees to bees and eels. But very little has been done into how it is triggered, says Amanda Ridley from the University in Western Australia in Perth. "We have scores of papers about cooperation, but we don't know how they do it," she says. "This paper has nicely encapsulated the fin display. It goes to the other and says 'hey how about it, let's go fish together'."
Journal Reference: Biology Letters, DOI: 10.1098/rsbl.2014.0281
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
