Crocodiles mating en masse due to low flying helicopters

Australia The vibrations and noise emitted when helicopters fly over crocodile farms can be mistaken for breeding signals.

Saltwater crocodile (Crocodylus porosus). Photo: Slowmotiongli/Shutterstock — Saltwater crocodile ( *Crocodylus porosus* ). Photo: *Slowmotiongli/Shutterstock*

A large-scale mass mating of saltwater crocodiles has just occurred due to an unlikely "suspect" - a Chinook helicopter. According to breeders at the Koorana Crocodile Farm in Queensland, Australia - home to more than 3,000 crocodiles - they became excited after the helicopter flew over and mated "crazily", Live Science reported on October 10.

Pilots use Koorana Farm as a landmark to change course mid-flight, according to farm owner John Lever. One pilot recently flew very low so those on board could take some photos of the crocodiles.

“All the big males rear up, roar, and point to the sky to roar. And after the helicopter leaves, they mate like crazy. There’s something about the sound waves that really excites them,” Lever said.

There are a number of reasons for this, says herpetologist Mark O'Shea of the University of Wolverhampton (UK), one of which could be that helicopters mimic many of the warning signs of an impending storm.

Heavy rains act as a sexual stimulant for many crocodile species. Meanwhile, saltwater crocodiles ( Crocodylus porosus ) appear to time their mating so that their hatchlings do not drown in floodwaters after heavy rainstorms. They pair during storms so that their young are more likely to hatch in milder conditions.

“Typically, mating is a seasonal activity because crocodiles want to match the best time to lay their eggs in a den or nest,” O’Shea says. Warm, humid weather often triggers mating behaviors. October is a good time for crocodiles to pair up in Northern Australia, where Koorana Crocodile Farm is located. But low-flying helicopters can create similar signals when thunderstorms are approaching.

Crocodiles have multisensory organs called integumentary sense organs (ISOs), which detect changes such as water movement, atmospheric pressure, and extremely low-frequency sounds. “I imagine that the downdraft from a large, heavy helicopter would create a pressure change that the ISOs on the crocodile’s skin would detect. The drop in atmospheric pressure caused by the downdraft would be similar to the pressure change caused by a hurricane,” O’Shea said.

A Chinook helicopter creates a downward airflow. Photo: Joris van Boven/Shutterstock — A Chinook helicopter creates a downward airflow. Photo: *Joris van Boven/Shutterstock*

Another explanation is that Chinook helicopters can produce infrasound—sounds so low-frequency they are invisible to the human ear. ISO can pick up such vibrations. “The Chinook helicopters can reproduce the sound of a thunderstorm starting,” O’Shea explains.

Such vibrations play a big role in crocodile communication, O'Shea said. The sound of a helicopter's powerful rotor blades can mimic the sounds of competing male crocodiles, such as the low growls they make when looking for a mate or the slapping of their jaws against the water—a courtship and territorial behavior.

However, O'Shea is not sure that the Chinook helicopter is the only factor that causes the alligators to mate en masse. The alligators may already be picking up on subtle cues that indicate the start of mating season (such as changes in temperature) and are influenced by the large aircraft.

Thu Thao (According to Live Science )

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