Researchers found that the nocturnal creatures, known as sand or beach hoppers (Megalorchestia californiana) can collectively shift around 310 tonnes of dry sand each day along a 15.5-mile stretch of coastline near Isla Vista, California.
At just around an inch long, individual sand hoppers might seem unlikely to have much influence on the landscape, but the sheer number of these industrious crustaceans means their combined efforts rival the sediment-shifting power of some nearby rivers.
“The impact of animals on beaches is a really understudied area, especially considering how much work they’re doing,” said lead author Tim Baxter, a geographer at the University of Oxford’s Pitt Rivers Museum.
“Sand hoppers are often overlooked or considered as a bit of a nuisance. We wanted to try and look at them in a different light.”
Sand hoppers are found on sandy beaches around the world, where they feed on seaweed and kelp washed ashore. The nocturnal animals spend their nights digging burrows, which help them find food, retain moisture and shelter from predators. By morning, their digging leaves distinctive mounds of loose, freshly excavated sand across the beach.
Published in the Journal of Geophysical Research: Earth Surface, the study revealed just how much work is being carried out by the tiny crustaceans. Each sand hopper can excavate more than 10 times its own body weight in sand for a single burrow. Across every three feet (one metre) of coastline, an estimated 21,450 sand hoppers collectively move around 110 pounds (50 kilograms) of sand each night – equivalent to roughly 16 half-gallon sandcastle buckets.
To measure how much material the animals were moving, researchers set up plots on the beach after high tide and returned the following morning to collect and weigh the sand deposited by the hoppers. They also dug into the beach to count the animals living beneath the surface.
- Why burrowing desert animals don't inhale sand - like humans would
- How to identify animal burrows and holes
- Sand lizard guide: how to identify, where they're found and the threats they face
The researchers combined these measurements with eight years of data on sand hopper populations to estimate their impact across the wider coastline.
“I have to admit, I did go back through the numbers multiple times just to double check my calculations,” Baxter said. “I was extremely surprised by how much they dug up.”
The findings highlight how animals can influence landscapes on a much larger scale than their size might suggest. Sand hoppers could even outperform South African sand prawns, which have previously been recorded mixing up to 9 pounds (12 kilograms) of sand per square metre of beach each day.
However, researchers say comparisons between burrowing animals are difficult because scientists measure their sediment-moving activities in different ways.
Sand-shifting benefits
The sand hoppers’ influence also extends beyond simply shifting sand around. Their burrowing can bring oxygen-rich seawater and nutrients into the beach, potentially benefiting other organisms living beneath the surface.
The loose sand excavated by the crustaceans can also be picked up by the wind and transported higher up the beach, potentially contributing to the formation of dunes. Meanwhile, the hoppers themselves provide an important food source for shorebirds. Other beach-dwellers, including bloodworms and sand crabs, also burrow through and mix the sediment, although their activities can be harder to measure because they don’t leave obvious piles of sand behind.
Researchers now want to understand how these different animals interact and how their combined efforts compare with physical forces such as wind and waves.
“The beach ecosystem involves both the organisms that live in it and the landscape that forms it – they’re components of the same thing,” Baxter said.
That relationship could also have implications for how beaches are managed. Practices such as beach grooming, in which machinery rakes sand and removes washed-up seaweed, can destroy sand hopper burrows and disturb the animals.
Discover more fascinating wildlife stories:
- Sea insects: why are there so few insects in the ocean?
- It looks like an alien, feasts on whale blubber, has multiple legs and hasn't changed for millions of years – meet this creepy, mysterious deep-sea giant
- 11 weirdest sharks in the ocean
- 13 of the strangest fish in the sea
Top image: Megalorchestia corniculata. Credit: Linda Tanner from Los Osos & Atascadero, California, U.S.A., CC BY 2.0, via Wikimedia Commons
