They march forward – not sideways – in rank of size, appear to like warm weather and low tide.
Beyond that, Soldier Crabs appear to be a law unto their own.
“We don’t know why they’re more active at times but not others, but it doesn’t appear to be seasonal,” NSW Fisheries marine ecosystems principal research scientist Tim Glasby said.
The waterfront at Tanilba Bay was alive with soldier crabs last week, particularly at low tide on Thursday when the sun beat back the clouds and showers that had hung heavy over Anzac Day.
“There’s a lot of them around,” Dr Glasby said.
“People haven’t studied them enough to be sure if it is seasonal but previous research suggests it’s more related to temperature and tides.
“There’s not been much research since the 60s.”
Just how many were around last week remains anyone’s guess.
A task made harder by their nature.
“We do know that not all of the crabs will surface with every tide, so what we see is only a fraction of their numbers,” Dr Gasby said.
“They are pretty important though because of their borrowing and feeding habits that help cycle the sediment and nutrients in tidal, sand flat environments.”