Brown Huntsman Spiders May Be Among World's Fastest

Anyone who has experienced a brown huntsman run at them knows these spiders are fast, but a new study says they may actually be one of the swiftest in the world.

The study, a preprint published on bioRxiv which is yet to be peer-reviewed, analysed the speeds of 258 species of spiders from new experiments and past research.

Australia's brown huntsman's medium size and relatively long legs were found to give it an edge in running past its competition.

The huntsman is a common sight across eastern Australia and is regularly found in homes, but, despite its scary appearance to some, it is harmless to humans.

According to the study, huntsman spiders can move at 3.59 metres per second.

Biomechanics researcher Christofer Clemente, from the University of the Sunshine Coast, said the new study, which used his huntsman data from 2021, "answers a really interesting question" about how animals like spiders move.

"We always noticed … that the fastest animals weren't the smallest or the biggest, but something intermediately sized," he said.

"And their results confirmed that … if you get too big, you slow down and if you get too small, you're also a bit slower."

Grid-based pursuit

To work out how fast different species moved, the UK and German team behind the new study put spiders from 162 species through their paces.

While the researchers collected most of the spiders from around England and Germany, they also sourced international species from pet stores.

Spiders were placed in a box with grid paper at the bottom, and a high-speed camera recording from above.

Then, the spiders were touched with a paintbrush or other blunt object, and when they went running the team recorded their speeds.

This is a common way to measure speed in animals like lizards and spiders, but getting access to the animals is one of the hardest parts.

The study compared this data from a further 96 species gathered from earlier research from North America, other parts of Europe and Australia, including the study by Dr Clemente.

The new study found the huntsman, which had a mass of about 1 milligram, moved faster than spiders with smaller masses such as the money spider Maso sundevalli, and faster than the much bigger salmon pink bird eater (Lasiodora parahybana), which weighed a whopping 51 grams.

What makes huntsman spiders fast?

Dr Clemente's earlier study, published in the Journal of Comparative Physiology A in 2021, also looked at the speed of spiders, but also how they moved.

Spiders use a hydraulic pressure system in their legs to push their legs out, while muscles pull them back in again.

When his team started investigating this movement in more detail, they were impressed with the huntsman's speeds.

"We didn't know it was the fastest spider at the time, because we just measured the speed in that spider, and we said, 'Wow, that's really fast,'" he said.

"But we had nothing to compare it to."

He noted that while 3.59 metres per second was the absolute top speed, about as fast as a human jogging, it was only for "a fraction of a second".

"What we call maximum speed, is measured over very short periods of time," he said.

"But even if we look at the mean speed over a run, they're still quite fast. And there wasn't any other species that were faster."

The question that both Dr Clemente's research, and the new study, were trying to answer was if, just like in other animals, medium-sized spiders were the fastest.

"The difference between the studies is that I just looked at two species of spiders that we find abundantly on the Sunshine Coast," he said.

"I just went out into the backyard with a head torch."

Mistaken identity

Despite the incredible speed of huntsman spiders, Dr Clemente suggested other spider species that had not been investigated yet might be even faster.

There is also the question of exactly what species the speedy huntsman was.

Two species of brown huntsman spider are found in south-east Queensland: Heteropoda jugulans and Heteropoda cervina, which Dr Clemente noted were extremely hard to tell apart.

He said more research could be done to analyse exactly what species was the speediest using DNA testing or other methods, but he was more interested in using models and robotics to understand how spiders moved.

"[Both research groups] are really interested in just trying to understand locomotion and the evolution of locomotion," he said.

"So, trying to understand basically why animals move the way they do and what limits them from moving faster?"