Climate change leading to Arctic spider baby boom
Scientists discover Arctic wolf spiders are doubling their egg production due to warmer weather.
An Arctic wolf spider mother with spiderlings riding on her back.
Scientists have already studied how extreme weather makes spiders more aggressive, and now they're also noticing that it can increase arachnids' numbers.
A new study published in Royal Society Open Science reveals Arctic wolf spiders (pardosa glacialis) are experiencing a baby population boom due to the impact of climate change in the Arctic.
Scientists from Denmark, the US and Canada worked with senior researcher Toke T. Hoye from the Arctic Research Center and the Department of Bioscience at Aarhus University on the new study published in June. At the Zackenberg Research Station in Greenland, the scientists observed wolf spider populations in the area between 1996 and 2014 and noticed the arachnids were laying many more eggs as the Arctic experienced warmer weather.
Female wolf spiders weave their eggs into an egg sac, with each egg sac regarded as a single clutch. The researchers discovered wolf spiders in the Arctic used to lay one clutch of eggs, but laid two clutches a year as the region began to have longer stretches of warmer weather.
The study, which spanned 19 years, not only showed wolf spiders were hatching eggs twice a year, but that they were also hatching larger quantities of eggs in the second batch of clutches.
"In years with earlier snowmelt, first clutches occurred earlier and the proportion of second clutches produced was larger," the study says.
The female spiders are growing larger too. "We note that earlier snowmelt is also leading to larger female body size in the same spider species," the study stated.
According to the study, Arctic wolf spiders sit at the top of the invertebrate food chain and have no natural insect predators in the Arctic. Wolf spiders don't make webs, but instead hunt prey on the ground. Wolf spiders living in the Arctic mainly eat ground-dwelling insects and other spiders.
"Smaller arthropod predators, such as other spiders, might also suffer from the increase in abundance of wolf spiders due to the limited differentiation in diet between predators in the high Arctic," the study says.
If wolf spiders living in the Arctic want to keep their larger numbers of baby spiders healthy, they'll need to have their food supply double as well or change their diet altogether.
Previous studies have shown warming weather also changed the types of insects Arctic wolf spiders liked to eat.
In 2018, researchers at Washington University in St. Louis discovered that Arctic wolf spiders ate fewer numbers of an insect called springtails during warmer temperatures, and instead opted for a diet of other spiders.
However, since Arctic wolf spiders also are cannibals, they will eat each other if their populations get too big.
"We can only speculate about how the ecosystems change," Hoye said, "but we can now ascertain that changes in the reproduction of species are an important factor to include when we try to understand how Arctic ecosystems react to the rising temperatures on the planet."
