The black Widow waiting for the kill (spotwin) (Credit: iStock)
Poisonous black widow spiders now range further north than scientists expected, in an area including the most inhabited parts of Canada. And there is a good reason to suggest that the warming temperatures are driving the fatal biters north.
That is a conclusion of a new study, published online Wednesday (Aug. 8) in the scientific journal PLOS One. The researchers in this study attempt to identify the geographic range of animals with the help of citizen science and other spotty data sources. They focused on two spider species: the northern black widow (Latrodectus variolus), and the black purse-web spider (Sphodros niger). The scientists found that the data between 1990 and 2016 showed a black widow range extends 58 miles (94 kilometers) further north than the northernmost observation from the period between 1960 and 1989. They suggested that black widow may be a different range, 30 miles (50 km) in the north to the Montreal area, although none have yet been reported in that region. [Creepy, Crawly & Incredible: Photos of Spiders]
The team could not conclusively demonstrate that climate change has pushed the spiders to the north. But a number of their findings suggest that the case, wrote:
- Reports from 1990 up to and including 2016 establish a much more northern black widow range than the reports from 1960 to 1989.
- Since 2012, individual black widows have started to turn in regions of the Canadian provinces of Ontario and southern Quebec, where they have never previously been reported.
- In all of the 46 years studied, both spider species were more likely to during warm weather than cold weather.
- The period of 1990 to 2016 is also much warmer than the period from 1960 to 1989, as the Earth is constantly warmed in the past few decades.
Black widows are especially able to move into new areas as the world warms, the researchers wrote in the study, because these spiders are “habitat and prey generalist[s].”
In other words, the dangerous critters living comfortably in a whole range of adequate warm environments and prey that eat what happens to all there. Plus, the researchers noted, black widows tend to lay many eggs at a time. So, as soon as the first black widow is in a new place, a lot more will probably appear soon.
Black widows may also be better able to move to the north, the researchers wrote, because unlike the black purse-web spiders, they are perfectly happy to nest in human dwellings which can enable them to ride out the cold winters.
The researchers noted that even in areas where black widows are present, the chance of getting bitten by one are low. But a black widow bite is enough dangerous, they wrote, that the threat is worth taking seriously.
For that reason, advocated a focused citizen science project to track the creatures and a proof of their potential northern migration. Black widows are very good candidates for the data of the citizen researchers, the authors of the study wrote, because the curved, jet-black female with red spots on their bellies are so recognizable and strange-looking.
Originally published on Live Science.