Just when you thought you had enough to worry about with the effect of climate change on the environment, here’s something that is sure to give you nightmares.
If you’re like me and think spiders are already big and scary enough, you’d better prepare yourself. They are getting even bigger.
In Australia, where I live, we have some of the biggest and nastiest creatures imaginable. For example, we are home to the world’s most venomous snake, the Inland Taipan. Luckily he lives very, very far from civilization. Its venom is so toxic that it makes a death adder look like a coward by comparison.
So the idea that our spiders might be getting even bigger isn’t exactly good news. Apparently, this trend is happening all over the world.
The cause of this has something to do with our cities becoming busier and more populated. Researchers have been examining how the common garden spider, like the harmless Golden Orb Weaver, suddenly grows exponentially.
A species of this type of spider has been gaining weight almost at the same time as the city grows. The researchers say that the further away they are from the bushes and the more concrete there is with a corresponding reduction in leaf litter, the larger the spider. And we are talking about significant weight gain. For example, spiders found in a park far from the city had an average mass of 0.5 grams. But those in a downtown park averaged 1.6 grams or three times the size. eeek
Scientists call it the urban heat island effect and prey availability. Spiders are very sensitive to temperature. If it’s hotter, they get bigger. And urbanization has been a great benefit. The food or prey that the spider eats tends to live well in small patches of thickets such as city parks. And they make it even better if there is lighting at night. So the spiders have more to eat so they can put more energy into growing.
Income also plays an important role. The scientists found that the wealthiest areas of the city tend to have the largest spiders. The reason for this is less clear. But it could be because they have more parks and more concrete that gets hot easily. Now the really bad news is that the trend is widespread. So poisonous spiders like the Australian Redback are also growing. Global warming will encourage spiders to grow, but they don’t like really hot weather.
All of this has been quite surprising to the scientific community. They expected the opposite to be true. An increase in heat generally means an increase in the rate of development. It also means that metabolic function speeds up, so they mature earlier and are smaller in size. But that is not what is happening.
Scientists say the relationship between heat and body size is complicated. The heat could be allowing the spiders to hatch earlier, giving them a longer growing season.
In any case, a healthy population of spiders is apparently to be celebrated. They feed on pests and provide food for birds. Spiders should be encouraged in urban areas. Safe. Anywhere but my backyard.