How much spiders eat

Using data from 65 previous studies, Nyffeler and Birkhofer first estimated how many spiders are currently to be found in seven biomes on the planet. Their conclusion: altogether there are about 25 million metric tons' worth of them around.

Most spiders are found in forests, grasslands and shrublands, followed by croplands, deserts, urban areas and tundra areas. The researchers then used two simple models to calculate how much prey all the world's spiders as a whole kill per year. In their first approach, they took into account how much most spiders generally need to eat to survive, as well as census data on the average spider biomass per square meter in the various biomes.

The second approach was based on prey capture observations in the field, combined with estimates of spider numbers per square meter. According to their extrapolations, to million tons of prey are being killed by spiders each year. For a sense of just how much this is, take the following into account: all humans together consume an estimated million tons of meat and fish annually. Whales feed on to million tons of seafood, while the world's total seabird population eats an estimated 70 million tons of fish and other seafood.

According to further calculations, spiders in forests and grasslands account for more than 95 percent of the annual prey kill of the global spider community. The figure reflects the fact that forests, grasslands and savannas are less frequently disturbed than for instance agricultural or urban areas, and therefore allow for greater spider biomass. According to the researchers, spiders are not only important predators, but are also valuable sources of prey.

The study, which was written by professors Martin Nyffeler and Klaus Birkhofer , noted there are 45, individual species of spider that have been identified thus far with a combined weight of around 25 million metric tons. The study suggests that while there are an average of spiders per square meter around the globe, while in ideal conditions, the density can reach up to spiders per square meter.

Nyffeler and Birkhofer used a pair of methods in their attempt to figure out how much spiders consume. First, they used existing data to estimate that spiders eat around 10 per cent of their body weight on a daily basis. The second method involved data from various sources in which scientists counted the number of insects that spiders actually consumed.

This led to a total of between million and million metric tons. He noted a study which said the entire global adult human biomass was approximately million tonnes. World Canada Local. Spiders could eat every human on earth in just 1 year. Full Menu Search Menu. There are 7. According to the AFP , there are approximately 45, known spiders species, all of them carnivores. For the most part, the critters eat insects and collembolans , a soft-bodied hexapod. As they pursue these tasty snacks, spiders can travel up to 19 miles per day on delicate strands of web.

As the authors of the study note, spiders play a significant role in controlling pests and disease-carrying insects.