In New York City and other urban places, where people discard tons of leftover food every day, spiders, ants and other insects serve as tiny cleanup crews that help prevent waste from piling up.
Researchers have also found that by scavenging on littered food, these creatures help curb the spread of diseases, which can potentially be transmitted by larger pests such as rats, pigeons and squirrels.
For a new study published in the journal Global Change Biology on Dec. 2, North Carolina State University entomologist Elsa Youngsteadt and colleagues wanted to see how much littered food waste arthropods such as insects, spiders and centipedes consume. The experiment involved dropping scraps of cookies, potato chips and hotdogs across Manhattan.
One set of food was a sort of buffet for any scavenging animal, while another set was placed in a container that only spiders, insects and other arthropods could access.
Youngsteadt and colleagues found that within 24 hours, the arthropods ate 32 percent of the caged food, which was much more than what the researchers had expected for the little creatures. Eighty percent of the unrestricted littered food, on the other hand, was consumed by all sorts of scavengers, including arthropods.
The researchers observed that when bigger animals had access to the food, more of it was consumed. This shows that the arthropods and larger animals compete for littered food. With the little critters consuming enough garbage, they can reduce the availability of littered food to less desirable scavengers.
"Arthropods and vertebrates compete for littered food," the researchers wrote. "We estimate that arthropods alone could remove 4-6.5 kg of food per year in a single street median, reducing its availability to less desirable fauna such as rats."
Youngsteadt and colleagues believe that in a year, arthropods can gobble up the equivalent of 60,000 hot dogs, which could be otherwise eaten by larger animals that carry pathogens. Disease-carrying rats, for instance, are known to thrive primarily on discarded food. The availability of food waste can feed their population. While these pests are known to pose harm to human health, most scavenging arthropods do not make people sick.
"They effectively dispose of our trash for us," Youngsteadt said. "Ants and rats are competing to eat human garbage, and whatever the ants eat isn't available for the rats. The ants aren't just helping to clean up our cities, but to limit populations of rats and other pests."
