Roly-polies, also known as pill bugs or woodlice, are small, segmented creatures familiar in gardens and damp environments. These terrestrial isopods are not insects but crustaceans, more closely related to crabs and shrimp. They are recognized by their oval shape, seven pairs of legs, and their characteristic ability to roll into a tight ball when disturbed, a defensive behavior that earned them the “roly-poly” nickname. Originally native to Mediterranean Europe, these creatures have since become naturalized across nearly all suitable ecosystems worldwide, often found hidden under rocks, logs, and leaf litter where moisture is abundant.
Are They Really Disappearing?
Many people have noticed a perceived decline in roly-poly populations. While no single global study definitively confirms a widespread disappearance, scientific observations and reports from entomologists and citizen scientists do indicate localized declines in many areas. Pill bugs serve as bioindicators, meaning their presence and population density can offer insights into the health of an ecosystem.
Understanding Their Decline
Several factors contribute to the observed reduction in roly-poly populations. Habitat loss is a significant cause, as urbanization and the trend towards manicured landscapes reduce the availability of their preferred damp, sheltered environments. The removal of leaf litter, decaying logs, and rocks eliminates the dark, moist spaces and organic matter these creatures rely upon for survival and shelter. They require consistent moisture to breathe through their gills, making dry conditions inhospitable.
The widespread use of chemical pesticides and herbicides in gardens and lawns also has a detrimental effect. Pesticides can directly increase mortality rates and reduce the reproductive success of isopods. Specific pesticides, such as molluscicides, are particularly toxic to terrestrial isopods. Herbicides indirectly affect them by reducing their food sources and altering soil pH, which is an important environmental parameter for these organisms.
Climate change further exacerbates these challenges. Prolonged droughts and extreme temperatures negatively impact their preferred damp habitats. Increasing temperatures and decreasing moisture can reduce their reproductive success. Faced with drier conditions, woodlice tend to spend more time seeking refuge and less time foraging, which can impact their ability to thrive.
Their Ecological Importance
Roly-polies play a fundamental role in maintaining healthy ecosystems. They are primary detritivores, meaning they consume dead organic matter such as decaying leaves, wood, and other plant debris. This feeding activity breaks down organic material and recycles nutrients back into the soil, which plants need to grow.
Their activity also improves soil health by enhancing aeration and structure as they tunnel through the earth. Pill bugs also have a unique ability to safely remove heavy metals from the soil. They crystallize these toxins within their guts, preventing them from leaching into groundwater and thus contributing to soil remediation. Beyond their role as decomposers, roly-polies serve as a food source for various creatures, including birds, spiders, and amphibians.
How to Support Roly-Polies
Supporting roly-poly populations involves adopting practices that restore and protect their natural habitats. Leaving leaf litter, decaying logs, and rocks in gardens provides them with the moist, dark shelters and food sources they need to thrive. Creating compost piles can also offer an ideal environment, as these areas are rich in the decomposing organic matter that forms their primary diet.
Reducing or eliminating the use of chemical pesticides and herbicides is another important step. These chemicals harm roly-polies and disrupt the delicate balance of the broader ecosystem. Embracing organic gardening practices benefits not only these crustaceans but also other beneficial soil organisms. While roly-polies primarily consume decaying matter, they might occasionally nibble on tender seedlings or fruits if their populations are unusually high or other food sources are scarce. In such cases, non-toxic methods can be used to attract and relocate them, rather than resorting to harmful extermination.