On a dry day in Madagascar, hissing cockroaches do something unexpectedly sweet: they huddle together in slow-moving bundles of roach cuddles. A new study in Ethology shows these clusters aren’t random social moments — they’re a humidity-triggered survival strategy that helps keep the large insects from drying out.
“The main takeaway from our study is that Madagascar hissing cockroaches actively adjust their social behavior based on humidity, showing that even large adult insects rely on behavioral plasticity to cope with environmental stressors,” said Lindsey Swierk, senior author, in a press release.
How Humidity Shapes Cockroach Behavior
Madagascar hissing cockroaches, which grow up to three inches long, are common in classrooms but still poorly understood in the wild. On Madagascar’s forest floor, they live in leaf litter, form loose social groups, and serve as decomposers and prey for other animals. Their environment swings between wet and increasingly harsh dry seasons, making humidity a constant challenge.
Those shifts matter. With their high surface-area-to-volume ratios, insects lose water quickly in dry air. Physiological defenses — like waxy hydrocarbons on their exoskeletons — help slow evaporation, but behavior plays a role too. Small insects and larvae often huddle to create humid microclimates; whether larger adults do the same has been less clear.
“Because we now know that these cockroaches adjust their aggregation behavior in response to humidity, more frequent or extreme dry periods could push them to aggregate more often to conserve water, which could potentially affect their foraging, reproduction, or broader ecological roles as decomposers,” Swierk said in the press release.
Read More: How Antarctica’s Only Native Insect Survives the Extreme Cold
Testing Cockroach Clusters
To explore how humidity influences this behavior, the Binghamton team placed groups of 10 adult hissing cockroaches in chambers set to three different relative humidity levels: 30 percent, 50 percent, and 80 percent. Each group spent 24 hours at a given level while researchers recorded how often the insects aggregated, how large the clusters became, and how much physical contact individuals maintained.
Under low humidity (30 percent), the insects gathered far more often, forming larger and denser groups. By pressing together, they reduced exposed surface area and created a small pocket of trapped moisture. At high humidity (80 percent), aggregations were smaller — or didn’t form at all.
“In general, insects can lose water pretty quickly because of their high surface area to volume ratios, and so humidity really affects their abilities to retain moisture,” Swierk said. “Our research shows that even larger adult insects, that may in theory be more resistant to low humidity than smaller or larval insects, still use aggregation as a flexible behavioral adaptation to reduce the risk of water loss.”
The findings show that humidity alone can shift an insect’s social behavior — a clear example of behavioral plasticity. Aggregation may come with costs, like more competition or greater visibility to predators, but when the alternative is drying out, the trade-off appears worthwhile.
Insects in a Changing Climate
“Our study suggests that such aggregation behavior under low humidity levels could more generally apply to larger insects, as well as small or larval insects, but of course this will also depend on species’ natural history and social behaviors,” Swierk said.
If Madagascar’s dry seasons continue to intensify, more frequent clustering could reshape how these cockroaches forage, reproduce, and interact with their ecosystem — a reminder that even tiny behavioral shifts can ripple outward. As Madagascar’s forests change, understanding how these oversized insects respond may help researchers predict how entire communities adapt.
Read More: Do Insects Have Feelings and Consciousness?
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
