Level 1 — Absolute Beginner
Woodlice are tiny creatures that usually hide under rocks and leaves during the day. They are related to crabs and shrimp.
Scientists in Israel found something strange happening at night. Thousands of woodlice gather under streetlights and walk around in big circles.
The circles are called death spirals. Once the woodlice start walking in a circle, they cannot seem to stop.
Scientists think the light first attracts the woodlice. Then they walk along the edge of the lit area and get stuck going in circles. Animals like centipedes come to eat the trapped woodlice.
- creature
- a living animal, especially one that is not a person
- crustacean
- an animal with a hard outer shell, like a crab or shrimp
- gather
- to come together in a group
- circle
- a round shape with no corners
- attract
- to pull something toward itself, or make it interested
- edge
- the outer boundary or line of an area
- trapped
- unable to escape from a place or situation
- predator
- an animal that hunts and eats other animals
Level 2 — Elementary
Researchers at the Hebrew University of Jerusalem have documented a strange and previously unseen behavior in woodlice, small land dwelling crustaceans related to crabs and shrimp that usually hide alone under rocks and damp leaf litter. At night, thousands of these creatures gather beneath streetlights and begin walking together in enormous circular processions.
The phenomenon, which researchers call a death spiral, was first noticed by an amateur naturalist who saw huge swirling groups of woodlice during summer nights in the Golan Heights. A team led by a PhD student, working under a professor at the university, then studied the behavior in detail and found it could involve more than 5,000 individuals moving together at once.
According to the researchers, the woodlice are initially drawn toward the streetlight itself. Once enough of them gather in the same area, they begin walking along the boundary of the circular patch of light on the ground, and this collective movement forms a self sustaining spiral that continues indefinitely, offering the animals no apparent benefit.
The consequences of this trapped behavior can be serious. Scientists observed a centipede, along with other species of woodlice, gathering near the lights, with the centipede apparently taking advantage of the dense, disoriented crowd to hunt more easily than it normally could.
- document
- to record and describe something in detail, as researchers do
- procession
- a group of people or things moving forward together, often in order
- phenomenon
- a fact or event that is observed and can be studied
- amateur naturalist
- a non professional person who studies plants and animals as a hobby
- collective
- done or shared by a whole group together
- self sustaining
- able to continue on its own without outside help
- indefinitely
- for an unknown or unlimited length of time
- disoriented
- confused about direction or surroundings
Level 3 — Intermediate
A team of researchers at the Hebrew University of Jerusalem has documented a striking and previously unrecorded behavioral phenomenon among woodlice, terrestrial isopods related to crabs and shrimp that typically lead solitary, sheltered lives beneath rocks and damp leaf litter. Under artificial streetlights at night, however, thousands of these small crustaceans have been observed abandoning their usual solitary habits to form massive, synchronized circular processions.
The behavior first came to scientific attention after an amateur naturalist reported observing huge swirling aggregations of woodlice during summer nights in Israel's Golan Heights. A subsequent investigation, led by a doctoral student under the supervision of a university professor, confirmed that these so called death spirals could encompass upward of 5,000 individuals moving in unison within a single mill.
The proposed explanation involves an initial phototactic attraction, the woodlice are drawn toward the light source itself, followed by a transition once population density in the illuminated area crosses a certain threshold. At that point, the animals appear to begin tracing the boundary of the circular patch of illumination on the ground, and this collective boundary following behavior becomes self perpetuating, sustaining the spiral indefinitely without providing any discernible advantage to the participants.
Beyond its intrinsic behavioral novelty, the phenomenon carries clear ecological consequences. Researchers documented a centipede, alongside additional woodlouse species, congregating near the illuminated aggregations, with evidence suggesting the centipede exploits the dense, disoriented masses as an unusually efficient hunting opportunity, one of several ways in which artificial light appears to be reshaping interactions among nocturnal invertebrates.
- terrestrial
- living on land, as opposed to water or air
- solitary
- living or existing alone rather than in a group
- synchronized
- happening at the same time and in a coordinated way
- aggregation
- a group of things or organisms gathered together
- phototactic
- relating to the movement of an organism in response to light
- threshold
- a point or level at which something begins to happen or change
- self perpetuating
- continuing on its own without needing an outside cause
- invertebrate
- an animal without a backbone, such as an insect or crustacean
Level 4 — Advanced
A research team at the Hebrew University of Jerusalem has documented a striking and hitherto unrecorded behavioral phenomenon among woodlice, terrestrial isopods phylogenetically allied to crabs and shrimp that ordinarily lead solitary, sheltered existences beneath rocks and moisture retaining leaf litter. Under artificial streetlights after dark, however, thousands of these small crustaceans have been observed abandoning their characteristic solitude to coalesce into massive, synchronized circular processions.
The behavior first entered scientific purview after an amateur naturalist reported observing immense swirling aggregations of woodlice during summer nights in Israel's Golan Heights, prompting a subsequent investigation led by a doctoral candidate under a university professor's supervision. That inquiry confirmed these so called death spirals can encompass upward of 5,000 individuals moving in unison within a single mill, a scale suggesting the phenomenon is neither anomalous nor confined to isolated instances.
The proposed mechanism posits an initial phototactic attraction toward the light source itself, followed by a behavioral transition once population density within the illuminated zone surpasses a critical threshold. At that juncture, the animals appear to begin tracing the perimeter of the circular patch of illumination, and this collective, boundary following locomotion becomes self perpetuating, sustaining the spiral indefinitely while conferring no discernible fitness advantage upon its participants, a hallmark of what behavioral ecologists term a maladaptive attractor.
Beyond its intrinsic novelty as a behavioral discovery, the phenomenon carries palpable ecological ramifications. Researchers documented a centipede, alongside additional woodlouse species, congregating near the illuminated aggregations, with evidence indicating the centipede exploits the dense, disoriented masses as an anomalously efficient predatory opportunity, one further illustration of how anthropogenic light appears to be restructuring interaction networks among nocturnal invertebrates in ways ecologists have only begun to catalog.
- phylogenetically
- in terms of evolutionary relationship between species
- coalesce
- to come together to form a single group or mass
- purview
- the range or scope of something's attention or authority
- anomalous
- different from what is normal or expected
- locomotion
- the ability or act of moving from one place to another
- maladaptive
- not helpful for survival; working against an organism's own interest
- attractor
- here, a state or pattern that a system tends to settle into and stay in
- anthropogenic
- originating from human activity
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