(A student-generated lab)
P.J., Alex, Augustine, Natalie, Mike, Tim and Andrew
December 15, 2004
In our student-generated lab, we investigated the sowbug and its behaviors. We were interested in these scurrying creatures because of their manageable size, fast breeding time and their complex social structure. Also, because (given organic matter and moisture) sowbugs can survive with minimal management, a replica lab environment would be easy to create. Their nocturnal behaviors provided a challenge for observance purposes, but allowed for an interesting comparison between day and night behaviors.
While maintaining the focus of investigating the behaviors and interactions of a sowbug community, we were interested in examining many aspects of sowbug life. For instance, what are their eating habits? Is there a vertical social ladder in the sowbug community? How do sowbugs react to different wavelengths of light? We used observational skills and techniques learned throughout the course thus far to gather data on this ancient species.
In the end we decided that many of our questions were too difficult to answer. We were without an accurate beginning count of our sowbugs, which made a population study near impossible. We also discovered through some of our experimentation that sowbugs were averse to being outside of their natural habitat regardless of the lighting. After observing basic structural patterns in sowbug society, we decided to modify our original sowbug question regarding light frequencies to the following: Does sowbug movement follow any basic logic pattern or are they driven mostly by scent and danger? Will they work cooperatively, or follow the path of other sowbugs? This ended up being the focus of our study.
Sowbugs are not actual bugs, but are crustaceans. They are approximately .25-.5 inches long, and live in small burrowing communities. They have one pair of jointed antennae, fused abdominal segments, a flattened body and seven pairs of legs. Sowbugs like to blend into their environment, and are generally brown or grey in color. Because they are crustaceans, sowbugs use gills for respiration, and must remain moist at all times. In order to achieve this state sowbugs prefer to live in damp underground places, or in rotting logs. The average lifespan of a sowbug is between 2-5 years.
Sowbugs begin reproducing in late March, and they have a gestation period of roughly 34 days, during which the infant sowbugs are stored in a pouch under the female sowbugs stomach. Sowbugs will hatch 2-3 broods each year, with about 35 young in each brood. They are very protective of their young; the female Sowbug searches for food while the male guards the young.
Being crustaceans, sowbugs must molt. After reaching adulthood after 1 year, sowbugs must molt their skin once every 28 days. In order to remain somewhat protected, the sowbugs molt half their shell first, then eat it for nutrition and to help form the new shell, before molting the other half and eating it.
Sowbugs are preyed on by numerous animals, including but not limited too birds, frogs, toads, and shrews. Sowbugs lack the ability to curl up into a ball like pillbugs (see handy diagram on the cover of this report…), and must rely on running away from predators. Some species of sowbugs have evolved to have a rather disgusting taste to help ward off predators.
Other Research on Sowbugs
1.) Nobl, Robert E. "Invertebrate Use of Natural Tree Cavities and Vertebrate Nest Boxes" American Midland Naturalist, Vol. 107, No. 1. (Jan., 1982), pp. 163-172.
Researchers at the Louisiana State University conducted nesting experiments with thirty-nine species of invertebrates. They provided artificial nesting boxes and natural burrowing areas and observed to which the separate species would gravitate due to preference. We opted to choose articles that would aid us in understanding sow bug behavior, and help us define a sophisticated experiment. The article Invertebrate Use of Natural Tree Cavities and Vertebrate Nest Boxes was selected because it contained information about Invertebrate burrows and nesting habits. We thought it helpful in discovering the machinations behind the burrows of our own sow bugs.
2.) Hackstein, Johannes H. P. "Methane Production in Terrestrial Arthropods" Proceedings of the National Academy of Sciences of the United States of America, Vol. 91, No. 12. (Jun. 7, 1994), pp. 5441-5445.
Faculty at the Catholic University of Nijmegan tested the methane production of 110 taxa of arthropods. They tested three different theories concerning the origins of this methane production, and found that methane-producing bacteria (methanogenic) in the hindguts of the arthropods were largely responsible for the methane content of the atmosphere. We needed an explanation for why the sow bugs in the maze followed similar paths or even one another. It was proposed that a chemical trail or scent was responsible, so we looked into Methane Production in Terrestrial Arthropods for a reason for the phenomenon. It is indeed a plausible explanation.
3.) Babcock H. L. "Some Observations on the Food Habits of the Short-Tailed Shrew" Science, New Series, Vol. 40, No. 1032. (Oct. 9, 1914), pp. 526-530.
Alexander McAdie at the Blue Hill observatory studied the dietary habits of a single species of shrew. Among its preferred diet was the sowbug. His findings go into graphic detail of exactly how the shrew dismembers its prey and devours it in pieces. The selection of the article Some Observations on the Food Habits of the Short-Tailed Shrew was based on potential predators of sowbugs. We wanted to know more about offensive strategy of predators, and defensive mechanisms of the sowbugs due to observations made during the maze experiment. When loud noises were made, the sowbugs stopped moving, and we hypothesized that this was a response to potential danger. Perhaps the sowbugs were trained to listen or feel for the vibrations created by the shrew? It was a question we wanted to look into.
Some Helpful Websites
We chose this website because it provides all the needed background information on sow bugs. The website also states how they like dark, moist places. This explains their search for the dark, moist dirt in the maze. This was our primary source for sowbug “basic facts”, such as those we utilized on our website
This website mainly speaks about the sow bug habits. It even mentions their reactions in mazes. The site mentions they would rather have dark places, hence why we chose to use a light during the experiment. An interesting quote that helped us to decide our first potential idea:
“Research has found that when the humidity is high sow bugs move slowly, in circles, keeping them in about the same spot. They tend to avoid light. If the spot should dry up they start to move out to the open to find another moist spot. Personal observation of a "pet" sow bug found that it was active in a dry environment but became uninterestingly quiet when given moisture.”
This observation was the basis for our initial sowbug light test, which later evolved into the maze experiment. Another good site for general information.
Small decaying log
Equine senior horse food
4 small glass beakers
The first thing we did in this experiment was to set up an environment in an aquarium that was suitable for sow bugs. We did this by first filling the bottom two inches of the aquarium with dirt. We also put a piece of decaying log and a dish with some water in it. The sow bugs were then introduced into the environment and cared for while they adjusted to their new settings. In order to ensure their survival we watered the soil daily in order to keep it moist enough for them. We also fed them a diet of Equine Senior horse food. We proceeded to observe their habits and actions.
For our main experiment we made a circular maze that was about two feet in diameter. We constructed the maze out of flaw board using half-inch high strips glued to the base to create the walls. The maze was constructed so that there was a central starting area and a finish area near the perimeter where we placed a small amount of dirt.
The class was then divided into four groups and we assigned each group a sow bug that we had collected from the aquarium and placed in a small glass beaker. Two groups at a time placed their sow bugs in the center of the maze. At this time we began a timer to see how long it would take them to find their way to the dirt at the finish. During this time we observed the way in which sow bugs navigated the maze in order to attempt to understand how they find their way around.
We repeated the same process in our trials. Sowbugs were stopped after ten minutes to avoid possible harm. Sowbugs were raced in both pairs or as singles. No sowbug repeated the maze. One last experiment was to see how the sowbugs would react to extreme sound and noise.
Sowbug 1 (Milton) and Sowbug 2 (Jonas) raced each other in the first heat. Sowbug 1 won, weaving his way through the maze and to the finish line in 4:15 min.
Sowbug 3 (Pierre) and Sowbug 4 (raced each other in the second heat. Sowbug 3 won in 7:43 min.
When Sowbug 1 and Sowbug 3 went head to head in the final race, neither performed as well as they had previously. After 10 minutes, no sowbug had made it to the finish line.
The tiebreaker was straight race from the center of a circle (radius of 20 cm) to its edge. Sowbug 3 won in a matter of seconds.
Sowbug Time Sowbug Race Noise
1 4.15 A No
2 6:30 A No
3 7:04 B Yes
4 5:32 C No
5 2:32 D No
6 3:46 D No
7 10:00 E Yes
8 8:43 E Yes
Observations about the Maze Run
Throughout the maze races, some interesting observations about the sowbugs’ behavior were made. None of supposedly photophobic little crustaceans seemed affected when the flashlight was shined on them. They seemed more concerned about getting out of the white flaw board landscape of the maze and back into the dirt. The sowbugs did, however, seem startled by loud noises erupting from the audience.
The sowbugs seemed to have a method of getting around. They followed along the edges of the walls of the maze. Over and over again, different sowbugs would travel up to the edge of a wall leading up to the finish line only to turn the wrong direction. The antenna that hit the wall first seemed to dictate the direction the sowbug would turn. The racers also seemed to follow the trails of their predecessors.
We discovered many things when conducting the experiment and several conclusions can be drawn. First, we have proven that sowbugs are indeed more intelligent than many people would expect. When we put sowbugs in a maze they were able to solve it using basic logic, dubbed the “right hand rule’. However, our observation was that Sowbugs would simply follow whatever antennae hit the wall first, leaving ample opportunity for a “left hand rule”. The sowbugs then made the same turn repeatedly until they came to the end. Though this method is slow, it shows development in the sowbug’s nervous system, beyond what we had initially expected. The fact that a creature as tiny as this would solve a maze with such a system is very intriguing.
In addition to the sowbug’s capabilities for solving mazes, we discovered that they are keenly vigilant and have methods for evading prey. When living in a comfortable habitat, there is always one sowbug on the surface. Our belief is that the sowbug on the surface looks out for predators and can warn the community if one approaches. Sowbugs also use their sense of sound to detect prey. During the maze experiment, the sowbugs always stopped when the room became noisy, a hypothesis we tested with subsequent experiments, which yielded in a physical stopping of the sowbugs along with a longer total time for running the maze.
During the experiment, we also learned what tests we couldn’t run on sowbugs. First, the counting of sowbugs is impractical. They are hard to strain out of the soil and the survey would destroy their environment each time. The entire environment would have to be strained in order to find them all, which would greatly alter the environment with each census. Second, we discovered that sowbugs are not greatly affected by light. When running the maze, the sowbug being illuminated did not run faster than the one in the dark. They are not as afraid of light as we had originally thought. Rather, sowbugs respond to a lack of moisture with a fierce amount of movement, not settling down until they have reached an area they considered “safe”
We also observed that sowbugs are very efficient. They survived on very little food, as well as recycling the dead sowbugs of the community by eating their bodies. This, when combined with the fact that sowbugs consume their “molted” shells, helped us to appreciate how resourceful these little creatures are.
Based on the observations we have made, new experiments could be derived. A new, orthogonal maze could be created, which would show with less doubt how sowbugs use a system for solving mazes. A controlled light test with very bright lights could be conducted to determine how bright a light must be to scare a sowbug away. Another important tool for observing sowbugs that we lacked was something to measure (and control) the relative humidity of our testing environment.
The experiment conducted proved our hypothesis that the sowbugs are intelligent enough to solve a maze. The fact that they followed a working principle to solve the maze shows that they have some intelligence. The discovery of this intelligence heightens our appreciation for the sowbugs. Along with our regular observations about the sowbug’s burrowing principles and structured lifestyle, we have decided that there is more to this little crustacean than meets the eye.
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