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Characteristics of rainfall and its effects on earthworms Natalie Rideout, Aaryn Tays, Kaitlyn VanKoppen Introduction ● Worm’s habitat is a burrow in moist, compacted soil ● Worms that come to the surface after a rainfall are vulnerable to predation ● Debate over the reason why earthworms come to the surface ○ ○ ○ ○ Flooding of the burrows Oxygen intake Migration Seismic vibrations simulating voles digging Purpose ● To determine what aspects of rainfall makes earthworms come to the surface ● Tested using o Control, moisture, vibrations, sound and a combination tank with all three stimuli Hypothesis We hypothesized that a combination of all the stimuli (vibrations, sound, and moisture) will result in the greatest number of worms coming to the surface. Methods ● 10 worms in 5 tanks ● Stimuli applied under red light for 2 minutes for each tank o Control, moisture, vibrations, sound and a combination of all three stimuli ● Number of worms at surface counted o Before stimulus, during stimulus and in 2 minute intervals for 30 minutes Preparing to apply stimulus Results ● Control o No worms surfaced ● Sound o No worms surfaced ● Vibrations o 2 worms surfaced ● Moisture o Mean of 2 worms surfaced during N=3 trials o Range from 0 to 5 ● Combination o Mean of 1.5 worms surfaced during N=3 trials o Range from 0 to 5 Figure 1. Average results for five trials. Stimuli included sound, vibration, moisture, and combination (n=10). A control tank was also tested where no stimuli was present. Number of earthworms observed in the moisture stimulus was 33% more than the combination stimulus. Discussion ● The results showed that moisture had the greatest effect on the worms o This disagreed with our hypothesis ● No results were obtained from the sound or the control condition ● Possible Confounding Variables: ○ High temperature of lamps ○ Variable species of earthworms ○ Grunting technique Real World Applications ● Increase in danger for earthworms to surface o Higher vulnerability to predators ● Could help researchers develop ecological plans o o More stable population size Helpful when working in areas of high flood ● Harvesting of earthworms by fishermen o Better understanding of why and when earthworms surface Future Research ● Focus on the reason why moisture encourages worms to leave their burrows ● Possible explanations include: o o o Facilitate rapid migration Avoidance of drowning in burrows Facilitation of gas exchange Conclusion Earthworms preferred to surface at a point with high moisture levels. It is possible this is due to flooded burrows or the need to migrate. Earthworms showed no preference for sound or vibration. Questions and Comments