Observation of Snail Behavior
Background
The purpose of this lab is to use the scientific method in studying snail behavior. We will
be observing the snail’s response to various stimuli, and collecting our observations. We will
then interpret those results by explaining why these responses would be useful to the snail for
surviving in its natural environment.
The natural environment of a snail involves humidity. The snails prefer cool, moist, and
dark environments during the day and they feed during the night.
Before the lab you are to collect a garden snail. Keep the snail in a container without any
food sources in a cool place: the refrigerator. When you collect your snail record your
observations of its habitat and what time you collected the snail.
Procedure
Observations: Record your observations of the snail’s behavior to the various stimuli and place
your results in a table. Put your snail in a shallow bowl of cool water and keep it there until it
becomes active.
Snail Behavior
1) Locomotion
(a) Place an active snail in a bowl and while holding the bowl above your head,
observe how the snail moves. Record your observations. The snail leaves behind
a trail of mucus – why is this mucus useful to the snail?
(b) Turn the bowl over and place the snail on the bottom of the bowl. Allow the snail
to move freely over the surface of the bowl. How does the snail respond to the
edge of the bowl? Record your observations.
(c) Rate of locomotion: You will measure the rate of locomotion of the snail in
millimeters traveled per minute on three different surfaces. Fore each surface
make three trials and average the rate of movement for each surface. Record your
observations in a table. The three surfaces are: table top, sand paper, cotton.
2) Movement in response to gravity (geotaxis)
(a) Attach a string to the upper part of the snail’s shell with some tape. Place the
snail on a clean table top. When the snail has begun to move steadily in one
direction, pull the string at right angles to the direction in which the snail is
moving. Pull firmly enough to displace the shell on the snail’s back, (but not hard
enough to injure the snail). Pull to the snail’s left and pull the snail’s right and
observe how pulling altered the snail’s movement. Record your observations.
(b) Place your snail on the bottom of a bowl and turn the bowl so the snail is moving
on a vertical surface.
(i) After the snail has established a direction of movement, rotate the bowl
90 degrees to the direction of its movement and record its newly
established direction.
(ii) Repeat, but rotate the bow 180 degrees and record its newly established
direction.
(iii) When the snail has once again established its direction of movement to
the vertical surface, pull the string in the direction of the movement.
Record any changes in the direction of movement.
3) Movement in response to chemicals (chemotaxis)
The snail ahs 2 pairs of tentacles which it uses to sample its surroundings.
(a) Crush some lettuce and place a thin streak of its juice across a clean, dry table
top. Place the snail on the table so its direction of movement is toward the juice.
Record your observations of the snail’s response.
(b) Dampen a cotton swab with water and bring it close to the tentacles. Record your
observations. (This is a control – testing the snail’s response to the damp cotton
swab).
(c) Dampen a cotton swab with vinegar and test the snail’s response. Record your
observations.
(d) Repeat, but this time dampen your cotton swab with amyl alcohol and record
your observations.
4) Movement in response to light (phototaxis)
Place the snail on a dry, clean surface and dim the lights in the room. Shine the light from
the dissecting microscope on the snail so it has its choice to travel on a illuminated or a
darkened surface. Record your observations.
Summarizing your data: Make a summary table of your observations.
Locomotion: What is the response of the snail’s locomotion to different surfaces?
Movement in response to gravity: Does the snail exhibit a positive (towards) or negative (away
from) response to gravity?
Movement in response to chemicals: Does the snail like lettuce, water, vinegar, amyl alcohol?
Movement in response to light: What is the snail’s response to light?
Analyzing your data:
You will interpret your data by answering the following questions: How does the snail’s
behavior help it survive in its environment? Remember your answer must be supported by your
observations. Use your observations from each of the lab – locomotion, movement in response
to gravity, chemical and light. You should also include your observations of the snail in its
natural environment.