What are Limpkins?

In 1999, two researchers looked at the changes in population of a freshwater snails in Costa Rica. In this environment, the snails have two main predators: a bird that flies around to find food, called the Snail Kite, and a second bird that typically finds food by walking around in shallow water, called the Limpkin. Use the information below to help you answer the questions that follow.

The researchers organized the snails in 2 different ways: by size and color. The below image shows the snails in order of both size and color. Darkest and smallest on the left and largest and lightest on the right.

NGSS Phenomena: 4 different snail shells, showing that smaller shells are darker and the larger shells are lighter in color.

Reed and Janzen, 1999

In the study, they found that limpkins would pile up the snail shells that they’d eaten. The below graph shows the number of shells they found of different sizes.

NGSS Phenomena: A graph showing that there were few smaller shells and few larger shells, but many shells of medium size.

Reed and Janzen, 1999

To see the eating patterns of the snail kite, the researchers looked at shells that were not piled up and did not have a hole in them. Limpkins tend to make holes in the shells they eat, but snail kites do not. The below graph shows the frequency of different colors of snails that had been eaten by snail kites.

NGSS Phenomena: A graph showing that there were not many dark snails, but many more lighter colored snails.

Reed and Janzen, 1999

NGSS Phenomena: A bird sitting on a branch.

A Male Snail Kite

Andreas Trepte, Wikipedia

References:

Reed, W.L., Janzen, F.J., 1999. Natural selection by avian predators on size and colour of a freshwater snail (Pomacea flagellata). Biol. J. Linn. Soc. 67, 331–342.

1. If a snail lives longer, it’s to be able to .

Drag the answers below into the grey placeholders above

more likely

pass on its genes

less likely

be eaten

2. What type of snail was eaten the most by limpkins?

The somewhat light snails.
The lightest snails.
The somewhat dark snails.
The darkest snails.

3. What scientific ideas that aren’t described here explains what you see happening in the sizes of the snails that are being eaten by limpkins?

4. Explain the different genetic variations of the snails in this study.

5. In places with a lot of limpkins, what type of snail is likely to live for the longest amount of time?

The smallest snails.
The darkest snails.
The largest snails.
The lightest snails.
The most average size snails.

6. What is the connection between being the size of a snail and their ability to reproduce, when around limpkins?

7. Write a claim about how you expect the snail population to change over time, if limpkins continue their feeding patterns? Discuss a cause and effect relationship as well as what data you would collect to justify this claim. Be sure to identify whether the data you collect is qualitative and/or quantitative and why.

Only use this space to write a claim, we’ll ask you for evidence and reasoning in future questions. (hide hints)

8. What evidence supports your claim about how you expect the snail population to change over time, if limpkins continue their feeding patterns?

You should cite evidence from prior knowledge or the information presented here. (hide hints)

9. What reasoning helps to support your claim with the evidence you’ve cited?

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This matching question aligns to the following standards

MS-LS4-4
LS4.B: Natural Selection

This multiple choice question aligns to the following standards

LS4.B: Natural Selection
Constructing Explanations and Designing Solutions