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The double life of a squirrel: seed disperser and predator

The double life of a squirrel: seed disperser and predator. 12.05.2012 Jakob Nalley , Liz Schultheis and Tomomi Suwa. Today’s Outline. Background on dispersal and predation Field Experiment Project Squirrel (citizen science project). Seeds. Why is there so much diversity in

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The double life of a squirrel: seed disperser and predator

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  1. The double life of a squirrel:seed disperser and predator 12.05.2012 JakobNalley, Liz Schultheis and Tomomi Suwa

  2. Today’s Outline • Background on dispersal and predation • Field Experiment • Project Squirrel (citizen science project)

  3. Seeds

  4. Why is there so much diversity in seed shape and size?

  5. Seeds evolved many strategies to interact with other species Seeds encounter … • Dispersers • Predators

  6. Dispersal Organism moves away from parent or current population

  7. Stickiness

  8. Bright color & fruits

  9. Mass Production

  10. Air & Wind

  11. Water

  12. Dispersal Why is it important to disperse?

  13. Seed Predators Pre-dispersal seed predators: small, sedentary, specialist feeders e.g. insect larvae Post-dispersal seed predators: larger, mobile and generalist. e.g. rodents, birds, ants

  14. Seed’s dilemma: Attractive for dispersers Defensive against predators vs.

  15. Squirrel as disperser and predator Caching– a food storing behavior of animals (hoarding) e.g. birds, rodents, ants, • Advantages of caching • (from seed perspective): • Disperse seeds • Predators do not eat all the seeds they cache (some are lost) • Death rates are lower for buried seeds than seeds exposed on the surface.

  16. Chocolate-chip cookie study Steven Lima, Thomas Valone, and Thomas Caraco. 1985. Foraging-efficiency -- predation-risk trade-off in the grey squirrel. Animal Behaviour 33:155-165.

  17. Chocolate-chip cookie study Squirrels are more likely to carry larger cookies Squirrels are more likely to carry cookies over shorter distances Size of Cookie

  18. Today’s Experiment sunflower seed If you give a squirrel a cookie

  19. ExperimentalDesign Forest Open Lawn

  20. What are the differences between these habitats from the perspective of a squirrel? Do you think a squirrel will behave more like a predator or a disperser depending on the habitat? Forest Open Lawn

  21. Hypothesis What are the differences between these habitats from the perspective of a squirrel? Do you think a squirrel will behave more like a predator or a disperser depending on the habitat? I predict that squirrels will behave more like a ___________ in the forest, compared to the open field. This is because _______________________. predator/disperser give a reason you might predict this

  22. Fox Squirrel Gray Squirrel Chipmunk black morph

  23. Data to collect: • Data on seed consumption: • Number of seed coats remaining (divide by 2 to get a number of seeds consumed at the tray) • Number of full seeds remaining • Number of seeds without coats remaining • Difference between number of seeds placed into tray (100, or 50g) and number remaining • Data on squirrel visitation: • Number of footprints in the sand • Squirrel observations when • collecting trays • Squirrel behaviors in each habitat type

  24. ExperimentalData Forest Open Lawn

  25. OpenLawn Forest observations?

  26. Data to collect:

  27. Data Analysis and Interpretation

  28. Citizen Scientists Unite! http://www.youtube.com/watch?v=Dxhn4W9NKnY

  29. Extra slides

  30. Predators Organism that kills and feeds on its prey

  31. Pathogen • is a microorganism that causes disease in its host e.g. virus, bacteria, fungi, • Pathogen do not necessarily kill the host animal/plant Need more pictures here

  32. Steven Lima, Thomas Valone, and Thomas Caraco. 1985. Foraging-efficiency -- predation-risk trade-off in the grey squirrel. Animal Behaviour 33:155-165. Predict that tendency to carry a food item should decrease with distance of food from cover (predation risk) and increase with item size (food reward). Both risk and reward should influence behavior Experiments were conducted in Highland Park in Rochester, New York. The reward was chocolate-chip cookies, cut to weigh 1, 2, or 3 g. More “natural” foods were buried rather than eaten and cookies may be a “natural” food for a park squirrel anyway. Food was placed at different distances from trees. II. Scientific Method

  33. II. Scientific Method Steven Lima, Thomas Valone, and Thomas Caraco. 1985.

  34. Steven Lima, Thomas Valone, and Thomas Caraco. 1985. Foraging-efficiency -- predation-risk trade-off in the grey squirrel. Animal Behaviour 33:155-165. The authors conclude that the results support their hypothesis. Simple models that only incorporate foraging rate or only exposure to predators are insufficient, as both are important. II. Scientific Method

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