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Cattle versus Endangered Kangaroo Rats

Cattle versus Endangered Kangaroo Rats Laura Prugh and Justin Brashares University of California Berkeley Background • Largest remnant of San Joaquin grassland ecosystem (810 km 2 ) • Key area in many T & E species recovery plans John Roser Alison Cleary Background

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Cattle versus Endangered Kangaroo Rats

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  1. Cattle versus Endangered Kangaroo Rats Laura Prugh and Justin Brashares University of California Berkeley

  2. Background • Largest remnant of San Joaquin grassland ecosystem (810 km2) • Key area in many T & E species recovery plans John Roser Alison Cleary

  3. Background Exotic grasses are a major problem

  4. Giant Kangaroo Rats (GKR) John Roser

  5. Soil disturbance John Roser

  6. John Roser Foraging Red Brome

  7. 1. Do GKR promote or control exotic grasses? Soil disturbance may exotics, foraging may Key Questions 2. Do cattle help or hurt GKR populations? Keep habitat open, but may compete for food 3. How do GKR and cattle affect other species? How to manage for endangered species that eat each other or compete for resources

  8. Study Design Control (grazed) plot Cattle exclosure 60 m 140 m Buffer zone around trapping grid Rodent exclosure Control plant sampling area Trapping grid

  9. Study Design grazed ungrazed

  10. Plant Surveys John Chestnut

  11. GKR Surveys 3 sessions, 6,615 captures, 1,098 individuals

  12. Antelope Squirrel Surveys 2 sessions, 440 captures, 131 individuals

  13. Reptile Surveys

  14. Food Choice Trials 12 seed piles per trial, n = 30 trials (1 per plot)

  15. Food Choice Trials

  16. PRELIMINARY RESULTS John Roser

  17. 1. Do GKR promote or control exotic grasses? Soil disturbance may exotics, foraging may Key Questions • Exotic plant cover on and off GKR precincts • GKR diet preferences

  18. Plant surveys 2008 2007

  19. Plant surveys

  20. Erodium circutarum (filaree) exotic plant, everywhere

  21. Amsinckia tessellata native plant, mainly on precincts

  22. GKR Diet Choice

  23. GKR Diet Choice vs. Composition Filaree r = -0.38 Plant composition tends to be negatively correlated with diet choice of local GKR (Sign test, P = 0.047)

  24. Key Questions 1. Do GKR promote or control exotic grasses? Soil disturbance exotics and some natives Preference for some exotics may limit their abundance

  25. Key Questions 2. Do cattle help or hurt GKR populations?

  26. GKR surveys

  27. Key Questions 3. How do GKR and cattle affect other species? How to manage for endangered species that eat each other or compete for resources

  28. Correlations (n = 30 plots) r = 0.41 r = 0.60

  29. Keystone Role of GKR John Roser John Chestnut John Roser

  30. Conclusions • Giant kangaroo rats have strong, and potentially opposing, influences on plants - disturbance promotes, foraging controls exotics • Giant kangaroo rats are keystone species - precincts benefit squirrels and reptiles • Grazing effects will take time to emerge - may benefit species by reducing cover, but may also compete for forage

  31. Acknowledgements Bureau of Land Management: Larry Saslaw, Kathy Sharum, Johna Hurl CDF&G: Bob Stafford, Deborah Hillyard TNC: Tom Maloney, Scott Butterfield Funding & Support: USFWS, TNC, BLM, UC Berkeley Field Assistants and Students: J. Roser, J. Chestnut, N. Petersen, C. Daman, N. Raubitschek, T. Bean, J. Castillo, P. Elsen, R. Wenk, G. Butterworth, L. Navarette, B. Olney, J. Miller, A. Cleary, K. Chu, A. Bruys, B. Berube, N. Tuttle, and M. Vance

  32. Questions? Alison Cleary

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