![Page 1: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/1.jpg)
Predator or Prey: Who’s in Control?
![Page 2: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/2.jpg)
![Page 3: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/3.jpg)
![Page 4: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/4.jpg)
Many real populations look like this. Why?
![Page 5: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/5.jpg)
What factors control population growth?
• Competition for:– space– food– mates
• Disease
• Catastrophic events
• Predation – this is what we’ll focus on today
![Page 6: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/6.jpg)
Question
Does the number of predators control the number of prey?
Or
Does the number of prey control the number of predators?
![Page 7: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/7.jpg)
Isle Royale: Wolves and Moose
• Today we’ll look at long-term data for the population of wolves and moose on Isle Royale, Michigan.
• Populations of these two species have fluctuated for the last several decades.
![Page 8: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/8.jpg)
Top-down or bottom-up?
• There’s 2 competing hypotheses:
Top-down: Wolf predation on moose keeps the moose population down
Bottom-up: Plant growth is limited by climate, which limits the amount of plants available to moose, which in turn limits the number of moose available for wolves
![Page 9: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/9.jpg)
Tree-rings
• Can provide records of temporal changes in climate and nutrient availability
• Ring widths larger on salmon spawning streams in Alaska (Helfield and Naiman 2001; Reimchen et al. 2002; Drake et al. 2003)
(photo © H.D. Grissino-Mayer)
![Page 10: Predator or Prey: Who’s in Control?. Many real populations look like this. Why?](https://reader035.vdocuments.us/reader035/viewer/2022062321/56649dba5503460f94aab249/html5/thumbnails/10.jpg)
Isle Royale (McLaren and Peterson 1994)
• Wolf→Moose→Balsam fir
• Three decade correlation study
• Wolves common when old moose (>9 yrs old) were abundant
• High wolf numbers led to low calf survival and release of balsam fir
• Over 30 years, balsam fir trees displayed cyclic intervals of ring growth suppression that accompanied elevated moose densities.
• Only when moose densities were low did tree ring growth correlate with climate