![]() As you can see, there does appear to be cycling over time in both hare and lynx number, but it's not as clean as in the simple mathematical models. While this is an indirect measure of predation, the assumption is that there is a direct relationship between the number of pelts collected and the numer of hare and lynx in the wild. However, as indicated by the second term, the predator growth rate rises as the prey. The rich dataset composed of 50 predator (spider) species and 974 prey operational taxonomic units (OTUs) allowed us to reveal how predatorprey interaction webs could be compartmentalized into. In the absence of prey (when P 0), the predator population would shrink at rate u. In turn, the growth rate of the predator population is determined by the equation Q Q u+v P where u and v are parameters. One of the classic studies of predator-prey interactions is the 90-year data set of snowshoe hare and lynx pelts purchased by the Hudson's Bay Company of Canada. as the predator population becomes larger. Part 3: Exploitation and population cycles Heterogeneity among prey in their susceptibility to predation is a potentially important stabilizer of predator-prey interactions, reducing the magnitude of population oscillations and enhancing total prey population abundance. Watch these short video lectures for a very nice overview of predator-prey interactions. What causes prey number to cycle in the absence of predators? Generally the answer is that without predators to suppress their number, prey outstrip available food resources, nesting sites, or some other limited resource and thus begin to suppress their further growth through competition. Interestingly though, there are situations where predators are absent, such as on islands or in other isolated areas where they either never became introduced or where they have died out, and yet prey continue to oscillate in number. Predatorprey relationships are a central component of community dynamics. As long as predator and prey numbers don't drop to zero, this cycle can repeat indefinitely. This can lead to cyclical patterns of predator and prey abundance, where prey increase in number and then, with abundant food, predator number increases until the predators begin to suppress prey numbers and then decrease as well. It also shows the following patterns: The number of predators increases when there is more prey. In this lab students will simulate the population dynamics in the lives of bunnies and wolves. What may require a bit more reflection is that prey, in turn, affect the number of predators because, when prey become scarce, predators may die of starvation or fail to reproduce. The graph shows that there is almost always more prey than predators. ![]() It should come as no surprise that predators influence the numbers of their prey. ![]()
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