Who Set the Moose Loose Kristi Hannam SUNYGeneseo

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Who Set the Moose Loose? Kristi Hannam SUNY-Geneseo 1

Who Set the Moose Loose? Kristi Hannam SUNY-Geneseo 1

It was the summer of 1993. Paul had just finished his first year of

It was the summer of 1993. Paul had just finished his first year of grad school, and was excited to start researching bird communities in riparian habitats of the Grand Teton / Yellowstone ecosystem. 2

CQ#1: Riparian habitats are: A. High altitude mountain habitats. B. Terrestrial habitats adjacent to

CQ#1: Riparian habitats are: A. High altitude mountain habitats. B. Terrestrial habitats adjacent to rivers and streams. C. Lake habitats. D. A forest-type habitat found in western North America. E. A type of grassland habitat. 3

Paul’s primary question for his research was: What aspects of the ecosystem most strongly

Paul’s primary question for his research was: What aspects of the ecosystem most strongly affect the diversity of bird species found there? He started by surveying the biodiversity in riparian habitats so he could understand the biological community the birds live in and the kinds of birds found there. 4

CQ#2: What do you think Paul will find are the aspects of the ecosystem

CQ#2: What do you think Paul will find are the aspects of the ecosystem that most strongly affect the diversity of bird species found there? A. Available food for the birds. B. Number of predators of birds. C. Number of trees that provide nest sites for the birds. D. Something else. 5

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Using the following list of species and your knowledge of food webs, create a

Using the following list of species and your knowledge of food webs, create a food web for the riparian area where Paul is working. • • • Moose Mule Deer Beavers Songbirds Grasses • • • Insects Coyotes Willows Aspen Rabbits Hawks 8

The food web Paul created looked like this. Compare your food web to Paul’s.

The food web Paul created looked like this. Compare your food web to Paul’s. Coyotes ? Grasses Rabbits Hawks? Elk Moose Songbirds Insects Willow Trees Mule Deer Aspen Beaver Where should coyotes and hawks fit in? 9

Coyotes Grasses Rabbits Elk Moose Songbirds Insects Willow Trees Mule Deer Aspen Beaver Hawks

Coyotes Grasses Rabbits Elk Moose Songbirds Insects Willow Trees Mule Deer Aspen Beaver Hawks 10

CQ#3: At what trophic level are songbirds? A. Primary Consumer B. Secondary Consumer C.

CQ#3: At what trophic level are songbirds? A. Primary Consumer B. Secondary Consumer C. Primary Producer D. Secondary Producer Coyotes Grasses Rabbits Elk Moose Songbirds Insects Mule Deer Willow Trees Aspen Beaver Hawks 11

CQ#4: What other organisms share a trophic level with songbirds? A. B. C. D.

CQ#4: What other organisms share a trophic level with songbirds? A. B. C. D. E. Coyotes Rabbits Aspen Mule Deer Beaver Coyotes Grasses Rabbits Elk Moose Songbirds Insects Mule Deer Willow Trees Aspen Beaver Hawks 12

CQ#5: The one kind of feeding relationship NOT illustrated in the food web is…

CQ#5: The one kind of feeding relationship NOT illustrated in the food web is… A. B. C. D. E. Carnivory Herbivory Omnivory Cannibalism All the above relationships are illustrated Coyotes Grasses Rabbits Elk Moose Songbirds Insects Mule Deer Willow Trees Aspen Beaver Hawks 13

If we rearrange the food web to make trophic levels more apparent, the food

If we rearrange the food web to make trophic levels more apparent, the food web looks like this: SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 14

This kind of food web can be referred to as a “connectedness” web –

This kind of food web can be referred to as a “connectedness” web – it focuses on the feeding relationships among all the organisms: SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 15

A “functional” food web emphasizes strong interactions which alter population growth rates: SECONDARY CONSUMERS

A “functional” food web emphasizes strong interactions which alter population growth rates: SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 16

A functional food web emphasizing what the influence of other populations on growth rates

A functional food web emphasizing what the influence of other populations on growth rates of SONGBIRD populations might look like: SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 17

What does this functional food web tell us about factors that may influence SONGBIRD

What does this functional food web tell us about factors that may influence SONGBIRD populations? Discuss with your neighbor. SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 18

CQ#6: What does this FUNCTIONAL food web suggest about other organisms that may influence

CQ#6: What does this FUNCTIONAL food web suggest about other organisms that may influence SONGBIRD population growth? A. Numbers of insects will substantially affect songbird populations. B. Numbers of willows and aspens will substantially affect songbird populations. C. Numbers of moose and elk will substantially affect songbird populations. D. More than one trophic level will affect songbird populations. E. More than one of the above answers is correct. 19

Remember, Paul’s goal was to determine what most strongly influenced the bird populations •

Remember, Paul’s goal was to determine what most strongly influenced the bird populations • Top-down control of productivity • “The Earth is Green” – Carnivores depress herbivore populations that would otherwise consume most of the vegetation. • Trophic Cascade – Changes in abundances of organisms at one trophic level can influence energy flow at multiple trophic levels. 20

Another look at Trophic Cascade 21

Another look at Trophic Cascade 21

Bottom-up control of productivity The abundance of organisms at a trophic level is determined

Bottom-up control of productivity The abundance of organisms at a trophic level is determined by the rate of food production for them to eat Increasing the availability of limiting resources will increase the abundance of primary producers. This in turn can increase trophic levels above the producers. 22

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CQ#7: Look at your food web diagram. If bottom-up control explains the size of

CQ#7: Look at your food web diagram. If bottom-up control explains the size of songbird populations in Paul’s riparian habitats, which graph best illustrates the critical population interactions? aspen C D songbirds hawks moose B songbirds A willows 24

CQ#8. Look at your food web diagram. If topdown factors control songbird populations, increasing

CQ#8. Look at your food web diagram. If topdown factors control songbird populations, increasing which population do you predict would result in reduced songbird populations? A. B. C. D. E. High hawk populations Low hawk populations High moose populations High coyote populations Low coyote populations 25

Paul investigated factors that might explain songbird populations in his study sites. Paul set

Paul investigated factors that might explain songbird populations in his study sites. Paul set up multiple study sites: • Three riparian areas inside Yellowstone National Park (YNP). • Three riparian areas outside YNP. He started by examining population sizes of songbirds, hawks, moose, insects, and willows. 26

Some results from Paul’s first year of study Measure Moose density (#/site 2) Average

Some results from Paul’s first year of study Measure Moose density (#/site 2) Average across all 6 study sites 4. 5 Hawks (#sighted/hr/site) 4 Insect abundance (#/m 2) Willow stem density (#/m 2) Songbird diversity 35 8. 5 Songbird abundance 5 8 What can you conclude from this data? 27

The summary data didn’t reflect differences Paul thought existed between his sites, so he

The summary data didn’t reflect differences Paul thought existed between his sites, so he looked more closely at his first year data. What conclusions about species interactions can you draw from this data? Moose density (#/site 2) INSIDE YNP 9 OUTSIDE YNP 2 Hawks (#sighted/hr/site) 4. 5 3. 3 Insect abundance (#/m 2) 29 38 Measure Willow stem density (#/m 2) 6 12. 5 Songbird diversity 1. 3 5 Songbird abundance 3. 4 9. 5 28

CQ#9. The summary data didn’t reflect differences Paul thought existed between his sites, so

CQ#9. The summary data didn’t reflect differences Paul thought existed between his sites, so he looked more closely at his first year data. What conclusions about trophic effects can you draw from these data? A. Hawks have a top-down effect on songbirds. B. Willows have a bottom-up effect on songbirds. C. Insects have a bottom-up effect on songbirds. D. Moose have a top-down effect on willows. E. More than one of the above statements is a valid conclusion. Measure INSIDE OUTSIDE YNP Moose density (#/site 2) 9 2 Hawks (#sighted/hr/site) 4. 5 3. 3 Insect abundance (#/m 2) 29 38 Willow stem density (#/m 2) 6 12. 5 Songbird diversity 1. 3 5 Songbird abundance 3. 4 9. 5 29

Paul observed a top-down effect of moose on willows, but he was really interested

Paul observed a top-down effect of moose on willows, but he was really interested in impacts on songbirds… CQ#10: If moose affect willows, what impact on songbirds might be expected if moose populations increase? Look at your food web diagram. A. No change in songbird populations B. Increase in songbird populations C. Decrease in songbird populations 30

Some interactions between organisms in a biological community are not feeding relationships. Look at

Some interactions between organisms in a biological community are not feeding relationships. Look at Paul’s data & the food web – what are some possible non-feeding relationships in this community? SECONDARY CONSUMERS Hawks PRIMARY CONSUMERS Moose Elk Deer Beaver Insects Rabbit PRIMARY PRODUCERS Coyotes Willows Songbirds Grasses Aspen 31

Some interactions between organisms in a biological community are not feeding relationships. Look at

Some interactions between organisms in a biological community are not feeding relationships. Look at Paul’s data & the food web – what are some possible non-feeding relationships in this community? • Willows provide habitat for insects. • Willows provide nest sites for birds. • Moose waste adds nutrients to soil for the willows. • Grasses provide material for bird and rabbit nests. 32

CQ#11: Paul thinks the moose-willow feeding interaction may affect the songbird populations. What non-feeding

CQ#11: Paul thinks the moose-willow feeding interaction may affect the songbird populations. What non-feeding relationship in this community likely provides a mechanism by which moose affect songbird populations? A. Willows provide habitat and food for insects. B. Willows provide nest sites for birds. C. Moose waste adds nutrients to soil for the willows. D. Grasses provide material for bird and rabbit nests. 33

Paul thinks the moose-willow feeding interaction may affect the songbird populations. What might explain

Paul thinks the moose-willow feeding interaction may affect the songbird populations. What might explain the difference in moose populations inside and outside the park? Moose density (#/site) INSIDE YNP 9 OUTSIDE YNP 2 * Hawks (#sighted/hr/site) 4. 5 3. 3 Insect abundance (#/m 2) 29 38 Measure Willow stem density (#/m 2) 6 12. 5 * Songbird diversity 1. 3 5 * Songbird abundance 3. 4 9. 5 * 34

Paul discovered an important role played by an organism NOT included in his biodiversity

Paul discovered an important role played by an organism NOT included in his biodiversity survey: • Hunting is allowed outside the park, but is NOT allowed inside the park. • One of the main species hunted is moose. • Hunting keeps moose populations outside the park at lower densities. • Therefore, high moose densities inside the park lead to lower willow densities which result in lower songbird densities. – This occurs because of TOP-down control of the community AND nonfeeding interactions of community members. 35

Now if Paul was to display the community interactions that most strongly influence songbird

Now if Paul was to display the community interactions that most strongly influence songbird populations, it might look like this: Humans Hawks Coyotes Songbirds Moose Elk Deer Beaver Insects Rabbit Where the green arrow indicates a non-feeding interaction among community members. Willows Grasses Aspen 36

CQ#12: Shortly after Paul’s first year of research, the first wolves were reintroduced to

CQ#12: Shortly after Paul’s first year of research, the first wolves were reintroduced to Yellowstone NP. How do you predict wolf reintroduction will affect songbird abundances? A. No change in songbird populations B. Increase in songbird populations C. Decrease in songbird populations 37

Epilogue • 14 wolves were reintroduced in 1995 to YNP. • By 2008, there

Epilogue • 14 wolves were reintroduced in 1995 to YNP. • By 2008, there were at least 124 wolves in 12 packs in the park, and other wolves have dispersed outside the park boundaries. 38

Epilogue Wolves Hawks Coyotes Songbirds Moose Elk Deer Beaver Insects Rabbit Where the green

Epilogue Wolves Hawks Coyotes Songbirds Moose Elk Deer Beaver Insects Rabbit Where the green arrow indicates a non-feeding interaction among community members. Willows Grasses Aspen 39