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## WHAT IS IT?

Netlogo model modeling the article Killer whales redistribute white shark foraging pressure on seals “Scientific Reports” (2019) (Salvador J. Jorgensen , Scot Anderson , Francesco Ferretti , James R.Tietz, Taylor Chapple , Paul Kanive , Russell W. Bradley, Jerry H. Moxley & Barbara A. Block)

Abstract: How do interactions between two top ocean predators, white sharks and killer whales affect the sharks predatory behavior along the Southeast Farallon Island and Northeastern Pacific.

## HOW IT WORKS
Figure 1. A line graph demonstrating Shark predation (orange line) on elephant seals decline in years when killer whales (blue line) are present

## HOW TO USE IT
When we open the Netlogo model, their is only a go and setup button along with a plot graph.
When we click on setup, the sharks, whales and seals all start at the spot in which they were programed to start depending on the x and y axis.
When we click on the go button, we will see the sharks start swiming towards the seals and if we look at the tick counter, we can see that once it reaches 50 ticks,
the whales will start moving towards the seals which is when whales migrate. When whales are present around the seals we can see how the sharks avoid them and stay back and once 180 ticks reaches, whales swim back to their starting point and sharks go back and eat the seals.
On the plot graph, we can see a blue line graph which represents the sharks and their activity around the seals and furthermore, we also see a pink line graph which represents the whales which we can see that the line is zero and once the whales migrate towards the whales the line graph on the plot graph shows their activity increase and the sharks activity decrease.
## THINGS TO NOTICE

Notice that when the model starts the whales don't swim towards the seals and only after the 50 tick mark will they start to move towards the seals and make the sharks distance themselves.
Also notice how after 180 ticks, the whales go back to the spot at which the whales started

## THINGS TO TRY

For this model, we would suggest that the user try to change the population of whales using the slider provded. Do this to see how often times, the migration pattern of the sharks is changed as it may decrease faster than normal when more whales are present. We suggest doing the same thing with the sharks and the seals to change all variables. We also suggest paying attention to the seal population as you increase the population of whales and sharks you are able to keep an equilibrium by increasing the seals reproduction.

## EXTENDING THE MODEL

We would also suggest going into the code section and changing the direction that the whales travel in, this sometimes affects the sharks dramatically as they are programmed to avoid the whales.
Secondly, we would suggest finding a way to make the whales and sharks reproduce only when they are in their initial positions as that is the only area in the study where they would reproduce.

## NETLOGO FEATURES

He said we dont have to do this

(interesting or unusual features of NetLogo that the model uses, particularly in the Code tab; or where workarounds were needed for missing features)

## RELATED MODELS

For this model, we relied our project on three different models. First, on the wolf and sheep predation model as we had the to program our sharks and whales to eat the seals and we also programmed our seals to reproduce. Secondly, we used a cat and mouse model since our sharks avoid the whales. Lastly, we used the fish and herons model since our sharks and whales had to only rarely prey on the seals.

## CREDITS AND REFERENCES
References:

Jorgensen, Salvador J., et al. “Killer Whales Redistribute White Shark Foraging Pressure on Seals.” Scientific Reports, vol. 9, no. 1, 2019, doi:10.1038/s41598-019-39356-2.

NetLogo 6.1.1 User Manual, ccl.northwestern.edu/netlogo/docs/.