1. Predator and Prey
Summit 2015

2. https://m.youtube.com/watch?v=ffcyVpqn9ng

3. Predator – organism that does the eating
The formation of a food web in an ecosystem is based on predation and competition.
Predation: when one species eats another species. Even top predators and large animals like lions and whales are vulnerable to predation when they are young.
Predator – organism that does the eating
Prey: the species that is eaten.
Competition: when two species use the same food source. Sometimes one organism will out-compete another, forcing the less successful organism to leave the ecosystem or switch to another food source.
Competition can also apply to living space, breeding habitat, nesting materials, hiding places, water, etc. Here we are only considering the issue of food.

4. Competition: When two species compete, their niches overlap
Competitive exclusion principle – no two species can occupy exactly the same ecological niche for very long
Both species suffer harm
Migration or predation will ultimately occur

5. To ponder: What effects the size of a population?
5. Population Size
To ponder: What effects the size of a population?
population grows
Decrease in predators
plenty of food
food shortage
Predators
Food
increase in predators
POPULATION SIZE
population falls
overcrowding
Disease
increased aggression / competition for resources

6. Most Consumer Species Feed on Live Organisms of Other Species
Predators may capture prey by:
Walking
Swimming
Flying
Pursuit and ambush
Camouflage
Chemical warfare

7. 9. Predator Adaptations – General
Predators have adaptations to catch and consume their prey.
birds of prey have keen eyesight and sharp beaks and talons
camouflage allows predators to blend in with their surroundings
venomous snakes have poisonous venom to subdue their prey
kingsnakes are immune to the venom of venomous snakes
treefrogs have special pads on their feet so they can cling to vertical surfaces

9. Most Consumer Species Feed on Live Organisms of Other Species
Prey may avoid capture by
Camouflage
Chemical warfare
Warning coloration
Mimicry
Deceptive looks
Deceptive behavior

10. 8. Prey Adaptations – General
Prey have adaptations to detect and prevent being eaten by predators.
mimicry
venomous coral snake
scarlet kingsnake
speed & keen senses
camouflage
warning colors & patterns

11. 11. Predator & Prey adaptations -Eyes
The eyes of predators face forwards. This gives them good depth perception allowing them to judge distances well. Can focus on a single point.
The eyes of prey are located on the side of the head. This allows them to see to the side and rear while eating, without moving their head. Some prey have almost 360° vision.

12. 12. The Lynx and the Snowshoe hare
This is the most common example of the predator prey relationship.

13. 15. Predator–prey graph There are always more prey than predators.
The prey always increases before the predators do.
To do: Explain why the predator increases after the prey.

14. 16. Predator–prey graph
This population data comes from fur trapping records.
How are the populations linked?

15. estimated population size (thousands)
17. Predator–prey graph
How does the lynx population depend on the number of snowshoe hares?
Take a closer
look at this part
of the graph.
150
snowshoe
hare
lynx
100
estimated population size (thousands) 50
1800
1820
1840
1860
1880
1900
time (year)

16. 18. Predator–prey graph section
Why does the peak for the lynx population always come after the peak for the number of snowshoe hares?
150
snowshoe
hare
lynx
For the populations
to survive, there will always be more hares than lynxes.
100
estimated population size (thousands) 50
1850
1855
1860
1865
time (year)

17. predator population decreases predator population increases
19. Predator–prey cycle
Predator and prey population sizes follow a cycle.
What happens if the prey population increases?
normal prey population
prey population
increases
prey population
increases
predator population decreases
as less food
predator population increases
as more food
prey population decreases
because of more predators

18. predator population decreases predator population increases
20. Predator–prey cycle
Predator and prey population sizes follow a cycle.
What happens if the prey population decreases?
normal prey population
prey population
decreases
prey population
decreases
predator population decreases
as less food
predator population increases
as more food
prey population increases
because of less predators

19. 21. Plenary
The population of any species is normally limited by the amount of food available.
If the population of the prey increases, then so will the population of the _______.
However, as the population of predators increases, the number of prey _______.
predators
decreases
Eg.
More grass means more ______.
More rabbits means more _____
But more foxes means less ______.
Eventually, less rabbits will mean ____ foxes again.
rabbits
foxes
rabbits
less

20. A population of predators cannot increase unless there is enough prey.
At the same time, the predators tend to keep the population of prey from increasing.
As a result there is usually a balance similar to a teeter-totter with more prey or predators at different times.

21. More examples of predator & prey relationships in antarctica……..

22. Here are are a few other animals that live in Antarctica and which compete for food or are predators of Adélie Penguins.
Weddell and Crabeater Seals
Leopard Seals
There are no land animals in Antarctica. All the animals are considered marine (ocean) organisms. There is no plant life on the continent that could sustain a land creature.
Minke whales
South Polar Skua

23. South Polar Skuas look like large seagulls, to which they are related
South Polar Skuas look like large seagulls, to which they are related. They eat fish mostly, but also penguin eggs and chicks. When seals come out onto the ice to bear their pups, the Skuas hang around to eat the after birth. These opportunist eaters are the scavengers of Antarctica.

24. HOW THEY ACT AS PREDATORS:
Mated pairs of skuas work together to steal penguin eggs and chicks. One bird will distract the adult penguin on the nest and the other will sneak from the other side to grab the prize.
Nests that are on the edge of a breeding group are more vulnerable to Skua attack. Nest built in the center are protected by the neighbors. Some penguins build their nest near large rocks which make it harder for the Skuas to attack.
The penguins will not leave the nest. So, a skua often will fly or walk around a penguin quickly to get it off balance and expose the egg or chick. It works most of the time for one but not both eggs.

25. Weddell seals do not eat penguins, but they do eat the same food that penguins do: Antarctic silver fish. For the time being there is enough for everyone, but as commercial fishing starts to deplete the Southern Ocean of fish, the delicate food web may get out of balance and competition for food between these species may become much more important.
Weddell seals do not have any land predators so are not afraid of us and we can walk quite close to them. These two were brown, but they come in many varieties of fur colorations, brown, black and spotted.

26. Crab eater seals do not prey on penguins, but do eat the same important prey item: krill. Like Weddell seals, for now this food source is plentiful, but things may change as the commercial fishing in the Southern Ocean continues to increase.

27. Whales
The two common whales in the Ross Sea area are the Minke and the Orca (killer whales). The Orcas have difficulty out-maneuvering the penguins in the water (penguins too quick) and Adélie Penguins are too small to spend energy in catching. Orcas go after the large Antarctic toothfish which live under the ice close to the bottom of the ocean.
In this picture you see killer whales moving through the cracks in the sea ice. They will dive to the bottom looking for the fish and stay submerged for several min, then surface and move on.
These Orcas are feeding along the ice edge where they can dive under the ice and search for the toothfish.

28. Minke Whales.
These whales feed on small fish and krill (shrimp) by taking in huge gulps and then sieving the water through the baleen in their mouths. These whales do not feed on penguins but because Adélies eat the same prey, they are competitors. Each Minke whale eats as much as 2000 penguins in a day!
3 Minke whales eat as much as the entire colony of penguins at Cape Royds.

29. As the whales leave in Feb the diet changes back to krill.
Look at the graphs on the left. Notice that as the whales appear in the area Dec and Jan, the diet of the penguins changes to fish.
As the whales leave in Feb the diet changes back to krill.
Your class can do an activity about the diet of penguins and the presence of whales. Go to the education page on penguinscience.com and click on classroom activities.

30. https://m.youtube.com/watch?v=Ls2Q55OOVHA