- Slides: 26
River Otters What factors affect the survival of river otters?
Hunted for Fur • River Otters were native to Ohio and Kentucky but were almost hunted to extinction in the early 20 th century. Otter fur is warm and very durable and was in high demand by early American settlers.
• Otters were re-introduced to Ohio and Kentucky rivers over a seven year period of time. • River Otters are no longer endangered and the population of river otters is on the rise.
What do River Otters Eat?
Carnivores • River otters are carnivores and are opportunistic feeders – meaning that they prefer certain types of food (crayfish and fish), but will eat anything that they can find (snakes, frogs, small organisms).
Factors that could affect the population of river otters 1. 2. 3. 4. 5. Food Water (amount or pollution) Space (loss of habitat) Disease Hunting Factors that affect the size of a population are called LIMITING FACTORS
CARRYING CAPACITY • As top level predators, adult river otters require a certain amount of prey in order to survive. The number of river otters an ecosystem can support is called CARRYING CAPACITY. When the otters can no longer find enough food in their environment, the environment has met its carrying capacity.
Populations are Growing • The otter populations in Kentucky and Ohio are still growing, which means that the environments have not reached their carrying capacity. • The otter population is being managed by trapping in order to keep the otters from becoming OVERPOPULATED.
Otter Activity • Each group has a set of river otter food cards • The cards represent all of the food available for the river otter in an environment. • We will see how large of an otter population one ecosystem can support.
ROUND 1 • One otter • Spread out all of the food cards – face up. • Rest of the group members – look at the cards to find out what the otters eat.
What otters eat • A river otter’s favorite foods are fish and crayfish, but because they are opportunistic feeders, they will eat whatever is available. • It is winter and the otters need to collect 60 pound of food to help them survive for one winter month.
Begin Round 1 • 15 seconds will be set on the stopwatch • When the I say “GO”, the otter has 15 seconds to collect 60 pounds of food • After 15 seconds, I will say “STOP” and the otter is to stop collecting food.
End Round 1 • Count the number of pounds the otter was able to collect. • Each group should record this number on the marker board. • How difficult was it for the one otter in your group to collect 60 pounds of food?
Round 2 • 2 otters • Spread out food cards • When I say “GO” two otters have 15 seconds to • gather 60 pounds of food each. When I say “STOP” at the end of the 15 seconds the otters must stop collecting food.
End of Round 2 • Each otter counts the number of pounds of food that they were able to collect. • Group records the number of pounds of food that each otter collected on the marker board.
Round 3 • Three otters • 15 seconds on the clock
End round 3 • Each otter counts the number of pounds of food that they were able to collect. • Group records the number of pounds of food that each otter collected on the marker board.
Questions • Did all of your otters get the amount of food that they needed? • What would happen to the otter that didn’t get enough food? • What is the carrying capacity of your river ecosystem? (How many otter’s can your ecosystem support before an otter would have to starve)?
River Carrying Capacity • The river ecosystem can only support a certain number of otters. • Just because the population of otters increases, that does not mean that the food supply increases.
Trapping Otters • Otters are trapped in order to keep the otters • • from becoming over populated. Otters are also trapped because they eat so much of the fish population that they can actually cause other animal species to starve. What would happen of one of the otters in your group were “trapped”? Would it make it easier for the other otters to survive? Why?
Polluting the water • How does water become polluted? • How would water pollution affect the population of otters?
Water Pollution Water/River’s can become polluted from: • Litter • Pesticides • Fertilizers • Run-off from factories, • sewers, cars, etc
How pollution can affect otters • The pollution could directly kill the otters • The pollution could kill the organisms that the otters eat and the otters could starve.
Round 4 • 2 otters • Spread out the food cards • Remove 3 crayfish cards and 6 fish cards because these organisms died from the pollution.
End Round 4 • What does the pollution do to your population of otters? • How does pollution affect the limiting factors of an ecosystem? • How does pollution affect the carrying capacity of an ecosystem?
JEFF CORWIN – RIVER OTTERS