Activity #1: How Sea Otters Thrive

 

Sea Otter Insulation
Share the following information with students.

The water temperature in Glacier Bay is about 37°-50° F. Sea otters don't have a lot of body fat (blubber) like seals and whales, but they do have very dense fur. In fact their fur is the thickest of any animal in the world and it allows them to maintain their body temperature.

Briefly, ask students to respond to the following questions:

1. How do you keep warm in cold temperatures?
2. What insulating materials do you prefer? Why?

Answer: Answers will vary. Accept all insulating possibilities as long as they can support their suggestion with reasonable data and/or experience.

 

Student Handout 1

Experiment: Insulating Properties
Divide students into teams to run an experiment to test the insulating ability of a variety of materials. The directions for the experiment are on Student Handout 1: Testing Insulating Materials. When they have completed the experiment, discuss their findings:

• Which insulating material was best? Why do you think this was a good insulator? Explain.
• What was the worst insulating material? Why was this not a good insulator?
• What happened to the jar that had no insulating wrap? Where did it occur in your ranking? How can you explain this?

Note: When students are testing the insulating abilities of dirt and leaves they will need to cover the jars with each material.

Answer: Answers will vary depending upon the material tested, the quantity of insulating materials and the conditions under which the materials are tested.

 

Student Handout 2

Experiment: Air as an Insulator
Next, ask teams to run another experiment to test the insulating ability of air. The directions for the experiment are on Student Handout 2: Air as an Insulator. When they have completed the experiment discuss their findings:

• Did the finger with the balloon that had air in it feel warmer? Why do you think that happened?
• Can you think of other ways in which air is used as an insulator? Interview your parents and teachers to find examples of the use of air as insulation.

Note: You may need to help students insure there is air in one of the balloons before putting them on their fingers. Practice this before introducing the activity to your students.

Answer: Students will discover that the balloon that has air will keep their fingers warmer than the balloon without air. The down vest is a good example of other insulators that use air, in this case between the feathers. Also, in many houses air is trapped between two layers of material and becomes a fairly effective insulator.

 

Sea Otters Fur Background
Share the following information with students:

Otters don't live in the air as we do. The down vest tested in Step 2 would keep them warm as long as it had a waterproof outer layer because down works by trapping air between feathers. The air-filled balloon is both waterproof and uses air as a fairly successful insulator. In Glacier Bay human divers use dry suits made of neoprene that trap a layer of air between their skin and the suit when diving in the Bay's cold waters. Otters also have a unique and very effective "covering" to keep them warm beneath the frigid waters of Glacier Bay.

Have students read about sea otter's fur, using the Resources below so that they can explain how otters' fur keeps them warm and dry in the frigid water in which they live. Then ask students to:

Describe the sea otter's fur, both the outer coat and underfur. Include color(s), measurements and density.
Answer: The underfur ranges from brown to almost black. Guard hairs on top may be black, pale brown or silver. Fur on the head is usually buff or even white. The otter's guard hairs are 34 mm. to 36 mm in length; the underfur is 19 mm. to 20 mm. Adults' fur has an estimated 650,000 to 1,000,000 hairs per square inch.

Explain the reason why the sea otter’s fur is able to insulate the animal from extreme cold.
Answer: Since sea otters do not have a heavy layer of blubber to protect them from the cold they must depend on air trapped in their fur to maintain body temperature. Clean guard hairs are waterproof, protecting the underfur, which traps a layer of air to provide insulation. The use of air as insulation is very efficient, providing four times the insulation of the same amount of fat or blubber.

Explain why sea otters are constantly grooming their fur.
Answer: If the sea otter's fur becomes soiled or matted by materials, such as oil, the insulation qualities are lost. This results in loss of body heat and eventual death.

 

Resources:

Animal Bytes: Sea Otters

US Fish and Wildlife Service: Marine Mammals Management: Sea Otters: History of the Sea Otter http://alaska.fws.gov/fisheries/mmm/seaotters/history.htm

Return of the Sea Otter
http://oceanlink.island.net/ONews/OceanNewsReader/ON2.pdf (pages 6-8)

Sea otters, Kelp and Killer Whales
http://www.sciencenewsforkids.org/articles/20040324/Feature1.asp

Wikipedia – Sea Otters
http://en.wikipedia.org/wiki/Sea_otter

The 2 sites that follow are excellent and very readable sites on sea otters. However, they both fail to state that sea otters are now found in healthy populations in SE Alaska, such as Glacier Bay National Park and Preserve.

Otternet: Species Profile – Sea Otter
http://www.otternet.com/species/seaotter.htm

Young People's Trust for the Environment: Otter (Sea)
http://www.ypte.org.uk/factsheet.php?id=151

 

Wise Old Sea Otter Activity
Have students complete this activity by writing a paper or staging a presentation, written by or led by a "wise old sea otter of Glacier Bay," about the science of staying warm below the waters of the bay.

 

Extension 1:
(Recommended for advanced students)

Since humans don’t have the otters' thick fur, we must find other ways to keep warm when swimming in the waters of Glacier Bay. Have students use the Resources listed below to learn about dry suits and the way they work. They can write a short paper to share their findings or make a short presentation. If appropriate, they might like to invite a local diver to class to enhance their presentation.

What does a typical cold water drysuit look like?
Answer: Dry suits can be made from a variety of materials including GorTex and neoprene. They have seals, made either of latex rubber or neoprene, at the wrists and neck to prevent water entering the suit. Modern diving drysuits have air inflation valves and air vent valves allowing the diver to control the amount of air held next to the diver's skin. Drysuits are generally worn over an insulating undersuit. Most drysuits have built-in boots and a zipper for entry and exit.

How does a dry suit keep a person warm?
Answer: Water draws heat from your body 25 times faster than air. The colder you are, the more at risk you become for hypothermia, out-of-air emergencies (cold divers use air faster) and decompression sickness (a 30% higher risk when chilled). Stay dry and you stay warm. With its system of zippers, attached boots, and seals at the neck and wrists, a drysuit keeps virtually all water out, leaving you surrounded by a cushion of air that your body warms to toasty levels. In other words, a drysuit is like a raincoat. It keeps you dry and allows you to adjust what you wear underneath depending on the outside temperature.

How does a drysuit work?
Answer: As you descend your body's internal pressure equalizes with the outside water pressure but the air and the clothing between the suit and your skin will be compressed. This can be uncomfortable. You can relieve this pressure by adding air to your suit or by changing your body position in the water. By adding or venting air from your drysuit you can control your buoyancy underwater. Control buoyancy by adding air as you descend and venting it as you ascend.

Resources:

Why Dive Dry?
http://www.dui-online.com/whydivedry.htm

Cold Water Diving Wearing A Drysuit is Fun
http://www.skin-diver.com/departments/WaterWork/ColdWaterDivingDRYSUIT.asp

Wikipedia: Diving Suit
http://en.wikipedia.org/wiki/Diving_suit

 

Extension 2:

The sea otter, a marine mammal, has adapted to an environment that would be impossible to sustain the human mammal. An even more difficult environment for a marine mammal, perhaps, would be the intertidal zone.

Have students research to discover what animals live within the intertidal zone. Are any of them mammals? What adaptations might a mammal have to make to survive in this constantly changing environment? They should design and illustrate an intertidal mammal that is perfectly adapted to the rigors of the intertidal zone and label or model the necessary adaptations.

Activity #2
The Otter Diet