Huddle & Cuddle: How Puppies Keep Warm

Abstract

Objective

To determine how much huddling reduces heat loss in warm-blooded animals.

Credits

Kristin Strong, Science Buddies

This science fair project is based on the following California State Science Fair (CSSF) project, also a winner of the Science Buddies Clever Scientist Award:
Adler, D.L. (2009). Chill Out.

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Introduction

Is there anything cuter than a dozen puppies all sleeping together in a pile? What makes a puppy want to sleep in a heap like that? Does his brother or sister make a good pillow? Probably so, but snuggling, also known as huddling, does more than create puppy pillows. Puppies, like other animals, huddle to keep warm.

Figure 1. This photo shows an adorable pile of puppies huddling together for warmth. (Flickr, 2007).

You might not realize it, but heat is constantly flowing into and out of everything that you see around you. See that tree? Think: Heat flow! See a rock? Think: Heat flow! See a puppy, a person, a shoe, a car, a key? Yep, think heat flow! Heat is everywhere.

Just as a ball always rolls downhill, heat "rolls downhill" too, and flows from an object that is hotter to an object that is colder. If, for instance, you put a cup of hot chocolate in a room-temperature room (and somehow manage to resist drinking it), the heat will flow from the hot chocolate to the room, and from the hot chocolate to the cup, and to the table. The room, the cup, and the table will actually heat up a tiny bit from the heat of the hot chocolate. As the temperature of the hot chocolate gets close to the temperature of the room, the heat flow slows down. When it reaches the temperature of the room, the heat flow between them stops until there is another temperature difference between them. Say, for example, somebody opens the door and lets in a blast of cold air, then the room temperature will drop, and heat will flow, once again, from the cup to the room until they have an equal temperature again.

Heat flows from a hotter object to a colder object in several different ways:

1. By direct touch (called conduction),
2. On energy waves through open space (called radiation), and
3. By the flow of liquids, like water, or gases, like air (called convection).

You don't have to touch something to get heat from it though. If you stand outside in the sunlight, you are receiving heat by radiation. You are not actually touching the Sun (thankfully), but the Sun's heat energy is flowing from a hotter object (the Sun) to a cooler object (you) on energy waves or rays. In fact, that ray of energy you feel right now left the Sun just 8 1/2 minutes ago and traveled 93 million miles through open space to get to you. What a trip! But the Sun is not the only thing that can radiate heat—everything acts like a little Sun. All the objects that you see around you, including you, are constantly moving heat into and out of themselves, as conditions change, through radiation. It's the reason why warm-blooded animals, including humans, need fur, feathers, fat, or clothing if they want to live in an environment that is cooler than their inside body temperature. Heat is constantly radiating off animal bodies into open space. A lot of food that a warm-blooded animal eats goes toward making heat to help its internal (inside) body temperature remain the same.

When it's windy, people and animals lose the heat from their bodies more quickly because of convection. In convection, heat is moved from warm bodies to the air as the wind blows by. It's the same thing that happens when you blow on hot soup. Your breath is like the wind, and as it blows by the soup, it takes some of the heat of the soup with it, so that it cools off faster and you can eat it up.

Heat flow greatly affects the behavior of animals. Warm-blooded animals, like humans and puppies, change their behavior in order to try and maintain a constant internal body temperature inside their core, called the core temperature. If their core temperature drops by even a few degrees, they lose their ability to function. The core of an apple is the inside part where the seeds are. The core of animals is the inside part, too—deep inside the body and away from the surface of the skin. The core is not inside the hands, feet, arms, legs, or limbs, or anywhere near the skin, because the temperature of those parts can change a lot as the body controls blood flow to them in order to protect the core. The core is actually the part inside the torso of the animal—the part of your body between your neck and bottom, where all the internal organs are, like the heart and liver.

When warm-blooded animals are placed in a cold environment, they will change their behaviors to try and maintain their core temperature. They will do things like:
• Fluff up their fur or feathers.
• Shorten their limbs.
• Pull their limbs in close to their bodies.
• Seek out any visible sunlight.
• Seek out a warm rock.
• Curl up in a bed of leaves or brush.
• Put on clothes (if they are humans, of course).
• Huddle together.

When animals huddle together, they are reducing the amount of their bodies (the amount of surface area) that is exposed to the open air, and so are reducing heat loss by radiation and convection. A puppy also gains heat by conduction if the puppy snuggled up next to him happens to be warmer than he is. It's nice to have a brother or sister puppy that's also a furnace!

In this mammalian biology science fair project, you will explore how much huddling helps to reduce heat loss. You'll create models of puppies out of glass jars, which aren't nearly as cute and soft as the real kind, but will let you measure heat loss. How much do you think huddling helps animals stay warm?

Terms and Concepts

• Huddle
• Heat
• Conduction
• Radiation
• Convection
• Warm-blooded animals
• Core temperature
• Surface area

Questions

• What kinds of objects experience heat flow?
• When do objects experience heat flow?
• What are the types of heat flow and how do they differ?
• Why do animals change their behavior in response to heat flow?
• What are some of the ways animals change their behavior when they are cold? Can you think of ways they might change their behavior when they are hot?

Bibliography

These sources describe ways in which animals change their behavior in cold weather:

• ScienceMadeSimple.com. (1995). How Do Animals Spend the Winter? Retrieved June 11, 2009, from http://www.sciencemadesimple.com/animals.html
• Ward, P. (2001). Cool Antarctica. Retrieved June 12, 2009, from http://www.coolantarctica.com/Antarctica%20fact%20file/science/cold_penguins.htm

This source describes the three methods of heat transfer (conduction, convection, and radiation):

• Watson, D. (2004). Energy, Heat Flow, and Life. Retrieved June 11, 2009, from http://www.ftexploring.com/energy/heatflow.htm

For help creating graphs, try this website:

• National Center for Education Statistics. (n.d.). Create a Graph. Retrieved June 2, 2009, from http://nces.ed.gov/nceskids/CreateAGraph/default.aspx

Materials and Equipment

• Glass jars or bottles, like canning jars, same size and shape, with lids (3)
• If using canning jars, you will need rings for the lids.
• Laboratory thermometers, same size; available online from suppliers such as Home Science Tools at www.hometrainingtools.com, Item#ME-THER30A (3)
• Must have a range of at least 200°F
• Water bath canner, Dutch oven, or large soup pot; should be big enough to hold three jars simultaneously
• Nail
• Hammer
• Measuring cups, liquid
• Oven mitts (2)
• Towel
• Timer
• Graph paper, with 1-inch (in.) squares
• Tape
• Lab notebook

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Experimental Procedure

You will be testing heat loss under the following conditions:

1. One puppy alone (with no huddling companions)
1. Modeled by a single jar of heated water
2. Two puppies huddling together
1. Modeled by two jars of heated water, touching each other
3. Three puppies huddling together
1. Modeled by three jars of heated water, touching each other to form a triangle
4. Three puppies not huddling
1. Modeled by three jars of heated water, separated by 1 in. on a sheet of graph paper

Preparing Your Puppy Models and Water Bath

1. Make a data table in your lab notebook for each of the four configurations, like the one below:
One Puppy Model Data Table

Time (min)	Trial 1 (°F)	Trial 2 (°F)	Trial 3 (°F)	Average (°F)
0
2
4
6
8
10

2. Using a hammer and a nail, make a hole in the center of each lid, just big enough for the thermometers to fit through.
1. Ask your parents about a good place to pound the nail, so that you don't damage any table tops or other surfaces.
3. Fill the jars about three-fourths full with equal amounts of the same-temperature tap water.
1. Some jars have lines marked on the side that you can use as a guide when filling the jars.
2. If your jars do not have lines, then you will need to use measuring cups to make sure you put the same amount of water in each jar.
3. Write down in your lab notebook how much water you put in each jar, or what line you used as a guide.
4. Put the lids on the jars. Each jar will represent one puppy.

Testing Your Puppy Models

1. Reset the timer.
2. Fill the canner, Dutch oven, or soup pot with a few inches of water to make a bath.
3. Put the canner, Dutch oven, or soup pot on the stove and put a jar inside.
4. Put a thermometer inside the lid on the jar, so that the thermometer is held upright inside the water in the jar.
5. Turn on the stove.
6. When the temperature of the water inside the jar reaches 190°F, turn off the stove.
7. Immediately remove the jar with the thermometer inside from the water bath with the oven mitts and dry the jar quickly on a towel.
8. Place the jar on a sheet of graph paper on a table.
9. Immediately start the timer and take your first measurement of the water temperature inside the jar. Enter this measurement into the correct data table for time equals 0.
10. Continue taking water temperature measurements every 2 min. for at least 10 min.
1. Enter your temperature measurements into the correct data table.
2. Feel free to take more-frequent temperature measurements.
3. Feel free to take temperature measurements for a period of time longer than 10 minutes.
4. The larger the jar, the greater the amount of water, and the longer it will take for the jar to cool off.
11. Empty the water out of your jar and allow it to come to near room temperature.
12. Repeat steps 1–11 two more times for one jar, so that you have a total of three trials. By repeating the experiment three times, you'll ensure your results are accurate and repeatable.
13. Repeat steps 1–11 three times for two touching jars, three times for three touching jars, and three times for three jars separated by 1 inch.
1. For the three touching-jars trials, be sure to arrange the jars so that each jar is touching two other jars, forming a triangle.
2. For the three separated-jars trials, also arrange the jars in a triangle.
1. Have each jar separated from the two others by 1 inch.
2. You can use graph paper to help you figure out where to place the jars, or mark up a piece of graph paper before starting the trial, so that you know where you will be placing each one when the jars come out of the water bath.
3. Be sure to put a thermometer inside each jar that you test.

Analyzing Your Data Tables

1. For each data table, calculate the average temperature at each time increment and enter your calculations in the last column of the data table.
2. Create a new data table by entering the averages from the other data tables at each of the time increments.
Average Temperature Data Table (°F)

Time (min)	One puppy	Two huddling puppies	Three huddling puppies	Three puppies separated by 1 inch
0
2
4
6
8
10

3. Make a line graph that plots the time on the x-axis and the average temperature on the y-axis.
1. If you put all your line graphs on the same plot, it will be easier to compare them.
2. Use a different symbol or a different-colored line for each condition.
1. For example, you could make the line color for the one-puppy results blue, and give them circle symbols for each data point, or make the line color for two-huddling-puppies results green, and give them square symbols for each data point.
3. You can make the plots by hand, use a spreadsheet program, or use a website like Create a Graph to make the graph on the computer and print it.
4. Looking at the line graph, which configuration of puppies reduced heat loss the most (had the highest temperatures)? Which configuration reduced heat loss the least (had the lowest temperatures)?
5. For each time increment, calculate how much huddling or having other puppies nearby reduced heat loss by using Equation 1.

Equation 1:

Percent reduction in heat loss = 100% - (Average temperature for one puppy/Average temperature for another configuration) × 100

1. For example, if the average temperature at time 0 for one puppy equals 150°F and the average temperature for two puppies huddling at time 0 equals 179°F, then having two puppies huddling slowed the heat loss by 16.2 percent, since 100%-(150/179) x 100=16.2%
2. Enter your calculations in a data table.
Percent Reduction in Heat Loss Data Table

Time (min)	Two puppies huddling	Three puppies huddling	Three puppies separated
0
2
4
6
8
10

6. Make a line graph that plots the time on the x-axis and the percent reduction in heat loss on the y-axis.
1. If you put all your line graphs on the same plot, it will be easier to compare them.
7. Looking at your line graph from step 6,
1. What was the greatest percentage reduction in heat loss and which configuration of puppies produced it?
2. At what time was the percentage reduction in heat loss the greatest?
3. Did more puppies huddling together (three instead of two) reduce heat loss more (was three better than two)? If so, how much better was it?
4. At any time, was there an advantage to having puppies together, even if they were not huddling?

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Variations

• Investigate how adding one or two more huddling puppies to the experiment affects heat loss. Can you predict how adding another puppy will affect heat loss?
• Add fur or fat to the outside of your puppy models to see how that affects heat loss.
• Compare large and small jars of the same shape. Which ones retain heat better? Hint: Look at the surface-area-to-volume ratio for each jar.
• Study increased heat loss by convection by blowing a fan on the huddling puppy models and comparing the data to heat loss without the use of a fan.
• Model the behavior of huddling Emperor penguins who trade off positions, so that one penguin doesn't get stuck on the outside of the huddling group for too long. Place one jar in the middle of three or four jars and evaluate its heat loss for a few minutes, then switch the middle jar to an outside position and move one of the outside jars to the middle. Compare the heat loss of a jar that is switched from the outside to the middle with one that remains on the outside the whole time.

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Related Links

• Science Fair Project Guide
• Other Ideas Like This
• Mammalian Biology Project Ideas
• My Favorites

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