1059 Main Avenue, Clifton, NJ 07011

The most valuable resources for teachers and students

(973) 777 - 3113


1059 Main Avenue

Clifton, NJ 07011

07:30 - 19:00

Monday to Friday

123 456 789


Goldsmith Hall

New York, NY 90210

07:30 - 19:00

Monday to Friday

A study of cleaning habits of mice

A study of cleaning habits of mice

Introduction: (Initial Observation)

Did you ever wonder why mice clean themselves? Do they want to look nice and attract the opposite sex? Is self-cleaning a reaction similar to scratching itchy skin?

Do mice learn how to clean themselves or is cleaning an instinct (a genetically based behavior)?

This project is a study on cleaning/grooming habits of mice. We want to know if cleaning is a conscious (pre-planned) behavior or a genetically inherited instinctive behavior. You may also want to know if cleaning is stimulated by environmental conditions, such as dirt or temperature.


This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Find out about what you want to investigate. Read books, magazines or ask professionals who might know in order to learn about the effect or area of study. Keep track of where you got your information from.

Background Information on Mice: (provided by Encarta)

Mouse is common name for any small member of three families of rodents; large species of one of the families to which mice belong are known as rats. The word mouse has no exact meaning in classification systems. Mice are numerous throughout most of the world, but for convenience they are often grouped as the Eurasian mice and the American mice. Fields and human habitations serve as homes for these animals. Mice, like rats, consume and damage large quantities of food and spread diseases.

The common house mouse is the most frequently observed species and is the ancestor of the white mice that are raised for scientific experimentation. In its wild state the house mouse is slightly less than 17 cm (less than 6.5 in) long including the tail, which is slightly more than 8 cm (more than 3 in) long; domestic mice, because of better nutrition, are often considerably larger. The house mouse is yellowish-gray above (on the back), sometimes streaked with black, and lighter gray beneath (on its belly). It breeds every 10 to 17 weeks throughout the year, producing five to ten young in a litter.

There are many species of common American wood mice. The deer mouse, slightly larger than the house mouse, is a common American outdoor mouse. Prevalent in the southern United States is the cotton mouse. Dark brown with grayish feet, it is injurious to cotton plants. The grasshopper, or scorpion, mice inhabit western North America and differ from typical mice in feeding primarily on insects and other arthropods. The common wood mouse inhabits Europe. Harvest mice are common in America and Europe. The so-called field, or meadow, mouse is classed as a vole. The name mouse is applied also to the pocket mouse, to jumping mice, and to the dormouse and its relatives.

Scientific classification: Mice belong to the families Muridae, Cricetidae, and Platacanthomyidae of the order Rodentia. The common house mouse is classified as Mus musculus, the deer mouse as Peromyscus maniculatus, and the cotton mouse as Peromyscus gossypinus. Grasshopper mice make up the genus Onychomys. The common wood mouse of Europe is classified as Apodemus sylvaticus. American harvest mice make up the genus Reithrodontomys. The harvest mouse of Europe is classified as Micromys minutus.


Differences between Genetics and Learning Experience:

Some behavior patterns are similar between different species, and some are found only in a particular species. For example, the neural programs that enable animals to walk are similar in most mammals. On the other hand, courtship rituals in birds are very species-specific. Some innate behavior patterns are very rigid and experience has little effect on them; other instinctive behaviors can be modified by learning and experience. The flehmann, or lip curl response of a bull when he smells a cow in estrus, and the kneel-down posture of a rat in estrus are examples of behaviors that are rigid. Suckling of the mother by newborn mammals is another example of a hard-wired behavioral system. Suckling behavior does not vary. Newborn mammals suckle almost anything put in their mouth.

An example of an innate behavior that is affected by learning is burrowing behavior in rats. R. Boice, in his 1977 experiment on rats, found that wild Norway rats and albino laboratory rats both dig elaborate burrows. Learning has some effect on the efficiency and quality of burrowing, but the configuration of the burrows was the same for both the wild and domestic rats. The albino laboratory rats dug excellent burrows the first time they were exposed to an outdoor pen. Nest building in sows is another example of the interaction between instinct and learning. When a sow is having her first litter, she has an uncontrollable urge to build a nest. Nest building is hard-wired and hormonally driven because prostaglandin F2a injections will induce it in sows. However, sows learn from experience how to build a better nest with each successful litter.

Other behaviors are almost entirely learned. Some seagulls learn to drop shellfish on rocks to break them open, while others drop them on the road and let cars break them open. Also, many animals ranging from apes to birds use tools to obtain food.

There is a complex interaction between genetic and environmental factors, which determines how an animal will behave. The animal’s temperament is influenced by both genetics and learning. Another principle is that changes in one trait, such as temperament, can have unexpected effects on other apparently unrelated traits. Over selection for a single trait may result in undesirable changes in other behavioral and physical traits. A great example of this is a study conducted by Mario Capecchi on mice. Capecchi’s study proved that single genes could cause undesirable changes in behavior, which can cause physical damage. The study is further explained below.

Mario Capecchi’s Knockout-Mouse Method:

Capecchi, a professor of human genetics, is widely known among geneticists as a developer of the “knockout mouse,” a method of breeding mice to “target” or deactivate a specific gene. By knocking a gene out of action in this way, researchers learn what goes wrong in the mouse without the gene, thus revealing the gene’s normal function.

The latest revelation from the knockout-mouse repository in Mario Capecchi’s lab at the University of Utah contains a true surprise. A gene (Hox b8) with no especially interesting past proves to be the basis of a complex behavior: grooming. Knockout mice for the Hox b8 gene groom themselves bald and bruised.

Concluding Article about Capecchi’s Knockout-Mouse Method:

Article Title: Hoxb8 is required for normal grooming behavior in mice.
Greer JM, Capecchi MR.

Howard Hughes Medical Institute, Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, UT 84112, USA.

Repertoires of grooming behaviors critical to survival are exhibited by most animal species, including humans. Genes that influence this complex behavior are unknown. We report that mice with disruptions of Hoxb8 show, with 100% penetrance, excessive grooming leading to hair removal and lesions. Additionally, these mice excessively groom normal cagemates. We have been unable to detect any skin or PNS abnormalities in Hoxb8 mutants. These observations suggest that the excessive, pathological grooming exhibited by these mice results from CNS abnormalities. Consistent with this interpretation, we demonstrate Hoxb8 expression in regions of the adult mouse CNS previously implicated in the control of grooming. The aberrant behavior observed in Hoxb8 mutants is not unlike that of humans suffering from the OC-spectrum disorder, trichotillomania. Interestingly, Hoxb8 is expressed in regions of the CNS known as the “OCD-circuit.”

Questions to ask about Capecchi’s Knockout-Mouse Method:

Many questions can arise from this study. According to the study conducted by Capecchi, it seems that the normal functioning version of this gene is not to make mice dirty, nor even to cause them to clean themselves. It is to stop the grooming repertoire once the mouse is clean enough. If there is any single function, which this gene seems to code for, it’s not grooming behavior, but the ability to feel clean, or groomed enough. This can go for any other behavior in mice or even humans. For example, assume that there is an identifiable gene responsible for the production of an identifiable enzyme, which is necessary for an animal to feel sated. If this is true for all genes, then one can knock out this particular gene, which gives the sated feeling and a mouse, or even a human will go on eating and eating and eating because they will never feel full.

One last and very interesting question to ask is the following:

If humans also have a grooming gene, and one where to alter or deactivate this gene in a human-being, would the human lacking this gene have an obsessive compulsive disorder towards grooming and self-hygiene?

Mouse Behavior – What influences animal behavior?

So far, it seems that a mixture of genetics and learning experience generate mice behavior. Just like mice, other animals and even humans behave according to genetics and experience.

Mice have very interesting cleaning habits. Unlike other animals, mice and rats generally groom themselves similar to the way humans do. This raises many new questions. Does this mean that humans and mice share a very similar grooming gene, which is missing in other animals such as dogs, horses, and cows?

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.

The purpose of this project is to study the cleaning habit of mice. Some specific questions for this study are:

  1. Is there any identifiable pattern in self-cleaning behavior of mice? (Why, When, Where, and How often do mice clean themselves?)
  2. Is self-cleaning behavior in mice a genetic or learned behavior?

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.

Variables for Experiment 1:

Independent Variable is the date

Dependant Variable is the time of day in which mice spend time in cleaning themselves.

Controlled Variables are the cage, the location of the cage, temperature, feeding time.

Constants are water (continuous access), type of food.

Variables for Experiment 2:

Independent variable is the chance to learn cleaning from another adult mouse.

Dependent variable is the cleaning habit (start date and frequency)

Controlled Variables are the cage, the location of the cage, temperature, feeding time.

Constants are water (continuous access).


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.

Sample Hypothesis for Experiment 1:

Mice groom themselves at certain times according to the activity they have previously done. For example, mice might groom themselves right after meals, or right after exercise. I have come up with this hypothesis due to human behaviors since we clean before and after meals, before or after rest, and especially after exercise.

Sample Hypothesis for Experiment 2:

I believe that mouse behavior is influenced by both genetic factors and learned experiences. My hypothesis is based on my gathered information.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:


In this experiment you will be observing the cleaning habits of mice in a controlled environment and record your observations. You would like to know what hours of the day mice clean themselves and if there is any relation between feeding time and cleaning time. You may use any combination of age/sex mice for this experiment.


Place your mouse cage where you can make frequent observation while doing your other activities.

Clean the cage, remove all the food and make sure that mice have sufficient supply of water.

Prepare a schedule to feed the mice. A sample feeding schedule can be 6:00 a.m., 12:00 p.m., 5:00 p.m. and 10:00 p.m..

Everyday place mouse food in the cage at exact times specified in your schedule. Leave the food in the cage for 15 minutes. At the end of this time, remove any excess food while continuing your observation at least for another 30 minutes.

Every time that you see a mouse is cleaning itself, record the time in a table like this. If your mice are identifiable or numbered, also include the name or number of the mouse and its sex (male/female).

Date Cleaning time Mouse name/number Sex

Your real data table will have many more rows and it may be in many pages. Your observations must last for at least 7 days. Make sure that you only make one entry for each time of cleaning. All cleanings that will happen with less that one minute apart will be counted as one cleaning.

Compile the results in the above table and find out how many cleanings have happened in each hour of the day. Write the results in a table like this:

Time slice Number of cleanings
6:00 to 7:00
7:00 to 8:00
8:00 to 9:00
9:00 to 10:00
10:00 to 11:00
11:00 to 12:00
12:00 to 1:00
1:00 to 2:00

This table will have one row for each hour of the day that you have made observations. If you can not make necessary observations because of going to school, you may do this only during weekends and holidays.

Questions to ask and answer while observing the cleaning habits of your mice:

  1. When do mice generally clean themselves the most? For example, do they clean themselves before/after eating, before/after sleeping, before/after being petted, before/after exercising, etc.?
  2. Why do mice clean themselves? Do they clean themselves only when they are dirty or is it a habit just like eating and sleeping?
  3. Where do mice clean themselves? There are two parts to this question. One can be where as in relation to the particular body part, and the other can be where as in relation to the area of the cage.
  4. How do mice clean themselves? What methods do mice use to clean themselves? Also, if more then one mouse is in a cage, will they clean and groom each other? Will they clean themselves at the same relative times?
  5. How many times a day to mice clean themselves?

After about 10 days of continuous observations, you will have enough data and analysis of the mouse cleaning habits to draw some conclusions. Include these in the conclusion section below along with any final analysis you have about your experiment. (As you see, your observations and recordings may cover much more than the time of cleaning. Your data tables may contain additional information based on the data that you gather.)

Experiment 2:

Introduction: In this experiment you try to find out if the cleaning habit of mice is an instinct or a learned behavior. For this experiment you will grow pet mice who have never met their parents or any other adult mouse; so, they have never had chance to learn cleaning from others. You will then make observations to determine if such mice ever clean themselves.

Procedure 1:

  1. Prepare two cages to hold mice. Proper food and water is the only thing required in this cage. You may decide to add props to your cage to enhance your display and for the enjoyment of the mice.
  2. Purchase a male and female mouse. Having a pair of opposite sex is vital to your experiment. The purpose of this is to have your mice reproduce a new litter of mice, which you will then use for your observations. You can quicken and simplify this experiment if you are able to buy an already pregnant female mouse. Ask a worker at your pet store to help you pick out the right mice for this sort of experiments. Explain the experiment to them if needed. Please note that if your mice do not reproduce, then this experiment cannot be completed. Once you have the two mice in the same cage, you will have to wait until the female mouse gives birth to the litter of baby mice. It generally takes about 4-5 weeks for a mouse to give birth to a litter after she has been impregnated.

At this point of the experiment, you will need to wait a month or more (however long it takes for your mouse to have a litter of baby mice) before you can continue.

Once the litter of baby mice are born, you may continue with your experiment. The litter will generally have about 5-10 mice. Usually, not all survive the first few weeks after birth. You will be separating half of the mice away from the mother and placing them into a separate cage with no visual connection between the cages. The other half of the litter will remain with the mother. It is important to separate the mice as soon as possible without them dying, since the point of the experiment is to avoid contact with the mother for half of the litter. Once you have separated the litter, you will begin your observation period.

3. Keep your baby mice warm and feed them with milk using a dropper. They will need continuous attention in the first few days.

4. Continue your observations similar to the experiment 1 with baby mice living with their mother and baby mice living in a separate cage.

Do these two groups of baby mice clean themselves at a similar rate and similar conditions?

How to evaluate the results?

The main aspect that you will be observing for is grooming. Mice generally groom themselves. We want to find out whether this is a genetic trait or whether the mouse learns this behavior from its mother. Observations must be made everyday. If the mice who are in the cage with the mother begin grooming themselves first, then this suggests that the mice have learned this behavior. Also, if the mice who are not around the mother eventually begin grooming themselves, then it suggests that this behavior is also genetic. So basically, these results that I just proposed would show that grooming is a mixture of genetics and learning experience. To explain it further, the mice in the cage with the mother learned and imitated their mothers grooming. This is why they began grooming themselves earlier. However, the other mice eventually groomed themselves and had no other mice around to learn from, which shows that it is a genetic trait which causes this behavior (grooming). Record all observations and write a report with your experimental results.

Materials and Equipment:

  • Two cages that can hold mice.
  • A female and male mouse (younger mice around the ages of 3-4 months are needed so they are sexually active and able to reproduce).
  • Mouse food and water
  • Data sheet to record observations
  • Information on how to properly care for mice.

You can go here to learn how to care for pet mice.

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


If you do any calculations, write your calculations in this section of your report.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.