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A study of territoriality in mice

A study of territoriality in mice

Introduction: (Initial Observation)

Territoriality is a behavior pattern in animals consisting of occupation and defense of a territory. We often study behavior in human and animals in order to understand the genetic factors and science behind each behavior. Such studies must be conducted on different species. For example in this project you study territoriality in one type of mouse (You choose the type of mouse, but note that you can not generalize your conclusion to cover all different types of mice).


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.
We first need to know a generally accepted definition for territoriality and comparison with personal space.

  • Territoriality is Ownership or control of a geographical area by one or more individuals. (contrast with personal space).
  • Territories are usually larger than personal spaces.
  • Territories are demarcated and defended.
  • Territories organize interactions between individuals and groups, can serve as ways of displaying one’s identity, and are sometimes imbued with sentimental feelings and attachment.

We then need to know what behavioral patterns can be associated with territoriality. This depends on the type of animal that we choose to study. Close observation is required to identify such behavioral patterns, however we may gather such information from other similar studies. Most territorial behaviors appear in the form of aggression toward the intruder.

Finally we need to know how does the animal set the boundary of his/her territory. This is called Demarcation. In general demarcation is in the following forms:

  1. -physical presence (proprietorship, physical contact)
  2. -touching, manipulation- some ritualized; (e.g., people touch their plates at restaurants during territorial encroachment).
  3. -vigilance and surveillance, particularly on the boundary of an area. Use of ritualized entry and greeting behaviors. Famous study by Julian Edney in which he found that residents of houses with “keep out” types of signs came to their doors faster. Compare in humans, dogs, and other species.
  4. -marking of territory: signals ownership in the absence of the owner (humans, dogs, hippos, pack rat middens)
  5. -personalization (only in humans)-decoration to fit one’s tastes and personality. Very important to humans. Connections between personalization of territory and:
  •  self-image and self-identity (“who am I?)
  •  mental health (e.g., in institutionalized environments such as rest homes and hospitals)

Functions and benefits of territoriality:

  1. -establishment of identity (individual differences in how important this is to people: some people can’t bear to leave home; need to get back to reestablish who they are; don’t like to travel. Some people need to have their home highly personalized, while others don’t. Some people need to have their body highly personalized, while others don’t (clothes, jewelry, make up, hair cut). Some people couldn’t bear to wear a uniform.
  2. -control and predictability (resources: space, objects, time; sensory inputs: when, how much, what, who)
  3. -safety and protection

More Information:

Source: http://www.stanfordalumni.org/birdsite/text/essays/Territoriality.html

Many birds attempt to exclude other birds from all or part of their home range — the area they occupy in the course of their normal daily activities. When they do, we say they are defending a “territory.” Most often this behavior occurs during the breeding season and is directed toward members of the same species. Territoriality appears, in most cases, to be an attempt to monopolize resources, especially food resources or access to mates. But territoriality may also serve, in part, as a predator defense mechanism.

Some birds defend their entire home range. Others defend only their food supply, a place to mate, or the site of their nest. Some tropical hummingbirds chase most other hummingbirds and other nectar-feeding birds (and some butterflies) away from favorite patches of nectar-bearing flowers. On their leks (patches of ground traditionally used for communal mating displays) grouse, some sandpipers, and some other birds defend small territories. Most colonial-nesting seabirds simply defend the immediate vicinity of their nests — presumably to protect their eggs and, at least in the case of some penguins, the pebbles from which the nest is constructed.

Territoriality tends to space some species of camouflaged birds and their nests rather evenly throughout their habitat; it prevents them from occurring in flocks or clusters while breeding. This, in turn, may reduce the danger from predation, since many predators will concentrate on one kind of prey after one or a few individuals of that prey type are discovered (that is, the predator forms a “search image”). Clustering can promote the formation of a search image by predators and thus reduce the security of each individual prey (birds that are not cryptic, however, may gain protection in clustering).

To minimize the need for actual physical contact in order to defend territories, animals have evolved “keep-out” signals to warn away potential intruders. In birds, of course, the most prominent are the songs of males. Far from being beautiful bits of music intended to enliven the human environment (as was long assumed), bird songs are, in large part, announcements of ownership and threats of possible violent defense of an area. If, of course, the aural warning is ineffective, the territory owner will often escalate its activities to include visual displays, chases, and even combat. This territorial behavior is typically quite stereotyped, and can usually be elicited experimentally with the use of recorded songs or with stuffed taxidermy mounts.

Territory size varies enormously from species to species, and even within species, from individual to individual. Golden Eagles have territories of some 35 square miles; Least Flycatchers’ territories are about 700 square yards; and sea gulls have territories of only a few square feet in the immediate vicinity of the nest. Territory size often varies in the same species from habitat to habitat. In relatively resource-poor Ohio shrublands, Song Sparrows have territories several thousand square yards in extent. In the resource-rich salt marshes of the San Francisco baylands they are about one-fifth to one-tenth as large. The San Francisco birds need to defend much less area to assure an adequate food supply.

Genetic grounds of Territoriality in mouse:

Two scientists have identified more than a thousand genes in mice dedicated to perceiving smells. Rodents, we now know, have many more genes for smell than humans do, a trait that may give them a greater entrée to the world of odors. In a related finding, scientists say the repertoire of pheromone genes in mice is larger than expected. Pheromones are chemical signals that mice and other species use to send and receive information about everything from aggression to love. Read more…

Rats and aggression – definitions of normal rat behaviour

Today in Sweden there is talk about extremely aggressive rats being common among the pet/fancy rats. But how do you know what is the normal amount of aggressivity in the rat? Well, you study how wild rats of the same species (the brown rat, Rattus norwegicus) behaves. Through the years many scientist have been studying wild rats. Read more …

About House Mouse


Length of the head and body is 150-190 mm and the tail is 70-95 mm long. Fur coloration is generally light brown to black above, with white or buffy below. The long, tapered tail has obvious circular rows of scales (annulations) and is very sparsely furred. The house mouse tend to have longer tails and darker coats when living communally with humans as opposed to the wild forms.


In the wild state, house mice generally dwell in cracks in rocks or walls or make underground burrows consisting of a complex network of tunnels, several chambers for nesting and storage, and three or four exits. When living with humans, house mice nest behind rafters, in woodpiles, storage areas, or any hidden spot near a source of food. They construct nests from rags, paper, or other soft substances and line them with finer shredded material. House mice are generally nocturnal, although some are active during the day in human dwellings. House mice are quick runners (up to 8 miles per hour), good climbers, jumpers, and also swim well. Despite this, they rarely travel more than 50 feet from their established homes.

The house mouse is generally considered both territorial and colonial when living communally with humans. Territoriality is not as pronounced in wild conditions, however. Dominant males set up a territory including a family group of several females and their young. Occasionally, subordinate males may occupy a territory or males may share territories. Females establish a loose hierarchy within the territories, but they are far less aggressive than males. Aggression within family groups is rare, but all the individuals in a territory will defend an area against outsiders. Young mice are generally made to disperse through adult aggression, although some (especially females) may remain in the vicinity of their parents.


The house mouse is characterized by tremendous reproductive potential. Breeding occurs throughout the year, although wild mice may have a reproductive season extending only from April to September. The estrous cycle is 4-6 days long, with estrus lasting less than a day. Females experience a postpartum estrus 12-18 hours after giving birth. Females generally have 5-10 litters per year if conditions are suitable, but as many as 14 have been reported. Gestation is 19-21 days but may be extended by several days if the female is lactating. Litters consist of 3-12 (generally 5 or 6) offspring, which are born naked and blind. They are fully furred after 10 days, open their eyes at 14 days, are weaned at 3 weeks, and reach sexual maturity at 5-7 weeks. Average life span is about 2 years in captivity, but individuals have lived for as long as 6 years. In the wild, most mice do not live beyond 12-18 months.

Feeding Habits

In the wild state, house mice eat many kinds of vegetable matter, such as seeds, fleshy roots, leaves and stems. Insects (beetle larvae, caterpillars, and cockroaches) and meat (carrion) may be taken when available. In human habitation, The house mouse consumes any human food that is accessible as well as glue, soap, and other household materials. Many mice store their food or live within a human food storage facility.
Source: http://www.animals-b-gone.com/Rodent_Info/rodent_info.html

Question/ Purpose:

The purpose of this project is to know if there are any territorial behavior in mouse. If there is, we want also want to know:

  • Does territorial behaviors vary among sexes?
  • Does territorial behaviors vary among ages?
  • Is territorial behavior against certain sex, species or age?
  • Does any other factor such as weather conditions, food, pregnancy, etc… affect territorial 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.

For any of the above questions you define a different set of variables. For example:

  • for the effect of sex in territoriality behaviors your independent variable is sex (male, female). Dependent variable is existence of territorial behavior (yes, no).
  • or the effect of age in territorial behaviors your independent variable is age (1 month, 2 months, 3 months, …). Dependent variable is existence of territorial behavior (yes, no).
  • For the type of intruders that will trigger territorial behavior , independent variables are different age, sex and animal type. Dependent variable is territorial behavior (yes/ no).

Note: You may want to focus your research on one of the proposed questions only. If you decide to work on more than one question, note that you can not combine your experiments. Each experiment must test one variable only. Also as scientific method requires, you need to have a large number of samples to be able to make a trustable conclusion. For example you may want to test one hundred male mouse in 10 different equal size age groups (1 month, 2 month, … 10 month) and see if they show territorial behavior while another one month old male mouse is placed in the cage. You may repeat this experiment with different male intruders in different ages). Experimenting on such a large scale requires large scale laboratories and staff that is not available to most students. That is why you may test smaller groups of 2 to 10 mouse, however in your conclusions you need to note possible errors caused by small number of samples.


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. For each question you may propose one hypothesis and perform one experiment to test that hypothesis. Following are some sample hypothesis:

  • I think male pet mice will have territorial behavior, but females will not be territorial.
  • I think territorial behavior does not exist in the first few months of a young mouse.
  • I think mouse will demonstrate territorial behavior only when the intruder is another mouse, in other words I think if there is no intruder or if the intruder is a frog or bird, there will be no territorial behavior.


Note that only experiments can show if any hypothesis is correct or wrong.

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.”


In order to examine territorial behavior we can use two different methods.

  • In first method one mouse will occupy the place first and establish a territory without any competition. The new mouse will enter after the first mouse is fully settled down. In this case the first mouse may defend his territory and attempt to force the other mouse out of his territory by aggression.
  • In the second method two stranger mouse will enter a cage at the same time and both of them have chance to establish a territory or share the territory or do not show any territorial behavior at all. (Sharing territory means that these two mice will not show any aggression against each other, but they show aggression against any new mouse that wants to enter the cage in future.)


How to introduce the intruder to the territory?

If you are using interconnected cages (for example those who are connected to each other via a clear plastic pipe), you can keep the connection closed and when the experiment starts, then you open the connection so mice can travel from one cage to the other. You may also need to encourage intrusion by limiting the amount of food in one cage. The benefit of this method is that the intruder will have chance to return to it’s own space if territorial behavior was observed.

If you are using regular cage, you can simply place a new mouse in the cage and observe the behavior of the other mouse.

Territorial behavior must be observed in a few minutes up to a day. If no territorial behavior was observed within this period, separate the mice so you can use them for further experiments. For example if a one month old mouse does not show territorial behavior, you will test the same mouse again when he is 2 months old.

Report the result of your experiments in a table like this:

Territorial behavior of a male mouse against another male mouse by age:

Age of intruder

The age of host mouse that may show territoriality

1 month 2 month 3 month 4 month 5 month 6 month
1 month
2 month
3 month
4 month
5 month
6 month

The above table can be color coded. For example red can represent territorial behavior by host and blue means no territorial behavior.

Need a graph?
If you have access to enough mice to repeat this experiment 10 times, then your results table can show a number instead of a color code. The number will show how many territorial behavior you observed in each age group. For example if you write 8 in row 3 column 4, it means that in 8 out of your 10 experiments 4 month old hosts showed territorial behavior against a 3 month old intruder. You can later convert this table to a 3D bar chart. A 3D chart can also be constructed by cutting wooden sticks and placing them vertically on your results table. For example you place an 8″ tall stick over the number 8 and a 3″ stick over the number 3. Taller stick bars indicate higher rate of territorial behavior for the age group they represent.

Materials and Equipment:

For the experiments of this project you need:

  1. one or more mouse cage (Plastic or metal)
  2. mouse food
  3. wood chips
  4. mouse water feeder
  5. papers for recording your observations

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.

The final results of your experiments will be in the form of tables. You will then use these results to draw a conclusion for each question.


If there are a large number of test subjects, you may need to do some calculations and find some ratios. For example you may calculate what percentage of male mice shows territoriality in the age of 3 months.

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.