Studying Territorial Behavior in Crickets: A Laboratory Guide

199 T W E LV E Animal Behavior: Territoriality in Crickets OBJECTIVES By the end of this laboratory exercise, you should be able to 1. Create an ethogram to study cricket behavior. 2. Measure territorial behavior in crickets. 3. Be able to design and carry out an experiment examining behavior in crickets. INTRODUCTION Humans have been interested in animal behavior for as long as our history has been recorded. The actions of animals were important in that humans were often items of prey for larger carnivores, and in turn many animals were prey for humans. It is necessary to understand the behaviors of animals in order to trap them for food as well as to avoid being eaten. This fascination with animals continues today and humans have many ways in which they interact with animals. Animal behavior is studied in a similar manner to the rest of science, beginning with the scientific method. However, the first step in the method, making observations is a much larger component of behavioral studies. Observing animal behavior is more than simply watching and listening; it involves systematic methods of recording, such as video, photography, drawing, audio recording, etc. These types of observations must be made over long periods of times, with many individuals, and in many diff erent situations before hypotheses can be made about animal behavior. Some of the greatest behavioral research was based on long hours of observation. Jane Goodall’s research with chimpanzees and Dian Fossey’s work with mountain gorillas are classic examples of this type of study. fis89553_ch12.indd 199 fis89553_ch12.indd 199 30/05/12 4:39 PM 30/05/12 4:39 PM

Laboratory 12 200 The most common approach to observing animal behavior is to construct an ethogram . An ethogram is simply a list of all of the behaviors exhibited by the species being studied. To create a truly complete ethogram would take many years of observation and would include every possible behavior. However, most behavior researchers use an operational ethogram, which focuses on some specific aspects of behavior for more intense study. For example, an operational ethogram could focus on the various types of grooming behavior in the great apes, or the mating behaviors of cheetahs. Figure 12.1 shows a sample operational ethogram for feeding behavior in gray squirrels. Today you will create your own operational ethogram for territorial behaviors in crickets. When you are observing behaviors you will find that they can be broken down into two different categories: states and events. Events are discrete actions of a short duration that can be easily identified. Events have a beginning and an end, and it is possible to record the length of the event as well as the number of times the event occurs. For example, eating an orange is an event, shaking a tree branch is an event, and neighing is an event. The other category of behavior is called a state. This is an action that lasts for a relatively long time such as sleeping, standing, grooming, etc. The breakdown of actions into events and states can differ depending on the animal being investigated, the type of study and the opinion of the observers. You should be able to observe both events and states in this laboratory and need to define each. The focus of today’s laboratory is territorial behavior. For the majority of animals on the planet, resources are limited and therefore organisms must find a way to gain access to these resources for survival and reproduction. One strategy for securing resources is for an animal to maintain a territory. A territory is typically defined as any area that an animal will defend, and it is usually located within the animal’s larger home range. Territories can be maintained by individual animals, mated pairs, or family groups and the size of the territory depends on the abundance of resources. If there are plenty of resources then the territory is often smaller than when resources are rare. In examining territoriality, researchers have identified four aspects of territorial behavior. The first is that the defensive behavior exhibited by the territory holder is confined to the territory and this behavior does not occur elsewhere. Another aspect of territorial behavior is that the area within the territory is only used by the territory holder(s). Other animals are not allowed into the territory. This is maintained by the third aspect of territorial behavior, which is referred to as agonistic behavior. This type of behavior can include vocal warnings, threat displays, posturing, growling, and physical aggression towards invaders of the territory. However, there is an interesting exception to this type of behavior, which is the fourth aspect of territoriality. In some cases other animals may enter the territory, but they must exhibit submissive behavior toward the territory holder. This is seen in wolves that will lie down and flatten their ears in the presence of the dominant male. Domesticated dogs often roll on their backs and lie still to show submission. Territoriality is quite common in the animal kingdom, so we assume that there are some significant advantages to this behavior. The most obvious advantage is the access to all the resources available in the territory. Some territories possess more resources than others and there can be fierce competition for the best territories. Another advantage of a territory is that it aids in the process of attracting mates. In many territorial species, the individual with the highest quality territory will gain the most mates. Often those animals that are unable to secure a territory will not mate and in some cases are not even able to survive. Even though territoriality has some distinct advantages, there are some disadvantages as well. It takes a great deal of energy to patrol a territory and keep out intruders. This is energy that could be spent on reproduction and basic survival, but must be expended in territory defense. The time required to defend the territory is yet another disadvantage. Th is takes time away from mating, rearing young, fis89553_ch12.indd 200 fis89553_ch12.indd 200 30/05/12 4:39 PM 30/05/12 4:39 PM

Animal Behavior: Territoriality in Crickets 201 obtaining food, and other such activities. For these reasons, there is both a cost and a benefi t to territorial behavior and it only occurs when the benefi ts are greater than the costs. In most natural systems, territories are only maintained when resources are limited. One aspect of territorial behavior that we will examine today is which animals are able to obtain territories and which are not. There appear to be two primary factors that determine who wins a dispute over territories. If the animals are unequally matched in size or aggressiveness then the larger and more aggressive animal usually wins. However, if the animals are equally matched in size and aggressiveness, then the animal that resides within the territory can usually force out the intruder. Apparently, there is a benefit to the possession of the territory that enables them to win more often. This may be because the resident animal knows the quality of the territory and will defend it more aggressively than the intruder who is unsure of the territory quality. In today’s laboratory exercise we will be examining territorial behaviors in the common house cricket, Acheta domestica . These animals are native to Asia but have been in the continental United States for a significant period of time. In the natural environment they feed on plant and vegetable debris, and in homes they survive on food scraps and crumbs. They are used in the United States primarily for reptile food and as bait for fisherman. We commonly recognize the presence of crickets by the sound that the males produce. Male crickets will rub together their hind wings, to produce sounds for mating and ter- ritory advertisement. The long continuous calls, known as trills, are used to attract mates. The frequency Figure 12.1 Operational ethogram of foraging in squirrels. Time Behavior 8:00 SE 8:02 FL 8:03 SE 8:04 RC 8:07 EA 8:09 RC 8:11 D 8:14 H Behavioral Definitions SE = Searching: Animal moves head around, looking over area FL = Flicking: Animal ﬂicks tail quickly back and forth RC = Removing Cap: Animal uses teeth to removing an acorn cap EA = Eating: Animal biting into acorn and swallowing D = Digging: Animal uses two front paws to dig small hole in soil H = Hiding: Animal places acorn in hole and pushes dirt over to cover fis89553_ch12.indd 201 fis89553_ch12.indd 201 30/05/12 4:39 PM 30/05/12 4:39 PM

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Laboratory 12 202 of the call varies with the size of the male, so females can actually choose the size of potential mates by listening to the calls produced. Males will typically climb onto something slightly higher than the surrounding area to broadcast their calls longer distances. A number of cricket species in this genus are aggressively territorial and will defend these higher places for calling. They advertise warnings to intruders by producing shorter calls, called chirps, usually three at a time. Although A. domestica is not as aggressive as some other species, it does display territorial behavior. By the end of today’s laboratory exercises you will be able to describe cricket behavior and determine which individuals are more likely obtain and protect territories. PROCEDURE E XERCISE 1: C REATING AN E THOGRAM 1. You will need to observe both male and female crickets to identify behaviors of both genders. 2. Obtain one male and one female cricket from the holding container. Males can be distinguished from females in that females possess a long ovipositor that extends from the posterior portion of the abdomen. Males do not possess an ovipositor. 3. Place both individuals into the same observational chamber. DO NOT LET THE CRICKETS ESCAPE!! If you let one escape, you are responsible for catching it and you will not be allowed to leave lab until it is found!! 4. Once you have placed them into the observational chamber, cover the top with plastic wrap. Use clothespins to secure the plastic wrap so that the crickets cannot escape. 5. Observe both crickets for a total of 15 minutes. 6. As a behavior occurs, write it down, clearly define it and determine if it is an event or a state. 7. You will also need to make an abbreviation for each behavior to save you time later. 8. When defining behaviors, you need to be very specific. Sleeping cannot be defined as “the act of not being awake”; instead, it could be defined as “eyes closed, no visible movement or action.” 9. Table 12.1 can be used as you generate your ethogram. fis89553_ch12.indd 202 fis89553_ch12.indd 202 30/05/12 4:39 PM 30/05/12 4:39 PM

Animal Behavior: Territoriality in Crickets 203 Behavior Name Abbreviation Definition Event or State Male or Female Table 12.1 Operational Ethogram for Cricket Behavior ( Continued ) fis89553_ch12.indd 203 fis89553_ch12.indd 203 30/05/12 4:39 PM 30/05/12 4:39 PM

Laboratory 12 204 Behavior Name Abbreviation Definition Event or State Male or Female fis89553_ch12.indd 204 fis89553_ch12.indd 204 30/05/12 4:39 PM 30/05/12 4:39 PM

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Animal Behavior: Territoriality in Crickets 205 E XERCISE 2: M EASURING T ERRITORIAL B EHAVIOR IN C RICKETS 1. Obtain three males from the tank and be sure you can tell them apart. 2. Place all three into an observation container that has two cardboard domes in it. The domes act as locations for attracting mates and therefore as territories for the animals. 3. Each member of the group should be assigned to record the behavior for one specific male. 4. Observe the behavior of all three individuals, including the number of contacts and any vocaliza- tions and threat displays. Be sure to record which animals are interacting and exactly what these interactions are. 5. Add any new behaviors that were not on your original ethogram. 6. Observe these animals for at least 15 minutes to ensure that the territory holders are established. What were the most common behaviors exhibited? What were the rarest behaviors exhibited? Were there any behaviors only exhibited by the female? If so, what were they? Were there any behaviors only exhibited by the male? If so, what were they? fis89553_ch12.indd 205 fis89553_ch12.indd 205 30/05/12 4:39 PM 30/05/12 4:39 PM

206 Laboratory 12 Table 12.2 Ethogram for One of the Three Males Observed. Time Behavior Notes/Comments fis89553_ch12.indd 206 fis89553_ch12.indd 206 30/05/12 4:39 PM 30/05/12 4:39 PM

207 Animal Behavior: Territoriality in Crickets Were the males able to establish territories in this time frame? How do you know? Describe the characteristics of the male(s) that did NOT establish territories. Describe the characteristics of the male(s) that did establish territories. E XERCISE 3: I MPORTANCE OF R ESIDENCE 1. Remove two crickets from your observational chamber and return them to the stock container. Be sure to leave one of the crickets that established a territory. 2. Remove one of the domes from the container. 3. Now place a new male cricket into the chamber and record the behavior of both for 15 minutes. 4. Again, have one individual assigned to watch a particular cricket. 5. Record your results in Table 12.3. Table 12.3 Ethogram of Territorial Behavior in Crickets: Effect of Residence Time Behavior Notes/Comments ( Continued ) fis89553_ch12.indd 207 fis89553_ch12.indd 207 30/05/12 4:39 PM 30/05/12 4:39 PM

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Laboratory 12 208 Time Behavior Notes/Comments fis89553_ch12.indd 208 fis89553_ch12.indd 208 30/05/12 4:39 PM 30/05/12 4:39 PM

Animal Behavior: Territoriality in Crickets 209 What was the hypothesis for this experiment? Did the cricket that had already established his territory keep it? How do you know? Why do you think residence is important in determining which individual gets a territory? E XERCISE 3: D ESIGN AN E XPERIMENT Work with your lab partners to design an experiment that tests some aspect of the behavior or crickets. Questions to consider: Do females have territorial behavior? Do males act differently with females pres- ent? Does size play a role in which animals win territories? Does behavior change in the dark? Does song style (chirping) differ when only males are present? Hypothesis: Experimental design: Draw a table to record your results. Carry out the experiment and record the results. fis89553_ch12.indd 209 fis89553_ch12.indd 209 30/05/12 4:39 PM 30/05/12 4:39 PM

Laboratory 12 210 Did your results support your hypothesis? Why or why not? If you conducted this experiment again, what would you change and why? E XERCISE 4: P LANT C OMPETITION 1. Flip to the last lab in the manual (Plant Competition). Today you will set up the experiments that you will finish in 2 weeks. fis89553_ch12.indd 210 fis89553_ch12.indd 210 30/05/12 4:39 PM 30/05/12 4:39 PM

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Questions for Review 211 Student Name: _____________________________________ Lab Day & Time: ________________________ 1. Humans (both males and females) also exhibit territorial behaviors associated with our living spaces. Give three examples of these types of behaviors. 2. Why is an ethogram necessary? 3. If the most aggressive individuals gain territories and mates, then the genes for aggression will be passed on differentially and more individuals in the next generation will be aggressive. What prevents a drastic increase in aggression over time? 4. Domesticated dogs maintain territories around their homes and other dogs must be able to find the boundaries of the territory. How do dogs mark their territories? 5. Bird song is one way that male birds mark their territory. Essentially some of the bird song is saying – “this is mine, go away!” Birds with larger territories are more likely to attract mates. Explain how bird song may have evolved over time. fis89553_ch12.indd 211 fis89553_ch12.indd 211 30/05/12 4:39 PM 30/05/12 4:39 PM

Laboratory 12 212 6. In many species, aggressive interactions over territorial disputes rarely involve direct fighting. Instead, threat displays are more common. However, aggressive interactions over mates are more likely to involve direct interaction and individuals can be wounded. Develop a hypothesis to explain this. 7. A researcher observed two male crickets sharing the same territory with no aggressive displays. When she examined them closely, she found that they were members of different species. Why is territory sharing acceptable in this situation? 8. As humans encroach on the natural habitat of lions, the amount of space they have to live is decreasing. Male lions are strongly territorial. Predict what types of behaviors should be more common in male lions in the future. What does this mean for their survival? fis89553_ch12.indd 212 fis89553_ch12.indd 212 30/05/12 4:39 PM 30/05/12 4:39 PM

Lab 3 Animal Behavior

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