Mice Response to Owl Call Behavior

Relindis Awah & Katie Weaver

Dr. Paulson

Animal behavior

26 April 2011

Introduction:

            Prey animals live a perilous life in which they are constantly estimating the risk of foraging and obtaining a mate against becoming a predator’s meal.  Small rodents have evolved many strategies in which they are better able to discern danger of a certain time or area.  Based on these environmental cues, they choose the most appropriate behavior to minimize mortality.  Rodents display a variety of avoidance tactics as well as the traditional freeze or flight scenarios, which will be looked at in the current study.  A closer look in to the relationship of predator avoidance can be useful in order to better understand how animals survive, remain fit, and keep a healthy population number despite a heavy density of predators (Eilam et al. 1999). 

                 Evolution has acted upon the behavior of rodents to give them advantages to elude their predators and better the fitness of the population as a whole.  Some mice studies show that although many rodents proceed with common ancestral behaviors some have evolved behaviors based on their species’ ecology to better suit their needs and waste less energy, as they do not always respond to owl calls.  Nevertheless, very complicated interactions are being discovered and shedding interesting light on how predation and avoidance influence ecological processes.  Although an older study subject, much is still being learned and new discoveries are being made that can be used in not only comparative studies, but also population management (Lime 2002).

            For this experiment, the hypothesis is that the white mice will have no change of behavior to the owl calls.  The wild mice should either freeze or run at the sound of the owl, but not the other sounds.  In addition, the mice should avoid the leaves during the study as it is noise and as prey, they would want to be as silent as possible.

Procedure:

              We obtained ten white mice bred in captivity.  These mice were placed in a metal cage measuring about 40 by 70 and 25cm high.  The mice were given standard food and water without restrictions.  In order to get wild mice, we trapped twice for mice using Sherman traps on fair weather nights.  Two different locations were trapped, the biology pond and around the soccer fields.  On the first day of trapping, two mice were obtained and on the second four mice were caught.  Both the wild and white mice were used to run the experiment.  The testing was done in a wide plastic container with an open top.  Its bottom was partitioned into three sections, a third was covered with soil, another third was covered with dried leaves, and the last third was filled with pieces of wood to simulate shelter.

            The mice were introduced to the test arena the same day the experiment was run.  We took the mice out of their cage or the Sherman trap and tested each individually for the entire experiment.  They were placed in the arena for about 4 minutes for habituation to the test conditions.  The acclimation was necessary in order to reduce stress before running the experiment.  Each mouse was tested only once.  During the testing, the other mice were kept in a separate area to prevent them from hearing the sounds.  Each mice placed in the test arena was exposed to different noises for about 1 minute. We observed the mice’s reaction to a Barred owl, an American robin, and a controlled call, which was white noise and use as a neutral stimulus.  The order of the calls was played in a random order so that it would not affect the results.  Two minutes of quiet was observed between calls.  This silence provided the mice with an opportunity to habituate to the test set-up and separate in time the effect of owl calls.  We made observations of each behavior and jotted down our findings.  Observations were categorized into active searching, freezing, and hiding (running to shelter).

Results:

               The wild mice had some change in activity level when the listened to the two bird calls.  While, regardless of what kind of sound was played, the mice did not change their activity.  No change in activity was observed with the white noise as expected.  Of the six wild mice, two froze for the robin call, one froze for the owl, and one went into hiding (Table 1). No significant results were found with a p-value of 0.785 using an ANOVA test.  Two wild mice and one white mouse did not explore the arena during the acclamation time.  Overall, the white mice calmly explode the arena, while the majority of the wild mice explored frantically.  During the owl calls, individuals in both groups were seen moving to the top of the shelter area, showing they were not expecting an aerial attack.  The two wild mice (wild 3 and 4) that had the owl call followed by the robin call showed reduced stress immediately following the owl call once the robin call was played.  

Table 1.  Mice reactions to calls of the Barred owl, the American Robin, and white noise.  All mice were actively searching during the white noise so it is not shown here.

Mice	Acclamation	Owl	Robin
White1	active searching	active searching	active searching
White2	active searching	active searching	active searching
White3	active searching	active searching	active searching
White4	active searching	active searching	active searching
White5	active searching	active searching	active searching
White6	hiding	active searching	active searching
White7	active searching	active searching	active searching
White8	active searching	active searching	active searching
White9	active searching	active searching	active searching
White10	active searching	active searching	active searching
wilds1	active searching	freeze	active searching
wilds2	hiding	active searching	freeze
wilds3	active searching	hiding	active searching
wilds4	active searching	active searching	active searching
wilds5	hiding	active searching	active searching
wilds6	active searching	active searching	freeze

Discussion:

              Our hypothesis was not fully supported.  It was supported in that the white mice had no response to the stimulus and that the mice would generally avoid the dry leaves during owl calls.  The hypothesis was not supported in that most of the wild mice had no change in behavior during the owl calls.  Also, two wild mice did also freeze with the sound of the robin call.

            There was a large inconsistency in the reactions of the wild mice.  This may be largely due to the multitude of stimulus and stresses perceived by the mice during the study.  Some of the active searching was most likely an attempt to find a way out of the arena and often forced attention on the walls of the arena.  Future studies should work on setting up a more calming and familiar arena for the wild mice before the experiment is run.  The next study should also work on obtaining a larger number of organisms to increase the strength of statistical tests.  These flaws were due to the period in which the study was run as well as housing difficulties for the wild mice.  We also did not want to risk infection to the white population and housing opportunities was at a minimum.  The two wild mice that showed reduced stress immediately following the owl call once the robin call was played may show that songbirds show there is not predator; however, there is too little data to speculate in this study.

            Freeze and flee are typical responses to predators previously described for a broad spectrum of prey species.  Many mammalian species flee in variable patterns that have an appreciable probability of leading to escape.  In contrast, other species rely on camouflage and freeze techniques.  The dichotomy of freeze or flee behavior may occur in different individuals of the same species under similar conditions.  This dichotomy raises the questions of why different individuals respond differently to the same predatory risk and whether different individuals are predisposed to one form of response or another.  Mice that fled in our study were more active before the exposure to owl calls than mice that froze, suggesting that the response is related to the behavior prior to the owl calls.  Alternatively, individuals may have an innate predisposition for a certain type of behavior, like the wild mice versus the white mice. White mice seemed to have no reaction to owl calls, suggesting that they had no genetic predisposition to react to the call or that it must be learned.  Such a difference between individuals might enable one to predict the pattern of response even before exposure to the stress stimulus.  The occurrence of such a pattern raises the hypothesis that the response (freeze or flee) is a characteristic of the individual prey animal and is relatively independent of the immediate predatory stimuli. However, this must be tested with a variety of predatory stimuli (Eilam et al. 1999).

Future Direction/ Extension Questions:

·         Innate or learned: Switch parents to see if response to owl call by mice is an innate behavior or learned.  Wild mice will raise white mice young and vice versa.  The response to owl calls between the four groups would be studied thereafter.

·         If white mice had previous experience with owls, would the act differently?  Does the age and experience of the mice matter?

·         Did the presence of the experimenters affect the reaction of the mice?  An experiment can be set up using video cameras only and pre-programmed sounds.

·         Did other calls from outside affect our study?  Birds and distant human voices were heard.

·         The experiment was conducted during the day.  The activity level of mice increase at night.  Could performing this same experiment at night yield different results?

·         Decibels of sound could have had an effect on the mice reaction.  The next study has to be done with more knowledge on the correct magnitude of sound that would elicit a response in the mice.

·         In the next study, a bigger test arena is required. Also, the mice need more time to acclimate to their environment. This would reduce their stress level and act more realistically.

·         A study could be done to measure the level of stress hormone increase in wild verse white mice when they hear owl calls, to determine the physiological response that they have.

Works Cited

Eilam, David, Tamar Dayan, Shamgar Ben-Eliyahu, Ifat Schulman, Gabi Shefer, and Colin A. Hendrie.  1999. Differential behavioral and hormonal responses of voles and spiny mice to owl calls. Animal Behavior 58: 1085–1093.

Lime, Steven L.  2002. Putting predators back into behavioral predator-prey interactions. TRENDS in Ecology and Evolution Vol 17 No. 2: 70-6.