Definition

Following is a type of affiliative behavior in which one mouse comes after the other, in a timely manner.

When performing this active behavior, a mouse is ahead and the other mouse is close to it, tagging along as if chasing or being led by the other mouse.

Description

Following is when mouse trails behind another, moving behind them around the cage. Following does not include running nor any fast, abrupt movements.

Following is considered to be an investigative and explorative behavior since it involves interacting and getting familiar with another mouse by means of moving behind them.

Supplementation can reduce or increase following. For example, when sociable mice are given 0.4 g/kg of ethanol, they will display a decrease in the amount of following that they perform.

Following is Not as Aggressive as Chasing

Following is similar to chasing. However, chasing is more aggressive and faster in nature. Also, while chasing can be interpreted as a form of aggression, following cannot.

During data gathering, chasing and following are frequently placed in the same behavioral category, “Social Interactions,” when researchers are quantifying behaviors. Yet, only chasing may be included in the “Aggression” category together with other behaviors such as biting.

Housing Conditions Impact Following

Behavioral differences in following can be influenced by how the mice are housed and genetics. For example, singly-housed mice will show less following, when paired with a new cagemate.

Function of Following

Following is an affiliative behavior that is exhibited when one mouse is interested or getting to know another mouse. Following is often categorized as an “active social behavior” in experiments that measure sociability in mice.

The importance for sociability is to increase relationships and bonds between the mice. Therefore, active social behaviors like following serve as a means to an end, in order to facilitate social living conditions between the mice.

Application

Following can be observed under the following circumstances:

  • In communal nesting: Since following is a social behavior requiring two mice, it is more likely to occur in a communal nesting set up.
  • Between young mice: Young mice are likely to display this behavior while playfully interacting with each other or during group play.

Behavioral Tests for Assessing Following

Following, since it requires two mice to occur, can be observed experimentally whenever social or explorative behaviors are being studied.

  • Video Analysis: Since following is very short in duration, typically failing to last for one second, it is commonly scored in terms of frequency. Researchers will track mice using video analysis and tally up the times that it followed another another mouse.
  • The Resident-Intruder Task: Tests such as the Resident-Intrudent Task are commonly used to quantify how much following has taken place. Depending on how the data gathering or experiment is organized or structured, following may be categorized as a “non-sniff” behavior during the Resident-Intruder Task.
  • The Social Interaction Test: In the Social Interaction Test, where a mouse is introduced to a novel mouse and is expected to interact with them, following behavior is typically measured as an affiliative gesture.

Mouse Strains Exhibiting Following Behavior

Following is a behavior commonly displayed by normal mice. However, depending on the animal model or strain being studied, significant differences will be found in the frequency in which the behavior is expressed.

C57BL/6J Mice Serve as Controls

C57BL/6J mice commonly used in behavioral research, are typically used as controls when studying mouse strain behavior, in order to establish behavioral parameters and characteristics. C57BL/6J, during the social interaction test, will almost always react with active social behaviors such as following when a novel, unknown mouse is placed in their cage.

BTBR T+tf/J Mice Rarely Follow

Other strains, especially those that model conditions with social deficits, will display the following behavior less. For example, BTBR T+tf/J mice, an inbred strain displaying multiple behaviors symptoms relating to autism spectrum disorder (ASD), very rarely follow a novel mouse during the social interaction test. In fact, one experiment noted that the BTBR T+tf/J strain did not once display the following behavior when introduced to a new cagemate within the 20 minute timeframe in which the interaction test was administered.

Abnormalities Influencing Following

Pediatric TBI Decreases Following Behavior in Adulthood

Conditions such as traumatic brain injury (TBI) affects the frequency in which mice will follow another mouse. Adult mice with pediatric TBI will follow another mouse significantly less than their sham-operated counterparts, a deficit in social interaction that is not observed in adolescent mice with pediatric TBI.

Stereotypy: Route-tracing

Stereotypy is a general term that refers to a class of abnormal behaviors which are repetitively and excessively performed without a clear goal or function.

The stereotypy which corresponds to following behavior is route-tracing. When route-tracing, a mouse is following (moving or running over) the same pattern for at least three consecutive times.

Thus, instead of following another cagemate, a mouse is following its own cage movements repetitively. The mouse traces the same areas in the cage, i.e. the route it has previously taken.

Summary

  • Following is a type of active social behavior in which one mouse comes after the other, in a timely manner.
  • Following is similar to chasing. However, chasing is more aggressive and faster in nature.
  • Following is an explorative behavior that is exhibited when one mouse is gathering information about the other mouse.
  • Behavioral assessments sensitive to following are the Resident-Intruder Task and the Social Interaction Test.
  • Typically, C57BL/6J mice serve as controls when this behavior is being studied.
  • Mice that model disorders with a social component, such as the BTBR T+tf/J mice which model ASD, rarely follow.

Furthermore, additional research is necessary to characterize this behavior in mouse strains. Not a lot of information is available in the scientific literature that clearly outlines the characteristics of each mouse strain. Since following is a behavior that can have investigative and affiliative connotations, more investigation is necessary in order to better understand its nuances.

References

  1. Kršiak, M. “Effect of ethanol on aggression and timidity in mice.” Psychopharmacology 51.1 (1976): 75-80.
  2. Kršiak, M. “Timid singly‐housed mice: Their value in prediction of psychotropic activity of drugs.” British Journal of Pharmacology 55.1 (1975): 141-150.
  3. Kaidanovich-Beilin, Oksana, et al. “Assessment of social interaction behaviors.” Journal of visualized experiments: JoVE 48 (2011).
  4. McFarlane, Hewlet G., et al. “Autism‐like behavioral phenotypes in BTBR T+ tf/J mice.” Genes, Brain and Behavior 7.2 (2008): 152-163.
  5. Semple, Bridgette D., Sandra A. Canchola, and Linda J. Noble-Haeusslein. “Deficits in social behavior emerge during development after pediatric traumatic brain injury in mice.” Journal of neurotrauma 29.17 (2012): 2672-2683.

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