Measuring Active and Passive Tameness Separately in Mice

Summary

Tameness in animals includes a reduction of avoidance responses to humans (passive tameness) and an increase in active approaches to humans (active tameness). Here, we describe detailed protocols for three behavioral tests (active tameness, passive tameness, and stay-on-hand tests) to separately measure the active and passive tameness of mice.

Abstract

Domesticated animals such as dogs and laboratory mice show a high level of tameness, which is important for humans to handle them easily. Tameness has two behavioral components: a reluctance to avoid humans (passive tameness) and a motivation to approach humans (active tameness). To quantify these components in mice, we previously developed behavioral tests for active tameness, passive tameness, and the willingness to stay on a human hand, each designed to be completed within 3 min. The data obtained were used for selective breeding, with a large number of mice analyzed per generation. The active tameness test measures the movement of the mouse toward a human hand and the contact it engages in. The passive tameness test measures the duration of time that a mouse tolerates human touch. In the stay-on-hand test, a mouse is placed on a human hand and touched slowly using the thumb of that hand; the duration of time that the animal remains on the hand is measured. Here, we describe the test set-up and apparatus, explain the procedures, and discuss the appropriate data analysis. Finally, we explain how to interpret the results.

Introduction

Selective breeding during domestication has changed the characteristics of domesticated animals to make them better adapted for living with humans^1,2,3. "Tameness" is a common behavioral trait observed in domesticated animals. The studies of selective breeding for tameness in animals reveal how their phenotypes have changed in the course of domestication. In a famous study, foxes were selectively bred for tameness and a group of foxes that exhibited a high level of tameness was established². The foxes also showed other phenotype changes involvi....

Protocol

All experiments were performed in accordance with the guidelines for animal experiments from the National Institute of Genetics (NIG), and all procedures were approved by the NIG Committee for Animal Care and Use (approval no. 26-9).

1. Animals

1. Selective breeding
   1. Create wild-derived heterogeneous stock (WHS)⁶ mice by crossing 8 inbred strains (MSM, HMI, BLG2, PGN2, KJR, CHD, NJL, and BFM/2) while avoiding any inbreeding (mating between siblings or cousins)⁷. Conduct a selective breeding, starting in the third generation (G3), by selecting mice that disp....

Results

We previously conducted selective breeding for active tameness in miceandsuccessfully produced mice that showed a high level of active tameness⁶. The representative results of the tameness tests for the selected and non-selected groups of mice at the 15^th generation (G15) are shown in Figure 4. Mice from the selected group scored higher on the active tameness test, exhibiting a significantly longer duration of contact with a.......

Discussion

The representative results cover nine behavioral indices from the active tameness, passive tameness, and stay-on-hand tests. A comparison of the scores between the selected and control groups revealed clear differences in tameness. These results show that the three tests are valid for measuring tameness in mice.

Tameness levels in animals can be difficult to quantify empirically. Several methods have been developed for evaluating tameness in deer, mice, and rats^8,<.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
open-field apparatus	O’Hara & Co. Ltd.	OF-3102	400×400×400 mm, grayish polyvinylchloride
compact digital camera	Ricoh Company, Ltd.	CX-5	production in the company is over
latex pure gloves	AS ONE	BioLab, IKG-8002
stopwatch	SEIKO	SSBJ018
Iodophor sanitizer	Ecolab G.K. (CLEA Japan)	CL-4123	Mikro Klene