Rating scales for wildness and ease of handling and its
application to 21 inbred strains are published in Wahlsten et al.,
2003. The behavior tests that were performed are summarized in Table 1.
The wildness rating scales are summarized in Table 2.
This study was conducted on the same set of mice that were tested for several behavioral parameters and examined for brain defects (Wahlsten1).
Virtually every procedure or test requires capture of the mouse, brief holding, then recapture for return to its cage. For example, one trial in the water maze requires capture of the mouse, picking it up and placing in the water, then capture and picking up for return to the cage at the end of the trial. Thus, one trial involves two episodes of capture and two of holding.
Ratings were developed (see Table 2) for these situations when handling mice:
2. Hold - when the mouse is lifted from the substrate and placed in a new location while holding it by the tail; occurs when changing cages, marking the tail, weighing, and testing in many kinds of apparatus; also while holding for injection with a hypodermic needle.
Wildness was rated only once per trial for capture and once per
trial for handling. By convention, the worst behavior score on
the trial was assigned. For example, if the mouse is easy to
capture and handle at the start of the trial but then it jumps
onto the floor and runs around the room during recapture, the
capture score for that trial would be 6 (the worst score; see
Table 2). Injection with a needle usually involves one capture,
then one handling, followed by return to the cage, but a mouse
may escape during the handling while being injected. If its
capture rating is 2 on initial capture but then it escapes during
injection and runs around the table, the capture score for that
trial would be 4 (see Table 2). For a session involving more
than one trial of a single kind, the worst score attained on all
trials was assigned (See Table 1 for number of trials per test).
Table 1. Behavioral tests used for rating wildness
Table 2. Rating scales for mouse wildnessEach scale yields a single integer rating. The scale is ordinal; differences between adjacent values may not be of equal size throughout the range.
Capture - from the home cage, the testing cage, or a test apparatus
Score Behavior Frequency Comments ----- ------------ --------- ------------------------------ 0 Minimal 4766 resistance to capture 1 Evades touch 542 Must complete at least one by running circuit of cage, going end to around cage end twice or following along the full perimeter 2 Jumps onto 191 While being pursued; does not wall of cage apply to cagemates awaiting their turn; mouse is often captured by the tail, once on the wall 3 Jumps out of 60 Either large jump from cage cage floor or short hop down from completely wall; often is captured after onto table landing on table 4 Runs from 36 With or without experimenter in vicinity of pursuit cage 5 Jumps off 48 Usually while being pursued, but table or could happen with one large jump apparatus from the cage floor; often onto floor captured soon after landing 6 Runs around 107 Need not complete a full room circuit; anything requiring active pursuit to recapture
Holding - when being picked up and then placed on a different substrate or held for injection
Score Behavior Frequency Comments ----- ---------- ---------- ---------------------------- 0 Minor 4527 struggle 1 Squeaks or 777 Must be clearly audible squeals 2 Vigorous 341 May attempt to pull away or struggle or climb up tail; can occur without twisting/shak any squeak being heard ing 3 Attempts to 51 Jaws open near hand or forceps bite 4 Bites 52 Teeth make contact with glove or experimenter skin or forceps; need not penetrate or draw bloodNotes: Frequencies are based on 392 mice from 21 inbred strains on 15 tests (Table 1). Some mice did not complete all 15 tests but no trial was terminated because of excess wildness.
Investigator NotesWe have found that it is too time consuming and distracting to rate wildness on every trial during a session, so we made note of mice that performed badly on several trials. If, however, one does a study mainly aimed at rating wildness, then a separate rating could be made for each trial.
It is common practice in many tests to first capture and then
hold the mouse by the tail, so one may add the two scales. In
this application, a score of 0 will certainly indicate a docile
or placid animal and a 10 will denote one that escaped capture
and ran around the room, then bit the experimenter when it was
finally captured. A score of 5, on the other hand, could arise
from extreme difficulties with either capture or handling, or
from mild difficulties with both. Consequently, if a total score
is calculated, it is important to record Capture and Hold