Adult female mice were sent to the International Space Station (ISS) as part of an early life science mission utilizing NASA's Rodent Habitat. Its primary purpose was to provide further insight into the influence of a microgravity environment on various aspects of mammalian physiology and well-being as part of an ongoing program of research aimed ultimately at understanding and ameliorating the deleterious influences of space on the human body. The present study took advantage of video collected from fixed, in-flight cameras within the habitat itself, to assess behavioral adaptations observed among in-flight mice aboard the ISS and differences in behavior with respect to a control group on the ground. Data collection consisted of several behavioral measures recorded by a trained observer with the assistance of interactive behavior analysis software. Specific behavioral measures included frequencies of conspecific interactionsociability, time spent feeding and conducting hygienic behavior, and relative durations of thigmotactic behavior, which is commonly used as an index of anxiety. Data were used to test tentative hypotheses that such behaviors differ significantly across mice under microgravity versus 1g conditions, and the assumption that the novel experience of microgravity itself may represent an initially anxiogenic stimulus which an animal will eventually acclimate to, perhaps through habituation

Cadena, Sam

Choi, S.

Globus, R. K.

Gong, C.

Lowe, M.

Moyer, E. L.

Ronca, A. E.

Stodieck, Louis

Strieter, I.

NASA Technical Reports Server

Behavioral Adaptations of Female Mice on the International Space Station 
I. Strieter, E.L. Moyer, M. Lowe, S. Choi, C. Gong, Sam Cadena, Louis Stodieck, R.K. Globus, 
A.E. Ronca 
 Adult female mice were sent to the International Space Station (ISS) as part of an early life 
science mission utilizing NASA’s Rodent Habitat. Its primary purpose was to provide further 
insight into the influence of a microgravity environment on various aspects of mammalian 
physiology and well-being as part of an ongoing program of research aimed ultimately at 
understanding and ameliorating the deleterious influences of space on the human body. The 
present study took advantage of video collected from fixed, in-flight cameras within the habitat 
itself, to assess behavioral adaptations observed among in-flight mice aboard the ISS and 
differences in behavior with respect to a control group on the ground. Data collection consisted of 
several behavioral measures recorded by a trained observer with the assistance of interactive 
behavior analysis software. Specific behavioral measures included frequencies of conspecific 
interaction/sociability, time spent feeding and conducting hygienic behavior, and relative durations 
of thigmotactic behavior, which is commonly used as an index of anxiety. Data were used to test 
tentative hypotheses that such behaviors differ significantly across mice under microgravity versus 
1g conditions, and the assumption that the novel experience of microgravity itself may represent 
an initially anxiogenic stimulus which an animal will eventually acclimate to, perhaps through 
habituation. 
 
 
https://ntrs.nasa.gov/search.jsp?R=20170010365 2019-08-31T01:34:03+00:00Z


Behavioral Adaptations of Female Mice on the International Space Station

National Aeronautics and Space Administration
www.nasa.gov
Behavioral Adaptations of Female Mice on the
International Space Station 
I. Strieter1,2, E.L. Moyer3,4, M. Lowe3,4, S. Choi5, C. Gong5, Sam Cadena6, Louis Stodieck7, R.K. Globus3, A.E. Ronca3,8-10
1University of California, Davis, Davis, CA, 2USRA, Mountain View, CA, 3Space Biosciences Division, NASA Ames Research Center, Moffett Field, CA, 4Blue Marble Space Institute of 
Science, Seattle, WA, 5Wyle, NASA Research Park, Moffett Field, CA, USA, 6BioServe Space Technologies, Boulder, CO, 7Novartis, San Carlos, CA, 8Obstetric & Gynecology, Program in 
Neuroscience, 9Molecular Medicine & Translational Science, 10Wake Forest School of Medicine, Winston-Salem, NC
Methods
Making use of video acquired daily for 33 days from
within the Rodent Habitat, a selection of behavioral measures
were recorded in an attempt to assess the acclimation of the mice
to the microgravity environment. The subjects are 16-week-old
female mice (N = 10 in-flight C57BL/J6; N = 10 ground control
C57BL/J6), but because tracking them as individuals across
videos is impossible, frequencies and durations of their
behaviors were pooled into single values for each flight day. The
left and right housing areas of the Rodent Habitat (5 mice
inhabiting each) are independent environments and were treated
as such in our statistical analysis. BORIS (Friard & Gamba
2016), a free, open-source event-logging program, was used to
record frequencies and durations of the behavioral categories,
and R was used for data processing and analysis.
The categories of behavior under analysis were: Allo-
Grooming, Aggression, Proximity, and five categories
representing thigmotaxis, an index of anxiety. However, because
it was observed so rarely, allo-grooming was ultimately excluded
from the later analyses. Behaviors are expressed as either
average occurrences per minute by flight day, or as total duration
normalized to video segment duration.
Operational Definitions of Key 
Behaviors
Sniff: mouse conspicuously directs its head toward another
mouse and appears to sniff her, i.e. snout is very close to and
oriented toward any part of the other mouse.
Aggression: any behavior that is unambiguously aggressive, i.e. 
one mouse nips another, pulls out another's fur, pulls its tail, etc.
Proximity: one mouse moves to within very close proximity of
another and remains in proximity for appreciable amount of
time, e.g. is clearly not just passing by. Joining is considered to
have stopped when either the mouse/mice being 'joined' moves
out of proximity to the 'joiner', or the 'joiner' orients away from
the mouse/mice and begins to move away. This was intended to
be a general measure of interaction among the mice and time
spent in close proximity with one another.
Thigmotaxis: whether the mouse was near a wall or corner
(thigmotactic) or in the ‘open-field’ (non-thigmotactic), and
whether the mouse was stationary or ambulating while in that
location, collectively forming five categories of ‘thigmotactic
state’.
Introduction
In 2014, 20 female mice (10 used by NASA) were flown to the International
Space Station (ISS) aboard SpaceX-4 as part of a 37-day validation mission designed
to assess the performance of the Rodent Research Hardware System as a suitable
housing environment for mice during long-duration spaceflight. This was the first
Rodent Research mission (RR-1), part of an ongoing program of research with the
aim of better understanding the influence of microgravity conditions on mammalian
physiology and well-being, with the ultimate goal of identifying potentially harmful
effects of the space environment and thereby facilitating Exploration Class missions
and the eventual human colonization of space. We previously found that the RR-1
flight mice exhibited on orbit the same forms and levels) of species-typical behavior
as identically-housed ground controls, and intact circadian timing assessed late during
the flight (unpublished data). As compared to controls, spaceflight mice exhibited
significantly greater overall activity, including a socially organized circling or ‘race-
tracking ’ behavior that emerged within 2 weeks of launch, and became the
predominant behavioral activity of spaceflight mice during the dark cycle phase. The
present study is the first attempt to analyze social interactions and possible anxiety-
related behaviors in mice to assess how well they adapt to potentially stressful long-
duration habitation of space. Thigmotaxis, or the tendency to remain in close
proximity to walls and corners, is a common measure of anxiety in rodents (e.g.
Lamprea et al., 2008). The expectation motivating the measurement of thigmotaxis in
this study was that the novel experience of microgravity may produce anxiety in the
mice, and if so, an effect of habituation to that anxiogenic stimulus may be apparent
within the first few days of spaceflight. That is, if the mice are initially anxious and
therefore more prone to stay within corners formed by two or more adjoining walls,
then we should see a clear and rapid decrease in thigmotaxis as they subsequently
become more comfortable within their new environment.
Results
As seen in Figure 1, the hypothesized linear trend of a rapid reduction in thigmotactic behavior across the first few days of
exposure to microgravity aboard the ISS failed to appear in either of the two environments, and the margin of error (MOE) for the
correlations between flight day and duration of thigmotaxis was unacceptably high for every condition described in Figure 1 (MOE on 95%
CI of r > 0.9), indicating no evidence of a linear association. A one-way analysis of variance, comparing normalized thigmotaxis durations
across all housing conditions, indicated statistically significant differences (F(3, 12) = 7.758, p = 0.0038). A post-hoc Tukey’s HSD test
illustrates that thigmotactic duration differed significantly only between the right ISS and left ISS environments (p < 0.05) and between the
right ISS and left KSC environments (p < 0.05), and approached significance between the right ISS and right KSC environments (p =
0.055). One additional noteworthy result was the finding of no aggressive interactions among the in-flight mice, in contrast to the ground
controls housed at Kennedy Space Center.
Summary and Conclusions
The results of the ANOVA and post-hoc Tukey’s test indicated that only one environment, the right housing area of the in-flight Rodent Habitat, was significantly different from the others in the duration of thigmotactic
behavior observed within it. These result are consistent with our past finding that have demonstrated greater activity in the right housed mice aboard the ISS. The observation of a statistically significant difference in thigmotaxis
between only one housing area of the in-flight habitat and the ground controls, as well as a significant difference in the same variable across the two in-flight housing, in combination with our past findings suggest that the space-
flight environment alone could not account for the differences in anxiety in the mice. However, the right sided phenomenon was not limited to just thigmotaxis, our results also showed that the GC right sided habitat had greater
instances of aggression than the left and that both GC habitats had much great occurrences of aggression than aboard the ISS. The influence of the habitat on mouse behavior is of great importance for the success of future
missions and further research is needed. However, our ability to interpret these findings are limited based on the novel adaption of the definition of “thigmotaxis,” the small sample size and the limited duration of usable video.
References and Acknowledgements
1) Lamprea, M. R., Cardenas, F. P., Setem, J., & Morato, S. (2008). Thigmotactic
responses in an open-field. Brazilian Journal of Medical and Biological Research, 
41(2), 135-140.
2) Friard, O., & Gamba, M. (2016). BORIS: a free, versatile open‐source 
event‐logging software for video/audio coding and live observations. Methods in 
Ecology and Evolution, 7(11), 1325-1330.
NASA Office of Education, NASA Space Biology Program, NASA Ames 
Biosciences Research Division, and members of the NASA Reproduction and 
Development Lab
Figure 1. Total, combined durations of thigmotactic states 
normalized to the duration of dark cycle video during which 
mice were visible (sum of total left and right filter time). 
“Right” and “Left” refer to the two sides of the habitat, 
treated as independent environments
Figure 2. Instances of “Proximity” normalized to total left 
and right filter time, plotted against day aboard the ISS. 
Error bars represent the standard error of the mean.
Figure 3. Instances of one mouse sniffing or moving into close 
proximity to another, normalized by dividing by the video duration 
in seconds, then multiplied by 60 to yield a value in terms of 
occurrences per minute by flight day.
Rodent Habitat (RH) Dual Housing Areas with 
Designated Camera Positions
Filter
Lixit
Left Right
Left Filter View
Lixit View X
L + 4 L + 5 L + 6                 L + 7 L + 4 L + 5 L + 6 L + 7
L + 4                   L + 5 L + 6 L + 7
https://ntrs.nasa.gov/search.jsp?R=20180000908 2019-08-30T13:39:16+00:00Z


Behavioral Adaptations of Female Mice on the International Space Station

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