Visualizing Circadian Patterns: Interactive Analysis of Mouse Biological Rhythms
When science surprises us, it often reveals our hidden assumptions. In biology, conventional wisdom has long held that female mammals, with their complex hormonal cycles, exhibit more variable behavioral patterns than males. But what if this fundamental assumption is wrong? This interactive analysis presents data from our study of 26 laboratory mice (13 male, 13 female) that challenges this widely accepted belief.
Through the visualizations that follow, we'll explore a surprising discovery about sex-based differences in activity patterns that challenges conventional scientific expectations.
1. Circadian Activity Patterns: Expectations vs. Reality
Mice exhibit distinct daily activity patterns that reflect their circadian rhythms and behavioral adaptations. Given the well-documented hormonal fluctuations in female mice due to estrus cycles, we initially expected to observe greater activity variability in females compared to males.
The estrus cycle in female mice typically occurs every 4-5 days, with periods of heightened hormone activity that can significantly affect behavior. This biological rhythm creates an additional layer of periodicity that we hypothesized would lead to more variable and intense activity patterns in females.
24-Hour Activity Patterns
This circular heatmap displays activity patterns throughout the day, with time shown around the clock face (hours) and consecutive days extending outward from the center as rings. Brighter colors (yellows to reds) indicate higher activity levels. This visualization allows us to see not only when mice are most active during the day but also how these patterns change over multiple days. You can hover over any sector to see detailed information for that specific hour and day.
Initial Observations:
- Both male and female mice show clearly defined nocturnal patterns, with peak activity occurring during the Early Morning to Morning phase (when laboratory lights are off).
- Activity sharply increases at the Evening-to-Early Morning transition (around 1am), reflecting the mice waking up and becoming active.
- Female mice appear to have more concentrated activity during specific time periods, primarily in early mornings.
- The pattern of activity is remarkably consistent across both sexes, despite their physiological differences.
Looking at these activity patterns, our initial expectations seemed confirmed - female mice showed distinct concentrated activity patterns that appeared to align with what we'd expect from animals experiencing hormonal cycles. But to better understand how activity relates to physiology, we needed to examine the relationship between activity and body temperature...
2. The Activity-Temperature Relationship: Challenging Assumptions
While examining the relationship between physical activity and body temperature, we discovered something unexpected that challenged our initial assumptions about gender-based differences in mice.
Mouse Activity vs. Temperature
This scatter plot reveals the relationship between activity levels and body temperature. Each point represents a single measurement, with males (blue) and females (red). Contrary to our expectations, male mice (blue) show greater dispersion in both axes, indicating more variability in their activity-temperature relationship than females. This is our first hint that our assumptions about female mice having more variable patterns might be incorrect.
Surprising Findings:
- Male mice demonstrate greater variability in activity levels than females, with more measurements at both extremely high and low ranges.
- While female mice maintain slightly higher average temperatures, their activity-temperature relationship shows more consistency.
- The male data points show a wider spread, suggesting less predictable activity patterns.
- This contradicts conventional understanding that female mice, with their estrus cycles, would show more variability in activity patterns.
This initial finding was puzzling – could male mice really have more variable activity patterns than females despite lacking the hormonal cycles? To investigate further, we needed to examine how these patterns played out over time...
3. Temporal Activity and Temperature Patterns: Confirming the Unexpected
To better understand the unexpected variability we observed in male mice, we examined how both temperature and activity changed over time. This allowed us to see if the variability was consistent or limited to specific time periods.
Temperature/Activity Patterns Over Time
This time series visualization shows how temperature and activity fluctuate throughout each day. Males (blue) and females (red) both display clear rhythmic patterns, but the male lines show greater variation in amplitude, especially when viewing the activity data. Click any line to focus on a single mouse's profile and see how individual animals may differ from others of the same sex.
Confirmation of the Unexpected:
- While daily rhythms show consistent oscillation between 35.0°C and 38.5°C for both sexes, male mice (blue) display greater range and variation in their peaks and valleys.
- When switching to activity view, the male variation becomes even more pronounced, with some males showing dramatically higher peaks than any females.
- Female mice show more harmonized patterns of activity, with their lines clustering more tightly together.
- This temporal view confirms our scatter plot finding – male mice consistently show more variable activity patterns throughout the study period.
The time series data reinforced our surprising discovery - male mice were consistently showing more variability in their activity patterns than females. But to truly understand the implications, we needed to directly compare individual mice against their gender averages to identify specific outliers...
4. Gender Comparison with Outlier Analysis: Understanding Individual Variation
Our final visualization allows us to directly compare how individual mice deviate from their gender's average, revealing the full extent of the gender differences we've discovered and helping us understand the biological implications.
Gender Averages with Outlier Comparison
This line chart displays average values for male (blue) and female (red) mice over time, with shaded areas representing standard deviation. When you select an individual mouse, its data appears as a dotted line, allowing you to directly compare how it deviates from its gender's average. The significantly wider blue shaded area confirms greater male variability, especially when examining activity data.
Key Findings:
- Male mice show significantly higher standard deviations in activity (visible in the wider blue shaded area), confirming greater variability within the male population.
- The most extreme outlier mice are predominantly male, with Mouse Male 3 consistently showing activity peaks up to 100 units above the male average.
- Female mice demonstrate more predictable patterns, with individual females generally staying closer to their gender average.
- While estrus does affect female mice activity, the magnitude of these hormonal effects is smaller than the natural variability observed in males.
- These findings directly contradict conventional wisdom about sex-based differences in rodent behavior.
Conclusion: Rewriting Our Understanding of Sex-Based Differences
Our journey through mouse circadian patterns revealed an unexpected twist in conventional understanding. While we anticipated female mice would show more variable activity patterns due to their estrus cycles, our data consistently demonstrated the opposite - male mice exhibited significantly higher variability in both temperature regulation and activity levels.
- First, we established the foundation - mice exhibit clear circadian rhythms with predictable patterns tied to day-night cycles, with activity and temperature closely correlated.
- Then came the surprising twist - male mice consistently displayed greater variability and more extreme deviations from average patterns than females.
- Finally, direct comparison confirmed that while female physiology is affected by hormonal cycles, the natural variability in male mice creates even more pronounced differences in behavior.
Final Takeaway:
Circadian rhythms provide a foundation for understanding activity and temperature patterns in mice, but our data reveals an unexpected twist that challenges conventional assumptions. The greater variability observed in male mice demonstrates how data visualization can overturn established beliefs about biological sex differences and reminds us that scientific discovery often lies in questioning what we think we already know.