Sleeping and Resting Behaviors in Mammals and Birds¶

Overview¶

This document summarizes research on sleep patterns, sleep site selection, vigilance during rest, social sleeping, sleep postures, and unihemispheric sleep across species.

Key Findings¶

Sleep Patterns and Activity Cycles¶

Three Main Temporal Patterns: - Diurnal (~20% of mammals, most birds): Active during day, sleep at night (e.g., humans, cows, ostriches) - Nocturnal (~70% of mammals): Active at night, sleep during day (e.g., most rodents, wild felids) - Crepuscular (~10% of mammals): Active primarily during twilight hours (dawn and dusk) - Cathemeral: Active sporadically day or night

Key Distribution: - Mammals are predominantly nocturnal (70%) - Birds are predominantly diurnal - These patterns influence sleep timing and anti-predator strategies

Sleep Site Selection¶

Predator Avoidance Hypothesis¶

Animals select sleeping sites specifically to minimize predation risk.

Key Factors: - Physical protection: Steep cliffs, dense vegetation, burrows, tree cavities - Concealment: Hidden spots that reduce detection probability - Escape routes: Sites with quick escape pathways - Remote locations: Larger groups seek more isolated sleeping areas - Regular site switching: Reduces predictability and parasite exposure

Species Examples: - Primates (titi monkeys, moor macaques, baboons): Select sleeping sites based on predator avoidance, often choosing tall trees or cliff edges - Small birds: Use hiding places rather than exposed branches - Deer: Select bed sites with cover and visibility for escape

Vigilance During Rest and Sleep-Vigilance Trade-offs¶

Core Trade-off¶

Animals balance sleep needs with maintaining awareness of predators.

Key Findings from Recent Research (2023-2025): - Increased predation risk causes animals to shift to lighter, more vigilant sleep states - Sleep-related rise in sensory thresholds creates vulnerability periods - Sleep restriction occurs when predatory risk is elevated

Vigilance Strategies¶

• Lighter sleep states: Reduced depth of sleep when threat perception is high
• Sentinel behavior: Coordinated vigilance where some individuals remain awake while others sleep
• Synchronized vigilance: Group members taking turns being alert
• Asynchronous sleep patterns: Not all group members sleep simultaneously

Recent Evidence: - Baboons must navigate trade-offs between sleep investment and anti-predator vigilance - Chimpanzees show sleep varies with social context and rank - Wild boar sleep patterns are influenced by environmental conditions and individual factors

Social Sleeping and Anti-Predator Benefits¶

Key Benefits of Group Sleeping¶

• Predator dilution effect: Individual risk decreases as group size increases
• Increased vigilance: More eyes watching for threats
• Shared sentinel duties: Group members take turns being alert
• Enhanced detection: Early warning systems through multiple observers

Costs¶

• Sleep disruption: Sharing sleeping sites can reduce sleep quality
• Social interference: Increased sleep disturbance from group members
• Reduced sleep may be the price for lower predation risk

Research Findings (2024): - Larger groups often choose safer but more remote sleeping sites - Group sleeping provides anti-predator benefits despite sleep disruption costs - Social status influences sleep: dominant individuals often have priority choice of safer sleeping positions

Sleep Postures¶

Birds¶

• Head tucked back: Bill tucked into back/scapular feathers (near-universal posture)
• Benefits: Heat conservation, neck muscle rest, lower energy consumption
• Trade-off: Reduced alertness increases predation risk
• Bill forward position: Alternative posture
• Standing on one leg: Common in many species
• Under wing tucking: Some species for additional protection

Mammals¶

• Cats: Various positions indicating vigilance levels
• Loaf/Sphinx pose: Alert resting
• Curled up: Protective position
• Side sleeping: Deep sleep
• Lateralized sleeping: Two-thirds prefer leftward position for right brain hemisphere vigilance
• Cattle: Can sleep while ruminating
• Many mammals: Sleep with eyes semi-open for vigilance

Posture Functions: - Thermoregulation: Heat conservation - Protection from predators: Defensive positioning - Parasite avoidance: Reducing exposure - Vigilance maintenance: Alert-ready positions

REM vs Non-REM Sleep Variation¶

Both Groups Exhibit Two-State Sleep: - REM (Rapid Eye Movement) sleep - NREM/Non-REM (Slow Wave Sleep)

Key Differences:

Mammals: - Average 18% of total sleep time is REM - REM duration varies widely across species - Influenced by body size, maturity at birth, predation risk - Highest REM early in life, then decreases

Birds: - Significantly less REM sleep than most mammals - Despite being small and immature at birth (factors that predict more REM in mammals) - REM primarily driven by circadian rhythm - Also highest early in life

Unihemispheric Slow-Wave Sleep (USWS)¶

Definition¶

One brain hemisphere sleeps while the other remains awake and alert.

Species Exhibiting USWS¶

Marine Mammals: - Dolphins and whales (cetaceans): Can maintain health and memory with USWS - Fur seals and sea lions (otariids): Can sleep unihemispherically while swimming - Manatees - Walruses: Can enter very deep sleep up to 19 hours on land; sleep during breath-holds underwater - True seals: Sleep during breath-holds underwater, wake to breathe

Birds: - USWS is widespread among birds (unlike mammals where it's rarer) - May also occur in some reptiles

Key Characteristics: - Eye asymmetry: Opposite eye often stays open when hemisphere sleeps - Duration: Up to two hours before switching hemispheres - EEG patterns: Slow-wave activity in one hemisphere, wakefulness in other - Can last extended periods in aquatic environments

Functional Benefits: 1. Breathing control: Surface to breathe while sleeping 2. Vigilance: Maintain awareness of predators 3. Thermoregulation: Maintain body temperature 4. Migration: Rest during long flights while maintaining navigation 5. Continuous swimming: Remain mobile while asleep

Sleep Duration Variation by Species¶

Extreme Variation Documented: - Range: 3 hours (donkeys) to 20 hours (armadillos) daily in mammals - Birds: Sleep on average 40% less than mammals - Mammals: Average 40% longer sleep duration than birds

Specific Examples: - Koalas: 18-22 hours/day - Sloths: 10-20 hours/day - Chicken: 11.7 hours (48.8% of day) - Jaguar: 10.8 hours (45% of day) - Duck: 10.8 hours (45% of day) - Dog: 10.6 hours (44.3% of day) - Northern elephant seals: 2 hours/day (at sea)

Influencing Factors: - Age, body size, environment, diet - Safety of sleep site - Predation risk - Trophic level (prey species often sleep less) - Foraging requirements

Safety Strategies During Sleep¶

1. Temporal Avoidance: Sleep when predators are less active
2. Spatial Avoidance: Choose inaccessible or concealed locations
3. Group Defense: Sleep in groups for dilution effect
4. Vigilance Maintenance: Light sleep, sentinels, asynchronous sleep
5. Rapid Awakening: Ability to wake quickly to threats
6. Unihemispheric Sleep: Maintain partial awareness
7. Postural Adaptations: Positions that allow quick escape
8. Site Switching: Reduce predictability

Species-Specific Examples¶

Cats¶

• Prefer leftward sleeping position (2/3 of cats) for right hemisphere vigilance
• Multiple sleep postures indicating different vigilance levels
• Balance between comfort and environmental awareness

Dogs¶

• 10.6 hours average sleep
• Sleep postures vary with safety perception
• Can sleep with eyes semi-open

Deer¶

• Select bed sites based on predator avoidance
• Use hiding as primary counter-strategy
• Alternate between slow-wave and REM sleep
• Both aggressive defense and flight tactics

Rodents¶

• Most are nocturnal
• Anti-predator behaviors become more complex with age
• Use burrows and concealed locations
• High vigilance during rest periods

Birds¶

• Head-tucking trade-off: energy conservation vs. safety
• Migratory birds in poor condition use head-tucking more (higher risk)
• Flocking provides collective vigilance
• Many species use unihemispheric sleep during migration

Key Academic References¶

Recent Research (2023-2025)¶

1. Chakravarty et al. 2024 - "The sociality of sleep in animal groups" - Trends in Ecology & Evolution
2. May 2024 - "Sleep in the wild: Individual effects and environmental conditions on sleep behaviour in wild boar"
3. June 2024 - "The interplay between sleep and ecophysiology" - JEB
4. 2025 - "The impacts of sleep disturbance on birds"
5. 2025 - "Sleeping under the risk of predation"
6. Hofmann et al. 2025 - "Conspicuous Animals Remain Alert When Under Cover"

Seminal Papers¶

1. Lima 2005 - "Sleeping under the risk of predation" (431 citations)
2. Campbell & Tobler 1984 - "Animal Sleep: A Review of Sleep Duration Across Phylogeny" (1,082 citations)
3. Capellini et al. 2008 - "Phylogenetic Analysis of the Ecology and Evolution of Sleep" (201 citations)

Unihemispheric Sleep¶

1. • "Unihemispheric slow-wave sleep" - Wikipedia (comprehensive overview)
2. • "Unihemispheric Sleep: An Enigma for Current Models"
3. • "Eye state asymmetry during aquatic unihemispheric slow-wave sleep" - PLOS One

Sleep Site Selection¶

1. • "Sleep to Survive Predators"
2. • "Sleeping site choice by black-fronted titi monkeys"
3. 2025 - "Sleeping Site Selection in Moor Macaques"
4. • "Haven for the night: sleeping site selection in wild primates"

REM Sleep and Comparative Studies¶

1. • "Sleep and memory in mammals, birds and invertebrates"
2. Rattenborg 2015 - "Avian Versus Mammalian Sleep"
3. • "Phylogeny and the function of REM sleep"
4. • "Local Aspects of Avian Non-REM and REM Sleep" - Frontiers

Vigilance and Sentinel Behavior¶

1. • "Sentinel Behavior: A Review and Prospectus"
2. • "Synchronizing vigilance or taking turns as sentinels"
3. • "Sharing sleeping sites disrupts sleep but catalyses social interactions" - Royal Society
4. • "Gazing Strategies among Sentinels"

Sleep Postures¶

1. • "Sleep Behaviour and Sleep Postures in Non-Human Animals" - Tetrapod Zoology
2. • "A Synthesis of Sleep in Wild Birds"
3. • "How Do Birds Sleep?" - Science of Birds
4. 2025 - "Lateralized sleeping positions in domestic cats" - Current Biology

Implementation Notes for Minecraft Mod¶

Key Behaviors to Implement¶

1. Activity cycle scheduling: Diurnal/nocturnal/crepuscular patterns
2. Sleep site selection: Animals choose safe locations to sleep
3. Vigilance during sleep: Lighter sleep when threatened
4. Social sleeping: Groups sleep together with sentinels
5. Sleep postures: Different positions for rest vs. deep sleep
6. Rapid awakening: Quick response to threats during sleep

Configuration Parameters¶

Minecraft Entity Considerations¶

Vanilla animals that could benefit: - Cats, Pandas, Foxes: Already sleep, could be enhanced with cycle patterns - Wolves: Pack sleeping with sentinel behavior - Cows, Sheep, Pigs: Diurnal grazing, sleeping at night - Rabbits: Crepuscular activity peaks - Bats: Nocturnal, sleep during day (already implemented) - Chickens: Diurnal, roost at night

Behavior improvements: - Animals choose covered/hidden spots for sleeping - Group animals sleep together with sentinels - Different sleep postures (alert rest vs. deep sleep) - Quick awakening response to nearby threats - Herd animals rotate sentinel duty

Code Structure Suggestion¶

public class SleepingBehavior {
    private final ActivityCycle cycle;
    private final int sleepStart;
    private final int sleepEnd;

    public boolean shouldSleep(AnimalEntity animal) {
        long dayTime = animal.level().getDayTime() % 24000;

        // Check activity cycle
        switch (cycle) {
            case DIURNAL:
                return dayTime >= sleepStart || dayTime < sleepEnd;
            case NOCTURNAL:
                return dayTime < sleepStart && dayTime >= sleepEnd;
            case CREPUSCULAR:
                // Active at dawn (23000-1000) and dusk (12000-14000)
                return dayTime >= 1000 && dayTime < 12000 &&
                       dayTime >= 14000 && dayTime < 23000;
        }
        return false;
    }

    public BlockPos findSleepSite(AnimalEntity animal) {
        // Look for covered, hidden locations
        // Prefer: under trees, in caves, under leaves
        // Avoid: open areas, near hostile mobs
        return findSafestNearbyPosition(animal, 16);
    }
}

public enum ActivityCycle {
    DIURNAL,    // Active day, sleep night (cows, sheep, chickens)
    NOCTURNAL,  // Active night, sleep day (wolves, ocelots, bats)
    CREPUSCULAR // Active dawn/dusk (rabbits, foxes)
}