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Annual Reproductive Success = Fertilization Success X Offspring Survival

Annual Reproductive Success = Fertilization Success X Offspring Survival. Male. Female. Previous difficulty in assigning paternity. Previous work on mammalian male reproductive success. Large mammals Pronounced sexual dimorphism (size and weaponry) Harem polygyny.

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Annual Reproductive Success = Fertilization Success X Offspring Survival

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  1. Annual Reproductive Success = Fertilization Success X Offspring Survival Male Female Previous difficulty in assigning paternity

  2. Previous work on mammalian male reproductive success Large mammals Pronounced sexual dimorphism (size and weaponry) Harem polygyny • Variation in Reproductive Success: • Lifetime: 0-24 calves (n=13) • Annual: 50% of males sire 0 calves; <5% sire >4

  3. Harem defense • Pronounced sexual dimorphism (Male/Female mass ratio ~ 1.70) • Exclusive territories • Minimal sexual dimorphism (Male/Female mass ratio ~ 1.05-1.11) • Asynchronous estrus

  4. Hypothesis Reproductive success in male red squirrels will be unrelated to size. Rather it will be driven by: • Age • Mobility • Resource Availability • Inbreeding Avoidance

  5. The Players • 74 Males and 57 Reproductive Females on 2 plots (KLOO and SUL) • Seasonal OSR = 1.3

  6. Methodology • Radio-collared females • Behavioural monitoring of mating chases • Time • Male/female behaviour • Male ID (attending and copulating) • Morphological measurements • Data set • Age • Relatedness

  7. Squirrel Mating at Kluane 2003 • February 19 - May 2 • 49 (usable) mating chases observed • 0-3 Estrus bouts/day • Number of males/chase = 10.4 ± 2.4 (N = 19; Range = 6-14)

  8. Mating Success • Male • KLOO: 3.2 ± 2.3 copulations/male • SUL: 4.5 ± 2.6 copulations/male • Female • KLOO: 5.9 ± 3.2 copulations/female • SUL: 8.5 ± 2.3 copulations/female • Proportion of males in chase receiving a copulation = 0.77 ± 0.19 (N = 41)

  9. Variation in copulatory success

  10. Variation in chase attendance

  11. R2 = 0.7; P <.001

  12. Hypothesis Reproductive success in male red squirrels will be unrelated to size. Rather it will be driven by: • Age • Mobility • Resource Availability • Inbreeding Avoidance

  13. n/s

  14. Hypothesis Reproductive success in male red squirrels will be unrelated to size. Rather it will be driven by: • Age • Mobility • Resource Availability • Inbreeding Avoidance

  15. Hypothesis: Age will affect male reproductive success Prediction: Older males will have a higher reproductive success than younger males • Have more experience • Selected for by females • Higher quality genome • Confounding issues Independent Variable: Age Dependent Variable: Mating Success

  16. Linear Increase Senescence Plateau

  17. Age Distribution • Mean Age = 3.8 ± 2.0 (N=44 ;Range 1-8)

  18. n/s

  19. Tentative Conclusions • Mating success largely unrelated to age or mass • Driven by reproductive effort • Factors affecting chase attendance • Sex ratio of neighbours • Inbreeding avoidance • Energetics • Behavioural attributes (e.g exploration forays) • Factors affecting fertilization success • Sperm competition • Behavioural attributes (e.g. mate guarding)

  20. Future Directions • Paternity (Coltman/Gunn) • Actual Reproductive Success • Relatedness (Inbreeding) • Sperm Competition • Energetics (Humphries) • Costs of reproduction for males • Effect of resources • Endocrinology (Boonstra) • Condition • Immunocompetence

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