Life history and dynamics of a platypus (Ornithorhynchus anatinus) population: four decades of mark-recapture surveys
Knowledge of the life-history and population dynamics of Australia’s iconic and evolutionarily distinct platypus (Ornithorhynchus anatinus) remains poor. We marked-recaptured 812 unique platypuses (total 1,622 captures), over four decades (1973-2014) in the Shoalhaven River, Australia. Strong sex-age differences were observed in life-history, including morphology and longevity. Apparent survival of adult females (Φ=0.76) were higher than adult males (Φ=0.57), as in juveniles: females Φ=0.27, males Φ=0.13. Females were highly likely to remain in the same pool (adult: P=0.85, juvenile: P=0.88), while residency rates were lower for males (adult: P=0.74, juvenile: P=0.46). We combined survival, movement and life-histories to develop population viability models and test the impact of a range of life-history parameters. While using estimated apparent survival produced unviable populations (mean population growth rate r=-0.23, extinction within 20 years), considering residency rates to adjust survival estimates, indicated more stable populations (r=0.004, p=0.04 of 100-year extinction). Further sensitivity analyses highlighted adult female survival and overall success of dispersal as most affecting viability. Findings provide robust life-history and viability estimates for a difficult study species. These could support developing large-scale population dynamics models required to underpin a much needed national risk assessment for the platypus, already declining in parts of its current distribution.