Life history and dynamics of a platypus (Ornithorhynchus anatinus) population: four decades of mark-recapture surveys

Abstract

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.

Insights into Platypus Population Structure and History from Whole-Genome Sequencing

“…These observations are consistent with an underlying pattern of limited dispersal of (at least some) relatives. This is somewhat surprising given that previous studies using mark-recapture approaches in the Shoalhaven River ( Grant 2004 ; Bino et al. 2015 ) and other streams ( Serena and Williams 2012 ; Serena et al.…”

The platypus: evolutionary history, biology, and an uncertain future

“…Fyke nets (checked every 2–4 h and allowing unimpeded access to air) are effective in small streams, although capture rates may vary substantially by age, sex, and season, and may also be affected by learned avoidance (Serena and Williams 2012b; Griffiths et al 2013). Mark–recapture methods that take into account detection probabilities can produce robust estimates of population size (Bino et al 2015). Environmental DNA (Ficetola et al 2008; Lugg et al 2018) is now used to detect the presence of platypuses and visual survey techniques provide useful information for assessing and monitoring population activity and relative abundance (Easton et al 2008).…”

“…Platypuses are sexually dimorphic, with males approximately 40% heavier and 15% longer than females (Burrell 1927; Temple-Smith 1973; Furlan et al 2012; Bino et al 2015), suggesting that males probably compete for territory, females, and other resources (Brown et al 2013). There is a clinal increase in size from north Queensland (~700–1,100 g) to Tasmania (1,200–3,000 g—Connolly et al 1998; Kolomyjec 2010; Gust and Griffiths 2011; Furlan et al 2012; Bino et al 2015). However, at finer geographical scales, size variation is confounded by inconsistencies, suggesting involvement of other environmental factors (Kolomyjec 2010; Furlan et al 2012).…”

“…obs. ), although most animals survive approximately 6–15 years (Grant et al 2004; Serena et al 2014; Bino et al 2015).…”

Insights into platypus population structure and history from whole-genome sequencing

“…These observations are consistent with an underlying pattern of limited dispersal of (at least some) relatives. This is somewhat surprising given that previous studies using mark-recapture approaches in the Shoalhaven River (Grant, 2004b;Bino and Grant, 2015) and other streams (Serena, 2012;Serena et al, 2014) have reported the dispersal of a high proportion of juveniles, especially males, few recaptures of adult males, and the continued capture of unmarked males and females. Of all the pairs of relatives we sampled at the same site, most were female-female or male-female, and not male-male (there are only three male-male relative pairs in Table S4), which is consistent with male-biased dispersal.…”