Biology subjects

Godfrey, S. S.

Publications and source records attributed to Godfrey, S. S..

3 recordsLinked to original sources

bioRxiv2025

Modelling the decline in Sporobolus anglicus detections toward functional eradication: a case study in the Marlborough Sounds, New Zealand

SummarySporobolus anglicus (C.E. Hubb) P.M. Peterson & Saarela (synonym Spartina anglica) is a highly invasive coastal weed that forms dense monocultures in intertidal mudflats and estuaries, displacing native reedbeds and associated fauna. Introduced to Aotearoa New Zealand from Britain in the early 1900s to aid coastal land reclamation, it became a conservation concern by the 1960s, prompting control efforts in the South Island from the 1970s. This study presents a detailed S. anglicus eradication case study from the Marlborough Sounds, where detections are nearing zero. We model changes in detection probability over time in Te Hoiere / Pelorus Sound, a complex estuarine catchment. We aim to inform control efforts and assess the effectiveness of ongoing management, by evaluating the probability of non-detection as a proxy for functional eradication. Using data from the Department of Conservation (DOC), we analysed detections across 79 search blocks between 2013 and 2024. A generalised linear mixed model was used to generate predicted detections through to 2040, using a modified dataset with pseudo-zero values for probable absences. The data were modelled as presence/absence with a binomial distribution, to identify the first year with a <0.01 probability of a positive detection (upper 99% confidence limit). Results suggest that by 2032, the likelihood of further detections under current management practices is remote, and that functional eradication may have occurred. We interpret this decline in detection probability as indicative of management success. Model outputs can support decision-making as to when active surveillance might reasonably be ceased. To accelerate the tail-end of eradication efforts, we recommend intensifying search effort and widening delimitations within the catchment over the next five years, to ensure removal of any remaining individuals. We also propose the use of environmental DNA as a cost-effective backstop for after operational wind-down. Implications for ManagersO_LIOur modelling predicts that S. anglicus detections in Te Hoiere / Pelorus Sound should decline to levels consistent with functional eradication by 2032, and may render continued manual surveillance uneconomical after this date. C_LIO_LIFull, regular and repeated surveillance of suitable habitats is needed within a five-year intensive monitoring period at the tail-end phase of eradication, as detections approach zero and managers consider withdrawal. C_LIO_LIWhile statistical analyses support eradication management decisions, absolute certainty of absence is unattainable. Decisions must balance technical feasibility with practical risk tolerance. C_LIO_LIEnvironmental DNA could provide an effective post-withdrawal monitoring tool, to allay the risk of re-invasion. C_LI

ecology↗

bioRxiv2025

How low temperatures affect long-tailed bat (Chalinolobus tuberculatus) and lesser short-tailed bat (Mystacina tuberculata) activity, central North Island, New Zealand

Bat activity generally increases with temperature, so bat surveys are considered more effective in summer. Less is known about survey effectiveness at low temperatures and whether activity ceases under certain thresholds. Literature provides piecemeal information on winter activity of threatened New Zealand lesser short-tailed bats (Mystacina tuberculata) and long-tailed bats (Chalinolobus tuberculatus), no data exist on lower temperature thresholds below which activity is halted in some regions. We recorded bat echolocation calls over seven nights in winter 2021 to determine whether a lower temperature threshold exists where both species are inactive in the Pikiariki Ecological Area, Pureora Forest Park, central North Island, Aotearoa New Zealand. Long-tailed bat detection rates greatly reduced at <5 {degrees}C, ceasing at <2.6 {degrees}C; at edge sites, long-tailed bats had higher activity rates at higher temperatures, but this pattern did not hold in the forest interior. Lesser short-tailed bats were detected at all sampled temperatures, (1 {degrees}C-10 {degrees}C), 56% of detections occurred at the forest edge; no lower temperature threshold beyond which activity ceased was found. While winter surveys may detect bats, rates are likely lower than in warmer months. Lesser short-tailed bat surveys could be worthwhile in winter due to their broader activity range, depending on the surveys objectives, but should be conducted over extended periods, and any conclusions about the presence or absence of bats made cautiously. Further research is needed to refine lower temperature thresholds and improve winter survey effectiveness.

zoology↗

bioRxiv2024

Density-dependent network structuring within and across wild animal systems

High population density should drive individuals to more frequently share space and interact, producing better-connected spatial and social networks [1-4]. Although this theory is fundamental to our understanding of disease dynamics [2,5-8], it remains unconfirmed how local density generally drives individuals positions within their networks, which reduces our ability to understand and predict density-dependent processes [4,9,10]. Here we provide the first general evidence that density drives greater network connectedness at fine spatiotemporal scales, at the scale of individuals within wild animal populations. We analysed 36 datasets of simultaneous spatial and social behaviour in >58,000 individual animals, spanning 30 species of fish, reptiles, birds, mammals, and insects. 80% of systems exhibited strong positive relationships between local density and network centrality. However, >80% of relationships were nonlinear and 75% became shallower at higher values, signifying that demographic and behavioural processes counteract densitys effects, thereby producing saturating trends [11-15]. Densitys effect was much stronger and less saturating for spatial than social networks, such that individuals become disproportionately spatially connected rather than socially at higher densities. Consequently, ecological processes that depend on spatial connections (e.g. indirect pathogen transmission, resource competition, and territory formation) are likely more density-dependent than those involving social interactions (e.g. direct pathogen transmission, aggression, and social learning). These findings reveal fundamental ecological rules governing societal structuring, with widespread implications. Identifying scaling rules based on processes that generalise across systems, such as these patterns of density dependence, might provide the ability to predict network structures in novel systems.

ecology↗