Factors influencing persistence of a threatened amphibian in restored wetlands despite severe population decline during climate change driven weather extremes

Abstract

Biodiversity is in global decline during the Anthropocene. Declines have been caused by multiple factors, such as habitat removal, invasive species, and disease, which are often targets for conservation management. However, conservation interventions are under threat from climate change induced weather extremes. Weather extremes are becoming more frequent and devastating and an example of this was the 2019/2020 Australian drought and mega-fires. We provide a case study the impacts of these extreme weather events had on a population of the threatened frog Litoria aurea that occurs in a constructed habitat which was designed to reduce the impact of introduced fish and chytrid-induced disease. We aimed to determine what factors influenced persistence so that the design of wetlands can be further optimised to future-proof threatened amphibians. We achieved this with 4 years (2016–2020) of intensive capture–recapture surveys during austral spring and summer across nine wetlands (n = 94 repeat surveys). As hypothesized, drought caused a sharp reduction in population size, but persistence was achieved. The most parsimonious predictor of survival was an interaction between maximum air temperature and rainfall, indicating that weather extremes likely caused the decline. Survival was positively correlated with wetland vegetation coverage, positing this is an important feature to target to enhance resilience in wetland restoration programs. Additionally, the benefits obtained from measures to reduce chytrid prevalence were not compromised during drought, as there was a positive correlation between salinity and survival. We emphasize that many species may not be able to persist under worse extreme weather scenarios. Despite the potential for habitat augmentation to buffer effects of extreme weather, global action on climate change is needed to reduce extinction risk.

Effects of simulating warming and heat waves on behaviour and survival after reproductive in Rana dybowskii

“…Animal mortality from heat waves is uncommon; however, it has been reported in a few studies. Extreme weather events can cause the threatened frog Litoria aurea to experience severe decreases in adult population size and reduced recruitment [7]. When simulated heat waves of 30°C were present for six days while frog larvae were developing, mortality increased [8].…”

“…However, the degree to which crucial qualities, such as longevity or fertility, are impacted ultimately determines how vulnerable animals are to all of these consequences. This is because animals' initial behavioural responses to heat waves play a signi cant role in their vulnerability [7]. This is particularly relevant given the sluggish physiological adaptation to temperature increases that many animals exhibit.…”

“…Understanding phenological variations is important because they can affect organism tness by changing resource availability [14]. Because they cannot thermoregulate independently of their habitats and are consequently more susceptible to changes in ambient conditions, ectotherms may show higher phenological reactions than endotherms [7]. A warmer environment may cause amphibians to spawn earlier and/or shorten their hibernation period, which could have a signi cant impact on population dynamics [15].…”

“…Compared to birds and mammals, amphibians are more vulnerable to niche alterations caused by the environment [3]. Amphibians may also be especially vulnerable to climate change, among other interrelated and compounding variables that affect them, such as illness, habitat loss, and fragmentation [4][5][6].Anthropogenic climate change poses the greatest threat to all life on Earth and has the greatest potential for the destruction of all these major factors [7]. For a more comprehensive understanding of the possible…”

Population size and survival of the Brazilian Torrent Frog Hylodes heyeri (Anura, Hylodidae)

“…For example, severe drought decreased the survival and fecundity of Bombina variegata during ontogeny (Cayuela et al, 2016). Also, both high temperatures and drought increased mortality in Litoria aurea (Beranek et al, 2022) and Polypedates cruciger (Weerathunga & Rajapaksa, 2020). Yet, usually variation in weather is associated with variation in frog behaviour, including estivation, calling sites, reproduction and essentially all aspects that influence population dynamics (Blaustein et al, 2010; Gao et al, 2015; Lawler et al, 2006; Varjão & Ribeiro, 2018).…”