Improving breed‐and‐release programmes in the face of a threatening pathogen, Batrachochytrium dendrobatidis

Abstract

As the proportion of threatened species increases, so too does the need for effective conservation strategies. In response, captive breed‐and‐release and habitat mitigation programmes are two conservation actions that are increasing in use and effectiveness. Success of these programmes is frequently hampered by the continued presence of threatening processes. In the case of amphibian reintroductions, a key threatening process that is difficult to eliminate is the deadly fungal pathogen, Batrachochytrium dendrobatidis (Bd). This pathogen is the proximate cause of decline for the threatened green and golden bell frog, Litoria aurea, and has contributed to the failure of previous breed‐and‐release programmes of this amphibian. To investigate whether is it possible to establish a captive‐bred population of L. aurea that could persist in the presence of Bd, a breed‐and‐release programme was conducted in a created habitat that included increased salinity to inhibit fungal growth rates, exclusion of potential reservoir hosts and source animals bred from parents ‘experienced’ with the strain of Bd present in the release environment. The population persisted in the created habitat for more than 4 years (the timescale of monitoring) but suffered higher infection levels compared with nearby extant populations of L. aurea. These infections significantly reduced apparent survival. Infection dynamics were linked to temperature, host density in the previous season, and size and age of the host, and these factors differed from those in extant populations and are likely to have contributed to the high levels of Bd infection at the created site. This article discusses how it may be possible to manipulate these factors to improve the success of future breed‐and‐release programmes, and recommends the construction of warm water bodies and a strategy of prioritizing the release of fewer, large propagules of high body condition and mixed‐age class, over large numbers of younger, smaller animals.

Severe wildfires promoted by climate change negatively impact forest amphibian metacommunities

“…It may be possible to create a future where species impacted by unnatural wildfires due to anthropogenic climate change can be protected (Shoo et al, 2011). We encourage research exploring options to bolster climate change adaptations within the paradigms of genetic management (Cummins et al, 2019), cryopreservation (Clulow & Clulow, 2016), reintroduction (Klop‐Toker et al, 2021) and habitat restoration (Beranek et al, 2021). However, these efforts may only offer a temporary solution because without global action to reverse or halt further climate change, wildfires are predicted to become larger and more severe, reducing the distributions of many forest‐dependent amphibians.…”

Complex Organisms Must Deal with Complex Threats: How Does Amphibian Conservation Deal with Biphasic Life Cycles?

“…Despite the overwhelming evidence of the negative impacts of chytrid, our literature review revealed that there have been few attempts to implement conservation actions across wild populations, with only a handful of studies attempting in situ actions to reduce the impacts of this disease. Three studies have manipulated different pond and water dynamics to reduce the infection load of chytrid [145,181,182]. As chytrid infection rates are positively correlated with cooler temperatures and a more neutral pH (optimal 6-7.5), Klop-Toker et al [181] manipulated temperature and salinity levels within discrete breeding ponds to establish persistent breeding populations of the endangered green and gold bell frog Litoria aurea.…”

“…Three studies have manipulated different pond and water dynamics to reduce the infection load of chytrid [145,181,182]. As chytrid infection rates are positively correlated with cooler temperatures and a more neutral pH (optimal 6-7.5), Klop-Toker et al [181] manipulated temperature and salinity levels within discrete breeding ponds to establish persistent breeding populations of the endangered green and gold bell frog Litoria aurea. However, the study produced mixed results, with frog populations in manipulated ponds still reporting high chytrid loads across the four years.…”

“…Aquatic habitat restoration and the creation of discrete breeding ponds is another popular and promising conservation action that bolsters amphibian populations. The construction of clustered ephemeral and permanent breeding habitats across the range of amphibians undergoing a decline has proven effective in significantly restoring amphibian populations and communities [84,181,[191][192][193]. This conservation action is especially important when nearby natural ponds have been degraded and connectivity between ponds within the landscape is reduced.…”