Apparent absence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) in frogs in Malaita Province, Solomon Islands

A major driver of global biodiversity loss is disease. One of the most devastating wildlife diseases known is chytridiomycosis, which is caused by the amphibian chytrid fungus Batrachochytrium dendrobatidis, and is implicated in population declines in over 500 frog species. Thought to originate in Asia, B. dendrobatidis now has a global distribution, likely due to human movement and trade. The pathogen has yet to be detected in Melanesia, but there have been few surveys for B. dendrobatidis in the region, and none in the Solomon Islands archipelago, a biogeographic region with a unique and culturally important frog fauna. We swabbed 200 frogs of eight species in three genera in lowland and highland sites in East Kwaio on the island of Malaita in the Solomon Islands. All frogs tested negative for the pathogen but it is possible that the pathogen is present despite non-detection, so further surveys for the pathogen are needed throughout the country. Despite this, it is safest to take a precautionary approach and assume that B. dendrobatidis has not yet been introduced to the Solomon Islands, and that naïve native amphibian populations may be at risk of decline if the pathogen is introduced. Protocols are needed to prevent the accidental import of infected frogs via tourism or in logging or mining equipment. Monitoring of frog populations near areas of high risk such as ports is also recommended. The frogs of the Solomon Islands archipelago are biologically unique and culturally significant, and protecting them from the potentially devastating impacts of B. dendrobatidis is vital

Why does Chytridiomycosis drive some frog populations to extinction and not others?: the effects of interspecific variation in host behaviour

Infectious diseases currently pose a great threat to global biodiversity. One of the most alarming wildlife disease to date is chytridiomycosis, a fatal disease of amphibians caused by the pathogen Batrachochytrium dendrobatidis. Chytridiomycosis has been implicated in mass mortalities, population declines, and local and global extinctions of many species of amphibians around the world. However, while some species have been severely affected by the disease, other, sympatric species remain unaffected. One reason why some species decline from chytridiomycosis and others do not may be interspecific differences in behaviour, which may affect the probabilities of acquiring and succumbing to infections. Host behaviour can either facilitate or hinder pathogen transmission, and transmission rates in the field are likely to vary among species according the frequency of factors such as physical contact between frogs, contact with infected water, and contact with environmental substrates that may serve as reservoirs. Similarly, the thermal and hydric environments experienced by frogs can strongly affect their susceptibility to chytridiomycosis, so some interspecific differences in the effects of the disease may also be caused by differences in microenvironment use among species. I examined the potential effects of behaviour on the susceptibility of different host species to declines caused by chytridiomycosis by tracking three species of stream-breeding frogs in northern Queensland, Australia. The species historically co-occurred at many sites in the Wet Tropics, but high elevation (> 400 m) populations of two species declined to differing degrees in association with outbreaks of chytridiomycosis in recent decades, while low elevation populations remained apparently unaffected. The waterfall frog Litoria nannotis, declined to local extinction at all known high elevation sites. All studied populations of the green-eyed tree frog Litoria genimaculata at high elevation sites declined to low numbers and then recovered. The third species, the stoney creek frog Litoria lesueuri, is not known to have experienced population declines even at high elevations. I used radio telemetry and harmonic direction finding to track frogs at five sites. Surveys lasted 16 days and were conducted in both the cool/dry season and the warm/wet season. The location of each frog was determined once during the day and once at night over the duration of the survey period. At each location, I recorded contact with other frogs, stream water, and other environmental substrates, its three-dimensional position, movement, habitat type, and body temperature. Retreat sites of L. lesueuri and L. nannotis were also sampled for B. dendrobatidis. Harmonic direction finding obtained fewer fixes on frogs but measures of movement and habitat use did not differ significantly between techniques. In total, 117 frogs were tracked: 28 L. nannotis, 27 L. genimaculata and 62 L. lesueuri. Frequency of contact with other frogs and with water was highest in L. nannotis, intermediate in L. genimaculata, and lowest in L. lesueuri. Environmental substrate use differed among species, and B. dendrobatidis was not detected at retreat sites. Movement and habitat use also differed significantly among species. Litoria lesueuri moved more frequently and greater distances and was often located away from streams, moving between intact rainforest and highly disturbed environments. Litoria genimaculata moved less frequently and shorter distances, and was more restricted to stream environments, occasionally moved large distances along and between streams, but was never located outside of intact rainforest. Litoria nannotis remained in streams during the day, did not move large distances along or move between streams, and was always located within intact rainforest. In addition to tracking data, I designed, tested, and deployed novel physical models to record the thermal conditions experienced by frogs, regardless of cutaneous resistance to water-loss. These models were placed in species-specific diurnal retreat sites; providing profiles integrated over time of the thermal and hydric regimes of the microenvironments experienced by each species. Microenvironmental conditions experienced by frogs differed markedly among species and seasons. Retreat sites of the most susceptible species, L. nannotis, were almost always within the thermal optimum and never above the thermal tolerance of B. dendrobatidis, while retreat sites of the least susceptible species, L. lesueuri, were commonly above the thermal optimum and thermal tolerance of B. dendrobatidis. Hydric conditions were most suitable for B. dendrobatidis growth at L. nannotis retreat sites. Species-specific differences in behaviour are therefore likely to have large implications for the susceptibility of species to decline due to chytridiomycosis. This thesis provides the first empirical confirmation that species-specific differences in behaviour are likely to affect the susceptibility in nature of amphibians to chytridiomycosis. The behaviour of the species most susceptible to B. dendrobatidis related declines was the most favourable for the transmission, growth and development of B. dendrobatidis, while the behaviour of the species least susceptible to B. dendrobatidis related declines had the least favourable for its transmission, growth and development. Species-specific differences in the behaviour of frogs in the field may also explain why infected individuals of some species experience rapid mortality in the laboratory, yet are able to carry infections for extended periods in the field. Temporal and spatial variation in microenvironments available to and used by frogs may also explain variation in infection prevalence and host mortality. Information on amphibian behaviour and microenvironmental use may be useful in evaluating the susceptibility to declines caused by chytridiomycosis in species that presently occur in areas without B. dendrobatidis

Movement and habitat use of the endangered Australian frog Nyctimystes dayi

The Australian Lacelid, Nyctimystes dayi, is an endangered,\ud stream-breeding hylid frog endemic to rainforests in the wet\ud tropics of northeastern Queensland, Australia. During the 1990s, populations of N. dayi declined dramatically, with the species disappearing from all upland (>300 m) areas, where they were once common (Richards et al. 1993; Northern Queensland Threatened Frogs Recovery Team 2001; Trenerry et al. 1994). The proximate cause of these population declines and disappearances was the amphibian disease chytridiomycosis (Berger et al. 1998). This disease had similar effects on several other species sympatric with\ud N. dayi (Berger et al. 1998). Habitat modification and fragmentation are also potential stressors for N. dayi populations, since approximately 20% of the wet tropics region has been clear cut since 1880 (Winter et al. 1987), and smaller-scale clearing still occurs in non-protected areas (e.g., for pastures, human settlement and associated infrastructure; Department of Natural Resources and Water 2007)

Amphibian declines in Australia

[Extract] Concern about the status of Australian frogs first arose in the 1980s with the disappearance of the famous gastric-brooding frogs: Rheobatrachus silus {described in 1973, and last seen in the wild in 1985}, and R. vitelinus {described in 1984, and last seen in the wild in 1985} (Ingram and Mcdonald 1993; and see Essay 6.1). Intensive searches for both of these species were conducted in teh late 1980s, with no individuals located then, or since, and they are both now listed as Extinct on the IUCN Red List. This represents the loss of an entire family, as well as a unique reproductive strategy

Non-contact infrared thermometers can accurately measure amphibian body temperatures

This publication does not have an abstract

Techniques for tracking amphibians: the effects of tag attachment, and harmonic direction finding versus radio telemetry

To gain information on the microhabitat use, home range and movement of a species, it is often necessary to remotely track individuals in the field. Radio telemetry is commonly used to track amphibians, but can only be used on relatively large individuals. Harmonic direction finding can be used to track smaller animals, but its effectiveness has not been fully evaluated. Tag attachment can alter the behaviour of amphibians, suggesting that data obtained using either technique may be unreliable. We investigated the effects of external tag attachment on behaviour in the laboratory by observing 12 frogs for five nights before and five nights after tag attachment, allowing one night to recover from handling. Tag attachment did not affect distance moved or number of times moved, indicating that the effects of tag attachment are unlikely to persist after the first night following attachment. We then compared harmonic direction finding and radio-telemetry using data collected in the field. We fitted rainforest stream frogs of three species with tags of either type, located them diurnally and nocturnally for approximately two weeks, and compared movement parameters between techniques. In the field, we obtained fewer fixes on frogs using harmonic direction finding, but measures of movement and habitat use did not differ significantly between techniques. Because radio telemetry makes it possible to locate animals more consistently, it should be preferred for animals large enough to carry radio tags. If harmonic direction finding is necessary, it can produce reliable data, particularly for relatively sedentary species

Behaviour of Australian rainforest stream frogs may affect the transmission of chytridiomycosis

The amphibian disease chytridiomycosis, caused by the pathogen Batrachochytrium dendrobatidis, has been implicated in mass mortalities, population declines and extinctions of amphibians around the world. In almost all cases, amphibian species that have disappeared or declined due to chytridiomycosis coexist with non-declining species. One reason why some species decline from chytridiomycosis and others do not may be interspecific differences in behaviour. Host behaviour could either facilitate or hinder pathogen transmission, and transmission rates in the field are likely to vary among species according the frequency of factors such as physical contact between frogs, contact with infected water and contact with environmental substrates containing B. dendrobatidis. We tracked 117 frogs (28 Litoria nannotis, 27 L. genimaculata and 62 L. lesueuri) at 5 sites where B. dendrobatidis is endemic in the rainforest of tropical northern Queensland and recorded the frequency of frog-to-frog contact and the frequency of contact with stream water and environmental substrates. Frequency of contact with other frogs and with water were highest in L. nannotis, intermediate in L. genimaculata and lowest in L. lesueueri. Environmental substrate use also differed among species. These species-specific opportunities for disease transmission were correlated with conservation status: L. nannotis is the species most susceptible to chytridiomycosis-related declines and L. lesueuri is the least susceptible. Interspecific variation in transmission probability may, therefore, play a large role in determining why chytridiomycosis drives some populations to extinction and not others

Models in field studies of temperature and moisture

In ectothermic organisms, variation in body temperature directly affects factors such as rates of energy acquisition, growth, and reproduction (Shoemaker and McClanahan 1975; McClanahan 1978). Temperature also exerts a strong infl uence on ecological interactions such as predator–prey and host–pathogen interactions, and changes in temperature can completely reverse the outcome of such interactions at both the individual and population levels (Elliot et al. 2002; Woodhams et al. 2003). Although the body temperature of terrestrial ectotherms is broadly correlated with environmental temperature, the actual\ud body temperatures of many species can differ considerably from macroenvironmental temperatures due to species-specifi c behavior, physiology, morphology, and microenvironment use. As a result, ectotherms exposed to identical macroenvironmental conditions can experience very different body temperatures (Kennedy 1997).\ud \ud The physiology and ecology of amphibians, and their thermal relations, are also strongly influenced by moisture. The degree of evaporative water loss (EWL) varies considerably within and among species (Shoemaker and Nagy 1977; Wygoda 1984; Buttemer et al. 1996; Young et al. 2005), and individuals of many species are able to adjust their rates of water loss over relatively short periods of time (Withers et al. 1982; Wygoda 1989a; Withers 1995; Tracy et al. 2008). The moisture and thermal environments, and interactions between them, can constrain the performance of amphibians (Snyder and Hammerson 1993; Tracy et al. 1993). However, the actual temperature and humidity experienced by an amphibian can differ dramatically within a range of available macroenvironmental conditions, depending on microenvironment use (Schwarzkopf and Alford 1996; Seebacher and Alford 2002; Rowley and Alford 2007a). To understand how the environment is experienced by amphibians in the field, both the thermal and moisture environments must be characterized as they are experienced by amphibians. \ud \ud Understanding the thermal and water relations of amphibians in the field is important not only for understanding their biology, but also for conservation. Recent declines in amphibian populations around the world have been attributed in part to the epidemic disease amphibian chytridiomycosis (Lips et al. 2006). Changes in thermoregulatory opportunities available to rainforest frogs may have contributed to their widespread declines in association with the disease (Pounds et al. 2006). Laboratory experiments have shown that elevated body temperatures, as can be produced by basking, can cure amphibians of the\ud disease (Woodhams et al. 2003). Global warming is also likely to have a large impact on many species, with\ud macroenvironmental modeling suggesting that the distributions of many ectothermic species will be dramatically altered (Thomas et al. 2004). This approach is limited by the fact that the present distributions of many species may not refl ect their fundamental climatic requirements (Parmesan et al. 2005). Understanding those requirements may aid in refi ning such predictions\ud (Kennedy 1997; Parmesan et al. 2005)

A new species of Delma Gray 1831 (Squamata: Pygopodidae) from the Hunter Valley and Liverpool Plains of New South Wales

Mahony, Stephen V., Cutajar, Timothy, Rowley, Jodi J.L. (2022): A new species of Delma Gray 1831 (Squamata: Pygopodidae) from the Hunter Valley and Liverpool Plains of New South Wales. Zootaxa 5162 (5): 541-556, DOI: https://doi.org/10.11646/zootaxa.5162.5.

FIGURE 4 in A new species of Delma Gray 1831 (Squamata: Pygopodidae) from the Hunter Valley and Liverpool Plains of New South Wales

FIGURE 4. Photos in life of Delma vescolineata sp. nov. (A–D), Delma impar (E–F), Delma plebeia (G), Delma inornata (H); A) AMS R.186619, Jerrys Plains NSW, B) AMS R.185999, Muswellbrook NSW, C) Not collected, Muswellbrook NSW, D) Not collected, Juvenile, Muswellbrook NSW, E) Not collected, Cooma NSW, F) Not collected, Naracoorte SA, G) Not collected, Muswellbrook NSW, H) Not collected, Canberra ACT.Published as part of Mahony, Stephen V., Cutajar, Timothy & Rowley, Jodi J.L., 2022, A new species of Delma Gray 1831 (Squamata: Pygopodidae) from the Hunter Valley and Liverpool Plains of New South Wales, pp. 541-556 in Zootaxa 5162 (5) on page 552, DOI: 10.11646/zootaxa.5162.5.5, http://zenodo.org/record/681688