Past and future potential range changes in one of the last large vertebrates of the Australian continent, the emu Dromaius novaehollandiae

In Australia, significant shifts in species distribution have occurred with the loss of megafauna, changes in indigenous Australian fire regime and land-use changes with European settlement. The emu, one of the last megafaunal species in Australia, has likely undergone substantial distribution changes, particularly near the east coast of Australia where urbanisation is extensive and some populations have declined. We modelled emu distribution across the continental mainland and across the Great Dividing Range region (GDR) of eastern Australia, under historical, present and future climates. We predicted shifts in emu distribution using ensemble modelling, hindcasting and forecasting distribution from current emu occurrence data. Emus have expanded their range northward into central Australia over the 6000 years modelled here. Areas west of the GDR have become more suitable since the mid-Holocene, which was unsuitable then due to high precipitation seasonality. However, the east coast of Australia has become climatically sub-optimal and will remain so for at least 50 years. The north east of NSW encompasses the range of the only listed endangered population, which now occurs at the margins of optimal climatic conditions for emus. Being at the fringe of suitable climatic conditions may put this population at higher risk of further decline from non-climatic anthropogenic disturbances e.g. depredation by introduced foxes and pigs. The limited scientific knowledge about wild emu ecology and biology currently available limits our ability to quantify these risks

A novel observation of food dunking in the Australian Magpie Gymnorhina tibicen

We document putative food-dunking behaviour in the Australian Magpie Gymnorhina tibicen. While conducting an experiment on the Mountain Katydid Acripeza reticulata, we presented one to a wild adult Magpie, which appeared to conduct 'dunking behaviour' while processing the insect. The Magpie carried the katydid to a puddle of water, dunked the katydid, and then dropped it. A nearby juvenile Magpie then retrieved the katydid and performed the same dunking behaviour before eating the katydid. To our knowledge, this is the frst reported instance of food dunking by Australian Magpies. We hope this observation will facilitate future investigations into behavioural adaptations to dietary choices of Magpies

The protective value of the colour and shape of the mountain katydid's antipredator defence

Deimatic behaviour is performed by prey when attacked by predators as part of an antipredator strategy. The behaviour is part of a sequence that consists of several defences, for example they can be preceded by camouflage and followed by a hidden putatively aposematic signal that is only revealed when the deimatic behaviour is performed. When displaying their hidden signal, mountain katydids (Acripeza reticulata) hold their wings vertically, exposing striking red and black stripes with blue spots and oozing an alkaloid-rich chemical defence derived from its Senecio diet. Understanding differences and interactions between deimatism and aposematism has proven problematic, so in this study we isolated the putative aposematic signal of the mountain katydid's antipredator strategy to measure its survival value in the absence of their deimatic behaviour. We manipulated two aspects of the mountain katydid's signal, colour pattern and whole body shape during display. We deployed five kinds of clay models, one negative control and four katydid-like treatments, in 15 grids across part of the mountain katydid's distribution to test the hypothesis that their hidden signal is aposematic. If this hypothesis holds true, we expected that the models, which most closely resembled real katydids would be attacked the least. Instead, we found that models that most closely resembled real katydids were the most likely to be attacked. We suggest several ideas to explain these results, including that the deimatic phase of the katydid's display, the change from a camouflaged state to exposing its hidden signal, may have important protective value

Divided by the range : evidence for geographic isolation of the highly mobile Emu (Dromaius novaehollandiae)

Conserving evolutionary processes is becoming increasingly important in conservation management as environmental changes continue to threaten wild populations. Characterising genetically distinct populations and assessing connectivity across the landscape enables wildlife managers to prioritise conservation efforts with limited resources. In the NSW North Coast bioregion of Australia, one of the last remaining coastal populations of the Emu (Dromaius novaehollandiae) has been state-listed as an Endangered Population, owing to its geographic isolation and small census size. Using mitochondrial and nuclear genetic markers, we examined the spatial genetic structure and diversity of Emus across south-eastern Australia. For the NSW North Coast population, we estimated the effective population size ((Formula presented.)) and carried out simulations to predict future levels of genetic variation. We show significant genetic divergence between the NSW North Coast Emu and other localities based on thousands of highly resolving nuclear markers. Among NSW North Coast Emus, we found less genetic diversity and a critically low-effective population size ((Formula presented.) = 14.84 and 22.49 based on independent methods). Our simulations predict that the (Formula presented.) of the NSW North Coast Emu population is insufficient to maintain genetic diversity and the population may be at risk of inbreeding depression. Incorporating genetic data into the design of captive-release and translocation projects would refine management plans for this locally important population and monitor risks to its long-term survival

Optimal clutch size and male incubation investment in the male-only incubating emu (Dromaius novaehollandiae)

Abstract: The incubation capacity hypothesis states that clutch size is limited by the number of eggs an adult can successfully incubate due to the individual’s morphology and physiology. Clutch size may be reduced in females because of the costs of egg production or in both parents due to the need to provide post-hatching care of young, complicating the testing of an individual’s incubation capacity. We tested the incubation capacity hypothesis by studying a species with male-only parental care and precocial young, the emu Dromaius novaehollandiae, in which males can theoretically maximise care during incubation. Clutch size in emus varied considerably from 3 to 32 eggs, with males with larger natural, unmanipulated clutch sizes investing most in incubation in terms of the time they spent attending the nest. However, we found that when manipulating clutch size (to 4, 11 and 20 eggs), males responded to both clutch size and the magnitude of clutch size change during early incubation. Males with a median-sized clutch hatched the greatest number of eggs with moderate investment in incubation, while large nests elicited greater investment but a lower probability of hatching and fewer eggs to hatch; though when clutch sizes were manipulated, the increase in incubation investment between median and large clutches was not significantly different. Median clutches likely represent the male’s incubation capacity, which moderates male fitness and may drive selection for median-sized clutches in stable environments. However, the large variation in emu clutch sizes suggests that optimal clutch size may be driven by where females choose to lay or that optimal clutch size might be seasonally variable, with changing environmental and predation pressures. Significance statement: Avian reproductive success is restricted by the number of eggs parents can successfully incubate. The incubation capacity of a species is often difficult to test, however, as care is often divided between the parents and between incubation and the substantial post-hatching care of young. Using the male-only incubating emu, who invests heavily in incubation but little in post-hatching care, we test the effect of clutch size on male behaviour and hatching success. Males with a median-sized clutch (~ 11 eggs) hatched the greatest number of eggs with moderate investment in incubation, while large nests elicited similar or greater investment but lower hatching success. Our findings suggest that for species with uniparental care and precocial young, the incubation capacity is a key driver of reproductive success

Taking the bait : the influence of attractants and microhabitat on detections of fauna by remote-sensing cameras

Autonomously triggered cameras are a common wildlife survey technique. The use of attractants and surrounding microhabitats is likely to influence detection probabilities and survey outcomes; however, few studies consider these factors. We compared three attractants (peanut butter-based, tuna-based and a control) in a Latin square design through a coastal shrubland with high microhabitat variability at Cape Otway, Victoria, Australia (38°50ʹS, 143°30ʹE). Deployments involved 36 cameras for four days in each of five years. The percentage cover of each vegetation structural type (low [no or sparse cover], moderate [grass] or high [shrubs]) within 20 m of each camera was calculated and reduced to a single variable using PCA. Dynamic occupancy modelling, with lure type and vegetation structure as covariates of detection probability, found that peanut butter attracted the greatest diversity of species (24 of 35 species, 69%) and yielded the greatest number of detections (50% of 319) when compared with tuna oil (66% and 24%, respectively) and the control (43% and 26%, respectively). Peanut butter attracted more Macropodidae (wallabies) and Muridae (rats and mice); however, vegetation structural variables were the greatest influence on Corvidae/Artamidae (raven/currawong) detections with higher detectability in more open areas. Vegetation structure also influenced Muridae detections. This study reinforces the critical choice of appropriate attractants and camera placement when investigating vertebrate groups and highlights the role of microhabitat in the detection of small mammals and birds. We suggest future large-scale camera surveys consider different bait types and microhabitats in their designs, to control for any biases and enable future advice on ‘optimal’ methods