Avifauna and urban encroachment in time and space

AIM: Urban expansion significantly alters fringe environments often with unde-sirable impacts on biodiversity. Consequently, there is a need to define clearconservation objectives for areas subject to urban encroachment. Urban fringe development is a highly dynamic process, both spatially and temporally, but few studies are equipped to examine its temporal effects on biota. We aimed to explore the impacts of urban encroachment on avifauna through space and time.LOCATION: The Australian Capital Territory, Australia. METHODS: We used records from an extensive 14-year monitoring programme undertaken in temperate woodland. We fitted hierarchical generalized linear models to assess individual species responses to the distance from monitoring sites to the urban boundary, and the temporal rate of change in this distance through time. We used factorial analysis on mixed data to examine trait group responses to these predictors.RESULTS: Our results indicated that the occurrence of approximately half of the study region’s avifauna is strongly linked to the proximity of their habitat to the urban fringe, but that the impact of urban fringe development on the occurrence of some species changed through time. We identified several species of conservation concern that respond negatively to large annual increases in urban fringe development, irrespective of its proximity to suitable habitat. Species responses to urban proximity were linked to life history traits, with small,migratory, woodland-dependent species that rely on mid- and upper-canopy structures, clearly disadvantaged by urban environments.MAIN CONCLUSIONS: Our findings demonstrate the breadth of species responses to urban encroachment over much larger distances than is typically investigated in urban ecological studies. We identify guilds vulnerable to the impacts of urban fringe development and therefore in need of ecologically sensitive urban design. We argue that future urban expansion towards important fringe habitats will need to be planned strategically through space and time.This research received funding support from Conservation Planning and Research, Environment and Sustainable Devel-opment Directorate ACT Government and the Fenner Schoolof Environment and Society. DBL, PG and KI were sup-ported by the National Environmental Research Program. ADM was supported by an ARC Future Fellowship (FT100100358)

Outfoxing the fox: effect of prey odor on fox behavior in a pastoral landscape

Invasive mammalian predators have had a devastating effect on native species globally. The European red fox (Vulpes vulpes) is one such species where it has been introduced in Australia. A novel but unexplored tactic to reduce the impact of mammalian predators is the use of unrewarded prey odors to undermine the effectiveness of olfactory hunting behavior. To test the viability of unrewarded prey odors in an applied setting we investigated how foxes responded to the odors of three different prey species. We used the odors of two locally extinct native Australian marsupials; the eastern quoll (a smaller carnivore) and eastern bettong (a fungivore), and the European rabbit, an introduced herbivore. Conducting our research over a period of 3 weeks in a pastoral environment in South-eastern Australia, we used video observations of foxes' behaviors, as they encountered the different odors. We found a reduction in the number of fox visits to bettong odors in the third week. In contrast, we observed a sustained number of visits to rabbit odors. Foxes also spent more time investigating rabbit odors and displayed longer durations of vigilance behavior at quoll odors. Our results support the hypothesis that the exposure of wild foxes to unrewarded odors of novel prey species can reduce their interest in these odors, which might translate to a reduction in predation pressure. Our results also suggest, however, that olfactory pre-exposure may not be as effective at reducing fox interest in a competitor species' odor

Nutrient and moisture transfer to insect consumers and soil during vertebrate decomposition

Decomposition of organic matter leads to the redistribution of nutrients to organisms and the environment. Yet knowledge of this process has focused largely on plant-derived organic matter, with little known about relative quantities of nutrients and moisture transferred from decomposing animal remains to insect consumers and soil. We used a replicated and spatially blocked experiment to quantify the moisture, carbon, nitrogen, and phosphorous content of rabbit carcasses, maggot consumers, and soil over 20 days of decomposition. We found that maggot biomass reached 22% of the fresh rabbit carcass, or 39% of the consumable soft tissues. Maggots were comprised of 68% moisture, and their dry mass was comprised of 25% carbon, 4.9% nitrogen, and 0.8% phosphorous. Soils accumulated approximately 12.9% of the total carcass moisture, but only 0.7% of the carcass dry mass. The largest quantity of carcass mass loss was attributable to evaporation of moisture to the atmosphere (45%). Approximately 9% of the initial carcass mass was left as unconsumed remains. Our study provides estimates of the quantities of nutrients moving from vertebrate carcasses to insect consumers and soil. This knowledge is critical to scaling up the effects of carcasses and to developing our understanding of their role in biogeochemical cycling in ecosystems

Short- and long- term effects of habitat fragmentation differ but are predicted by response to the matrix

Habitat loss and fragmentation are major threats to biodiversity and ecosystem processes. Our current understanding of the impacts of habitat loss and fragmentation is based largely on studies that focus on either short- term or long- term responses. Short- term responses are often used to predict long- term responses and make management decisions. The lack of studies comparing short- and long- term responses to fragmentation means we do not adequately understand when and how well short- term responses can be extrapolated to predict long- term responses, and when or why they cannot. To address this gap, we used data from one of the world’s longest- running fragmentation experiments, The Wog Wog Habitat Fragmentation Experiment. Using data for carabid beetles, we found that responses in the long term (more than 22 yr post- fragmentation ≈22 generations) often contrasted markedly with those in the short term (5 yr post- fragmentation). The total abundance of all carabids, species richness and the occurrence of six species declined in the short term in the fragments but increased over the long term. The occurrence of three species declined initially and continued to decline, whilst another species was positively affected initially but decreased in the long term. Species’ responses to the matrix that surrounds the fragments strongly predicted both the direction (increase/decline in occurrence) and magnitude of their responses to fragmentation. Additionally, species’ responses to the matrix were somewhat predicted by their preferences for different types of native habitat (open vs. shaded). Our study highlights the degree of the matrix’s influence in fragmented landscapes, and how this influence can change over time. We urge caution in using short- term responses to forecast long- term responses in cases where the matrix (1) impacts species’ responses to fragmentation (by isolating them, creating new habitat or altering fragment habitat) and (2) is likely to change through time.Funding to collect, process and identify samples between 2009 and 2013 was provided by NSF DEB 0841892 to KFD and BAM. KFD was also supported by NSF DEB 1350872. MJE was funded by an Australian National University PhD Scholarship

Pollination and resource limitation as interacting constraints on almond fruit set

Pollination and resource availability are factors determining reproductive success ofplants, and in agriculture these factors influence yield of fruit-bearing crops. Ourunderstanding of the importance of crop pollination is fast improving, but less isknown about how the interaction between pollination and resources constrains fruitproduction.•We conducted an experiment with almond trees (Prunus dulcis) to examine how thenumber of flowers, light availability and competition for resources affected nut (fruit)production on individual spurs (fruit-bearing structures) exposed to open-pollinationor hand-pollination.•We found a positive relationship between flower number and nut number on spurswith up to four flowers, but no further benefit after four flowers, suggesting a resourcethreshold expressed by individual spurs. Spurs with few flowers increased the conver-sion rate of flowers to nuts when supplemented with hand-pollination, but spurs withmore flowers were more likely to achieve the threshold number of nuts even underopen-pollination. Our experiment included a further treatment involving sprayingwhole trees with pollen. This treatment reduced nut production by spurs with manyflowers and high light availability, suggesting competition is experienced by well-re-sourced spurs when resources need to be shared among developing nuts across thewhole tree.•Our study supports the hypothesis that excess flower production in fruit treesincreases the potential for fruit production when pollinator and resource availability isvariable (bet-hedging). Spurs with more flowers typically produce more nuts (within alimited range), but only if both resources and pollen supply increase with flower num-ber. For almond growers, a focus on maintaining high flower numbers, especially inhigh light regions of the canopy, is the foundation for high levels of production.Strategies to lift flower number and light are complicated by trade-offs inherent in treearchitecture and orchard design. However, fruit set would be lifted above thatachieved by current practice by an increase in the pollination rate of flowersThe research was supported by funding from HorticultureInnovation Australia (AL14004). The research was conductedby CSIRO staff in collaboration with Victorian Department ofEnvironment and Primary Industries and the AustralianNational University. The Almond Board of Australia initiatedthe project and provided critical support throughout. SarinaMacfadyen (CSIRO) provided support to project management.The staff at the Lindsay Point CMV orchard generously allowedaccess to the orchard and were always helpfu

Insect abundance patterns on vertebrate remains reveal carrion resource quality variation

Resource quality is a key driver of species abundance and community structure. Carrion is unique among resources due to its high nutritional quality, rapidly changing nature, and the diverse community of organisms it supports. Yet the role resource quality plays in driving variation in abundance patterns of carrion-associated species remains poorly studied. Here we investigate how species abundances change with a measure of resource change, and interpret these findings to determine how species differ in their association with carrion that changes in quality over time. We conducted field succession experiments using pigs and humans over two winters and one summer. We quantified the effect of total body score, an objective measure of resource change, on adult insect abundance using generalised additive models. For each species, phases of increasing abundance likely indicated attraction to a high-quality resource, and length of abundance maxima indicated optimal oviposition and feeding time. Some species such as the beetle Necrobia rufipes had a rapid spike in abundance, suggesting a narrow window of opportunity for carrion resource exploitation, while species like the wasp Nasonia vitripennis had a gradual change in abundance, indicating a wide window of resource exploitation. Different abundance patterns were also observed between species occurring on pigs and humans, suggesting cadaver type is an important aspect of resource quality. Our findings show that species abundances, unlike species occurrences, can reveal additional detail about species exploitation of carrion and provide information about how resource quality may drive competition and variation in insect community succession

Dynamic soil nutrient and moisture changes under decomposing vertebrate carcasses

The decomposition of animal carcasses contributes to nutrient recycling in ecosystems worldwide, including by delivering nutrients to soil. Although several studies have characterised changes in soil chemistry occurring under carcasses, many ecological studies have occurred over extended post-mortem intervals and fine-scale temporal changes in physicochemical conditions are poorly understood. We examined changes in a suite of soil physicochemical properties occurring under decomposing rabbit carcasses during summer in a grassland ecosystem. We found that carcasses lost over 90% of their starting mass and reached dry decay and skeletonization after 20 days of decomposition. Carcass temperatures were up to 15 °C higher than ambient temperatures during the active decay stage (days 3 and 5) of decomposition. Soil moisture also increased by day 4, and this was matched with a simultaneous increase in total nitrogen and ammonium, as well increases in pH and electrical conductivity. Whereas these measures remained relatively stable as decay progressed, we found total phosphorus and phosphate continued to increase to day 20. The contrasting dynamics of N and P reflect the initial nutrient and fluid input during the rapid decay of soft tissues and intense activity of fly larvae, and the subsequent dry decay and exposure of skeletal components. Our study provides new information about the fine-scale timing of nutrient inputs and moisture and temperature changes occurring at the carcass/soil interface

Priority effects and density promote coexistence between the facultative predator Chrysomya rufifacies and its competitor Calliphora stygia

Highly competitive ephemeral resources like carrion tend to support much greater diversity relative to longer-lived resources. The coexistence of diverse communities on short-lived carrion is a delicate balance, maintained by several processes including competition. Despite this balance, few studies have investigated the effect of competition on carrion, limiting our understanding of how competition drives coexistence. We investigated how priority effects and larval density influence coexistence between two blowfly species, the facultative predator Chrysomya rufifacies and its competitor Calliphora stygia, which occupy broadly similar niches but differ in their ecological strategies for exploiting carrion. We examined how adult oviposition, larval survival, developmental duration, and adult fitness were affected by the presence of differently aged heterospecific larval masses, and how these measures varied under three larval densities. We found C. rufifacies larval survival was lowest in conspecific masses with low larval densities. In heterospecific masses, survival increased, particularly at high larval density, with priority effects having minimal effect, suggesting a dependency on collective exodigestion. For C. stygia, we found survival to be constant across larval densities in a conspecific mass. In heterospecific masses, survival decreased drastically when C. rufifacies arrived first, regardless of larval density, suggesting C. stygia is temporally constrained to avoid competition with C. rufifacies. Neither species appeared to completely outcompete the other, as they were either constrained by density requirements (C. rufifacies) or priority effects (C. stygia). Our results provide new mechanistic insights into the ecological processes allowing for coexistence on a competitively intense, ephemeral resource such as carrion

Landscapes of nausea: Successful conditioned taste aversion in a wild red fox population

Abstract Predation by invasive mammalian species is one of the key drivers of native species' population declines and extinctions. Current management of invasive species focuses on their removal from the landscape. However, total removal can be difficult, costly and even impossible. If eradication is not achieved, reductions in predator numbers are often temporary. New tactics are needed to target predators in situ, to reduce their negative impacts. We test the efficacy of conditioned taste aversion (CTA), a tactic that could reduce the impact of predation on target prey species. By associating nausea with a specific food source, it may be possible to condition an aversion to a target bait, and ultimately to live animals in the wild. To assess if wild invasive red foxes (Vulpes vulpes) can be conditioned to avoid a specific food source, we used baits (fried deboned chicken) containing encapsulated levamisole, an anthelmintic agent known to induce nausea leading to emesis and/or diarrhea at high dosages with no long‐term side effects. We buried baits at 30 stations across an open landscape. After treatment, reductions in control baits taken (at least 30%) were observed for 68 days, indicating the use of CTA had successfully reduced bait consumption by red foxes in a wild context. To our knowledge, this study represents the first successful test of CTA to a meat bait in a wild red fox population. Our results suggest that CTA shows promise as a tool to reduce the predation of vulnerable animals providing an alternative tactic to manage the impacts of invasive mammalian predators where eradication is currently impossible