CIE Spotlight: Human-modified habitats facilitate forest-dwelling populations of an invasive predator, Vulpes vulpes

Authors: Bronwyn A. Hradsky, Alan Robley, Ray Alexander, Euan G. Ritchie, Alan York & Julian Di Stefano

Source: Scientific Reports

Brief summary of the paper: Invasive and over-abundant predators pose a major threat to biodiversity and often benefit from human activities. Effective management requires understanding predator use of human-modified habitats (including resource subsidies and disturbed environments), and individual variation within populations.

We investigated selection for human-modified habitats by invasive red foxes, Vulpes vulpes, within two predominantly forested Australian landscapes. We predicted that foxes would select for human-modified habitats in their range locations and fine-scale movements, but that selection would vary between individuals. We GPS-tracked 19 foxes for 17–166 days; ranges covered 33 to >2500 ha. Approximately half the foxes selected for human-modified habitats at the range scale, with some ‘commuting’ more than five kilometres to farmland or townships at night. Two foxes used burnt forest intensively after a prescribed fire. In their fine-scale nocturnal movements, most foxes selected for human-modified habitats such as reservoirs, forest edges and roads, but there was considerable individual variation.

Native fauna in fragmented and disturbed habitats are likely to be exposed to high rates of fox predation, and anthropogenic food resources may subsidise fox populations within the forest interior. Coordinating fox control across land-tenures, targeting specific landscape features, and limiting fox access to anthropogenic resources will be important for biodiversity conservation.

CIE Spotlight: Sediment anoxia limits microbial-driven seagrass carbon remineralization under warming conditions

AuthorsStacey M. Trevathan-Tackett, Justin R. Seymour, Daniel A. Nielsen,  Peter I. Macreadie, Thomas C. Jeffries, Jonathan Sanderman, Jeff Baldock,  Johanna M. Howes, Andrew D. L. Steven, Peter J. Ralph

Source: FEMS Microbiology Ecology

Brief summary of the paper: Seagrass ecosystems are significant carbon sinks, and their resident microbial communities ultimately determine the quantity and quality of carbon sequestered. However, environmental perturbations have been predicted to affect microbial-driven seagrass decomposition and subsequent carbon sequestration. Utilizing techniques including 16S-rDNA sequencing, solid-state NMR and microsensor profiling, we tested the hypothesis that elevated seawater temperatures and eutrophication enhance the microbial decomposition of seagrass leaf detritus and rhizome/root tissues.

Nutrient additions had a negligible effect on seagrass decomposition, indicating an absence of nutrient limitation. Elevated temperatures caused a 19% higher biomass loss for aerobically decaying leaf detritus, coinciding with changes in bacterial community structure and enhanced lignocellulose degradation. Although, community shifts and lignocellulose degradation were also observed for rhizome/root decomposition, anaerobic decay was unaffected by temperature. These observations suggest that oxygen availability constrains the stimulatory effects of temperature increases on bacterial carbon remineralization, possibly through differential temperature effects on bacterial functional groups, including putative aerobic heterotrophs (e.g. ErythrobacteraceaeHyphomicrobiaceae) and sulfate reducers (e.g. Desulfobacteraceae). Consequently, under elevated seawater temperatures, carbon accumulation rates may diminish due to higher remineralization rates at the sediment surface. Nonetheless, the anoxic conditions ubiquitous to seagrass sediments can provide a degree of carbon protection under warming seawater temperatures.

CIE Spotlight: Using multiple lines of evidence to assess the risk of ecosystem collapse

AuthorsLucie M. Bland, Tracey J. Regan, Minh Ngoc Dinh, Renata Ferrari, David A. Keith, Rebecca Lester, David Mouillot, Nicholas J. Murray, Hoang Anh Nguyen, Emily Nicholson

Source: Proceedings of the Royal Society B

Brief summary of the paper: Effective ecosystem risk assessment relies on a conceptual understanding of ecosystem dynamics and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management.

We applied the IUCN Red List of Ecosystems criteria to quantify the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to backcast past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered (plausibly Vulnerable to Critically Endangered), with notable differences among Red List criteria and data types in detecting the most severe symptoms of risk. Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment.

CIE Spotlight: Intra- and inter-individual variation in the foraging ecology of a generalist subantarctic seabird, the gentoo penguin

AuthorsElodie C. M. Camprasse, Yves Chere, Paco Bustamante, John P. Y. Arnould, Charles-André Bost2

Source: Marine Ecology Progress Series

Brief summary of the paper: Individual specialisations have been suggested to improve foraging efficiency by optimising individual capacity (physiological and behavioural) and reducing intra-specific competition in exploiting prey resources. In this study, we investigated the inter- and intra-individual variation in behaviour in an opportunistic forager, the gentoo penguin Pygoscelis papua, at Kerguelen Island, southern Indian Ocean.

We used complementary bio-logging and stable isotope analyses, coupled with morphometric measurements, to: (1) determine the inter-individual variation in morphology and foraging behaviour; (2) quantify intra-individual variation in foraging behaviour; (3) investigate the links between consistency in foraging, distances travelled and body condition; and (4) determine if dietary specialisations exist and are maintained outside the breeding season. We show that this species exhibits a large inter-individual variation in foraging behaviour, with some individuals conducting very short trips close to the colony while others travelled considerably farther. Heavier individuals tended to forage in more distant locations, dive deeper and perform more benthic dives. Individual specialisation in behaviour was low to moderate at the population level, yet some individuals were very consistent. The rate of travel was not influenced by consistency, and there was a lack of correlation between body condition and foraging consistency. High inter-individual variation in feeding ecology and dietary specialisations outside of a single breeding season were observed, consistent with gentoo penguins being Type ‘B’ generalists (i.e. generalist populations composed of individuals each consuming a different range of foods).

CIE Spotlight: Avian nest abandonment prior to laying-a strategy to minimize predation risk?

AuthorsMark Flegeltaub, Peter A. BiroChrista Beckmann

Source: Journal of Ornithology

Brief summary of the paper: Nest abandonment prior to laying is poorly understood and rarely studied. One possible explanation is that it is a behavior which may have evolved in response to high predation risk in nesting birds as a strategy to avoid the even greater costs of losing eggs or chicks. We tested this hypothesis in the Grey Fantail (Rhipidura albiscapa), a species that builds and abandons multiple nests throughout its breeding season without laying eggs. We placed artificial nests (that contained natural and plasticine eggs) in the exact locations of natural nests from the previous breeding season (spanning a large elevational gradient) for which the fate was known (abandoned, predated, or fledged).

Trials were conducted early and late in the breeding season to test for temporal patterns. We postulated that should nest abandonment indeed reduce predation risk, then artificial nests placed at previously abandoned nest sites should have a greater risk of predation than nests placed at predated or fledged nest sites. Overall, we found that 74% of artificial nests were predated, with predation attributed to birds (66%), small mammals (7%), ants (8%), and unknown predators (19%). Artificial nest predation varied according to previous nest fate, whereby predation rates were lowest for predated sites, slightly higher for fledged, and highest at previously abandoned nest sites.

In addition, cover increased survival rates for all nest site types. However, we observed a shift in the proportion of nests predated by birds versus other predator taxa, whereby nest predation by birds was highest late in the season at high elevation; this increase may have been due to extreme high temperatures at low elevation resulting in bird predators moving to refuges at higher elevation.

CIE Spotlight: Implications of location accuracy and data volume for home range estimation and fine-scale movement analysis: comparing Argos and Fastloc-GPS tracking data

AuthorsJ. A. ThomsonL. Börger, M. J. A. Christianen, N. Esteban, J.-O. Laloë, G. C. Hays

Source: Marine Biology

Brief summary of the paper: The advent of Fastloc-GPS is helping to transform marine animal tracking by allowing the collection of high-quality location data for species that surface only briefly. We show how the improved location accuracy of Fastloc-GPS compared to Argos tracking is expected to lead to far more accurate home range estimates, particularly for animals moving over the scale of a few km.

We reach this conclusion using simulated data and home range estimates derived from empirical tracking data for green sea turtles (Chelonia mydas) equipped with Argos linked Fastloc-GPS tags at three different foraging areas (western Indian Ocean, Western Australia, and Caribbean). Poor-quality Argos locations (e.g., location classes A, B) produced home range estimates ranging from 10 to 100 times larger than those derived from Fastloc-GPS data, whereas high-quality Argos locations (location classes 1–3) produced home range estimates that were generally comparable to those derived from Fastloc-GPS data.

However, the limited number of Argos class 1–3 locations obtained for all three turtles—an average of 14.6 times more Fastloc-GPS locations were obtained compared to Argos class 1–3 locations—resulted in blurred patterns of space use. In contrast, the high volume of Fastloc-GPS locations revealed fine-scale movements in striking detail (i.e., use of discrete patches separated by just a few 100 m). We recommend careful consideration of the effects of location accuracy and data volume when developing sampling regimes for marine tracking studies and make recommendations regarding how sampling can be standardized to facilitate meaningful spatial and temporal comparisons of space use.

CIE Spotlight: A citizen-trapper effort to control Common Myna: Trap success, specificity and preferred bait type

Authors: Grant D. Linley, David C. Paton, Michael A. Weston

Source: Ecological Management & Restoration

Brief summary of the paper: We describe a community-run effort to cull Common Myna (Acridotheres tristis) in Melbourne undertaken with modest funding (overall: $30.14 per trap day, $5.17 per euthanized Common Myna). Trap success (overall, 0.04 birds per trap per day) peaked early in the effort and slowly declined. Trap specificity was high (83.8%) and similar between bait types. Dry cat food captured more Common Myna, and a similar assemblage of animals, to dry dog food. Bread baits captured a broader assemblage of animals. The community-led trapping programme reduced the mean density of Common Myna and achieved high target specificity with relatively few unintended trap deaths. While long-term impacts on the population of Common Myna or native birds are yet to be analysed, the results suggest that ongoing effort is required for population suppression.

CIE Spotlight: Fastloc-GPS reveals daytime departure and arrival during long-distance migration and the use of different resting strategies in sea turtles

AuthorsAntoine M. DujonGail SchofieldRebecca E. LesterNicole Esteban, Graeme C. Hays

Source: Marine Biology

Brief summary of the paper: Determining the time of day that animals initiate and end migration, as well as variation in diel movement patterns during migration, provides insights into the types of strategy used to maximise energy efficiency and ensure successful completion of migration. However, obtaining this level of detail has been difficult for long-distance migratory marine species. Thus, we investigated whether the large volume of highly accurate locations obtained by Argos-linked Fastloc-GPS transmitters could be used to identify the time of day that adult green (n = 8 turtles, 9487 locations) and loggerhead (n = 46 turtles, 47,588 locations) sea turtles initiate and end migration, along with potential resting strategies during migration.

We found that departure from and arrival at breeding, stopover and foraging sites consistently occurred during the daytime, which is consistent with previous findings suggesting that turtles might use solar visual cues for orientation. Only seven turtles made stopovers (of up to 6 days and all located close to the start or end of migration) during migration, possibly to rest and/or refuel; however, observations of day versus night speed of travel indicated that turtles might use other mechanisms to rest. For instance, turtles travelled 31% slower at night compared to day during their oceanic crossings.

Furthermore, within the first 24 h of entering waters shallower than 100 m towards the end of migration, some individuals travelled 72% slower at night, repeating this behaviour intermittently (each time for a one-night duration at 3–6 day intervals) until reaching the foraging grounds. Thus, access to data-rich, highly accurate Argos-linked Fastloc-GPS provided information about differences in day versus night activity at different stages in migration, allowing us, for the first time, to compare the strategies used by a marine vertebrate with terrestrial land-based and flying species.

CIE Spotlight: The causes and ecological correlates of head scale asymmetry and fragmentation in a tropical snake

Authors: Gregory P. Brown, Thomas Madsen, Sylvain Dubey, Rick Shine

Source: Scientific Reports

Brief summary of the paper: The challenge of identifying the proximate causes and ecological consequences of phenotypic variation can be facilitated by studying traits that are usually but not always bilaterally symmetrical; deviations from symmetry likely reflect disrupted embryogenesis. Based on a 19-year mark-recapture study of >1300 slatey-grey snakes (Stegonotus cucullatus) in tropical Australia, and incubation of >700 eggs, we document developmental and ecological correlates of two morphological traits: asymmetry and fragmentation of head scales.

Asymmetry was directional (more scales on the left side) and was higher in individuals with lower heterozygosity, but was not heritable. In contrast, fragmentation was heritable and was higher in females than males. Both scale asymmetry and fragmentation were increased by rapid embryogenesis but were not affected by hydric conditions during incubation. Snakes with asymmetry and fragmentation exhibited slightly lower survival and increased (sex-specific) movements, and females with more scale fragmentation produced smaller eggs. Counterintuitively, snakes with more asymmetry had higher growth rates (possibly reflecting trade-offs with other traits), and snakes with more fragmentation had fewer parasites (possibly due to lower feeding rates). Our data paint an unusually detailed picture of the complex genetic and environmental factors that, by disrupting early embryonic development, generate variations in morphology that have detectable correlations with ecological performance.

CIE Spotlight: Genetic isolation in an endemic African habitat specialist

Authors: Natalie dos Remedios, Clemens Küpper, Tamás Székely, Neil Baker, Wilferd Versfeld, Patricia L. M. Lee

SourceIBIS: International Journal of Avian Science

Brief summary of the paper: The Chestnut-banded Plover Charadrius pallidus is a Near-Threatened shorebird species endemic to mainland Africa. We examined levels of genetic differentiation between its two morphologically and geographically distinct subspecies, C. p. pallidus in southern Africa (population size 11 000–16 000) and C. p. venustus in eastern Africa (population size 6500). In contrast to other plover species that maintain genetic connectivity over thousands of kilometres across continental Africa, we found profound genetic differences between remote sampling sites.

Phylogenetic network analysis based on four nuclear and two mitochondrial gene regions, and population genetic structure analyses based on 11 microsatellite loci, indicated strong genetic divergence, with 2.36% mitochondrial sequence divergence between individuals sampled in Namibia (southern Africa) and those of Kenya and Tanzania (eastern Africa). This distinction between southern and eastern African populations was also supported by highly distinct genetic clusters based on microsatellite markers (global FST = 0.309, math formula = 0.510, D = 0.182). Behavioural factors that may promote genetic differentiation in this species include habitat specialization, monogamous mating behaviour and sedentariness. Reliance on an extremely small number of saline lakes for breeding and limited dispersal between populations are likely to promote reproductive and genetic isolation between eastern and southern Africa. We suggest that the two Chestnut-banded Plover subspecies may warrant elevation to full species status. To assess this distinction fully, additional sample collection will be needed, with analysis of genetic and phenotypic traits from across the species’ entire breeding range.