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Research Interests: Biology, Ecology, Population Dynamics, Multidisciplinary, Ecological Modelling, and 15 moreModel, Population, Computer Model, New Zealand, Forests, Population Size, Food Availability, Field Study, Mathematical Model, House Mouse, Mustela Erminea, Outbreak, Population dynamic, Mus Musculus, and Natural Mortality
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The biodiversity hotspot of New Caledonia hosts high levels of endemism (74% of flora) that is threatened increasingly by climate change, habitat reduction, and invasive species. The fruit‐eating red‐vented bulbul (Pycnonotus cafer) is... more
The biodiversity hotspot of New Caledonia hosts high levels of endemism (74% of flora) that is threatened increasingly by climate change, habitat reduction, and invasive species. The fruit‐eating red‐vented bulbul (Pycnonotus cafer) is currently invading the main island of the archipelago, and its recent dispersal out of urbanized habitats raises questions about its potential to disperse noxious plant seeds along urban corridors and beyond. Indeed, the red‐vented bulbul is considered a vector of several introduced plant species in its alien range including Miconia calvescens, Lantana camara, and Schinus terebinthifolius. We conducted a quantitative assessment of the bulbul's fruits consumption by analyzing the gut contents of shot birds. We estimated gut passage times for four species of fruit found in gut contents (S. terebinthifolius, Myrtastrum rufopunctatum, Passiflora suberosa, and Ficus prolixa) and tested the effects of bird digestion on seed germination rates for two spe...
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ABSTRACT During mating, male bush-crickets transfer a complex spermatophore to the female. The spermatophore is comprised of a large nuptial gift which the female consumes while the sperm from the ejaculate-containing ampulla are... more
ABSTRACT During mating, male bush-crickets transfer a complex spermatophore to the female. The spermatophore is comprised of a large nuptial gift which the female consumes while the sperm from the ejaculate-containing ampulla are transferred into her. Two main functions of the nuptial gift have been proposed; the ejaculate protection hypothesis has evolved in a sexual selection context and predicts that the time to consume the gift is no longer than necessary to allow for full ejaculate transfer. The parental investment hypothesis maintains that gift nutrients increase the fitness or quantity of offspring and hence the gift is likely to be larger than is necessary for complete sperm transfer. With an aim to better understanding the primary function of nuptial gifts, we examine sperm transfer data from field populations of five Poecilimon bush-cricket taxa with varying spermatophore sizes. In the species with the largest spermatophore, the gift was four times larger than necessary to allow for complete sperm transfer and is likely to function as paternal investment. Species with medium and small gifts were respectively sufficient and insufficient to allow complete sperm transfer and are likely to represent various degrees of ejaculate protection. Controlling for body mass and relatedness, we also found that species producing larger spermatophores apparently transfer a greater proportion of available sperm than species producing smaller spermatophores, and thus result in a higher paternal assurance.
This study aimed to investigate whether the infection intensity of Theileria orientalis Ikeda type organisms within Haemaphysalis longicornis larvae and nymph stages fluctuated over 6 mo after feeding as larvae on infected calves in the... more
This study aimed to investigate whether the infection intensity of Theileria orientalis Ikeda type organisms within Haemaphysalis longicornis larvae and nymph stages fluctuated over 6 mo after feeding as larvae on infected calves in the field. Naïve larvae, hatched from eggs, were fed on infected calves for 5 days while contained within cotton socks glued over the calves' ears. Larvae were first sampled immediately post-feeding and then sampled every 3 wk for 23 wk in total, after molting to nymphs. All larvae and nymphs were tested for T. orientalis Ikeda organisms using quantitative PCR. The qPCR results showed that the infection intensity of Haemaphysalis longicornis larvae and nymphs was not constant over the sampling period, and after initially dropping after molting to nymphs, it then rose with fasting to a maximum at 17 and 23 wk post-feeding. The significant rise in T. orientalis Ikeda organisms observed at 23 wk postfeeding may explain why more severe clinical cases of bovine theileriosis in New Zealand are seen in the spring when nymphs are the predominant instar questing.
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Calluna vulgaris (heather) is an aggressive invasive weed on the Central Plateau, North Is., New Zealand (NZ), where it encounters different environmental factors compared to its native range in Europe, such as high ultraviolet radiation... more
Calluna vulgaris (heather) is an aggressive invasive weed on the Central Plateau, North Is., New Zealand (NZ), where it encounters different environmental factors compared to its native range in Europe, such as high ultraviolet radiation (UV) and a lack of specialist herbivores. The specialist herbivore Lochmaea suturalis (heather beetle) was introduced from the United Kingdom (UK) in 1996 as a biocontrol agent to manage this invasive weed. Like other plant invaders, a novel environment may be challenging for heather as it adjusts to its new conditions. This process of “adjustment” involves morphological and physiological changes often linked to phenotypic plasticity. The biochemical responses of exotic plants to environmental variables in their invaded range is poorly understood. The production and release of volatile organic compounds (VOCs) is essential to plant communication and highly susceptible to environmental change. This study therefore aimed to explore the VOC emissions o...
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Heather (Calluna vulgaris) and broom (Cytisus scoparius), originally from Europe, are the main invasive plants on New Zealand’s North Island Central Plateau, where they threaten native flora and fauna. Given the strong link between... more
Heather (Calluna vulgaris) and broom (Cytisus scoparius), originally from Europe, are the main invasive plants on New Zealand’s North Island Central Plateau, where they threaten native flora and fauna. Given the strong link between arthropod communities and plants, we explored the impact of these invasive weeds on the diversity and composition of associated arthropod assemblages in this area. The arthropods in heather-invaded areas, broom-invaded areas, and areas dominated by the native species mānuka (Leptospermum scoparium) and Dracohyllum (Dracophyllum subulatum) were collected and identified to order. During summer and autumn, arthropods were collected using beating trays, flight intercept traps and pitfall traps. Diversity indices (Richness, Shannon’s index and Simpson’s index) were calculated at the order level, and permutational multivariate analysis (PERMANOVA) was used to explore differences in order-level community composition. Our results show a significant variation in c...
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Invasive plants pose a threat to natural ecosystems, changing the community composition and ecological dynamics. One aspect that has received little attention is the production and emission of volatile organic compounds (VOCs) by invasive... more
Invasive plants pose a threat to natural ecosystems, changing the community composition and ecological dynamics. One aspect that has received little attention is the production and emission of volatile organic compounds (VOCs) by invasive plants. Investigating VOCs is important because they are involved in vital ecological interactions such as pollination, herbivory and plant competition. Heather, Calluna vulgaris, is a major invasive weed in New Zealand, especially on the Central Plateau, where it has spread rapidly since its introduction in 1912, outcompeting native species. However, the chemical behaviour of heather in its invaded ranges is poorly understood. We aimed to explore the natural variation in volatile emissions of heather and the biotic and abiotic factors influencing them on the Central Plateau of New Zealand. To this end, foliar volatiles produced by heather at four different sites were collected and analysed using gas chromatography coupled to mass spectrometry. Soi...
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Plasma corticosterone concentrations increase when birds experience a stressor, and plasma corticosterone responses to a capture and handling stressor have been measured in many species of birds. Whilst it is assumed that the reported... more
Plasma corticosterone concentrations increase when birds experience a stressor, and plasma corticosterone responses to a capture and handling stressor have been measured in many species of birds. Whilst it is assumed that the reported corticosterone responses reflect the inherent sensitivity of each bird to the stressor, responses of the same birds have rarely been measured at intervals of one or more years. The current study was conducted to measure the repeatability in two successive years of corticosterone responses of little penguins (Eudyptula minor) at Oamaru, New Zealand. There was a wide range of individual corticosterone responses to capture and restraint in 96 little penguins in 2012 and 50 penguins sampled at the same time of year in 2013. There were significant repeatabilities for the ranks of corticosterone at 15, 30 and 60 min (r = 0.416 ± 0.160, r = 0.636 ± 0.115 and r = 0.380 ± 0.166 respectively) and for the ranks of integrated corticosterone responses (r = 0.594 ± ...
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SummaryBar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris are long-distance migratory shorebirds with declining numbers in the East Asian-Australasian Flyway. One of the most important staging sites for these two... more
SummaryBar-tailed Godwits Limosa lapponica and Great Knots Calidris tenuirostris are long-distance migratory shorebirds with declining numbers in the East Asian-Australasian Flyway. One of the most important staging sites for these two species during northward migration is Yalu Jiang coastal wetland in the north Yellow Sea. Historical counts have been limited to once a year and conducted at different periods; these yield inadequate data for population monitoring. We estimated the numbers of Bar-tailed Godwits and Great Knots and described their migration phenology during northward migration from 2010 to 2012 at the Yalu Jiang coastal wetland, using a combination of periodic area-wide counts over the migration period and a modelling approach that estimates passage times and total numbers of birds transiting. The mean arrival date for L. l. baueri godwits was 29 March and mean departure date was 8 May. Corresponding dates were 11 April and 15 May for L. l. menzbieri godwits and 7 Apri...
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ABSTRACT The tidal flats of the Yellow Sea support benthic communities that are vitally important to migratory birds, but baseline information on benthic community structure and variability is largely lacking. We investigated spatial and... more
ABSTRACT The tidal flats of the Yellow Sea support benthic communities that are vitally important to migratory birds, but baseline information on benthic community structure and variability is largely lacking. We investigated spatial and temporal patterns of macrobenthic invertebrates in areas used by large numbers of shorebirds and how these patterns related to environmental factors at Yalu Jiang coastal wetland in the north Yellow Sea during boreal spring (March–May) from 2010 to 2012. At least 61 species were documented during the study. Monthly benthos sampling from 54 stations indi-cated that polychaetes and bivalves dominated the benthic communities, with capitellid or maldanid polychaetes domi-nating upper tidal flats and the bivalve Potamocorbula laevis dominating intermediate and lower tidal flats. The middle and eastern sites approximately 10 km apart showed substantial differences in benthic species abundance and distribution, with bivalves dominating in the middle but not the eastern site. The spatial distribution of benthos was correlated with both exposure time during the tidal cycle and sediment parti-cle size. Benthic communities showed both annual and within season variation. Two of the frequent prey for migratory birds, namely ghost shrimps Nihonotrypaea japonica and young Potamocorbula laevis, were relatively common in 2010 and 2011, respectively, but not in 2012.
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The earthworm Eisenia fetida was exposed to artificial soil supplemented with 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to investigate its effects on earthworm mortality, growth, avoidance, burrowing behavior and respiration. The... more
The earthworm Eisenia fetida was exposed to artificial soil supplemented with 18-crown-6 (1,4,7,10,13,16-hexaoxacyclooctadecane) to investigate its effects on earthworm mortality, growth, avoidance, burrowing behavior and respiration. The results revealed that 18-crown-6 had the potential to negatively affect the behavior of earthworms. The 7-d LC50 was 585 mg kg(-1) soil. Avoidance behavior was the most sensitive endpoint, with a 48-h EC50 of 120 mg kg(-1) soil. Growth, burrow length and respiration showed general decreases with increasing 18-crown-6 concentrations. Behavioral endpoints and respiration may be regarded as sensitive parameters in evaluating the toxicity of this chemical to earthworms.
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The plankton communities (phytoplankton and zooplankton) and physicochemical properties in seawater were monitored between January to December 2008 at nine coastal mariculture and local fisheries piers in Phang Nga Province, Thailand, to... more
The plankton communities (phytoplankton and zooplankton) and physicochemical properties in seawater were monitored between January to December 2008 at nine coastal mariculture and local fisheries piers in Phang Nga Province, Thailand, to assess water quality rehabilitation following the Tsunami disaster of 2004. All physical and chemical values fell within the ranges that are considered normal for unpolluted water: temperature ranged from 29.84 (± 0.47) - 31.29 (± 0.27) °C; transparency ranged from 49 (± 7) - 108 (± 7) cm; total dissolved solids ranged from 17,060 (± 162) - 26,240 (± 68) mg/l; electrical conductivity ranged from 34.12 (± 3.48) - 52.48 (± 1.62) mS/cm; pH ranged from 6.69 (± 0.13) - 7.94 (± 0.07); salinity ranged from 19.48 (± 1.78) - 30.28 (± 0.44) ppt.; dissolved oxygen ranged from 6.36 (± 0.35) - 7.49 (± 0.35); biochemical oxygen demand ranged from 2.04 (± 0.25) - 3.80 (± 0.20) mg/l; and chemical oxygen demand ranged from 34.0 (± 0.95) - 63.3 (± 0.84) mg/l. Phytopl...
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Direct and dendrographic comparison of the profiles of abundant fatty acids in depot fat was unable to separate 10 avian species on a basis of their overall proportions but was able to distinguish broad dietary groups or those in a... more
Direct and dendrographic comparison of the profiles of abundant fatty acids in depot fat was unable to separate 10 avian species on a basis of their overall proportions but was able to distinguish broad dietary groups or those in a habitat with distinctive nutritional characteristics such as avian marine carnivores. In all species considered, including North Island brown kiwi (Apteryx mantelli), oleic (C18:1) and palmitic acids (C16:0) were most abundant. The relative proportions of linolenic (C18:3) acid were 4% or lower across all species, while the relative proportions of palmitoleic acid (C18:0) were less than 7% in nine of the avian species, with the exception being the insectivorous red-eyed vireo (Vireo olivaceous). The levels of linoleic acid (C18:2) were lower in avian marine carnivores than in avian herbivores, insectivores, and omnivores. Whilst the mean values of the individual fatty acids in fat from various avian species were separated by hierarchical cluster analysis,...
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A technique for trapping and immobilising small macropods is described and tested on forest-dwelling Tammar wallabies (Macropus eugenii Desmarest). The trapping method uses wire fencing and a monofilament nylon drop-net. The animals were... more
A technique for trapping and immobilising small macropods is described and tested on forest-dwelling Tammar wallabies (Macropus eugenii Desmarest). The trapping method uses wire fencing and a monofilament nylon drop-net. The animals were immobilised with ketamine hydrochloride and xylazine. Tammar wallabies are reputedly hard to catch, but our technique produced higher trapping rates, lower trap-avoidance rates and lower death rates than other methods. In all, 46 Tammars were captured in 29 trap-nights. No deaths occurred during, or in the four weeks following, trapping.
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Research Interests: Engineering, Physics, Chemistry, Biology, Medicine, and 5 moreMultidisciplinary, Birds, Animals, Animal migration, and PLoS one
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Plasma corticosterone concentrations increase when birds experience a stressor, and in this study we quantified variation in corticosterone responses for the first time in a species of free-living bird. Adelie penguins (Pygoscelisadeliae)... more
Plasma corticosterone concentrations increase when birds experience a stressor, and in this study we quantified variation in corticosterone responses for the first time in a species of free-living bird. Adelie penguins (Pygoscelisadeliae) nesting at Cape Bird on Ross Island in Antarctica were sampled on three occasions. Penguins with relatively low or high corticosterone responses on the first occasion had consistently low or high responses, as previously found for great tits and chickens. A model for birds is proposed in which birds with low corticosterone responses and proactive personalities are likely to be more successful (have greater fitness) in constant or predictable conditions, whilst birds with reactive personalities and high corticosterone responses will be more successful in changing or unpredictable conditions. There is thus no linear relationship between the size of a corticosterone response and fitness. Whilst the absolute magnitude of corticosterone responses varies markedly across species of birds, coefficients of variation are similar. Individual corticosterone responses are generally repeatable, with significant statistical repeatabilities for 30 min corticosterone concentrations and integrated corticosterone concentrations in the Adelie penguin, great tit and chicken. Coefficients of variation in corticosterone responses between birds and power analyses were used to provide a rule of thumb for determining differences between groups of birds in mean corticosterone concentrations to enable statistical analyses to have acceptable levels of statistical power for given sample sizes. It is suggested that power analyses and this rule of thumb be adopted in future investigations of corticosterone responses in birds.
Research Interests: Physiology, Zoology, Biology, Stress, Medicine, and 15 moreApplied Animal Behavior, Birds, Female, Animals, Corticosterone, Male, Power Analysis, Statistical Power, Coefficient of Variation, Sample Size, Individual variation, Repeatability, Veterinary Sciences, Spheniscidae, and Stress Physiological
A computer model of the population dynamics of introduced house mice (Mus musculus L.), ship rats (Rattus rattus L.) and stoats (Mustela erminea L.) in New Zealand forest was constructed, to test the relative importance of food... more
A computer model of the population dynamics of introduced house mice (Mus musculus L.), ship rats (Rattus rattus L.) and stoats (Mustela erminea L.) in New Zealand forest was constructed, to test the relative importance of food availability and predation in shaping observed small-mammal population dynamics. Ship rats and mice are the two common rodent species present in most New
Research Interests: Biology, Population Dynamics, Multidisciplinary, Ecological Modelling, Model, and 15 moreComputer Model, New Zealand, Forests, Population Size, Food Availability, Predator, Field Study, Mathematical Model, Prey, House Mouse, Mustela Erminea, Outbreak, Population dynamic, Mus Musculus, and Natural Mortality
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Plasma corticosterone concentrations increase when birds experience a stressor, and in this study we quantified variation in corticosterone responses for the first time in a species of free-living bird. Adelie penguins (Pygoscelisadeliae)... more
Plasma corticosterone concentrations increase when birds experience a stressor, and in this study we quantified variation in corticosterone responses for the first time in a species of free-living bird. Adelie penguins (Pygoscelisadeliae) nesting at Cape Bird on Ross Island in Antarctica were sampled on three occasions. Penguins with relatively low or high corticosterone responses on the first occasion had consistently low or high responses, as previously found for great tits and chickens. A model for birds is proposed in which birds with low corticosterone responses and proactive personalities are likely to be more successful (have greater fitness) in constant or predictable conditions, whilst birds with reactive personalities and high corticosterone responses will be more successful in changing or unpredictable conditions. There is thus no linear relationship between the size of a corticosterone response and fitness. Whilst the absolute magnitude of corticosterone responses varies markedly across species of birds, coefficients of variation are similar. Individual corticosterone responses are generally repeatable, with significant statistical repeatabilities for 30 min corticosterone concentrations and integrated corticosterone concentrations in the Adelie penguin, great tit and chicken. Coefficients of variation in corticosterone responses between birds and power analyses were used to provide a rule of thumb for determining differences between groups of birds in mean corticosterone concentrations to enable statistical analyses to have acceptable levels of statistical power for given sample sizes. It is suggested that power analyses and this rule of thumb be adopted in future investigations of corticosterone responses in birds.
Research Interests: Physiology, Zoology, Biology, Stress, Medicine, and 15 moreApplied Animal Behavior, Birds, Female, Animals, Corticosterone, Male, Power Analysis, Statistical Power, Coefficient of Variation, Sample Size, Individual variation, Repeatability, Veterinary Sciences, Spheniscidae, and Stress Physiological
Birds that forage by probing must often use senses other than vision to find their prey. Remote touch is a sense based on the interception of vibrations produced by moving prey in the substrate or on the evaluation of pressure patterns... more
Birds that forage by probing must often use senses other than vision to find their prey. Remote touch is a sense based on the interception of vibrations produced by moving prey in the substrate or on the evaluation of pressure patterns produced by hard-shelled sessile prey. In ...
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RG Lentle, MA Potter, BP Springett, KJ Stafford Wildlife Research 24:33, 373-377, 1997. A technique for trapping and immobilising small macropods is described and tested onforest-dwelling Tammar wallabies (Macropus eugenii Desmarest). ...
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The particle size distribution of stomach contents from 25 tammar wallabies (Macropus eugenii Desmarest) shot in the Okataina State Forest and adjoining farmland near Rotorua, New Zealand, were determined. There was a greater percentage... more
The particle size distribution of stomach contents from 25 tammar wallabies (Macropus eugenii Desmarest) shot in the Okataina State Forest and adjoining farmland near Rotorua, New Zealand, were determined. There was a greater percentage of finer, and a smaller percentage of larger, particles than reported in the stomach contents of larger macropods. The chewing and biting activities of four free-ranging tammars fitted with radio-microphone collars were monitored. Chewing rates (chews per minute) were similar to those of other small herbivorous vertebrates. There were significantly lower rates of chewing and higher chew-to- bite ratios when browsing than when grazing. Observations of browsing by three captive tammars showed inefficient handling by mutually opposed palms and digitopalmar grip, resulting in low rates of ingestion. We suggest that tammars lower the time necessary for fermentation of food by reducing the size of food particles, and that their choice between graze and browse is influenced by food handling and chewing investment.
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Research Interests: Geography, Human Geography, Spatial Analysis, Data Mining, Logistic Regression, and 15 moreModel Selection, Habitat, Regression, Scale, New Zealand, Prediction Model, Sensitivity, Spatial Data, Applied Geography, Akaike Information Criterion, Native Species, Mean curvature, Field Data, Geographic Information System, and GIS
J. Econ. EntomoJ. 87(5): 1251-1255 (1994) ABSTRACT New Zealand Thrips obscuratus (Crawford) adults were exposed to combi-nations of temperature (0, 7, 13, or 20°C), gas (air, or 0, 9, or 18% carbon dioxide [C02] ... 2% oxygen [02], with... more
J. Econ. EntomoJ. 87(5): 1251-1255 (1994) ABSTRACT New Zealand Thrips obscuratus (Crawford) adults were exposed to combi-nations of temperature (0, 7, 13, or 20°C), gas (air, or 0, 9, or 18% carbon dioxide [C02] ... 2% oxygen [02], with the balance nitrogen ...
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Birds that forage by probing in sand, soil or mud substrates must often use senses other than vision to find their prey. Kiwis (Apterygidae) are nocturnal probing birds inhabiting forested areas in New Zealand. Their visual sense is... more
Birds that forage by probing in sand, soil or mud substrates must often use senses other than vision to find their prey. Kiwis (Apterygidae) are nocturnal probing birds inhabiting forested areas in New Zealand. Their visual sense is reduced, but they have a highly developed sense ...