Managing kangaroo grazing for the conservation of grassland and grassy woodland fauna

Large mammalian grazers are ecosystem engineers that alter the resources available to other species through selective consumption of plant matter, redistribution of nutrients and trampling. While some level of grazing is considered critical for maintaining species diversity, alteration to natural grazing regimes can have a severe impact on native biodiversity. Restoration of grazing regimes which promote conservation of biodiversity is a priority in many protected areas. However, the ability to achieve this goal is limited by a lack of understanding of what ‘appropriate’ grazing regimes for conservation of biodiversity are. In south-eastern Australia, high intensity grazing by the native eastern grey kangaroo (Macropus giganteus) has been linked to the decline of multiple taxa. While efforts to manage the impact of kangaroo grazing on other taxa have been undertaken, the effectiveness of these interventions are limited by a lack of knowledge of what constitutes optimal grazing levels. In this thesis, I used kangaroo population counts, tree canopy cover maps, ground vegetation structure, and reptile and birds counts to investigate the relationship between kangaroos, grass structure, and fauna. I found that: 1) there was a strong negative relationship between the abundance of kangaroos and grass structure (Paper I); 2) high intensity kangaroo grazing had a negative effect on the reptile community (Paper I); 3) birds with similar traits favoured similar grazing intensities, with different grazing intensities favoured by different trait groups (Paper II); 4) the occurrence of a threatened grassland reptile, the striped legless lizard (Delma impar) was positively related to fine scale grass complexity, and negatively related to kangaroo density at the broad scale (Paper III); 5) kangaroos selected forage habitat away from roads, in areas with a high cover of short grass (Paper IV); and 6) line transect sampling undertaken from vehicles driven along tracks can provide an accurate method to survey the kangaroo population provided knowledge of kangaroo distribution relative to tracks is known and accounted for (Paper V). My investigation into the relationships between kangaroos, grass structure and fauna indicated that grass structure has a strong effect on many reptiles and birds, and that intervention may be needed to change kangaroo habitat selection in a way that mimics natural foraging patterns in order to promote optimal vegetation structures for the conservation of native biodiversity. Therefore, to preserve a full-complement of species in these grassy habitats, I recommend that: 1) management of grazing is based on direct measures of grass structure, not herbivore abundance, 2) the extent and duration of intense grazing is limited; and 3) grazing pressure is rotated to create mosaics of different levels of grass structure in space and time. In making these recommendations, I emphasise that management of grazing by kangaroos will be necessary for ongoing conservation of biodiversity in grasslands and grassy woodland and that further research is needed on how to manage kangaroo grazing patterns for the conservation of biodiversity in grasslands and grassy woodlands in south-eastern Australia

Eaten out of house and home:impacts of grazing on ground-dwelling reptiles in Australian grasslands and grassy woodlands

Large mammalian grazers can alter the biotic and abiotic features of their environment through their impacts on vegetation. Grazing at moderate intensity has been recommended for biodiversity conservation. Few studies, however, have empirically tested the benefits of moderate grazing intensity in systems dominated by native grazers. Here we investigated the relationship between (1) density of native eastern grey kangaroos, Macropus giganteus, and grass structure, and (2) grass structure and reptiles (i.e. abundance, richness, diversity and occurrence) across 18 grassland and grassy Eucalyptus woodland properties in south-eastern Australia. There was a strong negative relationship between kangaroo density and grass structure after controlling for tree canopy cover. We therefore used grass structure as a surrogate for grazing intensity. Changes in grazing intensity (i.e. grass structure) significantly affected reptile abundance, reptile species richness, reptile species diversity, and the occurrence of several ground-dwelling reptiles. Reptile abundance, species richness and diversity were highest where grazing intensity was low. Importantly, no species of reptile was more likely to occur at high grazing intensities. Legless lizards (Delma impar, D. inornata) were more likely to be detected in areas subject to moderate grazing intensity, whereas one species (Hemiergis talbingoensis) was less likely to be detected in areas subject to intense grazing and three species (Menetia greyii, Morethia boulengeri, and Lampropholis delicata) did not appear to be affected by grazing intensity. Our data indicate that to maximize reptile abundance, species richness, species diversity, and occurrence of several individual species of reptile, managers will need to subject different areas of the landscape to moderate and low grazing intensities and limit the occurrence and extent of high grazing

Herbivore management for biodiversity conservation: A case study of kangaroos in the Australian Capital Territory (ACT)

Populations of macropods are higher than estimated pre-European densities in many parts of Australia. To achieve appropriate densities of macropods in the Australian Capital Territory's nature reserves, multi-tenure kangaroo management units are used to tailor management of kangaroos and total grazing pressure to achieve conservation objectives. An adaptive management framework is recommended that monitors the state of the ground-layer vegetation and alters the cull accordingly. This case study may provide insights for kangaroo management in other temperate areas of Australia

Stable isotope analysis and chronology building at the Hokfv-Mocvse Cultural Site, the earliest evidence for South Atlantic shell-ring villages

Open AccessCircular shell rings along the South Atlantic coast of the United States are vestiges of the earliest sedentary villages in North America, dating to 4500-3000 BP. However, little is known about when Indigenous communities began constructing these shell-ring villages. This article presents data from the Hokfv-Mocvse Shell Ring on Ossabaw Island, Georgia. Although shell rings are often associated with the earliest ceramics in North America, no ceramics were encountered in our excavations at Hokfv-Mocvse, and the only materials recovered were projectile points similar to points found over 300 km inland. Bayesian modeling of radiocarbon dates indicates that the ring was occupied between 5090 and 4735 cal BP (95% confidence), making it the earliest dated shell ring in the region. Additionally, shell geochemistry and oyster paleobiology data suggest that inhabitants were living at the ring year-round and had established institutions at that time to manage oyster fisheries sustainably. Hokfv-Mocvse therefore provides evidence for Indigenous people settling in year-round villages and adapting to coastal environments in the region centuries before the adoption of pottery. The establishment of villages marks a visible archaeological shift toward settling down and occupying island ecosystems on a more permanent basis and in larger numbers than ever before in the region. Copyright © The Author(s), 2024. Published by Cambridge University Press on behalf of Society for American Archaeology

Mesobot : An Autonomous Underwater Vehicle for Tracking and Sampling Midwater Targets

Mesobot, a new class of autonomous underwater vehicle, will address specific unmet needs for observing slow-moving targets in the midwater ocean. Mesobot will track targets such as zooplankton, fish, and descending particle aggregates using a control system based on stereo cameras and a combination of thrusters and a variable buoyancy system. The vehicle will also be able to collect biogeochemical and environmental DNA (eDNA) samples using a pumped filter sampler

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Accounting for animal density gradients using independent information in distance sampling surveys

Distance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue

Accounting for animal density gradients using independent information in distance sampling surveys

Distance sampling is extensively used for estimating animal density or abundance. Conventional methods assume that location of line or point transects is random with respect to the animal population, yet transects are often placed along linear features such as roads, rivers or shorelines that do not randomly sample the study region, resulting in biased estimates of abundance. If it is possible to collect additional data that allow an animal density gradient with respect to the transects to be modelled, we show how to extend the conventional distance sampling likelihood to give asymptotically unbiased estimates of density for the covered area. We illustrate the proposed methods using data for a kangaroo population surveyed by line transects laid along tracks, for which the true density is known from an independent source, and the density gradient with respect to the tracks is estimated from a sample of GPS collared animals. For this example, density of animals increases with distance from the tracks, so that detection probability is overestimated and density underestimated if the non-random location of transects is ignored. When we account for the density gradient, there is no evidence of bias in the abundance estimate. We end with a list of practical recommendations to investigators conducting distance sampling surveys where density gradients could be an issue

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