Mapping out bare-nosed wombat (Vombatus ursinus) burrows with the use of a drone

Background Wombats are large, nocturnal herbivores that build burrows in a variety of habitats, including grassland communities, and can come into conflict with people. Counting the number of active burrows provides information on the local distribution and abundance of wombats and could prove to be an important management tool to monitor population numbers over time. We compared traditional ground surveys and a new method employing drones, to determine if drones could be used to effectively identify and monitor bare-nosed wombat burrows. Results We surveyed burrows using both methods in eight 5-ha transects in grassland, that was interspersed with patches of tussock grassland. Ground surveys were conducted by systematically walking transects and searching for burrows. Drone surveys involved programming flights over transects to capture multiple images, from which an orthomosaic image of each transect was produced. These were subsequently viewed using ArcMap to detect burrows. A total of 204 individual burrows were recorded by drone and/or ground survey methods. In grassland, the methods were equally effective in terms of the numbers of burrows detected in transects. In the smaller areas of tussock grassland, ground surveys detected significantly more burrows, because burrow openings were obscured in orthomosaic images by overhanging grasses. There was agreement between the methods as to whether burrows were potentially active or inactive for most burrows in both vegetation communities. However, image interpretation tended to classify grassland burrows as potentially active. Overall time taken to conduct surveys was similar for both methods, but ground surveys utilised three observers and more time in the field. Conclusions Drones provide an effective means to survey bare-nosed wombat burrows that are visible from the air, particularly in areas not accessible to observers and vehicles. Furthermore, drones provide alternative options for monitoring burrows at the landscape level, and for monitoring wombat populations based on observable changes in burrow appearance over time.

Soil aggregation and soil fraction associated carbon under different vegetation types in a complex landscape

Land cover change has been shown to affect soil characteristics and soil organic carbon (SOC) storage. However, little is known about the driving factors associated with soil carbon (C) stabilisation in complex landscapes. This study was conducted to investigate the effects of both inherent soil characteristics and recent vegetation cover change on soil aggregation and soil fraction associated C in a complex landscape. The specific objectives were: (1) determine bulk soil properties and SOC saturation deficit; (2) quantify soil aggregation, soil size-density fractions, and soil fraction associated C; and (3) identify the factors that influence soil fractions and soil fraction associated C in two adjacent catchments differing in vegetation cover, Central Otago, New Zealand. Catchment GH1 (n = 17 plots) was dominated by tussock grassland and native shrubs. Catchment GH2 (n = 21 plots) was converted from tussock grassland into a pine forest in 1981. The catchments differed in soil texture (e.g. sand content GH1: 62.9%, GH2: 50.7%, P = 0.007), soil SOC stocks (GH1: 5.0 kg C m−2, GH2: 4.3 kg C m−2, P = 0.04), mean weight diameter (MWD) (GH1: 782.3 µm, GH2: 736.5 µm, P = 0.002), and proportion of the macroaggregate heavy fraction (macro_HF) (GH1: 72%, GH2: 55%, P = 0.01). No significant differences were found in SOC saturation deficit (GH1: 14.8 mg g−1, GH2: 13.1 mg g−1, P = 0.13). Dominant vegetation cover explained 21% of the variation in MWD in GH1, whereas silt+clay C content explained 31.6% of the MWD variation in GH2. The macro_HF fraction was negatively correlated with the proportion of silt+clay. Our findings illustrate that physical and chemical soil characteristics are important drivers in such a complex landscape and may have masked the effect of recent vegetation change on soil aggregation, and soil fraction associated C.

Farmed red deer home range, habitat use and daily movement patterns in a Southland, New Zealand, tussock grassland over calving and lactation

Considerable expansion of red deer farming has occurred in the South Island high country of New Zealand. On these farms, breeding hinds are usually continuously grazed (set-stocked) at low population densities in large highly modified native-tussock grassland paddocks during their calving and lactation seasons. The present study determined how these hinds use the tussock grassland over this critical period, identifying the most essential resources for them and also some potential long-term consequences of their behaviour on the grassland ecosystem. This was achieved by tracking nine GPS-collared hinds over 2 years on a high-country deer farm in Te Anau, Southland, New Zealand. The home ranges of the GPS-tracked hinds varied widely, occupying between 15% and 52% of the total paddock area. Vegetation dominated by naturalised exotic pasture species covered the greatest proportion (>60%) of eight of nine hind home ranges. In contrast, tussock-dominant vegetation coverage was far more variable (0.4–46%), with several indicators suggesting that this vegetation type was used as a substitute for pasture areas under high intra-specific competition among the deer. Both pasture- and tussock-dominant vegetation was used in proportion to its availability. In contrast, shrub-dominated vegetation was used less than its proportional availability, indicating that it was not being put under as much foraging or grazing pressure. This has implications for the further ingression of this vegetation type over time. There was also clear evidence that certain paddock topography was being favoured by the hinds, namely steeper and higher-altitude areas of a paddock. On the basis of these findings, some potential methods for aiding in the management of these extensive tussock grassland paddocks under deer grazing are suggested.

A new species of scincid lizard in the genus Oligosoma (Reptilia: Scincidae) from the mid-Canterbury high country, New Zealand

New Zealand has a diverse, endemic skink fauna, which is recognised as the most species rich skink assemblage of any cool temperate region on earth. All native New Zealand skink species are assigned to a single genus, Oligosoma Girard. A new species of Oligosoma is described from screes in montane tussock grassland in the mid-Canterbury high country, New Zealand, where it is currently known from four sites on two mountain ranges. The new species (Oligosoma hoparatea sp. nov.) can be distinguished from all congeners by a combination of mid-body scale row and lamellae counts, scale morphologies, and a bold striped pattern with smooth-edged, dark lateral bands. It is part of the O. longipes Patterson species complex, and occurs in sympatry with its closest relative, O. aff. longipes ‘southern’. The species is currently highly threatened, and is listed as Nationally Critical in New Zealand. Predation by a suite of introduced mammals is assumed to be a major threat to its survival.

Distribution and habitat preference of the broad-toothed rat (Mastacomys fuscus) in the Australian Capital Territory, Australia

The broad-toothed rat (Mastacomys fuscus) is a small to medium-sized rodent found in south-eastern Australia. Recent surveys across the southern portion of its range indicate that the species is in decline, and climate change has been identified as a key threat to the localised persistence of this species. The present study reports on a rapid field survey across 14 high montane and subalpine sites (including moist tussock grassland, sedgelands, heathlands and bogs) in the southern Australian Capital Territory, Australia. M. fuscus scats were recorded along transects, and habitat, vegetation, distance to drainage lines and disturbance due to feral animals were recorded. Relative abundance of M. fuscus was positively related to specific vegetation types (heath, sedge and Poa) and site size. Conversely, relative abundance of M. fuscus was negatively related to disturbance due to feral animals, and distance from creek drainage lines. This study indicates that M. fuscus has specific habitat preferences and threats associated with environmental change and introduced species may threaten populations in the Australian Capital Territory.

The rise to dominance over two decades of Lupinus polyphyllus among pasture mixtures in tussock grassland trials

In two trials near Lake Tekapo, one started from sown binary mixtures of 14 different legumes, of which Lupinus polyphyllus was one, was cross sown with 16 different grasses, while in the other trial L. polyphyllus and Trifolium hybridum were over-drilled across established swards of previous 25 different grass and legume species. In both L. polyphyllus persisted, increased and spread by seeding in the presence of repeated mob grazing by sheep to become the dominant species over two decades. Keywords: New Zealand, rangeland pasture development, Lupinus polyphyllus, Bromus inermis.