Using thresholds to determine priorities for apex predator conservation in an urban landscape

Nick Bradsworth, John G. White, Anthony R. Rendall, Nicholas Carter, Desley A. Whisson, Raylene Cook

As landscapes are increasingly modified due to anthropogenic processes such as urbanisation or development for agriculture, the need to understand wildlife habitat requirements is imperative. This is particularly pertinent for species that are threatened, or apex predators with specific nest, den, or food requirements. Identifying responses to habitat with thresholds can provide an understanding of what resources species are using or avoiding, and their interaction with the surrounding environment. In this research we investigated space use and habitat requirements of the threatened apex predator, the powerful owl (Ninox strenua) in Greater Melbourne, Australia. We deployed GPS devices to 21 urban powerful owls over five years and found owls had an average home range size of 397 hectares, and an average core-range of 84 hectares. Home range size and positioning was driven by tree cover and urban land cover, while core ranges were restricted to treed environments with a limited area of impervious surfaces and housing. We used thresholds to identify three priorities for powerful owl conservation in Melbourne. Priority 1: Ensuring river corridors and public open spaces are adequately protected. Priority 2: Limit property densities near rivers and protected areas. Priority 3: Finding opportunities for revegetation to expand and enhance habitat over time. Our research demonstrates how species-specific thresholds can inform land use planning to ensure wildlife species are maintained within highly modified environments.

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Can NDVI identify drought refugia for mammals and birds in mesic landscapes?

John G. White, Jacinta Sparrius, Tomas Robinson, Susannah Hale, Luke Lupone, Tom Healy, Raylene Cooke, Anthony R Rendall

Refugia within landscapes are increasingly important as climate change intensifies, yet identifying refugia, and how they respond to climatic perturbations remains understudied. We use Normalized Difference Vegetation Index (NDVI) developed during extreme drought to identify drought refugia. We then utilise camera trapping to understand the ecological role and importance of these refugia under fluctuating rainfall conditions. Ground foraging mammals and birds were surveyed annually from 2016 to 2019 whereby 171 remote-sensing cameras were deployed in the southern section of the Grampians, Australia. NDVI values were calculated during Australia’s millennium drought, allowing the assessment of how NDVI calculated during extreme drought predict drought refugia and the response of biodiversity to NDVI under rainfall fluctuations. Site occupancy of bird and mammal assemblages were dependent on NDVI, with areas of high NDVI during drought exhibiting characteristics consistent with refugia. Rainfall pulses increased site occupancy at all sites with colonisation probability initially associated with higher NDVI sites. Extinction probabilities were greatest at low NDVI sites when rainfall declined. Within mesic systems, remotely sensed NDVI can identify areas of the landscape that act as drought refugia enabling landscape management to priortise species conservation within these areas. The protection and persistence of refugia is crucial in ensuring landscapes and their species communities therein are resilient to a range of climate change scenarios.

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Natural and anthropogenic processes influence the occurrence of vertebrate fauna in coastal dunes

Alicia Chadwick, Michael A. Weston, Thomas Burns, Georgia Randall, Max Radvan, Anthony R. Rendall

Coastal dunes represent habitat for wildlife yet are chronically understudied and are threatened by anthropogenically driven processes from their landward and seaward margins. We deployed 93 downward-facing cameras along the coastal dunes of Venus Bay, Victoria, Australia, to examine the influence of natural and anthropogenic processes on the occurrence of vertebrate fauna. Of the 32 species identified, ten had sufficient data for single-species, single-season occupancy modelling. Four species occurred ubiquitously in dunes and can be regarded as generalists within the dunescape. For six species, site occupancy increased with increasing distance from the coast. Areas with less modified dune trended towards lower species site occupancy for five species. More structurally complex vegetation was associated with a higher site occupancy for two species. Tow species had higher site occupancies where natural and urban hinterland types occurred. Normalised Difference Vegetation Index (NDVI) featured in one species model, with a weak negative trend of vegetation productivity on occurrence. We confirm that coastal dunes represent a diverse faunal ecosystem, with species varying in their occurrence and the processes (from the seaward and hinterland margins, natural and anthropogenic) which influence it.

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Assessing the efficacy of electronic quail callers in attracting stubble quail and non-target predators

Ray, M., White, JG., Weston, MA., Rendall, AR., Toop, SD., Dunstan, H., Hampton, JO. & Cooke, R.

Hunting is a prominent feature of many human societies. Advancements in hunting technologies can challenge the ethics and sustainability of hunting globally. We investigated the efficacy of an electronic acoustic lure (‘quail caller’), in attracting the otherwise difficult-to-hunt stubble quail Coturnix pectoralis in Victoria, Australia. Using distance sampling, the density and abundance of stubble quail was estimated at 79 sites across a range of habitat types in an agricultural setting, each with an active ‘quail caller’ station continuously broad-casting for 48 hours, and a control station (no broadcast). Quail detectability at the active stations (62.9%) far exceeded that at control stations (6.3%). Most (57%) detections occurred within 30 m of active ‘quail callers’. Stubble quail relative abundance was substantially greater when ‘quail callers’ were broadcasting. Cameras mounted near ‘quail callers’ identified the predatory red fox as a non-target predator, although rates of attraction appear similar between active and control sites. ‘Quail callers’ are highly effective at attracting stubble quail and concentrating them to a known area, raising questions in relation to sustainable hunting practices, indirect effects, and ethical implications. ‘Quail callers’ do, however, also offer a tool for estimating quail abundance and developing more accurate population size estimates.

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Defense of eggs and chicks in the polyandrous Pheasant-tailed Jacana Hydrophasianus chirurgus in Sri Lanka: Sex-roles, stage of breeding and intruder type

Fernando, C., Kotagama, S.W., Rendall, A.R., Weston, MA.

Pheasant-tailed Jacanas Hydrophasianus chirurgus have a polyandrous mating system, with females defending larger territories within which males compete for and defend smaller territories. The role of the sexes in territorial defense is therefore potentially complex yet remains poorly known. Studies of sex-roles in polyandrous jacanas have generally investigated direct parental care contributions, female contributions to parental defence are less well known in some species. We monitored the sex-roles of defensive responses to intruders at Anawilundawa Ramsar site, North-Western province, Sri Lanka, where birds encountered conspecifics and other potential predators: Purple Coots Porphyrio porphyrio, aerial predators and other waterbirds. Females contributed to defence though males performed most defence. Females increased their propensity to defend as breeding progressed; but the chick rearing phase defence was shared more or less equitably between the sexes. Females were more likely to defend against aerial predators than males, and males were more likely to defend against conspecifics than they were to other intruders. When defending against conspecifics, most male defence was directed at intruding males, and most female defence at intruding females. Defence in this polyandrous species relied on cooperation between the sexes but also on some defence specialization whereby females focussed on defending against aerial predators and conspecific females, perhaps because of their larger body size. Both female and male Pheasant-tailed Jacanas therefore contribute to parental care via their defensive activities.

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Asian elephant movements between natural and human-dominated landscapes mirror patterns of crop damage in Sri Lanka

Fernando, C., Weston, MA., Corea, R., Pahirana, K., Rendall, AR.

Wildlife movements within a landscape are influenced by environmental factors such as food availability and, as human-modified landscapes continue to expand, the risks associated with encountering people. For Asian elephants Elephas maximus, human-dominated landscapes can be a risky but also rewarding habitat. When elephants share space with people, negative human-elephant interactions are common, sometimes resulting in injuries or deaths of both people and elephants. We monitored elephant movements in and out of a forest reserve in central Sri Lanka to test four predictions regarding elephant behaviour: 1) visits to agricultural areas occur at times of the year when crops are plentiful, 2) elephants exploit these areas by night to avoid interactions with people, 3) increased nocturnal illumination reduces use of agricultural areas, and 4) males make greater use of anthropogenic food sources than family groups. Analysis of camera-trap data confirmed that elephants visited human-dominated areas mostly at night. The frequency of such incursions was not influenced by moon phase for males, but there was a weak effect of moon phase for family groups. Males moved more frequently into human-dominated landscapes than family groups, and their movements showed a distinct seasonal pattern, peaking at times of rice and fruit harvest. Our findings suggest that elephants primarily venture into human-dominated areas to consume crops. Encouraging farmers in areas frequented by elephants to adapt existing land-use practices such as using fencing and citrus trees as buffers integrated with early warning systems could help limit the damage caused by elephants.

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Does the foraging ecology of feral cats change after the eradication of foxes?

Rendall, AR., Sutherland, DR., Cooke, R., White, JG.

Invasive species control has resulted in unintended consequences where the control of one species causes increased impacts of a co-occurring species. Red foxes (Vulpes vulpes) and feral cats (Felis catus) co-occur throughout Australia – with control and regulation of foxes commonplace, a greater understanding of how feral cats will respond in the absence of foxes is needed. In this study we use feral cat diet to assess potential prey switching after red fox control. Feral cat stomach contents were sampled between 1983 – 1994 on Phillip Island, Victoria, Australia when both feral cats and red foxes were abundant; and again from 2016 – 2019 when foxes were eradicated. A total of 277 feral cats were sampled between 1983 – 1994 and 415 from 2016 – 2019. Although we did not track feral cat diet throughout the red fox decline, diet comparisons between the two time periods suggest no substantial shift in feral cat diet with only slight increases in invertebrates and black rats observed. Invasive prey (European rabbits, black rats, and house mice) still formed the majority of feral cat diet. We further reinforce the role of seasonality, surrounding land use and sex as factors influencing cat diet. Our results suggest red fox control in the presence of cats may still achieve conservation benefits with feral cats maintaining a comparable diet, dominated by invasive species, despite fox control – though this may be context dependent. Given the abundance and frequency of invasive prey species within cat diet, we further support the idea that invasive prey control could be a viable indirect method to control the impacts of feral cats.

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New paper: Logging and wildfire limit the distribution of a vulnerable arboreal mammal

Lefoe, M., Rendall, AR., McKinnon, F., Whisson, DA.

Habitat loss and degradation are two of the greatest threats to biodiversity conservation globally. In Australia, the incidence of wildfire and native forest logging contribute substantially to these processes and have been linked to reduced species diversity and abundance. Arboreal species such as the Yellow-bellied Glider (Petaurus australis), are thought to be susceptible to these disturbances due to their reliance on large patches of forest and hollow-bearing trees. We aimed to assess the impact of logging and wildfire on site occupancy by the Yellow-bellied Glider in Mountain Ash forest of the Central Highlands of Victoria. We deployed autonomous recording units for 14 nights at 70 sites and searched recordings for Yellow-bellied Glider vocalisations. Yellow-bellied Gliders were detected at 30% (N=21) of sites. Site occupancy increase with an increasing proportion of the landscape (within 400m of the recorder) that had not been logged within the last 100 years or burnt by wildfire in the last 10 years. Habitat disturbance caused by logging and fire therefore limit the site occupancy of Yellow-bellied Gliders and likely impact its conservation status. It is therefore critical that appropriate management of timber resources protects large patches of old-growth forest providing food resources and hollows, and the connectivity between large forest patches.

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New paper: Passive Acoustic Monitoring for detection the Yellow-bellied Glider

Whisson, DA., McKinnon, F., Lefoe, M., Rendall, AR.

Passive acoustic monitoring (PAM) is increasingly being used for the survey of vocalising wildlife species that are otherwise cryptic and difficult to survey. Our study aimed to develop PAM guidelines for detecting the Yellow-bellied Glider, a highly vocal arboreal marsupial that occurs in native Eucalyptus forests in eastern and south-eastern Australia. To achieve this, we considered the influence of background noise, weather conditions, lunar illumination, time since sunset and season on the probability of detecting vocalisations. We deployed Autonomous Recording Units (ARUs) at 43 sites in the Central Highlands of Victoria during two periods: spring/summer (October 2018 to January 2019), and autumn/winter (May to August 2019). ARUs were programmed to record for 11 hours from sunset for 14 consecutive days during each period. Background noise resulted from inclement weather (wind and rain) and masked vocalisations in spectrograms of the recordings, thus having the greatest influence on detection probability. Vocalisations were most common in the four hours after sunset. Rainfall negatively influenced detection probability, especially during the autumn/winter sampling period. Detection of Yellow-bellied Gliders with PAM requires deploying ARUs programmed to record for four hours after sunset, for a minimum of six nights with minimal inclement weather (light or no wind or rain). The survey period should be extended to 12 nights when rain or wind are forecast. Because PAM is less labour intensive than active surveys (i.e., spotlighting and call playbacks with multiple observers and several nights’ survey per site), its use will facilitate broad-scale surveys for Yellow-bellied Gliders.

Where wildlife and traffic collide: drivers of roadkill rates change through time in a wildlife-tourism hotspot

Rendall, AR. Webb, V. Sutherland, DS. White, JG. Renwick, L. Cooke, R.

Understanding when and where roadkill is most likely to occur is vital to reducing wildlife-vehicle collisions. However, little is known about how roadkill rates change through time and whether or not the key influences on roadkill also change. Understanding changes in roadkill will facilitate the best implementation of mitigation measures. We aimed to determine how roadkill rates have changed between two distinct time periods and assess whether the spatial and temporal drivers of roadkill rates may have changed: with a view to informing species-specific mitigation strategies.

Roadkill hotspots in 1998-99 versus 2014 on Phillip Island between February and June. The size of dot represents the number of roadkill per segment per year (square root transformed). Yellow outlined circles represent roadkill locations only sampled within the 2014 data.