Do Exotic Vertebrates Structure the Biota of Australia? An Experimental Test in New South Wales

Davey, Chris; Sinclair, A. R. E.; Pech, Roger P.; Arthur, Anthony D.; Newsome, A. E.; Hik, David S.; Molsher, Robyn; Allcock, Kimberly G.

doi:10.1007/s10021-004-0173-0

Cited by 32 publications

(28 citation statements)

References 45 publications

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“…Over-winter survival of cats may therefore have been influenced not solely by rabbits, but also by the availability of alternative prey including birds, lizards and invertebrates [16], as well as by environmental factors such as extreme minimum winter temperatures and long periods of snow cover. Overall, our results extend previous work from New Zealand [29], [35] and support studies elsewhere, which report that rabbit declines lead to predator declines [55]–[58].…”

Section: Discussionsupporting

confidence: 92%

Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits

2013

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Predator-prey systems can extend over large geographical areas but empirical modelling of predator-prey dynamics has been largely limited to localised scales. This is due partly to difficulties in estimating predator and prey abundances over large areas. Collection of data at suitably large scales has been a major problem in previous studies of European rabbits (Oryctolagus cuniculus) and their predators. This applies in Western Europe, where conserving rabbits and predators such as Iberian lynx (Lynx pardinus) is important, and in other parts of the world where rabbits are an invasive species supporting populations of introduced, and sometimes native, predators. In pastoral regions of New Zealand, rabbits are the primary prey of feral cats (Felis catus) that threaten native fauna. We estimate the seasonal numerical response of cats to fluctuations in rabbit numbers in grassland–shrubland habitat across the Otago and Mackenzie regions of the South Island of New Zealand. We use spotlight counts over 1645 km of transects to estimate rabbit and cat abundances with a novel modelling approach that accounts simultaneously for environmental stochasticity, density dependence and varying detection probability. Our model suggests that cat abundance is related consistently to rabbit abundance in spring and summer, possibly through increased rabbit numbers improving the fecundity and juvenile survival of cats. Maintaining rabbits at low abundance should therefore suppress cat numbers, relieving predation pressure on native prey. Our approach provided estimates of the abundance of cats and rabbits over a large geographical area. This was made possible by repeated sampling within each season, which allows estimation of detection probabilities. A similar approach could be applied to predator-prey systems elsewhere, and could be adapted to any method of direct observation in which there is no double-counting of individuals. Reliable estimates of numerical responses are essential for managing both invasive and threatened predators and prey.

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Section: Discussionsupporting

confidence: 92%

Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits

2013

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“…C3 rabbits ha -1 : Cooke 1988; Leigh et al 1987;Chapuis et al 2004). Possibly the lowest-density record from such areas is that of Davey et al (2006) who recorded rabbit damage to Casuarina glaucophylla seedlings when spotlight transect counts averaged 2.1 rabbits km -1 , although Allcock and Hik (2004) suggest seedling impact within that study was measured where rabbit counts were 5 rabbits km -1 . By comparison, damage continued at the Cooroong in rabbit control areas where counts were an order of magnitude lower (Fig.…”

Section: Discussionmentioning

confidence: 90%

Damage caused by low-density exotic herbivore populations: the impact of introduced European rabbits on marsupial herbivores and Allocasuarina and Bursaria seedling survival in Australian coastal shrubland

et al. 2011

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The impact of over-abundant exotic herbivores is well recognised, but their impact at low population densities is poorly understood. This study examined interactions between European rabbits and native herbivores, and their impact on seedling recruitment in coastal South Australia, 2 years after rabbit haemorrhagic disease (RHD) had reduced rabbit density to 4.48 rabbits ha -1 . Rabbit density was further reduced to 0.44 rabbits ha -1 in replicated experimental treatments. Rabbit control reduced total grazing pressure by 39% despite compensatory grazing increases of [100% for both western grey kangaroos and common wombats. Rabbit control slowed the rate of grazing and mortality for planted drooping sheoak and sweet bursaria seedlings, but few survived for 12 months: 0 and 3% of sheoak, in untreated areas and rabbit control treatments, respectively, and 3 and 11% of bursaria, respectively. Planted sheoaks survived well if protected by rabbit-proof netting (60%). Within treatments, seedling grazing and survival rates were negatively correlated with rabbit density but kangaroo and wombat density had no measurable effect. We conclude that RHD may briefly have reduced rabbit densities enough to allow recruitment of bursaria but that sheoak require much lower rabbit densities than those provided by existing biological control agents. If left unaddressed, rabbit grazing could ultimately lead to the loss of sheoaks throughout most of their current range, irrespective of other attempts to conserve them. More generally, these data show how species-specific damage caused by low-density exotic herbivore populations may occur in the presence of more abundant but less-damaging native herbivores.

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“…After 16 months, in October 1995, foxes were subject to lethal control at two of the sites, referred to as removal site 1 and 2 hereafter. The control program consisted of shooting all foxes observed on monthly visits using a low velocity 0.222-calibre rifle and burying 1080-poison baits at intervals of 200–400 m along ridge tops and unsealed roads [25]. At removal site 1 baits were set and replaced where necessary each month, but were exposed for 10 days every three months at removal site 2.…”

Section: Methodsmentioning

confidence: 99%

“…Baiting continued at both sites until the end of the study. Although the two removal sites were not subjected to the same intensity of control, reductions in fox activity at both sites provided an effective experimental treatment [25]. Fox densities were not manipulated at the other two sites, referred to as untreated site 1 and 2 hereafter.…”

Section: Methodsmentioning

confidence: 99%

Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats

Molsher¹,

Newsome

et al. 2017

PLoS ONE

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Apex predators are subject to lethal control in many parts of the world to minimize their impacts on human industries and livelihoods. Diverse communities of smaller predators—mesopredators—often remain after apex predator removal. Despite concern that these mesopredators may be 'released' in the absence of the apex predator and exert negative effects on each other and on co-occurring prey, these interactions have been little studied. Here, we investigate the potential effects of competition and intraguild predation between red foxes (Vulpes vulpes) and feral cats (Felis catus) in south-eastern Australia where the apex predator, the dingo (Canis dingo), has been extirpated by humans. We predicted that the larger fox would dominate the cat in encounters, and used a fox-removal experiment to assess whether foxes affect cat abundance, diet, home-range and habitat use. Our results provide little indication that intraguild predation occurred or that cats responded numerically to the fox removal, but suggest that the fox affects some aspects of cat resource use. In particular, where foxes were removed cats increased their consumption of invertebrates and carrion, decreased their home range size and foraged more in open habitats. Fox control takes place over large areas of Australia to protect threatened native species and agricultural interests. Our results suggest that fox control programmes could lead to changes in the way that cats interact with co-occurring prey, and that some prey may become more vulnerable to cat predation in open habitats after foxes have been removed. Moreover, with intensive and more sustained fox control it is possible that cats could respond numerically and alter their behaviour in different ways to those documented herein. Such outcomes need to be considered when estimating the indirect impacts of fox control. We conclude that novel approaches are urgently required to control invasive mesopredators at the same time, especially in areas where apex predators are absent.

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Do Exotic Vertebrates Structure the Biota of Australia? An Experimental Test in New South Wales

Cited by 32 publications

References 45 publications

Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits

Modelling Landscape-Level Numerical Responses of Predators to Prey: The Case of Cats and Rabbits

Damage caused by low-density exotic herbivore populations: the impact of introduced European rabbits on marsupial herbivores and Allocasuarina and Bursaria seedling survival in Australian coastal shrubland

Mesopredator Management: Effects of Red Fox Control on the Abundance, Diet and Use of Space by Feral Cats

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