Brook, Leila Amy (2013) Predator guild interactions in northern Australia: behaviour and ecology of an apex predator, the dingo Canis lupus dingo, and an introduced mesopredator, the feral cat Felis catus. PhD thesis, James Cook University.

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Abstract

Predation can be an important force in ecosystem dynamics, imposing top-down effects on lower trophic guilds. Dominant apex predators can suppress smaller mesopredator populations, both directly via aggressive, sometimes lethal interactions, and indirectly through resource competition and/or changes to behaviour, as mesopredators attempt to reduce the risk of interactions. In the absence of apex predators, behavioural restrictions on mesopredators are lifted. This process of 'mesopredator release' can lead to increased mesopredator abundance and improved access to prey, and may culminate in stronger flow-on effects of mesopredators on prey. Understanding the mechanisms of intraguild interactions will clarify the role of apex predators in regulating trophic interactions, through the suppression of smaller predators.

In the tropical savannas of northern Australia, the introduced feral cat Felis catus cooccurs with the dingo Canis lupus dingo, a mammalian apex predator. Feral cats prey on native wildlife and are implicated in the recent declines of small mammals in northern Australia. Further, feral cats are extremely difficult to control with current technologies. It has been suggested that dingoes could suppress feral cat populations in northern Australia, given recent evidence of negative impacts of dingoes on red foxes Vulpes vulpes, the interspecific killing of foxes and cats by dingoes, and international studies demonstrating mesopredator suppression.

In this thesis, I examine the ecological interactions between dingoes and feral cats in northern Australia. I investigate a) whether dingoes can numerically suppress feral cat populations; and b) how dingoes influence the behaviour of cats. I used two contrasting methods to address these aims. Firstly, I examined broad-scale trends in predator abundance and behaviour with remote camera surveys on multiple, paired rangeland properties, where one property practiced dingo control, and the other left dingoes alone. Secondly, I collected highfrequency telemetry data from sympatric dingoes and feral cats in the Kimberley in northwestern Australia, to investigate fine-scale patterns of space use and potential effects of dingoes on cat behaviour.

Lethal control can affect both the abundance and behaviour of apex predators, which may influence top-down effects on mesopredators. I assessed how predator control affects abundance indices and activity patterns of dingoes and feral cats in nine areas across central and northern Australia, spanning more than 2,500 km. Predator control generally reduced dingo abundance indices. In areas with greater contrasts in dingo activity between paired sites, feral cat indices were higher on sites with lower dingo activity, indicating an inverse correlation between species. Feral cat visitation rates were lower at cameras used frequently by dingoes, with no cats recorded where dingo rates exceeded 1 night -1. This suggests that dingoes may potentially exclude feral cats at a local scale. Dingoes in areas without predator control were broadly crepuscular, similar to their major prey (kangaroos), but controlled populations were less active in the early evening. Reduced evening activity of dingoes in areas with predator control was associated with increased cat activity in the early evening, which is a time when many small native prey (e.g. rodents and geckos) emerge to feed. These results suggest that cats adjust their behaviour to avoid times or places with higher dingo activity.

I explored whether feral cats select habitat features to reduce the risk of interactions with dingoes in two regions of north Queensland, using generalised linear mixed models and remote camera data. In woodland habitats of Cape York Peninsula, both predators used roads, potentially for ease of movement. Where dingo activity was high, feral cats were recorded more frequently in open areas with less ground cover. Open habitats may enable feral cats to detect dingoes earlier, allowing them to reach nearby trees upon encounter. Dingo activity was low on the Gulf Plains, and cats were recorded more frequently in areas with relatively few refuges (tree cover). Treeless habitats would be expected to increase risk associated with dingo encounters, but the low dingo risk in this region could be insufficient to counter benefits of using open areas. Habitats with sufficient escape routes, such as woodlands, could reduce the risk of interactions and facilitate predator co-existence.

Spatial and temporal characteristics of space use may influence predator-prey interactions. I estimated predator space use and core area intensity in the Kimberley region of Western Australia. Dingoes used larger areas than cats, but focussed activity on relatively small core areas. Cats used space more evenly, spreading activity over core areas that formed a larger proportion of their total range, than in the case of dingoes. Dingoes moved more over time, although both species exhibited low temporal overlap in high-use areas. Predation pressure on small prey may therefore be more continuous within feral cat core areas, while the contrast in dingo activity could create areas of both low and high risk for large herbivores, mesopredators and small prey.

Mesopredators should minimise the risk of intraguild interference when making space use decisions, in addition to maximising access to prey. I examined spatial interactions between sympatric dingoes and feral cats using telemetry data. Overlap between dingo and cat core areas was much lower than for overall space use. Use of shared space between the two predators was variable, ranging from avoidance to attraction. The number of occasions on which dingoes and feral cats were recorded within 1 km of each other was lower than expected, suggesting that cats either avoided close encounters with dingoes or responded to such encounters by moving away. While dingoes and feral cats are sympatric, cats appear to minimise intraguild interactions by either limiting spatial overlap or maintaining a safe distance from dingoes.

In summary, feral cats may be excluded from areas used heavily by dingoes in northern Australian savannas, potentially providing refuge for prey from cat predation. However, as dingoes are mobile, these interactions are likely to be spatially and temporally dynamic. The strength of top-down control may be context-dependent, influenced by factors such as predator control, which alters dingo behaviour, and habitat complexity and resource availability, which can affect the rate of encounter and degree of aggressive interactions. This study demonstrates that behavioural shifts may be a critical component of suppression of mesopredators by apex predators, as feral cats appear to alter behaviour to avoid dingoes. Behavioural effects on mesopredators should be considered when assessing the potential benefits of dingoes for lower trophic guilds.

Item ID:	36291
Item Type:	Thesis (PhD)
Keywords:	behavior; behaviour; Canis lupus dingo; dingoes; ecology; Felis catus; feral cats; habitat; interactions; introduced species; mesopredators; northern Australia; Nth Australia; predation; predators; prey
Related URLs:	http://researchonline.jcu.edu.au/24578/
Additional Information:	Publications arising from this thesis are available from the Related URLs field. The publications are: Brook, Leila A., Johnson, Christopher N., and Ritchie, Euan G. (2012) Effects of predator control on behaviour of an apex predator and indirect consequences for mesopredator suppression. Journal of Applied Ecology, 49 (6). pp. 1278-1286.
Date Deposited:	05 Aug 2015 05:41
FoR Codes:	05 ENVIRONMENTAL SCIENCES > 0501 Ecological Applications > 050103 Invasive Species Ecology @ 34% 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050211 Wildlife and Habitat Management @ 33% 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 33%
SEO Codes:	97 EXPANDING KNOWLEDGE > 970106 Expanding Knowledge in the Biological Sciences @ 33% 96 ENVIRONMENT > 9604 Control of Pests, Diseases and Exotic Species > 960405 Control of Pests, Diseases and Exotic Species at Regional or Larger Scales @ 34% 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960805 Flora, Fauna and Biodiversity at Regional or Larger Scales @ 33%
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