Functional responses of an apex predator and a mesopredator to an invading ungulate: Dingoes, red foxes and sambar deer in south-east Australia

Biological invasions by large herbivores involve the establishment of novel interactions with the receiving mammalian carnivore community, but understanding these interactions is difficult due to the large spatiotemporal scales at which such dynamics would occur. We quantified the functional responses of a native apex predator (the dingo (Canis familiaris), which includes wild dogs and their hybrids) and a non-native mesopredator (red fox; Vulpes vulpes) to an invading non-native ungulate (sambar deer; Cervus unicolor) in Australia. We predicted that the apex predator would exhibit a stronger functional response to increasing sambar deer abundance than the mesopredator. We used a state–space model to link two 30-year time series: (i) sambar deer abundance (hunter catch-per-unit-effort); and (ii) percentages of sambar deer in dingo (N = 4531) and fox (N = 5002) scats. Sambar deer abundance increased over fourfold during 1984–2013. The percentages of sambar deer in dingo and fox scats inc...