More buck for less bang: Reconciling competing wildlife management interests in agricultural food webs

Abstract

Mammalian top-predators can have positive, negative and negligible effects on economic, environmental and social values, which vary spatially and temporally. Harnessing 'pros' while mitigating 'cons' of top-predators remains a key management challenge, particularly outside reserves in agroecosystems. In this study, long-term (1972-2008) and broad-scale (250,000 km 2 ) datasets were used to explore co-relationships between rainfall, kangaroo abundance, beef-cattle calf production and dingo control effort in arid Australia. Best subsets and multiple regression analyses show that calf production fluctuates independently of dingo control, and kangaroo populations comprise 13-36% (mean 26%) of the combined kangaroo-cattle herd in any given year. Kangaroo abundance was associated most strongly with bottom-up forces (rainfall) as expected, but a combination of bottom-up (rainfall) and topdown (dingo control) processes best explained variation in kangaroo abundance trends. Supplementary economic analysis indicated that ongoing kangaroo competition with cattle is far more costly to beef producers than the occasional predation of calves by dingoes. These results suggest that lethal toppredator control practices in arid Australia may not be achieving their fundamental aim (to increase livestock production) because increased competition from native herbivores freed from top-predator suppression erodes the accrued economic benefits of a reduction in livestock predation. These data suggest that retaining top-predators outside reserves in agro-ecosystems may be advantageous to livestock producers and ecosystems where and/or when top-predators exert stronger effects on livestock competitors than they do on livestock. These data also highlight how increased knowledge of species interactions can reconcile competing wildlife management interests in agricultural food webs.

Can we save large carnivores without losing large carnivore science?

“…Equally, perceived negative impacts of carnivores on livestock have historically been addressed by wholesale lethal control without any recognition of the positive impacts that carnivores may have on the herbivores that compete with livestock or the consequences of lethal control on livestock losses (e.g. Wicks and Allen, 2012;Allen, 2014;Allen, 2015a;Prowse et al, 2015;Allen, 2017). Treves et al (2016) and others (e.g.…”

Environmental effects are stronger than human effects on mammalian predator-prey relationships in arid Australian ecosystems

“…Other predator and prey species are present (Van Dyck and Strahan, 2008), but persist in variable or low densities that likely have relatively minimal influence on these mammals (Allen et al, 2014a). Beef-cattle grazing is the primary land use in this region (Allen, 2015a). Dingoes, foxes, cats and rabbits were each introduced to Australia.…”

Absence of evidence and evidence of absence for dingo control-induced trophic cascades

“…However, dingoes can and certainly do occasionally kill large numbers of calves, which can be as high as 32% of calves at times, causing substantial economic loss to beef producers (Fleming et al 2012b;Allen 2014). The few studies to investigate the effects of dingo baiting on calf losses have reported mixed results; baiting can sometimes increase calf losses, reduce calf losses as expected, or have no influence on calf losses at all (Fleming et al 2012b;Allen 2015). Complex interactions between prey 158 availability and mammal assemblage appear to drive these outcomes.…”

“…For example, dingoes may kill calves on the one hand, but may also suppress competitors of calves (e.g. macropods) on the other hand (Allen 2015). So far as dingoes can suppress calf competitors, the value of dingo control will ultimately be a trade-off between reducing calf predation and increasing calf competition for pasture with other herbivores (Wicks and Allen 2012).…”

“…So far as dingoes can suppress calf competitors, the value of dingo control will ultimately be a trade-off between reducing calf predation and increasing calf competition for pasture with other herbivores (Wicks and Allen 2012). Top-predators could benefit livestock producers by suppressing livestock competitors when predators exert stronger effects on livestock competitors than they do on livestock (Allen 2015). For threatened fauna, dingoes may kill foxes and feral cats on the one hand, but dingoes may likewise suppress the same fauna threatened by foxes and feral cats on the other hand.…”