The necessity of tailored control of irrupting pest populations driven by pulsed resources

Abstract

Resource pulses are widespread phenomena in diverse ecosystems. Irruptions of generalist consumers and corresponding generalist predators often follow such resource pulses. This can have severe implications on the ecosystem and also on the spread of diseases or on regional famines. Suitable management strategies are necessary to deal with these systems. In this study, we develop a general model to investigate optimal control for such a system and apply this to a case study from New Zealand. In particular, we consider the dynamics of beech masting (episodic synchronous seed production) leading to rodent outbreaks and subsequent stoat (Mustela erminea) irruptions. Here, stoat control happens via secondary poisoning. The results show that the main driver of the optimal control timing (June) is the population density of the control vector. Intermediate control levels are superior to higher levels if the generalist consumer is necessary as a control vector. Finally, we extend the model to a two-patch metapopulation model, which indicates that, as a consequence of the strong vector dependence, a strategy of alternating control patches yields better results than static control. This highlights that besides control level, also the design impacts the control success. The results presented in this study reveal important insights for proper pest management in the New Zealand case study. However, they also generally indicate the necessity of tailored control in such systems.

Understanding mast seeding for conservation and land management

“…Future management strategies for forests and other plant populations, especially under climate change, will benefit from considering variable seed production. The interpretation of models that anticipate the likelihood of regeneration in particular forests North American forests [12,39] assessing population viability of plants targeting conservation activities to plant populations and growth stages perennial sedges [40], limber pine [41] collecting seed for restoration timing seed collection trips and restoration projects island oak [42], New Caledonian forests [43] timing shelterwood forestry timing timber harvests during 'establishment cuts' oak [44], fir forests biological control using seed predators forecasting efficacy of biocontrol agents Russian olive [10] increasing seed crops to enhance dispersal mutualisms bolstering bird populations, restoring forests island scrub-oak-scrub jay [9], pedunculate oak-Eurasian jay [45] timing of animal relocations relative to mast cycles reintroducing rare or extirpated seed predators kākāpō [46] timing of animal culls relative to mast cycles culling invasive predators, setting hunting regulations invasive stoat culls in Nothofagus forests [47];…”

“…In New Zealand, introduced stoats (Mustela erminea) are a major threat to native avifauna, which evolved without mammal predation pressure. The New Zealand Department of Conservation uses aerially deployed sodium fluoroacetate to poison rodents, which are then consumed by the stoats [47]. To maximize the impact on the temporal fluctuations in the trophic cascades, theoretical models of masting impacts on population dynamics were developed by Köhnke et al [47].…”

“…The New Zealand Department of Conservation uses aerially deployed sodium fluoroacetate to poison rodents, which are then consumed by the stoats [47]. To maximize the impact on the temporal fluctuations in the trophic cascades, theoretical models of masting impacts on population dynamics were developed by Köhnke et al [47]. The results show that poison deployment in June, when rodent populations peak following seed drop, maximizes the effect on the targeted generalist predator.…”

The ecology and evolution of synchronized reproduction in long-lived plants

“…Bumper seed crops in forest trees create pulses of food resources and cause population booms in primary consumers that can reverberate across trophic levels and thus affect the timing of management actions aimed at animal populations [93,94]. For example, forecasts of seed and fruit crops in New Zealand inform both the management of invasive mammals and translocation programmes of the endangered kakapo [ 95,96]. Similarly, the effect of masting on zoonotic, tick-borne disease incidents in human populations, driven by the effect of cycling rodent populations on tick numbers, can be forecast with a time horizon of up to 2 years [97].…”

Immigration drives ship rat population irruptions in marginal high‐elevation habitat in response to pulsed resources

“…Understanding the relative contributions of these two processes to population growth in marginal habitat is important because resource pulses often drive irruptions of invasive animals that necessitate landscape‐scale control operations (Griffiths & Barron, 2016; Köhnke et al, 2020). Rodent outbreaks, in particular, can have “dramatic economic, ecological, societal, and even political ramifications” (Andreassen et al, 2020), and understanding the ecology of these outbreaks is important for controlling them efficiently.…”