Anthropogenic disturbance in a changing environment: modelling lifetime reproductive success to predict the consequences of multiple stressors on a migratory population

Abstract

Animals make behavioural and reproductive decisions that maximise their lifetime reproductive success, and thus their fitness, in light of periodic and stochastic variability of the environment. Modelling the variation of an individual's energy levels formalises this tradeoff and helps to quantify the population‐level consequences of stressors (e.g. disturbance from human activities and environmental change) that can affect behaviour or physiology. In this study, we develop a dynamic state variable model for the spatially explicit behaviour, physiology and reproduction of a female, long‐lived, migratory marine vertebrate. The model can be used to investigate the spatio‐temporal patterns of behaviour and reproduction that allow an individual to maximise its overall reproductive output. We parametrised the model for eastern North Pacific blue whales Balaenoptera musculus, and used it to predict the effects of changing environmental conditions and increasing human disturbance on the population's vital rates. In baseline conditions, the model output had high fidelity to observed energy dynamics, movement patterns and reproductive strategies. Simulated scenarios suggested that environmental changes could have severe consequences on the population's vital rates, but that individuals could tolerate high levels of anthropogenic disturbance. However, this ability depended on where, when and how often disturbance occurred. In scenarios with both environmental change and anthropogenic disturbance, synergistic interactions caused stronger effects than in isolation. In general, larger body size offered a buffer against stochasticity and disturbance, and, consequently, we predicted juveniles to be more susceptible to disturbance. We also predicted that females prioritise their own survival at the expense of the current reproductive attempt, presumably the result of their long lifespan. Our approach provides a general framework to make predictions of the cumulative and synergistic effects of human disturbance and climate change on migratory populations, which can inform effective management and conservation efforts.

Dolphins and Boats: When Is a Disturbance, Disturbing?

“…The constraints the ecological context places upon individuals' ability to fill these needs also impacts dolphins' response to disturbance, contributing to their ability to avoid a stressor and compensate for a negative response. Individual-based models have been used to explore the relationship between internal drivers and behavior, and have proven able to simulate realistic dynamics (e.g., New et al, 2013;Pirotta et al, 2014Pirotta et al, , 2019). Here we take advantage of an existing model for dolphin populations (New et al, 2013) and generalize it to investigate broad patterns in population response to disturbance.…”

Scales of Blue and Fin Whale Feeding Behavior off California, USA, With Implications for Prey Patchiness

“…Further, spatial variability in the type and rate of calling has been documented in blue whales off southern California, suggesting there may be spatial separation of behavioral activities (Lewis and Sirovic, 2018), although a lack of direct observation makes the underlying process unclear, as both feeding and reproductive calls are recorded throughout the feeding season in southern California (Lewis and Sirovic, 2018). Considering that animals in southern California waters are exposed to a variety of regional stressors like ship strikes (Berman-Kowalewski et al, 2010;Redfern et al, 2013) and anthropogenic sound (Goldbogen et al, 2013;DeRuiter et al, 2017), a potential spatial segregation arising from behavioral differences between sexes could lead to disproportionate impacts (Sprogis et al, 2016) over short temporal scales (Pirotta et al, 2018) or on long-term population fitness (Pirotta et al, 2019).…”

Population-level effects of acoustic disturbance in Atlantic cod: a size-structured analysis based on energy budgets

“…Previous theoretical studies applied a bioenergetics approach to study population consequences of sound exposure for several species of marine mammals (e.g. [15,[42][43][44]). Our study is, to our knowledge, the first to develop such methodology for a species of fish.…”