Density feedbacks mediate effects of environmental change on population dynamics of a semidesert rodent

Abstract

Population dynamics are the result of an interplay between extrinsic and intrinsic environmental drivers. Predicting the effects of environmental change on wildlife populations therefore requires a thorough understanding of the mechanisms through which different environmental drivers interact to generate changes in population size and structure. In this study, we disentangled the roles of temperature, food availability and population density in shaping short- and long-term population dynamics of the African striped mouse, a small rodent inhabiting a semidesert with high intra- and interannual variation in environmental conditions. We parameterized a female-only stage-structured matrix population model with vital rates depending on temperature, food availability and population density, using monthly mark-recapture data from 1609 mice trapped over 9 years (2005-2014). We then applied perturbation analyses to determine relative strengths and demographic pathways of these drivers in affecting population dynamics. Furthermore, we used stochastic population projections to gain insights into how three different climate change scenarios might affect size, structure and persistence of this population. We identified food availability, acting through reproduction, as the main driver of changes in both short- and long-term population dynamics. This mechanism was mediated by strong density feedbacks, which stabilized the population after high peaks and allowed it to recover from detrimental crashes. Density dependence thus buffered the population against environmental change, and even adverse climate change scenarios were predicted to have little effect on population persistence (extinction risk over 100 years <5%) despite leading to overall lower abundances. Explicitly linking environment-demography relationships to population dynamics allowed us to accurately capture past population dynamics. It further enabled establishing the roles and relative importances of extrinsic and intrinsic environmental drivers, and we conclude that doing this is essential when investigating impacts of climate change on wildlife populations.

Compensatory Breeding in Years Following Drought in a Desert-Dwelling Cooperative Breeder

“…The sequential, and often cyclical (Korpimäki, 1986;Marra et al, 2015;Nater et al, 2018), nature of biological systems means that each event or process experienced by an individual may have measurable downstream effects (Harrison et al, 2011). Non-fatal effects, such as poor physical condition or delayed breeding, can influence reproduction or survival over time (Marra et al, 2015).…”

“…Species living in more arid sub-tropical environments are potentially useful models for studying the effects of weather patterns and extreme events between years, because these ecosystems are characterized by high interannual variability and frequent extremes in temperature and rainfall (McKechnie et al, 2012). High temperatures and droughts have been linked to delayed or failed reproduction in a number of arid and semiarid-zone species (Cunningham et al, 2013;Cruz-McDonnell and Wolf, 2016;Nater et al, 2018;van de Ven et al, 2020a). Compensatory responses to severe weather events, like heat waves and droughts, may act over relatively long timescales to reduce or offset the negative effects of exposure to high temperatures or drought on reproductive success.…”

Basking African striped mice choose warmer locations to heat up: evidence from a field study

“…This semi‐desert species is known for its behavioral, physiological and social adaptations to cope with harsh environmental conditions (Mallarino et al , ). However, the species is facing temporary size and population viability declines due to more frequent droughts in the Succulent Karoo region (Nater et al , ). Temperature increases and droughts may also affect basking patterns in this and other arid species.…”

“…The most dramatic examples come from Australia where heat waves caused mass fatalities in birds and bats (McKechnie & Wolf, 2009;O'Shea et al, 2016, Ratnayake et al, 2019. Baseline knowledge on how animals cope with challenging thermal conditions via physiological and behavioral plasticity is essential to predict future changes in animal communities in arid ecosystems (Chown et al, 2010, Huey et al, 2012, Mitchell et al, 2018, Nater et al, 2018.…”

Reproductive adaptations to high densities in social mammals

“…Typically, these squirrels live through two breeding seasons. 17) Nater et al (2018). Subject: African striped mouse.…”