Elk population dynamics when carrying capacities vary within and among herds

Abstract

Population and land management relies on understanding population regulation and growth, which may be impacted by variation in population growth parameters within and among populations. We explored the interactions between variation in carrying capacity (K), intrinsic population growth rate (r), and strength of density dependence (β) within and among elk (Cervus elaphus) herds in a small part of the geographic range of the species. We also estimated stochastic fluctuations in abundance around K for each herd. We fit linear Ricker growth models using Bayesian statistics to seven time series of elk population survey data. Our results indicate that K and β varied among herds, and that r and β varied temporally within herds. We also found that herds with smaller K had less stochastic fluctuation in abundances around K, but higher temporal variation in β within herds. Population regulation and the rate of return to the equilibrium abundance is often understood in terms of β, but ecological populations are dynamic systems, and temporal variation in population growth parameters may also influence regulation. Population models which accommodate variation both within and among herds in population growth parameters are necessary, even in mild climates, to fully understand population dynamics and manage populations.

A new framework to understand context dependence of two-species population dynamics: A case study of rocky intertidal sessile assembly

“…Here, the strength of intraspecific density dependence decreased as the intrinsic growth rate of the focal species increased, which is contrary to the results of many previous studies in which the strength of intraspecific density dependence increased as the intrinsic growth rate increased (Lillegård et al 2008;Zehnder & Hunter 2008;Pasinelli et al 2011;Roy et al 2016;Gamelon et al 2019;Koetke et al 2020). On the other hand, a few studies have shown a negative relationship between environmental suitability and the strength of density dependence (Agrawal et al 2004;Lines et al 2020).…”

“…First, this framework cannot be applied to situations in which invasion has failed in order to evaluate the causes, because it requires that both target species can be continuously observed. Second, the relationship between the strengths of intra-and interspecific density dependence and the intrinsic growth rates indicates pattern but not processes, because differences in intrinsic growth rates among localities will be multicausal phenomena, as suggested by the inconsistent relationship between strength of intraspecific density dependence and intrinsic growth rate in various studies (e.g., Agrawal et al 2004;Lillegård et al 2008;Zehnder & Hunter 2008;Pasinelli et al 2011;Roy et al 2016;Gamelon et al 2019;Koetke et al 2020;Lines et al 2020). Compared with the framework proposed here, future work should focus on the integration of this framework with the environmental gradient approach, which could be helpful for interpreting the mechanism underlying the pattern between strength of intraspecific density dependence and intrinsic growth rate through decomposing the effect of each environmental component.…”

Identifying the determinants of COVID-19 preventative behaviors and vaccine intentions among South Carolina residents

“…For example, a recent set of studies by Koetke et al . [ 54 ] found that the effect of political ideology on social distancing was moderated by trust in science, whereby conservative participants were more likely to social distance when they also reported higher trust in science. Thus, there appears to be interactive effects between political beliefs/affiliations and scientific trust that predict incremental variance in COVID-19 related behaviors, such as social distancing.…”

Influences on food supply from elk abundance and precipitation early in the growing season

“…Predators of elk are mountain lions (Puma concolor) and black bear (Ursus americanus). Neither predator appears to exert much top-down influence on elk population dynamics in the parks [19,20].…”

“…This setting makes it feasible to reliably estimate the bulk of the food supply. Across the 15 years of our study elk abundance varied 3.9-fold and density dependent population dynamics were evident, implying negative feedbacks between elk abundance and the food supply [19][20][21]. Herein, we measured elk abundance, precipitation, and forage biomass at two spatial scales across 15 years in winter which is early in the growing season in this temperate rainforest.…”