The interplay between hunting rate, hunting selectivity, and reproductive strategies shapes population dynamics of a large carnivore

Abstract

Harvest, through its intensity and regulation, often results in selection on female reproductive traits. Changes in female traits can have demographic consequences, as they are fundamental in shaping population dynamics. It is thus imperative to understand and quantify the demographic consequences of changes in female reproductive traits to better understand and anticipate population trajectories under different harvest intensities and regulations. Here, using a dynamic, frequency-dependent, population model of the intensively hunted brown bear (Ursus arctos) population in Sweden, we quantify and compare population responses to changes in four reproductive traits susceptible to harvest-induced selection: litter size, weaning age, age at first reproduction, and annual probability to reproduce. We did so for different hunting quotas and under four possible hunting regulations: (i) no individuals are protected, (ii) mothers but not dependent offspring are protected, (iii) mothers and dependent offspring of the year (cubs) are protected, and (iv) entire family groups are protected (i.e., mothers and dependent offspring of any age). We found that population growth rate declines sharply with increasing hunting quotas. Increases in litter size and the probability to reproduce have the greatest potential to affect population growth rate.Population growth rate increases the most when mothers are protected. Adding protection on offspring (of any age), however, reduces the availability of bears for hunting, which feeds back to increase hunting pressure on the nonprotected categories of individuals, leading to reduced population growth. Finally, we found that changes in reproductive traits can dampen population declines at very high hunting quotas, but only when protecting mothers. Our results illustrate that changes in female reproductive traits may have context-dependent consequences for demography. Thus, to predict population consequences of harvest-induced selection in wild populations, it is critical to integrate both hunting intensity and regulation, especially if hunting selectivity targets female reproductive strategies.

Human‐induced evolution: Signatures, processes and mechanisms underneath anthropogenic footprints on natural systems

“…In contrast to translocations or anthropogenic hybridization, harvesting activities such as hunting, or fishing exert a predictable selection because its strong intensity and direction are largely dictated by specific harvesting strategies (Allendorf & Hard, 2009;Hočevar & Kuparinen, 2021;Van de Walle et al, 2021).…”

“…in Sweden exposed to four different hunting regimes, that is, no protection, only mothers are protected, mothers and dependent offspring are protected and entire family groups are protected, showed that reproductive traits such as litter size and annual probability for females to reproduce have a large impact on population growth (Van de Walle et al, 2021). This result is particularly Human-induced responses that contrast those that emerged through natural selection are not exclusive to harvesting regimes.…”

“…In contrast to translocations or anthropogenic hybridization, harvesting activities such as hunting, or fishing exert a predictable selection because its strong intensity and direction are largely dictated by specific harvesting strategies (Allendorf & Hard, 2009 ; Hočevar & Kuparinen, 2021 ; Van de Walle et al, 2021 ). Consequently, harvesting re‐shapes selection regimes that populations have adapted to and can result in antagonistic phenotypic responses of fitness‐related life history traits (Heino et al, 2015 ; LaSharr et al, 2019 ).…”

“…Modelling the population dynamics of Brown bear ( Ursus arctos ) in Sweden exposed to four different hunting regimes, that is, no protection, only mothers are protected, mothers and dependent offspring are protected and entire family groups are protected, showed that reproductive traits such as litter size and annual probability for females to reproduce have a large impact on population growth (Van de Walle et al, 2021 ). This result is particularly evident when specific hunting regulations are designed to protect only mothers (Van de Walle et al, 2021 ). Furthermore, expected hunting‐induced selection on female reproductive traits increases selectivity to produce larger litters at younger ages with increasing hunting quotas.…”

“…evident when specific hunting regulations are designed to protect only mothers(Van de Walle et al, 2021). Furthermore, expected hunting-induced selection on female reproductive traits increases selectivity to produce larger litters at younger ages with increasing hunting quotas.…”