Predator-mediated interactions through changes in predator home range size can lead to local prey exclusion

Abstract

The effects of indirect biotic interactions on species occurrence are difficult to quantify in the wild. In theory, the exclusion of a prey species can occur through the numerical and functional responses of a predator to another prey. Few studies assessed the relative effects of these responses on the net interaction strength between multiple prey sharing common predators, in part because empirically based multi-species functional response models are very rare. To investigate whether the presence of a prey species affects predation rates and population growth rate of another prey species, we used a multi-prey mechanistic model of predation along with a population matrix model. The models were parameterized using a combination of behavioral, demographic, and experimental data acquired in an arctic vertebrate community which includes the arctic fox (Vulpes lagopus), a territorial predator feeding primarily on small mammals as well as eggs of various bird species such as sandpipers and colonial nesting geese. Our results showed that the positive effects of the presence of a goose colony on sandpiper nesting success (via predator egg handling time) were outweighed by the negative effect of an increase in fox density, caused by a reduction in fox home range size in the goose colony. Thus, the net interaction resulting from the presence of geese was negative. Our results also showed that this interaction could lead to local exclusion of sandpipers over a range of adult sandpiper annual survival observed in the wild. Our approach takes into account diverse proximate mechanisms underpinning interaction strengths in a multi-prey system and generates novel insights on some of the predator behavioral responses that may influence prey coexistence in vertebrate communities.

Predator-mediated interactions through changes in predator home range size can lead to local prey exclusion

“…Data accessibility. All data and code for the analysis of the data are available at: http://doi.org/10.5281/zenodo.8135999 [68].…”

Predator home range size mediates indirect interactions between prey species in an arctic vertebrate community

“…Such changes in predator behavioural traits typically respond faster to fluctuating prey density than demographic rates and could be a primary mechanism driving indirect interactions (Werner & Peacor, 2003). Recent empirical‐based models also indicate that numerical response mediated by changes in predator space use, especially home range size, can ultimately affect prey species coexistence in the wild (Beardsell et al, 2023).…”

“…The relationships between the abundance of multiple distinct prey species and predator home range size, and the consequences of changes in predator home range size on prey demographic parameters, are rarely quantified in natural communities (Beardsell et al, 2023). This strongly reduces our ability to (i) fully integrate behavioural‐numerical responses in multispecies predator–prey models and (ii) identify the dominant mechanisms driving predator‐mediated interactions in the wild.…”

“…For many birds, fox predation is the primary cause of nest failure (Bety et al, 2002; McKinnon & Bêty, 2009; Smith et al, 2007). This shared predation generates numerous predator‐mediated interactions among the prey (Bety et al, 2002; Mckinnon et al, 2013; Nolet et al, 2013; Summers et al, 1998), which can impact their population dynamics (Beardsell et al, 2023; Nolet et al, 2013) and distribution (Duchesne et al, 2021; Lamarre et al, 2017; Léandri‐Breton & Bêty, 2020). The proximal mechanisms driving these indirect interactions are uncertain.…”

“…Interestingly, the different prey types (cyclic lemmings and goose eggs) induce opposing indirect effects (Duchesne et al, 2021), leading to either short‐term apparent mutualism (Bêty et al, 2001; McKinnon et al, 2014; Pedersen et al, 2018) or apparent competition (Flemming, Nol, et al, 2019; Lamarre et al, 2017; Mckinnon et al, 2013) with other incidental prey. Indeed, predation risk for nesting birds is generally released at high lemming abundance (Bêty et al, 2001; McKinnon et al, 2014) partly due to predators spending less time foraging and travelling smaller distances within their home range (Beardsell et al, 2022), whereas high availability of goose eggs increases nest predation risk for prey species located in the goose colony (Lamarre et al, 2017; Mckinnon et al, 2013), likely through predator numerical response (Beardsell et al, 2023; Giroux et al, 2012; Lamarre et al, 2017). Arctic fox presents strong territoriality (Grenier‐Potvin et al, 2021), and home range size is expected to vary according to prey availability (Eide et al, 2004; Pletenev et al, 2021).…”