Age and sex differences in numerical responses, dietary shifts, and total responses of a generalist predator to population dynamics of main prey

Masoero, Giulia; Laaksonen, Toni; Morosinotto, Chiara; Korpimäki, Erkki

doi:10.1007/s00442-020-04607-x

Cited by 15 publications

(25 citation statements)

References 61 publications

(78 reference statements)

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“…In late autumn and early winter, pygmy owls collect large food stores in natural cavities and nest‐boxes for over‐winter survival (Halonen et al , Terraube et al , Masoero et al ), whereas Tengmalm's owls are not able to do so probably because larger cavities suitable for them are also accessible to larger food robbers, such as pine martens Martens martens (Korpimäki and Hakkarainen ). The proportion of forest‐sites with a food‐store of pygmy owls increased with the vole abundance in the current autumn (Masoero et al ), and also numbers of over‐wintering adult (+1‐year old) female pygmy owls and hatch‐yearlings of both sexes increased with vole abundance in the current autumn (Masoero et al ). This resulted in higher breeding densities in the next spring.…”

Section: Discussionmentioning

confidence: 99%

The difference between generalist and specialist: the effects of wide fluctuations in main food abundance on numbers and reproduction of two co‐existing predators

Korpimäki

Hongisto²,

Masoero

et al. 2020

Journal of Avian Biology

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Specialist individuals within animal populations have shown to be more efficient foragers and/or to have higher reproductive success than generalist individuals, but interspecific reproductive consequences of the degree of diet specialisation in vertebrate predators have remained unstudied. Eurasian pygmy owls (hereafter POs) have less vole‐specialised diets than Tengmalm's owls (TOs), both of which mainly subsist on temporally fluctuating food resources (voles). To test whether the specialist TO is more limited by the main prey abundance than the generalist PO, we studied breeding densities and reproductive traits of co‐existing POs and TOs in central‐western Finland during 2002–2019. Breeding densities of POs increased with augmenting densities of voles in the previous autumn, whereas breeding densities of TOs increased with higher vole densities in both the previous autumn and the current spring. In years of vole scarcity, PO females started egg‐laying earlier than TOs, whereas in years of vole abundance TO females laid eggs substantially earlier than PO females. The yearly mean clutch size and number of fledglings produced of both POs and TOs increased with abundance of voles in the current spring. POs laid large clutches and produced large broods in years of both high and low vole abundance, whereas TOs were able to do so only in years of high vole abundance. POs were able to raise on average 73% of the eggs to fledglings whereas TOs only 44%. The generalist foraging strategy of POs including flexible switching from main prey to alternative prey (small birds) appeared to be more productive than the strictly vole‐specialized foraging strategy of TOs. In contrast to earlier studies at the individual‐level, specialist predators at the species level (in this case TOs) appear to be less effective than generalists (POs), but diet specialisation was particularly costly under conditions when scarcity of main foods limited offspring production.

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Section: Discussionmentioning

confidence: 99%

The difference between generalist and specialist: the effects of wide fluctuations in main food abundance on numbers and reproduction of two co‐existing predators

Korpimäki

Hongisto²,

Masoero

et al. 2020

Journal of Avian Biology

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“…Pygmy owls are generalist predators, the main prey of which in boreal areas of Northern Europe are voles of the genera Myodes and Microtus. Most important alternative prey are shrews and small forest birds, particularly tit species (Paridae) both during the breeding season [31] and in winter [29,30]. Consumption of cached prey is widespread and virtually all such prey are consumed later.…”

Section: Introductionmentioning

confidence: 99%

“…Large fluctuations in vole populations induce rapid numerical responses of pygmy owls and other avian predators to main prey populations (e.g. [33,34]), which in turn results in densities of over-wintering pygmy owls are much larger in years of high vole abundances than in those of vole scarcity [29,30]. Therefore, the predation risk caused by pygmy owls on small birds in boreal forests varies greatly by being higher in years of abundant main prey than in years with a scarcity of such prey [30].…”

Section: Introductionmentioning

confidence: 99%

“…Many species of predators generally consume the brain of their prey before any other part of their body (e. g. [ 19 – 22 ], making it hard to estimate brain size of prey and non-prey. Exceptions to this general pattern in predator-prey interactions are some species of shrikes ( Lanius spp., [ 23 – 25 ]) and the Eurasian pygmy owl Glaucidium passerinum [ 26 ], in which both males and females hoard large numbers of mammals and birds in nest-boxes and natural cavities from late autumn to early winter to survive the winter and facilitate successful reproduction [ 27 – 30 ] ( Fig 1 ). This behavior allows for comparison of brain size of individuals that fell prey to this predator with that of conspecifics that were not captured.…”

Section: Introductionmentioning

confidence: 99%

“…(3) We also tested whether this relationship was independent of body condition of prey and non-prey. We collected data at a long-term study site of pygmy owls in Finland for assessing these predictions in two autumns with varying predation risk imposed by pygmy owls [ 28 – 30 , 35 ].…”

Section: Introductionmentioning

confidence: 99%

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Predation risk in relation to brain size in alternative prey of pygmy owls varies depending on the abundance of main prey

Møller

Hongisto²,

Korpimäki

2020

PLoS ONE

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Large brains in prey may select for adoption of anti-predator behavior that facilitates escape. Prey species with relatively large brains have been shown to be less likely to fall prey to predators. This results in the prediction that individuals that have been captured by predators on average should have smaller brains than sympatric conspecifics. We exploited the fact that Eurasian pygmy owls Glaucidium passerinum hoard small mammals and birds in cavities and nest-boxes for over-winter survival, allowing for comparison of the phenotype of prey with that of live conspecifics. In Northern Europe, main prey of pygmy owls are voles of the genera Myodes and Microtus, while forest birds and shrews are the most important alternative prey. Large fluctuations (amplitude 100-200-fold) in vole populations induce rapid numerical responses of pygmy owls to main prey populations, which in turn results in varying predation pressure on small birds. We found, weighed and measured 153 birds in foodstores of pygmy owls and mist-netted, weighed and measured 333 live birds of 12 species in central-western Finland during two autumns with low (2017) and high (2018) pygmy owl predation risk. In two autumns, individuals with large brains were captured later compared to individuals with small brains, consistent with the hypothesis that such individuals survived for longer. Avian prey of pygmy owls had smaller heads than live birds in autumn 2018 when predation risk by pygmy owls was high. This difference in head size was not significant in 2017 when predation risk by pygmy owls was reduced. Finally, avian survivors were in better body condition than avian prey individuals. These findings are consistent with the hypothesis that pygmy owls differentially prey on birds in poor condition with small brains. These findings are consistent with the hypothesis that predation risk imposed by pygmy owls on small birds in boreal forests varies depending on the abundance of the main prey (voles).

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Resource pulses shape seasonal and individual variation in the diet of an omnivorous carnivore

Jensen,

Muthersbaugh,

Ruth

et al. 2024

Ecology and Evolution

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Resource pulses are ecologically important phenomenon that occur in most ecosystems globally. Following optimal foraging theory, many consumers switch to pulsatile foods when available, examples of which include fruit mast and vulnerable young prey. Yet how the availability of resource pulses shapes the ecology of predators is still an emerging area of research; and how much individual variation there is in response to pulses is not well understood. We hypothesized that resource pulses would lead to dietary convergence in our population, which we tested by tracking both population‐level and individual coyote diets for 3 years in South Carolina, USA. We (1) described seasonal dietary shifts in relation to resource pulses; (2) compared male and female diets across seasons; and (3) tested this dietary convergence hypothesis by quantifying individual dietary variation both across and within periods when resource pulses were available. We found that pulses of white‐tailed deer fawns and blackberries composed over half of coyote diet in summer, and persimmon fruits were an important component in fall. Male and female coyotes generally had similar diets, but males consumed more deer in fall, perhaps driven by scavenging more. We found support for our dietary convergence hypothesis, where individuals had more similar diets during resource pulses compared to a non‐pulse period. We also found that this convergence happened before peak availability, suggesting a non‐symmetric response to pulse availability. We show that nearly all coyotes eat fawns, suggesting that targeted efforts to remove “fawn killers” would be in vain. Instead, given how quickly coyotes collectively converge on resource pulses, our findings show that resource pulses could potentially be used by managers to alter the behavior of apex predators. More broadly, we open a new line of inquiry into how variation in individual foraging decisions scales up to shape the effects of resource pulses on ecological communities.

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Age and sex differences in numerical responses, dietary shifts, and total responses of a generalist predator to population dynamics of main prey

Cited by 15 publications

References 61 publications

The difference between generalist and specialist: the effects of wide fluctuations in main food abundance on numbers and reproduction of two co‐existing predators

The difference between generalist and specialist: the effects of wide fluctuations in main food abundance on numbers and reproduction of two co‐existing predators

Predation risk in relation to brain size in alternative prey of pygmy owls varies depending on the abundance of main prey

Resource pulses shape seasonal and individual variation in the diet of an omnivorous carnivore

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