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Human activities are a major evolutionary force affecting wild populations. Selective pressure from harvest has mainly been documented for life-history and morphological traits. The probability for an individual to be harvested, however, may also depend on its behaviour. 2.We report empirical studies that examined whether harvesting can exert selective pressures on behavioural traits. 3.We show that harvest-induced selection on behavioural traits is not specific to a particular harvest method and can occur throughout the animal kingdom. 4.Synthesis and applications. Managers need to recognize that artificial selection caused by harvesting is possible. More empirical studies integrating physiological, behavioural, and life-history traits should be carried out to test specific predictions of the potential for harvest-induced selection on heritable traits using models developed in fisheries. To limit selective pressure on behaviour imposed by harvesting, managers could reduce harvest quotas or vary harvest regulations over time and/or space to reduce the strength of selection on a particular phenotype. This article is protected by copyright. All rights reserved.
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COMMENTARY
Harvesting as a potential selective pressure on
behavioural traits
Martin Leclerc*
,1
, Andreas Zedrosser
2,3
and Fanie Pelletier
1
1
Canada Research Chair in Evolutionary Demography and Conservation & Centre for Northern Studies, D
epartement
de biologie, Universit
e de Sherbrooke, Sherbrooke, QC J1K2R1, Canada;
2
Faculty of Technology, Natural Sciences
and Maritime Sciences, Department of Natural Sciences and Environmental Health, University College of Southeast
Norway, N-3800 Bø i Telemark, Norway; and
3
Department of Integrative Biology, Institute of Wildlife Biology and
Game Management, University of Natural Resources and Applied Life Sciences, Vienna, Gregor Mendel Str. 33,
A1180 Vienna, Austria
Summary
1. Human activities are a major evolutionary force affecting wild populations. Selective pres-
sure from harvest has mainly been documented for life-history and morphological traits. The
probability for an individual to be harvested, however, may also depend on its behaviour.
2. We report empirical studies that examined whether harvesting can exert selective pressures
on behavioural traits.
3. We show that harvest-induced selection on behavioural traits is not specific to a particular
harvest method and can occur throughout the animal kingdom.
4. Synthesis and applications. Managers need to recognize that artificial selection caused by
harvesting is possible. More empirical studies integrating physiological, behavioural, and life-
history traits should be carried out to test specific predictions of the potential for harvest-
induced selection on heritable traits using models developed in fisheries. To limit selective
pressure on behaviour imposed by harvesting, managers could reduce harvest quotas or vary
harvest regulations over time and/or space to reduce the strength of selection on a particular
phenotype.
Key-words: angling, evolutionary consequences, exploitation, fisheries, gillnet, harvest-
induced selection, hunting, passive and active gear, vulnerability
Introduction
Humans are considered as one of the major selective forces
shaping traits of species (Palumbi 2001) and may cause faster
phenotypic changes than many natural drivers (Hendry,
Farrugia & Kinnison 2008; Darimont et al. 2009). Pheno-
typic changes are particularly drastic when humans act as
predators and harvest wild populations (Darimont et al.
2009). Harvesting can induce selective pressures on wild ani-
mal populations by increasing mortality and by non-random
removal of specific phenotypes. Harvesting has been shown
to induce selective pressure in several species (Allendorf
et al. 2008) that may ultimately result in evolutionary
responses (Jørgensen et al. 2007; Pigeon et al. 2016).
Selective pressure caused by human harvest, hereafter
referred to as harvest-induced selection, has mostly been
documented for life-history and morphological traits and
can be caused by size-selective harvesting. For example,
trophy hunting of male bighorn sheep (Ovis canadensis)
selected for smaller horn size (Coltman et al. 2003; Pigeon
et al. 2016), and size-selective fishing affected the evolu-
tion of life histories in zebra fish (Danio rerio) (Uusi-
Heikkil
aet al. 2015). In size-selective harvesting, typically
a specific phenotype is targeted leading to harvest-induced
selection. Harvest-induced selection on behavioural traits,
however, can be due to behavioural differences between
individuals affecting their probability of being harvested
(Heino & Godø 2002; Uusi-Heikkil
aet al. 2008). This
pattern was observed in behavioural studies showing that
the probability of capturing or sampling (for scientific
research instead of harvesting) a specific individual in a
population could be biased due to consistent individual
differences in behaviour, i.e. animal personality (Biro &
Dingemanse 2009; Carter et al. 2012; Biro 2013). These
individual behavioural differences are often heritable
(Postma 2014; Dochtermann, Schwab & Sih 2015).
*Correspondence author. E-mail: martin.leclerc2@usherbrooke.ca
©2017 The Authors. Journal of Applied Ecology ©2017 British Ecological Society
Journal of Applied Ecology 2017, 54, 1941–1945 doi: 10.1111/1365-2664.12893
Humans can therefore, consciously or not, modulate the
evolution of animal behaviour by removing (harvesting)
or reproducing (breeding) specific individuals within a
population (Price 1984). Although important for wildlife
management and conservation, much less attention has
been devoted to harvest-induced selection on behavioural
traits compared to life-history or morphological traits
(Uusi-Heikkil
aet al. 2008; Heino, D
ıaz Pauli & Dieck-
mann 2015) and to whether this selection may lead to
evolution of behaviours that are different from those
favoured by natural selection (e.g. Olsen & Moland 2011
for morphological traits).
Harvesting as a selective pressure on
behavioural traits
Most of the theoretical work and predictions for beha-
vioural harvest-induced selection are derived from the
fisheries literature. Arlinghaus et al. (2016) suggested that
harvest should select for shyer and more vigilant individ-
uals. In fisheries, predictions made on harvest-induced
selection often depend on the gear type used, and Al
os,
Palmer & Arlinghaus (2012) predicted that passive gear
should select for individuals with lower activity levels. In
sport hunting, a hunter must see an individual of the
species of interest before she/he can select a target ani-
mal based on a morphological trait or a sex/age class.
Therefore, we hypothesize that behavioural traits that
increase vulnerability or visibility, such as selection of
open areas, more active individuals during hunting
hours, or boldness, should have a strong effect on the
probability that an individual will present itself as a pos-
sible target.
Here, we report studies where harvest-induced selection
of behavioural traits was clearly investigated. We searched
the scientific literature database Scopus
Ò
for peer-
reviewed papers using different combinations of the fol-
lowing seven keywords: harvesting, hunting, fisheries,
behaviour, vulnerability, exploitation and selective pres-
sure. The literature contains numerous studies on the
immediate effects of harvesting on behaviour (i.e. plastic
response or ‘learning’) (e.g. Raat 1985; Ordiz et al. 2012)
or studies showing behavioural differences between high
and low vulnerability fish strains (e.g. Nannini et al. 2011;
Sutter et al. 2012), or studies showing behavioural differ-
ences between fish caught with different methods or lures
(e.g. Wilson et al. 2015), which suggests that harvesting
might induce a selective pressure on behaviours. Here,
however, we only retained studies that directly examined
whether harvesting acted as a selective pressure on beha-
vioural traits. The limited amount of literature examining
harvest-induced selection on behaviour likely reflects the
difficulties in collecting quantitative information on beha-
vioural traits expressed by harvested and non-harvested
individuals necessary to investigate behavioural harvest-
induced selection. This is particularly true for fish,
because it is rarely possible to make observations on fish
that are not captured (H
ark
onen et al. 2016, but see
Olsen et al. 2012), and longitudinal behavioural time-ser-
ies data from wild populations hardly exist (Jørgensen &
Holt 2013). We categorized the 13 retained studies in two
groups: experimental studies in the laboratory or natural
conditions, and observational studies in the wild.
Experimental studies
We found seven experimental studies showing that harvest
can act as a selective pressure on behavioural traits
(Table 1; but see Vainikka, Tammela & Hyv
arinen 2016).
From the seven studies showing harvest-induced selection
of behavioural traits, six were conducted in fishes and one
in a crustacean. Individuals showed different vulnerability
to angling in largemouth bass (Micropterus salmoides)
(Philipp et al. 2009) and common carp (Cyprinus carpio)
(Klefoth, Pieterek & Arlinghaus 2013), and traps removed
bolder guppies (Poecilia reticulata) and common yabby
(Cherax destructor) (Biro & Sampson 2015; Diaz Pauli
et al. 2015). Trawling removed shyer guppies (Diaz Pauli
et al. 2015) and minnows (Phoxinus phoxinus) with lower
swim speed (Killen, Nati & Suski 2015). These studies
suggest that harvesting can act as a selective pressure on a
behavioural trait and that passive gear should select
against boldness and more explorative individuals, while
active gear should select against shyness, and angling
selects against more aggressive, bold and vulnerable indi-
viduals (Heino & Godø 2002; Arlinghaus et al. 2016).
Harvest-induced selection patterns obtained in laboratory
experiments appear to be consistent with those observed
in experiments conducted in natural settings (Biro & Post
2008), suggesting that harvesting can act as a selective
pressure in the wild.
Observational studies
We found six studies showing harvest-induced selection
on different behavioural traits in the wild, ranging from
the timing of migration to boldness and defensiveness
(Table 1). These studies involved fishes, snakes, birds and
mammals in Japan, Norway, United Kingdom, Canada
and the USA. Similar to experimental studies, observa-
tional studies showed that harvest-induced selection was
caused by different harvest methods (shotgun, rifle hunt-
ing, passive gear, angling), and that behavioural traits
under selection may vary in relation to the harvest
method used (Table 1). In sockeye salmon (Oncorhynchus
nerka) harvesting selected against individuals that
migrated later in the season in a population where
exploitation rates vary systematically over the course of
the fishing season (Quinn et al. 2007). In this population,
migration timing became earlier over the years (Quinn
et al. 2007). Such temporal behavioural changes could be
caused by environmental factors, but could also be, at
least partly, a response to harvest-induced selection if
migration timing is heritable (Quinn et al. 2007).
©2017 The Authors. Journal of Applied Ecology ©2017 British Ecological Society, Journal of Applied Ecology,54, 1941–1945
1942 M. Leclerc, A. Zedrosser & F. Pelletier
Consequences of behavioural harvest-induced
selection
Behavioural traits under harvest-induced selection can
only evolve if they are heritable (Postma 2014; Dochter-
mann, Schwab & Sih 2015). In addition to the changes in
migration timing of sockeye salmon discussed above
(Quinn et al. 2007), two studies suggested that harvest
might have been important in the evolution of a genetic
locus related to habitat use of Atlantic cod (Gadus mor-
hua) in Iceland (
Arnason, Hernandez & Kristinsson 2009;
Jakobsdottir et al. 2011). However, we found no observa-
tional studies that could unequivocally show evolution in
behaviour caused by harvesting. Absence of evidence for
harvest-induced evolution of behavioural traits in the
wild, however, does not imply that such evolution is unli-
kely or uncommon. Instead, it may reflect the difficulties
to obtain the necessary longitudinal data on behaviours in
harvested populations (Clutton-Brock & Sheldon 2010;
Jørgensen & Holt 2013). Even when adequate data are
available, it remains challenging to show that harvest is
the driver of evolutionary change and to disentangle phe-
notypic plasticity from genetic change (Meril
a & Hendry
2014). Although they have not been documented in the
wild, evolutionary changes in behavioural traits due to
harvest have been shown in experimental studies (Philipp
et al. 2009). Laboratory experiments are useful to evaluate
the potential for harvest-induced selection and
evolutionary response in behavioural traits, but extrapola-
tion of results to natural systems is difficult, as some rela-
tionships observed in the laboratory might not persist in
the wild (Wilson et al. 2011).
Conclusions
Humans have harvested wild animals for millennia and
human evolution is strongly linked with harvesting. How-
ever, technological developments have increased our effi-
ciency to harvest, with many consequences (Milner,
Nilsen & Andreassen 2007; Allendorf et al. 2008; Fenberg
& Roy 2008). Morphological, life-history and behavioural
traits form the phenotype of an individual and thus affect
its vulnerability to harvest (Uusi-Heikkil
aet al. 2008).
There is increasing evidence that behavioural traits are
correlated with physiological and life-history traits (Biro
& Stamps 2008; R
eale et al. 2010). Therefore, even if har-
vesting specifically targets a behavioural trait, changes in
life-history, morphological, and/or physiological traits can
be observed. For example, changes in behaviours were
observed due to size-selective harvesting in zebra fish
(Uusi-Heikkil
aet al. 2015), and size-selective harvesting
of Atlantic silverside (Menidia menidia) resulted in lower
larval growth rate, food consumption rate and conversion
efficiency, and vertebrae number (Walsh et al. 2006;
Duffy et al. 2013). If individuals with certain life-history,
morphological and behavioural phenotypes are heavily
Table 1. Examples of experimental and observational studies showing that harvest can act as a selective pressure on behaviour
Species Harvest method Trait
Direction of the selective effect
ReferenceHarvest selects against individual that are:
Experimental studies in the laboratory or in natural conditions
Poecilia reticulata Trap BoldShy Bolder Diaz Pauli et al. (2015)
Trawl BoldShy Shyer Diaz Pauli et al. (2015)
Phoxinus phoxinus Trawl Swim speed Slower Killen, Nati & Suski
(2015)
Salmo trutta Fly-fishing Exploration More explorative H
ark
onen et al. (2014)
Cyprinus carpio Angling Vulnerability More vulnerable Klefoth, Pieterek &
Arlinghaus (2013)
Micropterus salmoides Angling Vulnerability More vulnerable Philipp et al. (2009)
Oncorhynchus mykiss Gillnet Bold/ShyFast/Slow Faster-bolder Biro & Post (2008)
Cherax destructor Trap BoldShy Bolder Biro & Sampson (2015)
Observational studies
Oncorhynchus nerka Angling Migration timing Migrated later in season Quinn et al. (2007)
Gadus morhua Passive gear Habitat use Use more shallow water Olsen et al. (2012)
Passive gear Vertical migration Have a strong diel vertical migration Olsen et al. (2012)
Passive gear Horizontal movement Have a predictable movement pattern Olsen et al. (2012)
Gloydius blomhoffii Not mentioned Flight distance Have lower flight distance Sasaki, Fox & Duvall
(2009)
Not mentioned Defensiveness More defensive Sasaki, Fox & Duvall
(2009)
Phasianus colchicus Shotgun hunting BoldShy Bolder Madden & Whiteside
(2014)
Cervus elaphus Rifle hunting Habitat use Use habitat with less concealing cover Lone et al. (2015)
Rifle hunting Habitat use Use open areas Ciuti et al. (2012)
Rifle hunting Habitat use Closer to roads and use flatter terrain Ciuti et al. (2012)
Rifle hunting Movement rate Have higher movement rate Ciuti et al. (2012)
©2017 The Authors. Journal of Applied Ecology ©2017 British Ecological Society, Journal of Applied Ecology,54, 1941–1945
Behavioural harvest-induced selection 1943
harvested, selection may quickly lead to the evolution of a
population with a lower harvest yield (Conover & Munch
2002), because this population will now mostly be com-
posed of individuals with lower growth rate (Conover &
Munch 2002; Biro & Sampson 2015) that are also more
difficult to harvest (Philipp et al. 2009). In many cases,
selective pressures imposed by harvesting oppose natural
selection (Conover 2007; Olsen & Moland 2011). While
some traits can genetically recover after harvest-induced
selection ceases (Conover, Munch & Arnott 2009), some
traits may not (Salinas et al. 2012; Pigeon et al. 2016),
which can impair population recovery after harvest has
ceased (Laugen et al. 2014).
Recommendations
Even though behaviours are often easier to observe and
quantify in terrestrial ecosystems, most of the literature
and predictions on behavioural harvest-induced selection
come from fisheries. Despite differences in the harvest
methods used in fisheries and hunting, behavioural data
from terrestrial harvested populations can be complemen-
tary to fisheries data and could offer an opportunity to
test predictions developed for fisheries in terrestrial
ecosystems. For example, predictions made for passive
gear in fisheries could be applied to ‘still hunting’ or ‘bait
hunting’, but might not be appropriate for ‘stalking’.
Therefore, we suggest a synergistic approach and recom-
mend to increase discussions and collaborations between
researchers studying harvest-induced selection in fisheries
and terrestrial ecosystems.
Integrating genetic and evolutionary effects of harvest-
ing into management and conservation is central for
achieving sustainable harvesting (Conover & Munch 2002;
Allendorf et al. 2008). Acknowledging that harvest is
selective by nature is the first step towards that goal. Even
if harvest is random regarding phenotypes, it increases
mortality and therefore selects for faster growing and ear-
lier reproducing individuals (rlife-history strategy) rather
than slow growing and late reproducing individuals (K
life-history strategy) (Pianka 1970). Ideally, in harvested
populations, monitoring programs should be introduced
to detect and monitor potential harvest-induced selection
and its consequences. Such programs would require longi-
tudinal data on multiple phenotypic traits, including
behavioural traits, of harvested and non-harvested indi-
viduals in the population. This would allow evaluating the
direction and strength of harvest-induced selection in
comparison to natural selection. When required, different
mitigation measures could be implemented in manage-
ment plans to reduce the impacts of harvest-induced
selection. For example, reducing harvest quotas should
reduce the strength of selection or managers could estab-
lish harvest regimes that mimic natural selection (Milner,
Nilsen & Andreassen 2007).
Such monitoring programs are challenging tasks requir-
ing a considerable amount of time and money. In the
meantime, we suggest using a precautionary approach
when harvesting natural populations. Harvest quotas
should not be based on maximum yield but rather aim at
preserving natural variation shaped by natural selection
(Fenberg & Roy 2008). We suggest, based on our results,
to vary harvest regulations (e.g. based on sex, age or
phenotypes harvested and harvest methods used) spatio-
temporally to reduce the strength of selection on a
particular phenotype.
Authors’ contributions
All authors conceived the idea; M.L. conducted the literature search and
the first draft of the manuscript. All authors contributed critically to the
drafts and gave final approval for publication.
Acknowledgements
We thank M. Festa-Bianchet and two anonymous reviewers for com-
ments on an earlier version of this manuscript. M.L. was supported
financially by NSERC and FRQNT. F.P. was funded by NSERC
discovery grant and by the Canada Research Chair in Evolutionary
Demography and Conservation. A.Z. acknowledges funding from the
Polish-Norwegian Research Program operated by the National Center
for Research and Development under the Norwegian Financial Mecha-
nism 2009-2014 in the frame of project contract no. POL-NOR/198352/
85/2013. This is paper no. 229 of the Scandinavian Brown Bear Research
Project.
Data accessibility
Data have not been archived because this article does not contain data.
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Behavioural harvest-induced selection 1945
... Moreover the choice to be in a certain habitat might be linked to personality (i.e. matching habitat choice hypothesis Edelaar et al., 2008, Holtmann et al., 2017, Leclerc et al., 2017. Consequently, one might consider that it is relevant to keep habitat variation in the repeatability estimates to not underestimate it. ...
... In the same roe deer population, Bonnot et al., (2018) and Monestier et al., (2015) demonstrated that there was a habitat-specific survival of offspring and ultimately, reproductive success according to behavioural phenotypes. Furthermore, hunting intensity might vary in time and space and can act as an important selective pressure on behaviour (Leclerc et al., 2017). Collectively, this might cause fluctuating selection, with some behavioural types differently selected across time and space. ...
... Previous research highlights that among-individual differences in behavior, i.e., animal personality, are a key aspect of variation in "internal states" underlying movement and space use [11] with individuals varying consistently in how, where, and when they move [2,12]. Variation, particularly along the shy-bold continuum [13,14], is suggested to affect crucial ecological processes, e.g., predation rates [15] or population structure [12,16], and to generate spatio-temporal variability that influences individuals' interactions with biotic and abiotic factors [5,[17][18][19][20]. For example, boldness and exploration have been shown to correlate with variation in foraging patterns [21,22] or habitat use [2,23]. ...
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Background Animal personality has emerged as a key concept in behavioral ecology. While many studies have demonstrated the influence of personality traits on behavioral patterns, its quantification, especially in wild animal populations, remains a challenge. Only a few studies have established a link between personality and recurring movements within home ranges, although these small-scale movements are of key importance for identifying ecological interactions and forming individual niches. In this regard, differences in space use among individuals might reflect different exploration styles between behavioral types along the shy-bold continuum. Methods We assessed among-individual differences in behavior in the European hare (Lepus europaeus), a characteristic mammalian herbivore in agricultural landscapes using a standardized box emergence test for captive and wild hares. We determined an individuals’ degree of boldness by measuring the latencies of behavioral responses in repeated emergence tests in captivity. During capture events of wild hares, we conducted a single emergence test and recorded behavioral responses proven to be stable over time in captive hares. Applying repeated novel environment tests in a near-natural enclosure, we further quantified aspects of exploration and activity in captive hares. Finally, we investigated whether and how this among-individual behavioral variation is related to general activity and space use in a wild hare population. Wild and captive hares were treated similarly and GPS-collared with internal accelerometers prior to release to the wild or the outdoor enclosure, respectively. General activity was quantified as overall dynamic body acceleration (ODBA) obtained from accelerometers. Finally, we tested whether boldness explained variation in (i) ODBA in both settings and (ii) variation in home ranges and core areas across different time scales of GPS-collared hares in a wild population. Results We found three behavioral responses to be consistent over time in captive hares. ODBA was positively related to boldness (i.e., short latencies to make first contact with the new environment) in both captive and wild hares. Space use in wild hares also varied with boldness, with shy individuals having smaller core areas and larger home ranges than bold conspecifics (yet in some of the parameter space, this association was just marginally significant). Conclusions Against our prediction, shy individuals occupied relatively large home ranges but with small core areas. We suggest that this space use pattern is due to them avoiding risky, and energy-demanding competition for valuable resources. Carefully validated, activity measurements (ODBA) from accelerometers provide a valuable tool to quantify aspects of animal personality along the shy-bold continuum remotely. Without directly observing—and possibly disturbing—focal individuals, this approach allows measuring variability in animal personality, especially in species that are difficult to assess with experiments. Considering that accelerometers are often already built into GPS units, we recommend activating them at least during the initial days of tracking to estimate individual variation in general activity and, if possible, match them with a simple novelty experiment. Furthermore, information on individual behavioral types will help to facilitate mechanistic understanding of processes that drive spatial and ecological dynamics in heterogeneous landscapes.
... The remaining subset of the population (~14%, avoiders) selected to limit themselves to smaller areas that are closed to the public. This reflects what is widely accepted in random capture studies, that is, that we are less likely to trap, or in this case observe, the shy-inactive individuals present in any population due to their careful avoidance of humans (Biro & Dingemanse, 2009;Leclerc et al., 2017Leclerc et al., , 2019Wilson et al., 1994). Notably, the proportions of different begging behaviours seen within this deer population are reflected in similar proportions in other populations relating to different foraging techniques, such as in the classical examples of producers and scroungers in pigeons and zebra finches (David et al., 2011;Giraldeau & Lefebvre, 1986). ...
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The artificial selection of traits in wildlife populations through hunting and fishing has been well documented. However, despite their rising popularity, the role that artificial selection may play in non‐extractive wildlife activities, for example, recreational feeding activities, remains unknown. If only a subset of a population takes advantage of human‐wildlife feeding interactions, and if this results in different fitness advantages for these individuals, then artificial selection may be at work. We have tested this hypothesis using a wild fallow deer population living at the edge of a capital city as our model population. In contrast to previous assumptions on the randomness of human‐wildlife feeding interactions, we found that a limited non‐random portion of an entire population is continuously engaging with people. We found that the willingness to beg for food from humans exists on a continuum of inter‐individual repeatable behaviour; which ranges from risk‐taking individuals repeatedly seeking and obtaining food, to shyer individuals avoiding human contact and not receiving food at all, despite all individuals having received equal exposure to human presence from birth and coexisting in the same herds together. Bolder individuals obtain significantly more food directly from humans, resulting in early interception of food offerings and preventing other individuals from obtaining supplemental feeding. Those females that beg consistently also produce significantly heavier fawns (300–500 g heavier), which may provide their offspring with a survival advantage. This indicates that these interactions result in disparity in diet and nutrition across the population, impacting associated physiology and reproduction, and may result in artificial selection of the begging behavioural trait. This is the first time that this consistent variation in behaviour and its potential link to artificial selection has been identified in a wildlife population and reveals new potential effects of human‐wildlife feeding interactions in other species across both terrestrial and aquatic habitats. Human‐wildlife feeding interactions are increasingly popular, yet the role that they may play in the artificial selection of behavioural traits in wildlife populations remains unexplored. This work begins to unravel the complex dynamics and impacts of these interactions, opening up new dimensions for human‐wildlife studies.
... In terrestrial systems, evidence of harvest-induced evolution includes two studies of plant collections (Law and Salic 2005;Niu et al. 2021) and a few long-term studies or harvest records of large mammals (Kuparinen and Festa-Bianchet 2017;Leclerc et al. 2017). Evidence of harvest-induced evolutionary changes in life-history traits is limited (Gamelon et al. 2011;Zedrosser et al. 2011;Kvalnes et al. 2016). ...
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Trophy hunting can affect weapon size of wild animals through both demographic and evolutionary changes. In bighorn sheep (Ovis canadensis Shaw, 1804), intense harvest of young males with fast-growing horns may have partly driven long-term decreases in horn size. These selective effects could be dampened if migrants from protected areas, not subject to artificial selection, survived and reproduced within hunted populations. Bighorn rams undertake long-distance breeding migrations in the weeks preceding the late-November rut. We analysed records of >7 800 trophy bighorn rams shot from 1974 to 2019 in Alberta, Canada, to test the hypothesis that high harvest pressure during breeding migrations was correlated with a greater decrease in horn size. We compared areas with and without a pronounced harvest peak in late October, when male breeding migrations begin. Areas without a pronounced harvest peak in late October, that likely experienced a lower harvest rate, showed a similar temporal decline in horn size, but no increase in age at harvest suggesting a possibly weaker decline in horn growth. Our study suggests that unselected immigrants from protected areas could partly buffer the effects of intense trophy hunting only if harvest pressure was reduced when breeding migrations commence.
... For one thing, population resistance to environmental perturbations and implications of harvesting depend on the species' life-history strategy. Moreover, density-independent stochastic mechanisms (Lande et al., 2003;May et al., 1978), as well as ecological and evolutionary consequences of selective harvesting (Anderson et al., 2008;Leclerc et al., 2017;Pigeon et al., 2016), can make populations more sensitive to temporal variation in the environment . Population resistance to environmental perturbations also depends on the harvesting strategy (Beddington & May, 1977;Lande et al., 1995) and stochasticity in harvesting processes (Jonzén et al., 2002), sometimes causing lagged responses in effort and quota regulations to resource fluctuations (Fryxell et al., 2010). ...
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Harvesting can magnify the destabilising effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population‐dynamic theory predicts that impacts of harvesting depend on the type and strength of density‐dependent regulation. Here, we used logistic population growth models and an empirical reindeer case study to show that low to moderate harvesting can actually buffer populations against environmental perturbations. This occurs because of density‐dependent environmental stochasticity, where negative environmental impacts on vital rates are amplified at high population density due to intra‐specific resource competition. Simulations from our population models show that even low levels of harvesting may prevent overabundance, thereby dampening population fluctuations and reducing the risk of population collapse and quasi‐extinction following environmental perturbations. Thus, depending on the species' life history and the strength of density‐dependent environmental drivers, low to moderate harvesting can improve population resistance to increased climate variability and extreme weather expected under global warming. Both theoretical and empirical evidence across taxa now indicate that population dynamics are often characterised by density‐dependent effects of environmental stochasticity. For the first time, we provide evidence that harvesting can buffer such climate‐density interactions, leading to stabilised population fluctuations and reducing the danger of collapsing due to environmental perturbations.
... These factors may impact several phenotypic components, such as morphological, behavioral, physiological, and life-history traits (cf. Coltman et al., 2003;Isaac, 2009;Leclerc et al., 2017). ...
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Investigating the impact of ecological factors on sex-and age-specific vital rates is essential to understand animal population dynamics and detect the potential for interactions between sympatric species. We used block count data and autoregressive linear models to investigate variation in birth rate, kid survival, female survival, and male survival in a population of Alpine chamois Rupicapra rupicapra rupicapra monitored over 27 years within the Stelvio National Park, Central Italian Alps, as function of climatic variables, density dependence, and interspecific competition with red deer Cervus elaphus. We also used path analysis to assess the indirect effect of deer abundance on chamois growth rate mediated by each demographic parameter. Based on previous findings, we predicted that birth rate at [t] would negatively relate to red deer abundance at year [t−1]; survival rates between [t] and [t+1] would negatively relate to red deer abundance at year [t−1] and to the interactive effect of winter precipitation at [t+1] and chamois density at [t]. Our results showed that birth rate was positively related to spring-summer precipitation in the previous year, but this effect was hampered by increasing red deer abundance. Kid and female survival rates were negatively related to the combined effect of chamois abundance and winter precipitation. Male and female survival rates were negatively related to lagged red deer abundance. The path analysis supported a negative indirect effect of red deer abundance on chamois growth rate mediated by birth rate and female survival. Our results suggest that chamois population dynamics was largely explained by the synergistic effect of density dependence and winter harshness, as well as by interspecific competition with red deer, whose effects were seemingly stronger on the kid-female segment of the population.
... Because of this, human harvest has emerged as an important driver of trait change in the wild (Darimont et al., 2009;Palumbi, 2001), inducing selective pressures that vary both in strength and in direction, depending on harvest levels and practices, as well as on the phenotypes being targeted (Darimont et al., 2015). Harvestinduced selection on life-history, morphological, and behavioral traits has been documented in both fishery and hunting systems (Allendorf & Hard, 2009;Boyce, 1981;Leclerc et al., 2017;Palkovacs et al., 2018;Van de Walle et al., 2018). ...
Article
Full-text available
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 non‐protected 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.
... Natural predation is not the only force that selects behavioural traits in the natural populations (Leclerc et al. 2017). Effectively, human harvesting exceeds natural predation in magnitude in harvested wild populations (Darimont et al. 2009) and may conflict with natural selection resulting in increase of unnatural phenotypes (Allendorf and Hard 2009). ...
... This artificial survival gain through longer maternal care could explain why, in parallel with the increasing hunting pressure, the duration of maternal care has increased over the last ~30 years in the South ( Van de Walle et al., 2018). It is also in line with the growing evidence of human activities, for example, overexploitation, as the most important agent of trait change in wild populations (Darimont et al., 2009;Law, 2000;Leclerc et al., 2017), with hunting-induced changes in life-history traits, through its regulation or selectivity, being well-documented in game hunting species (Festa-Bianchet, 2003;Mysterud, 2011). ...
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The duration of maternal care, an important life history trait affecting population dynamics, varies greatly within species. Yet, our understanding of its predictors is limited, mostly correlative, and subject to misinterpretations, due to difficulties to disentangle the role of maternal‐ and offspring‐related characteristics. We conducted path analysis on a dataset including 217 brown bear litters captured over a 29‐year period in two populations in Sweden (“North” and “South”) facing contrasting environmental conditions to identify and quantify the causes of variation in the duration of maternal care (1.5 years or 2.5 years). We showed that the causal determinants of the duration of maternal care were context dependent. Contrary to their expected central role in the determination of the duration of maternal care, yearling mass and its direct determinants (i.e., litter size and maternal mass) were only important in the North population, where environmental conditions are harsher and the cost of extended maternal care presumably higher. In the South, the duration of maternal care was not caused by yearling mass nor any maternal or litter characteristics. Extension of maternal care may thus result from factors independent from maternal and offspring condition in the South, such as an artificial hunting‐induced selection for longer maternal care through the legal protection of family groups. Our results provide an important contribution to our very limited knowledge of the direct and indirect determinants of the duration of maternal care and highlight the importance of accounting for the environmental context when assessing maternal reproductive tactics.
Preprint
Harvesting can magnify the destabilizing effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population-dynamic theory predicts that impacts of harvesting depend on the type and strength of density-dependent regulation. Here, we used logistic population growth models and an empirical reindeer case study to show that low to moderate harvesting can actually buffer populations against environmental perturbations. This occurs because of density-dependent environmental stochasticity, where negative environmental impacts on vital rates are amplified at high population density due to intraspecific resource competition. Simulations from our population models show that even low levels of harvesting may prevent overabundance, thereby dampening population fluctuations and reducing the risk of population collapse and quasi-extinction following environmental perturbations. Thus, depending on the species' life history and the strength of density-dependent environmental drivers, low to moderate harvesting can improve population resistance to increased climate variability and extreme weather expected under global warming.
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Consistent individual differences (CIDs) in behavior are of interest to both basic and applied research, because any selection acting on them could induce evolution of animal behavior. It has been suggested that CIDs in the behavior of fish might explain individual differences in vulnerability to fishing. If so, fishing could impose selection on fish behavior. In this study, we assessed boldness-indicating behaviors of Eurasian perch Perca fluviatilis using individually conducted experiments measuring the time taken to explore a novel arena containing predator (burbot, Lota lota) cues. We studied if individual differences in boldness would explain vulnerability of individually tagged perch to experimental angling in outdoor ponds, or if fishing would impose selection on boldness-indicating behavior. Perch expressed repeatable individual differences in boldness-indicating behavior but the individual boldness-score (the first principal component) obtained using principal component analysis combining all the measured behavioral responses did not explain vulnerability to experimental angling. Instead, large body size appeared as the only statistically significant predictor of capture probability. Our results suggest that angling is selective for large size, but not always selective for high boldness.
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The potential for selective harvests to induce rapid evolutionary change is an important question for conservation and evolutionary biology, with numerous biological, social and economic implications. We analyze 39 years of phenotypic data on horn size in bighorn sheep (Ovis canadensis) subject to intense trophy hunting for 23 years, after which harvests nearly ceased. Our analyses revealed a significant decline in genetic value for horn length of rams, consistent with an evolutionary response to artificial selection on this trait. The probability that the observed change in male horn length was due solely to drift is 9.9%. Female horn length and male horn base, traits genetically correlated to the trait under selection, showed weak declining trends. There was no temporal trend in genetic value for female horn base circumference, a trait not directly targeted by selective hunting and not genetically correlated with male horn length. The decline in genetic value for male horn length stopped, but was not reversed, when hunting pressure was drastically reduced. Our analysis provides support for the contention that selective hunting led to a reduction in horn length through evolutionary change. It also confirms that after artificial selection stops, recovery through natural selection is slow. This article is protected by copyright. All rights reserved.
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Recently, there has been growing recognition that fish harvesting practices can have important impacts on the phenotypic distributions and diversity of natural populations through a phenomenon known as fisheries-induced evolution. Here we experimentally show that two common recreational angling techniques (active crank baits versus passive soft plastics) differentially target wild largemouth bass (Micropterus salmoides) and rock bass (Ambloplites rupestris) based on variation in their behavioural tendencies. Fish were first angled in the wild using both techniques and then brought back to the laboratory and tested for individual level differences in common estimates of personality (refuge emergence, flight-initiation-distance, latency-to-recapture and with a net, and general activity) in an in-lake experimental arena. We found that different angling techniques appear to selectively target these species based on their boldness (as characterized by refuge emergence, a standard measure of boldness in fishes) but not other assays of personality. We also observed that body size was independently a significant predictor of personality in both species, though this varied between traits and species. Our results suggest a context-dependency for vulnerability to capture relative to behaviour in these fish species. Ascertaining the selective pressures angling practices exert on natural populations is an important area of fisheries research with significant implications for ecology, evolution, and resource management.
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The harvest of animals by humans may constitute one of the strongest evolutionary forces affecting wild populations. Vulnerability to harvest varies among individuals within species according to behavioural phenotypes, but we lack fundamental information regarding the physiological mechanisms underlying harvest-induced selection. It is unknown, for example, what physiological traits make some individual fish more susceptible to capture by commercial fisheries. Active fishing methods such as trawling pursue fish during harvest attempts, causing fish to use both aerobic steady-state swimming and anaerobic burst-type swimming to evade capture. Using simulated trawling procedures with schools of wild minnows Phoxinus phoxinus, we investigate two key questions to the study of fisheries-induced evolution that have been impossible to address using large-scale trawls: (i) are some individuals within a fish shoal consistently more susceptible to capture by trawling than others?; and (ii) if so, is this related to individual differences in swimming performance and metabolism? Results provide the first evidence of repeatable variation in susceptibility to trawling that is strongly related to anaerobic capacity and swimming ability. Maximum aerobic swim speed was also negatively correlated with vulnerability to trawling. Standard metabolic rate was highest among fish that were least vulnerable to trawling, but this relationship probably arose through correlations with anaerobic capacity. These results indicate that vulnerability to trawling is linked to anaerobic swimming performance and metabolic demand, drawing parallels with factors influencing susceptibility to natural predators. Selection on these traits by fisheries could induce shifts in the fundamental physiological makeup and function of descendent populations. © 2015 The Authors.
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Geffroy et al. [1] proposed that nature-based tourism reduces the fearfulness and antipredator behavior of animals, leading towards a boldness syndrome that elevates natural predation rates and could trigger cascading effects on populations and communities. We agree with the framework, hypotheses, and future research needs proposed in [1], but they apply strictly to nonthreatening human–wildlife interactions. However, nature-based tourism is often consumptive, where wild-living animals are chased, stressed, and eventually harvested in activities such as recreational fishing and hunting.
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Increased mortality from fishing is expected to favor faster life histories, realized through earlier maturation, increased reproductive investment, and reduced postmaturation growth. There is also direct and indirect selection on behavioral traits. Molecular genetic methods have so far contributed minimally to understanding such fisheries-induced evolution (FIE), but a large body of literature studying evolution using phenotypic methods has suggested that FIE in life-history traits, in particular maturation traits, is commonplace in exploited fish populations. Although no phenotypic study in the wild can individually provide conclusive evidence for FIE, the observed common pattern suggests a common explanation, strengthening the case for FIE. This interpretation is supported by theoretical and experimental studies. Evidence for FIE of behavioral traits is limited from the wild, but strong from experimental studies. We suggest that such evolution is also common, but has so far been overlooked.
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Animal personalities, i.e. consistent individual differences in behaviour, are currently of high interest among behavioural and evolutionary biologists. The topic has received increasing attention also in fisheries science because selective harvesting of certain behavioural types might impose fishing-induced selection on personality. Here, we ice-fished wild Eurasian perch (Perca fluviatilis) from three native populations and investigated whether differences in relative catchability would explain behavioural differences observed in experimental conditions. We inferred relative catchability differences indirectly by fishing each location first with generally inefficient artificial bait and then by more efficient natural bait. The captured, individually tagged fish were tested in groups for their exploration tendency, activity and boldness under authentic predation risk in semi-natural stream channels. Fish that were easily captured first with artificial bait expressed fast exploration and acute activity, whereas the fish captured with natural bait showed less active and explorative behaviour. Differences in relative catchability did not explain variation in boldness or body size. In conclusion, we found that (1) Eurasian perch differing in relative catchability differ in certain behavioural traits, (2) fast explorers are more common among fish that get easily caught compared to fish that are more difficult to catch, (3) relative catchability explains more behavioural variation in a novel environment than in a familiar one and (4) selectivity of recreational angling on fish behaviour may depend on applied angling method and the effort spent on each location.
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Size-selective harvesting is assumed to alter life histories of exploited fish populations, thereby negatively affecting population productivity, recovery, and yield. However, demonstrating that fisheries-induced phenotypic changes in the wild are at least partly genetically determined has proved notoriously difficult. Moreover, the population-level consequences of fisheries-induced evolution are still being controversially discussed. Using an experimental approach, we found that five generations of size-selective harvesting altered the life histories and behavior, but not the metabolic rate, of wild-origin zebrafish (Danio rerio). Fish adapted to high fishing pressure invested more in reproduction, reached a smaller adult body size, and were less explorative and bold. Phenotypic changes seemed subtle but accompanied by genetic changes in functional loci. Thus, our results provided unambiguous evidence for rapid, harvest-induced phenotypic and evolutionary change when harvesting is intensive and size-selective. According to a life-history model, the observed life-history changes elevated population growth rate in harvested conditions, but slowed population recovery under a simulated moratorium. Hence, the evolutionary legacy of size-selective harvesting include populations that are productive under exploited conditions, but selectively disadvantaged to cope with natural selection pressures that often favor large body size.This article is protected by copyright. All rights reserved.