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Harvesting as a potential selective pressure on behavioural traits

February 2017
Journal of Applied Ecology 54(6)

DOI:10.1111/1365-2664.12893

Authors:

Martin Leclerc

University of Québec in Chicoutimi

Andreas Zedrosser

University of South-Eastern Norway

Fanie Pelletier

Université de Sherbrooke

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. We report empirical studies that examined whether harvesting can exert selective pressures on behavioural traits. We show that harvest‐induced selection on behavioural traits is not specific to a particular harvest method and can occur throughout the animal kingdom. 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.

. Examples of experimental and observational studies showing that harvest can act as a selective pressure on behaviour

…

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COMMENTARY

Harvesting as a potential selective pressure on

behavioural traits

Martin Leclerc*

, Andreas Zedrosser

2,3

and Fanie Pelletier

Canada Research Chair in Evolutionary Demography and Conservation & Centre for Northern Studies, D 

epartement

de biologie, Universit

e de Sherbrooke, Sherbrooke, QC J1K2R1, Canada;

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

Department of Integrative Biology, Institute of Wildlife Biology and

Game Management, University of Natural Resources and Applied Life Sciences, Vienna, Gregor Mendel Str. 33,

A–1180 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

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

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).

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 Bold–Shy Bolder Diaz Pauli et al. (2015)

Trawl Bold–Shy 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/Shy–Fast/Slow Faster-bolder Biro & Post (2008)

Cherax destructor Trap Bold–Shy 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 Bold–Shy 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)

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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e Villard

Behavioural harvest-induced selection 1945

The Harvest Effect on Dynamics of Northern Fur Seal Population: Mathematical Modeling and Data Analysis Results

Article

Full-text available

Aug 2022

We examine population trends in light of male harvest data considering the long-time series of population data on northern fur seals at Tyuleniy Island. To answer the question has the way males were harvested influenced the population trajectory, we analyzed the visual harem size and birth rate dynamics of the population, as well as the strategy and intensity of the harvest. We analyzed the dynamics of the sex ratio in the early (1958–1988) period to estimate parameters in the late period (1989–2013) based on the observed number of bulls and pups, while utilizing the distribution of reproductive rates obtained from pelagic sealing. Using a matrix population model for the observed part of the population (i.e., the male population), we analyzed the population growth rate associated with changes in both birth and survival rates considering the stochastic effects. Observations allow us to reject the hypothesis of nonselective harvest. Among the variety of natural and anthropogenic factors that could contribute to the decrease in the birth rate in the population, the effect of selective harvesting seems to be the most realistic.

Behavioral Ecology Size-selective harvesting impacts learning and decision-making in zebrafish, Danio rerio

Article

Full-text available

May 2023

Size-selective harvesting common to fisheries is known to evolutionarily alter life history and behavioral traits in exploited fish populations. Changes in these traits may, in turn, modify learning and decision-making abilities through energetic trade-offs with brain investment that can vary across development or via correlations with personality traits. We examined the hypothesis of size-selection induced alteration of learning performance in three selection lines of zebrafish (Danio rerio) generated through intensive harvesting for large, small and random body-size for five generations followed by no further selection for ten generations that allowed examining evolutionarily fixed outcomes. We tested associative learning ability throughout ontogeny in fish groups using a color-discrimination paradigm with a food reward, and the propensity to make group decisions in an associative task. All selection lines showed significant associative abilities that improved across ontogeny. The large-harvested line fish showed a significantly slower associative learning speed as subadults and adults than the controls. We found no evidence of memory decay as a function of size-selection. Decision-making speed did not vary across lines, but the large-harvested line made faster decisions during the probe trial. Collectively, our results show that large size-selective harvesting evolutionarily alters associative and decision-making abilities in zebrafish, which could affect resource acquisition and survival in exploited fish populations.

Landscape of fear or landscape of food? Moose hunting triggers an antipredator response in brown bears

Article

Mar 2023

Hunters can affect the behavior of wildlife by inducing a landscape of fear, selecting individuals with specific traits, or by altering resource availability across the landscape. Most research investigating the influence of hunting on wildlife resource selection has focused on target species and less attention has been devoted to non-target species, such as scavengers that can be both attracted or repelled by hunting activities. We used resource selection functions to identify areas where hunters were most likely to kill moose (Alces alces) in south-central Sweden during the fall. Then, we used step-selection functions to determine whether female brown bears (Ursus arctos) selected or avoided these areas and specific resources during the moose hunting season. We found that, during both day and nighttime, female brown bears avoided areas where hunters were more likely to kill moose. We found evidence that resource selection by brown bears varied substantially during the fall and that some behavioral changes were consistent with disturbance associated with moose hunters. Brown bears were more likely to select concealed locations in young (i.e., regenerating) and coniferous forests and areas further away from roads during the moose hunting season. Our results suggest that brown bears react to both spatial and temporal variations in apparent risk during the fall: moose hunters create a landscape of fear and trigger an antipredator response in a large carnivore even if bears are not specifically targeted during the moose hunting season. Such antipredator responses might lead to indirect habitat loss and lower foraging efficiency and the resulting consequences should be considered when planning hunting seasons.

Personality drives activity and space use in a mammalian herbivore

Article

Full-text available

Jan 2023

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.

Movement and habitat selection of a large carnivore in response to human infrastructure differs by life stage

Article

Full-text available

Nov 2022

Background: The movement extent of mammals is influenced by human-modified areas, which can affect population demographics. Understanding how human infrastructure influences movement at different life stages is important for wildlife management. This is true especially for large carnivores, due to their substantial space requirements and potential for conflict with humans. Methods: We investigated human impact on movement and habitat selection by GPS-collared male brown bears (Ursus arctos) in two life stages (residents and dispersers) in central Sweden. We identified dispersers visually based on their GPS locations and used hidden Markov models to delineate dispersal events. We used integrated step selection analysis (iSSA) to infer movement and habitat selection at a local scale (availability defined by hourly relocations), and resource selection functions (RSFs) to infer habitat selection at a landscape scale (availability defined by the study area extent). Results: Movement of residents on a local scale was facilitated by small forestry roads as they moved faster and selected areas closer to forestry roads, and they avoided areas closer to larger public roads and buildings on both scales. Dispersers were more ambivalent in their response to human infrastructure. Dispersers increased their speed closer to small forestry roads and larger public roads, did not exhibit selection for or against any road class, and avoided areas closer to buildings only at local scale. Dispersers did not select for any features on the landscape, which is likely explained by the novelty of the landscape or their naivety towards it. Conclusion: Our results show that movement in male brown bears is life stage-dependent and indicate that connectivity maps derived from movement data of dispersing animals may provide more numerous and more realistic pathways than those derived from resident animal data alone. This suggests that data from dispersing animals provide more realistic models for reconnecting populations and maintaining connectivity than if data were derived from resident animals alone.

Lead exposure in American black bears increases with age and big game harvest density

Article

Oct 2022

Hunting has multiple consequences for wildlife, and it can be an important source of environmental pollution. Most big game hunters use lead (Pb) ammunition that shed metal fragments in the tissues of harvested animals. These Pb fragments become available to scavengers when hunters discard contaminated slaughter remains in the environment. This exposure route has been extensively studied in avian scavengers, but few studies have investigated Pb exposure from ammunition in mammals. Mammalian scavengers, including American black bears (Ursus americanus), frequently use slaughter remains discarded by hunters. The objective of this study was to investigate whether big game harvest density influenced long-term Pb exposure in American black bears from Quebec, Canada. Our results showed that female black bears had higher tooth Pb concentrations in areas with higher big game harvest densities, but such relationship was not evident in males. We also showed that older bears had higher tooth Pb concentrations compared to younger ones. Overall, our study showed that Pb exposure increases with age in black bears from and that some of that Pb likely comes from bullet fragments embedded in slaughter remains discarded by hunters. These results suggest that hunters may drive mammalian scavengers into an evolutionary trap, whereby the long-term benefits of consuming slaughter remains could be negated due to increased Pb exposure.

Is hunting nonintentionally selective? A test using game bird capture-dead recoveries

Article

Full-text available

Sep 2022

Selective hunting has various impacts that need to be considered for the conservation and management of harvested populations. The consequences of selective harvest have mostly been studied in trophy hunting and fishing, where selection of specific phenotypes is intentional. Recent studies, however, show that selection can also occur unintentionally. With at least 52 million birds harvested each year in Europe, it is particularly relevant to evaluate the selectivity of hunting on this taxon. Here, we considered 211,806 individuals belonging to 7 hunted bird species to study unintentional selectivity in harvest. Using linear mixed models, we compared morphological traits (mass, wing, and tarsus size) and body condition at the time of banding between birds that were subsequently recovered from hunting during the same year as their banding, and birds that were not recovered. We did not find any patterns showing systematic differences between recovery categories, among our model species, for the traits we studied. Moreover, when a difference existed between recovery categories, it was so small that its biological relevance can be challenged. Hunting of birds in Europe therefore does not show any form of strong selectivity on the morphological and physiological traits that we studied and should hence not lead to any change of these traits either by plastic or by evolutionary response.

Personality drives activity and space use in a mammalian herbivore

Article

Full-text available

Aug 2022

Artificial selection in human‐wildlife feeding interactions

Article

Full-text available

Aug 2022

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.

Effects of hunting pressure and timing of harvest on bighorn sheep horn size

Article

Full-text available

Apr 2021

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.

Does boldness explain vulnerability to angling in Eurasian perch Perca fluviatilis ?

Article

Full-text available

Mar 2016

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.

Intense selective hunting leads to artificial evolution in horn size

Article

Full-text available

Jan 2016
EVOL APPL

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.

Does Angling Technique Selectively Target Fishes Based on Their Behavioural Type?

Article

Full-text available

Aug 2015
PLOS ONE

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.

Vulnerability of individual fish to capture by trawling is influenced by capacity for anaerobic metabolism

Article

Full-text available

Aug 2015
Proc Biol Sci

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.

On r- and K−selection

Article

E.R. Pianka

Consumptive Tourism Causes Timidity, Rather Than Boldness, Syndromes: A Response to Geffroy et al

Article

Dec 2015
TRENDS ECOL EVOL

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.

Fisheries-Induced Evolution

Article

Nov 2015
ANNU REV ECOL EVOL S

Beatriz Diaz Pauli

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.

Behavioural variation in Eurasian perch populations with respect to relative catchability

Article

Feb 2016
ACTA ETHOL

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.

The evolutionary legacy of size-selective harvesting extends from genes to populations

Article

Apr 2015
EVOL APPL

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.

R-Selection and K-Selection

Article