Kaj Hulthén

Kaj Hulthén
Lund University | LU · Department of Biology

PhD

About

38
Publications
30,209
Reads
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1,230
Citations
Citations since 2017
25 Research Items
908 Citations
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2017201820192020202120222023050100150200
2017201820192020202120222023050100150200

Publications

Publications (38)
Article
Full-text available
Most animals are visually oriented, and their eyes provide their “window to the world”. Eye size correlates positively with visual performance, because larger eyes can house larger pupils that increase photon catch and contrast discrimination, particularly under dim light, which have positive effects on behaviours that enhance fitness, including pr...
Article
Full-text available
Predation risk and resource availability are two primary factors predicted by theory to drive the evolution of life histories. Yet, disentangling their roles in life-history evolution in the wild is challenging because (1) the two factors often co-vary across environments, and (2) environmental effects on phenotypes can mask patterns of genotypic e...
Article
Full-text available
Predator-inducible defenses constitute a widespread form of adaptive phenotypic plasticity, and such defenses have recently been suggested linked with the neuroen- docrine system. The neuroendocrine system is a target of endocrine disruptors, such as psychoactive pharmaceuticals, which are common aquatic contaminants. We hy- pothesized that exposur...
Article
Animal migration is one of the most spectacular and visible behavioural phenomena in nature with profound implications for a range of ecological and evolutionary processes. Successful migration hinges on the ability to exploit temporary resources (e.g. food) and evade threats (e.g. predators) as they arise, and thus the timing of migration is often...
Article
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Inducible defences allow prey to increase survival chances when predators are present while avoiding unnecessary costs in their absence. Many studies report considerable inter-individual variation in inducible defence expression, yet what underlies this variation is poorly understood. A classic vertebrate example of a predator-induced morphological...
Article
Piscivorous fish are important predators in aquatic systems and as such they can have far-reaching effects on ecosystem composition and function. These effects depend on piscivore predation rates and behaviour, and recruitment of young-of-the-year fish into piscivory can hereby govern ecosystem properties. Growth and recruitment can differ between...
Article
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The propensity to kill and consume conspecifics (cannibalism) varies greatly between and within species, but the underlying mechanisms behind this variation remain poorly understood. A rich literature has documented that consistent behavioural variation is ubiquitous across the animal kingdom. Such inter-individual behavioural differences, sometime...
Article
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Diel vertical migration (DVM) is the most common behavioral phenomenon in zooplankton, and numerous studies have evaluated DVM under strong seasonality at higher latitudes. Yet, our understanding of the environmental drivers of DVM at low latitudes, where seasonal variation is less pronounced, remains limited. Therefore, we here examined patterns o...
Article
Hemispheric brain lateralization can drive the expression of behavioral asymmetry, or laterality, which varies notably both within and among species. To explain these left–right behavioral asymmetries in animals, predator-mediated selection is often invoked. Recent studies have revealed that a relatively high degree of lateralization correlates pos...
Article
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Predation risk is often invoked to explain variation in stress responses. Yet, the answers to several key questions remain elusive, including: 1) how predation risk influences the evolution of stress phenotypes, 2) the relative importance of environmental versus genetic factors in stress reactivity, and 3) sexual dimorphism in stress physiology. To...
Article
1. Evolutionary ecology aims to better understand how ecologically important traits respond to environmental heterogeneity. Environments vary both naturally and as a result of human activities, and investigations that simultaneously consider how natural and human‐induced environmental variation affect diverse trait types grow increasingly important...
Article
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Predation is a well‐studied driver of ecological selection on prey traits, which frequently drives divergence in anti‐predator performance across environments that vary in predation risk. However, predation also alters prey mortality regimes, where low predation risk often results in higher prey densities and consequently higher intensities of intr...
Article
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While lake systems in temperate regions have been extensively studied, tropical and subtropical systems have received less attention. Here, we describe the water chemistry and biota of ten inland blue holes on Andros Island, The Bahamas, representative of the morphological, abiotic, and biotic variation among Androsian inland blue holes. The majori...
Article
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Different migratory species have evolved distinct migratory characteristics that improve fitness in their particular ecological niches. However, when such species hybridize, migratory traits from parental species can combine maladaptively and cause hybrids to fall between parental fitness peaks, with potential consequences for hybrid viability and...
Article
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Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with...
Article
PIT‐tagging is commonly used in behavioural studies of fish, although long‐term evaluations of effects from tagging under natural conditions are scarce. We PIT‐tagged common bream Abramis brama, European perch Perca fluviatilis, pike Esox lucius and roach Rutilus rutilus, released them in their lakes of origin and recaptured them after 103–3269 day...
Article
Most animals constitute potential prey and must respond appropriately to predator-mediated stress in order to survive. Numerous prey also adaptively tailor their response to the prevailing level of risk and stress imposed by their natural enemies, i.e. they adopt an inducible defence strategy. Predator exposure may activate the stress axis, and dri...
Article
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Crustacean copepods in high-latitude lakes frequently alter their pigmentation facultatively to defend themselves against prevailing threats, such as solar ultraviolet radiation (UVR) and visually oriented predators. Strong seasonality in those environments promotes phenotypic plasticity. To date, no one has investigated whether low-latitude copepo...
Article
Numerous species adopt inducible defence strategies; that is, they have phenotypically plastic traits that decrease the risk of capture and consumption by potential predators. The benefits of expressing alternative phenotypes in high‐ vs. low‐risk environments are well documented. However, inducible anti‐predator traits are also expected to incur c...
Article
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Fishery‐dependent communities in coastal environments are often vulnerable to hurricanes, but diverse and accessible fisheries may buffer effects of extreme storms and promote community resilience. We began evaluating this possibility with a qualitative study in the Lowe Sound and Red Bays communities in The Bahamas immediately after the impact of...
Article
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Removal of cyprinid fish is a widely used biomanipulation tool to transform turbid shallow eutrophic lakes in north temperate regions into a clear water state. We here evaluate the removal of cyprinids from streams as a supplement to lake fishing. Since cyprinids often aggregate in high densities in lake inlet/outlet streams during winter migration...
Article
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Individual variation in the behavior of prey can influence predation risk in complex ways. We ran individual roach (Rutilus rutilus), a common freshwater fish, through a standard refuge emergence protocol to characterize their boldness, a key animal personality trait. We then paired a bold and a shy roach and exposed the pair to one of two predator...
Article
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Studies of predator-mediated selection on behaviour are critical for our understanding of the evolution and maintenance of behavioural diversity in natural populations. Consistent individual differences in prey behaviour, especially in the propensity to take risks (“boldness”), are widespread in the animal kingdom. Theory predicts that individual b...
Article
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Species integrity can be challenged, and even eroded, if closely related species can hybridize and produce fertile offspring of comparable fitness to that of parental species. The maintenance of newly diverged or closely related species therefore hinges on the establishment and effectiveness of pre-and/or post-zygotic reproductive barriers. Ecologi...
Article
Patterns of animal migration often vary dramatically within species. Understanding the mechanisms, which shape this variation, is important due to the powerful impacts migratory species can have upon ecosystem processes. Migratory timing is thought to be especially critical for survival and reproductive success and variance in migratory timing has...
Article
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Although migratory plasticity is increasingly documented, the ecological drivers of plasticity are not well understood. Predation risk can influence migratory dynamics, but whether seasonal migrants can adjust their migratory behaviour according to perceived risk is unknown. We used electronic tags to record the migration of individual roach (Rutil...
Article
Full-text available
1.Migration is a widespread phenomenon, with powerful ecological and evolutionary consequences. Morphological adaptations to reduce the energetic costs associated with migratory transport are commonly documented for migratory species. However few studies have investigated whether variation in body morphology can be explained by variation in migrato...
Article
Full-text available
Organisms display an impressive array of defence strategies in nature. Inducible defences (changes in morphology and/or behaviour within a prey's lifetime) allow prey to decrease vulnerability to predators and avoid unnecessary costs of expression. Many studies report considerable interindividual variation in the degree to which inducible defences...
Article
Full-text available
This study evaluated a technique to allow the long-term monitoring of individual fishes of known sex in the wild using sex confirmation in close proximity to the reproductive period combined with individual tagging. Hundreds of partially migratory roach Rutilus rutilus were tagged with passive integrated transponders (PIT) following sex determinati...
Article
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Animal migration is an amazing phenomenon that has fascinated humans for long. Many freshwater fishes also show remarkable migrations, whereof the spectacular mass migrations of salmonids from the spawning streams are the most well known and well studied. However, recent studies have shown that migration occurs in a range of freshwater fish taxa fr...
Article
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In the present study, we aim at relating Forbes’ remarkable paper on “The lake as a microcosm”, published 125 years ago, to the present status of knowledge in our own research group. Hence, we relate the observations Forbes made to our own microcosm, Lake Krankesjön in southern Sweden, that has been intensively studied by several research groups fo...
Article
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Migration has evolved as a strategy to maximise individual fitness in response to seasonally changing ecological and environmental conditions. However, migration can also incur costs, and quantifying these costs can provide important clues to the ultimate ecological forces that underpin migratory behaviour. A key emerging model to explain migration...
Article
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The importance of predation risk in shaping patterns of animal migration is not well studied, mostly owing to difficulties in accurately quantifying predation risk for migratory versus resident individuals. Here, we present data from an extensive field study, which shows that migration in a freshwater fish (roach, Rutilus rutilus) that commonly mig...
Article
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Partial migration, where only some individuals from a population migrate, has been widely reported in a diverse range of animals. In this paper, what is known about the causes and consequences of partial migration in fishes is reviewed. Firstly, the ultimate and proximate drivers of partial migration are reflected upon: what ecological factors can...
Article
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Partial migration, where populations are composed of both migratory and resident individuals, is extremely widespread across the animal kingdom. Researchers studying fish movements have long recognized that many fishes are partial migrants, however, no detailed taxonomic review has ever been published. In addition, previous work and synthesis has b...
Article
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Ecology Letters (2011) 14: 871–876 Partial migration, whereby only a fraction of the population migrates, is thought to be the most common type of migration in the animal kingdom, and can have important ecological and evolutionary consequences. Despite this, the factors that influence which individuals migrate and which remain resident are poorly u...

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