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Automated data collection methods, such as using GPS collars and animal-borne cameras, represent an efficient way of data collection and may be instrumental in the research of animal orientation, including magnetoreception. In this study, we designed a wearable dog action camera (DAC) system for hunting dogs consisting of a Garmin Virb Elite camera housed in the stainless mount attached to the dog harness. We evaluated the DAC’s reliability and potential to capture various behaviour, and we tested the effect of the DAC on the dog’s activity and well-being. We found no significant impact of the DAC on the dogs’ average speed. The tested system was reliable, efficient and safe for dogs. We recorded various behaviours connected to orientation, such as olfactory behaviour and head scanning, the latter described for the first time in domestic dogs. Furthermore, we observed other important behaviours such as hunting, exploration and comfort behaviour. Using wearable action cameras for studying domestic and free-roaming tame animals can bring new opportunities for future behavioural and sensory ecology research.

The knowledge about the mortality rate of offspring is crucial for estimating bird population dynamics and conserving species with declining populations. Parents of predatory birds provide food for their offspring during the post-fledging dependency period, which is frequently described as essential due to inexpert flying skills. Using radio telemetry, we studied fledglings’ probability of dying by starvation and predation in Tengmalms’ owls (Aegolius funereus). Nestlings (21 and 39) from 10 and 14 broods in 2019 and 2021, respectively, were equipped with leg-mounted tags and monitored throughout the post-fledging dependency period in west-central Finland. In total, 28 out of 60 fledglings did not survive the post-fledging dependency period (12 died due to starvation, and 16 were predated). The fledglings’ probability of dying by starvation and predation was 3.7 and 2.4 times higher, respectively, in the decreasing (2019) than during the increasing (2021) abundance of main foods (voles), showing that prey availability is essential for survival during the post-fledging dependency period. The probability of starvation increased with augmenting agricultural lands in the home range and increasing precipitation after fledging, which indicated that parent owls avoided hunting in open areas and during rainy nights. The predation rate during the post-fledging dependency period increased with augmenting cover of old-growth forests in the home range. This result suggested that coverage of old-growth forests is nowadays so small in the study area that they act as ecological traps for newly-fledged owlets. The reason is that the main avian enemies of Tengmalm’s owls’ (goshawks and Ural owls) also prefer old-growth forests for breeding and hunting.

Male infanticide has been reported in wide range of mammalian taxa however it remains very rare in even-toed ungulates where it was documented in two species only. Among six hypotheses explaining this phenomenon, the sexual selection hypothesis is supported by the largest evidence in mammals. Here, we report the first case of male infanticide in sika deer (Cervus nippon) which occurred at Ostrava Zoo. At the end of rutting season, new male had been joined with two pregnant females that successfully gave birth and reared offspring in his presence then. However, in the next season, the same male attacked and killed his own newborn female offspring. Since this male was separated from the herd for most of the time in the rut, we argue that he could be confused about paternity. Therefore, this case of infanticide might be driven by the same mechanism as that which is in line with the sexual selection hypothesis. In addition, based on our evidence we cannot reject the social pathology hypothesis as an alternative explanation.

Physical condition is important for the ability to resist various parasites and diseases as well as in escaping predators thus contributing to reproductive success, over-winter survival and possible declines in wildlife populations. However, in-depth research on trends in body condition is rare because decades-long datasets are not available for a majority of species. We analysed the long-term dataset of offspring covering 34 years, male parents (40 years) and female parents (42 years) to find out whether the decline of Tengmalm’s owl population in western Finland is attributable to either decreased adult and/or juvenile body condition in interaction with changing weather conditions and density estimates of main foods. We found that body condition of parent owl males and females declined throughout the 40-year study period whereas the body condition of owlets at the fledging stage very slightly increased. The body condition of parent owls increased with augmenting depth of snow cover in late winter (January to March), and that of offspring improved with increasing precipitation in late spring (May to June). We conclude that the decreasing trend of body condition of parent owl males and females is important factor probably inducing reduced adult survival and reduced reproduction success thus contributing to the long-term decline of the Tengmalm’s owl study population. The very slightly increasing trend of body condition of offspring is obviously not able to compensate the overall decline of Tengmalm’s owl population, because the number of offspring in turn simultaneously decreased considerably in the long-term. The ongoing climate change appeared to work in opposite ways in this case because declining depth of snow cover will make the situation worse but increased precipitation will improve. We suggest that the main reasons for long-term decline of body condition of parent owls are interactive or additive effects of reduced food resources and increased overall predation risk due to habitat degradation (loss and fragmentation of mature and old-growth forests due to clear-felling) subsequently leading to decline of Tengmalm’s owl study population.

The objective of the study was to investigate the effects of housing (deep litter + concrete floor vs. deep litter + ground soil with the possibility to dig burrows), and genotype (Mecklenburg or Hyplus) on aggressive behaviour, social contacts, does’ and kits’ injuries, and progeny mortality. Twelve groups of six rabbit does (n = 72) were assigned to four treatments (two housing systems and two genotypes). Aggressive behaviour of does, number of injuries on does and kits, and postnatal kit mortality were recorded. The effects of housing and genotype were tested using multivariate GLMM Models. We found that the housing treatment in interaction with the genotype had a significant effect on aggressive behaviours in group housed does (F3,12 = 14.34, p = 0.0003), where the lowest incidence of aggression was in Mecklenburg does housed on ground soil. Reduced aggression was reflected in a lower number of injuries in does (F3,68 = 10.51, p < 0.0001), number of injuries in kits, and kit mortality (F3,1 = 4.59, p < 0.0001, F3,54 = 43.94, p < 0.0001). The results indicate that the proper combination of genotype and housing should be carefully considered for breeding to reduce aggression and injury in group housed does.

It is well known that gibbons emit a pattern of vocalizations, which is specific for species and sex. A previous study showed, however, that immature southern yellow-cheeked gibbon (Nomascus gabriellae) males produce only female-like great calls from 2.3 to 5.3 years of age in co-singing interactions with their mothers. To date, nothing is known about how the vocal repertoire of a male changes from the female-like call (great call) to the male call (staccato notes and multi-modulation phrase) during vocal ontogeny. The goal of this study was to describe the transition from the female-like great call to the male call and the ontogeny of the male call. We predicted that the transition from the female-like great call to the male-specific call and the development of the male call is a normal part of the aging proces. If this is the case, the following phenomena will occur: (a) female vocalization should no longer be produced with the mature form of the multi-modulation phrase and (b) all stages of the male vocalization should occur gradually as the young male ages. Young males regularly emit both female-like great calls and male-specific calls between the ages of 5.6 to 7.1 years. Once the young males reached 7.1 years of age, they emitted male calls exclusively, and they continued to do so until the end of the observation period (at 8.11 years of age). It was confirmed that the young males emitted only female-like great calls during periods when they produced non-mature forms of a multi-modulation phrase (Fm0,1—none or one frequency modulation in second notes). Furhermore, the decrease in the number of female-like great calls was attributed to the development of the mature form of the multi-modulation phrase (Fm2—two or more frequency modulation in second notes), which developed with age. We also confirmed that the multi-modulation phrase developed gradually, while the development of the staccato notes occurred in leaps. A multi-modulation phrase developed as the initial part of the male-specific call. It was evolved from a simpler to a more complex form as the maximum frequency and age of the young males increased. Staccato notes subsequently developed in certain young males. Possible explanations for such vocal ontogeny in young males are discussed in this work.

Parents can enhance their fitness by favouring that sex whose reproductive value is expected to be highest. In species in which females are the larger sex with potentially greater fitness returns, one can assume that parents should bias their investment toward daughters to increase their daughters’ reproductive value (i.e. age-specific expectation of all present and future offspring) and, thereby, indirectly increase their own inclusive fitness. In the study reported here, we investigated sex allocation in Tengmalm’s Owl (Aegolius funereus), a bird species with a pronounced female-biased sexual size dimorphism in which females are larger than the males. Assuming that parental investment would have the greatest effect on the fitness of larger daughters, we hypothesized that daughters should be favoured in good conditions and sons in poor conditions. Our study was conducted in the Czech Republic over seven breeding seasons (2006–2012). In total, 205 nestlings from 52 nests were sexed. The mean nestling sex ratio, 48.5 ± 4.6% (± standard error), did not depart from parity, and we did not identify any variable to be related to it. However, we did find that at fledging (1) the body mass of female offspring was approximately 8% heavier than that of male offspring, and (2) surprisingly, the body mass of female offspring tended to increase with decreasing prey abundance in the autumn, i.e. prior to breeding. One possible explanation of this “carry-over effect” is that parents increased their investment toward daughters to maximize their daughters’ survival and reproductive value in a poor environment. This explanation could be supported by the sex-specific effect of the adult’s condition on reproductive success. Whereas the number of fledglings tended to increase with increasing age of the mother, it also increased with decreasing wing length of the father. These results indicate that in the Tengmalm’s Owl large body size may be mainly important for female reproduction, while male reproductive success is independent of body size or is even associated with small body size. To the best of our knowledge, our study is the first to have found such a positive, relatively long-lasting, sex-specific carry-over effect of pre-breeding prey abundance on the condition of female offspring in a bird of prey species.

To elucidate the role of domestication, we used the impossible task paradigm to test Czechoslovakian Wolfdogs with a known proportion of 'wolfblood' in their DNA and, as a control group for our subjects, we used German shepherd dogs. We hypothesized that the difference between wolves and domestic dogs is based on genetics and modified by obedience; if so, the looking back performance of the subject should be linked to its proportion of wolf-genes. To prove that, we observed 73 Czechoslovakian Wolfdogs, and 27 German shepherd dogs, and analysed their human-directed gazing behaviour during our test. Our apparatus consisted of a glass container placed upside down over a small amount of food. The test proceeded with three solvable trials, in which the subject could obtain the food by manipulating the container, followed by an unsolvable one in which the container was fixed onto the board. Our results suggest that there is no significant correlation between the probability of looking back in Czechoslovakian Wolfdogs and their proportion of 'wolf blood'. However, the probability of looking back was higher in German Shepherd dogs than in Czechoslovakian Wolfdogs (odds ratio = 9.1). German Shepherd dogs showed not only a higher frequency of looking back, but also the duration of their looks was longer.

It was shown earlier that dogs, when selecting between two dishes with snacks placed in front of them, left and right, prefer to turn either clockwise or counterclockwise or randomly in either direction. This preference (or non-preference) is individually consistent in all trials but it is biased in favor of north if they choose between dishes positioned north and east or north and west, a phenomenon denoted as “pull of the north”. Here, we replicated these experiments indoors, in magnetic coils, under natural magnetic field and under magnetic field shifted 90° clockwise. We demonstrate that "pull of the north" was present also in an environment without any outdoor cues and that the magnetic (and not topographic) north exerted the effect. The detailed analysis shows that the phenomenon involves also "repulsion of the south". The clockwise turning preference in the right-preferring dogs is more pronounced in the S-W combination, while the counterclockwise turning preference in the left-preferring dogs is pronounced in the S-E combination. In this way, south-placed dishes are less frequently chosen than would be expected, while the north-placed dishes are apparently more preferred. Turning preference did not correlate with the motoric paw laterality (Kong test). Given that the choice of a dish is visually guided, we postulate that the turning preference was determined by the dominant eye, so that a dominant right eye resulted in clockwise, and a dominant left eye in counterclockwise turning. Assuming further that magnetoreception in canines is based on the radical-pair mechanism, a "conflict of interests" may be expected, if the dominant eye guides turning away from north, yet the contralateral eye "sees the north", which generally acts attractive, provoking body alignment along the north-south axis.

Recent wildlife population declines are usually attributed to multiple sources such as global climate change and habitat loss and degradation inducing decreased food supply. However, interactive effects of fluctuations in abundance of main foods and weather conditions on population densities and reproductive success have been studied rarely. We analysed long-term (1973–2018) data on Tengmalm’s owl (Aegolius funereus) and the influence of prey abundance and weather on breeding densities and reproductive success in western Finland. We found that fledgling production per breeding attempt declined and laying date of the owl population delayed during the period between 1973 and 2018. The breeding density of the owl population decreased with increasing temperature in winter (October–March), fledgling production increased with increasing temperature and precipitation in spring (April–June), whereas the initiation of egg-laying was delayed with increasing depth of snow cover in late winter (January–March). The decreasing trend of fledgling production, which was mainly due to starvation of offspring, was an important factor contributing to the long-term decline of the Tengmalm’s owl study population. Milder and more humid spring and early summer temperatures due to global warming were not able to compensate for lowered offspring production of owls. The main reason for low productivity is probably loss and degradation of mature and old-growth forests due to clear-felling which results in loss of coverage of prime habitat for main (bank voles) and alternative foods (small birds) of owls inducing lack of food, and refuges against predators of Tengmalm’s owls. This interpretation was also supported by the delayed start of egg-laying during the study period although ambient temperatures increased prior to and during the egg-laying period.

Despite anecdotal reports of the astonishing homing abilities in dogs, their homing strategies are not fully understood. We equipped 27 hunting dogs with GPS collars and action cams, let them freely roam in forested areas, and analyzed components of homing in over 600 trials. When returning to the owner (homewards), dogs either followed their outbound track ('tracking') or used a novel route ('scouting'). The inbound track during scouting started mostly with a short (about 20 m) run along the north-south geomagnetic axis, irrespective of the actual direction homewards. Performing such a 'compass run' significantly increased homing efficiency. We propose that this run is instrumental for bringing the mental map into register with the magnetic compass and to establish the heading of the animal. European Social FundEuropean Social Fund (ESF) [EVA 4.0, CZ.02.1.01/0.0/0.0/16_019/0000803]; Ministry of Agriculture of the Czech RepublicMinistry of Agriculture, Czech Republic [MZE-RO0718]; Czech University of Life Sciences Prague CIGA CZU [20174319]; Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague IGA [B07/16]; Grant Agency of the Czech RepublicGrant Agency of the Czech Republic [15-21840S]; European Regional Development FundEuropean Union (EU) [EVA 4.0, CZ.02.1.01/0.0/0.0/16_019/0000803] European Social Fund Operational Programme Research, Development and Education, EVA 4.0 Hynek Burda; European Social Fund Operational Programme Research, Development and Education, CZ.02.1.01/0.0/0.0/16_019/0000803 Hynek Burda; Ministry of Agriculture of the Czech Republic MZE-RO0718 Ludek Bartos; Czech University of Life Sciences Prague CIGA CZU (Project No. 20174319) Hynek Burda; Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague IGA (Project No. B07/16) Hynek Burda; Grant Agency of the Czech Republic No. 15-21840S Hynek Burda; European Regional Development Fund Operational Programme Research, Development and Education, EVA 4.0 Hynek Burda; European Regional Development Fund Operational Programme Research, Development and Education, CZ.02.1.01/0.0/0.0/16_019/0000803 Hynek Burda; The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Many ungulate populations have a complex history of isolation and translocation. Consequently, ungulate populations may have experienced substantial reductions in the level of overall gene flow, yet simultaneously have augmented levels of long-distance gene flow. To investigate the effect of this dual anthropogenic effect on the genetic landscape of ungulates, we genotyped 35K SNPs in 47 red deer (Cervus elaphus) of The Netherlands, including putative autochthonous relic populations as well as allochthonous populations established in private estates and rewilding areas. We applied FST and ordination analyses to determine the meta-population genetic structure and thereby the occurrence of hybridization. At population level, we investigated levels of inbreeding through individual-based diversity measures, including Runs of Homozygosity. We documented that both spatial genetic structure and within-population genetic variation differed markedly from patterns assumed from present-day abundance and distribution. Notwithstanding the small spatial scale, red deer populations formed distinct genetic clusters, and some had higher genetic similarity to distant than to nearby populations. Moreover, the putative autochthonous relic deer populations had much reduced levels of polymorphism and multi-locus heterozygosity, despite relatively large current population sizes. Accordingly, genomes of these deer contained a high proportion of long (>5Mb) Runs of Homozygosity. Whereas the observed high levels of inbreeding warrant defragmentation measures, the presence of adjacent autochthonous and allochthonous genetic stocks imply that facilitation of gene flow would cause genetic homogenization. Such distortions of the genetic landscape of ungulates creates management dilemmas that cannot be properly anticipated without baseline genetic monitoring.

An animal’s social environment can influence individual physiological and reproductive status, which might have implications for the success of ex situ conservation programs. This study investigated the relationship between an individual’s position in the social hierarchy, body and antler size, testosterone concentration, and seminal traits in male pampas deer maintained in all-male groups. The study was performed in a semi-captive population in Uruguay during the rut. Data were collected over a 4 year period from 18 different males kept in five groups each of 4–7 adult males (2–7 y old). An index of individual hierarchical success (hierarchical index; HI) was determined based on agonistic interactions with other males within the group. Males positioned higher in the social hierarchy had larger antlers (p = 0.02). In three out of four groups, testosterone was positively correlated with HI (p

Few cases of adoption have been reported in solitary breeding raptors, and in owls adoption has only been reported in two species. Here we report four cases of brood-switching of juvenile Tengmalm’s Owls (Aegolius funereus), recorded during and after the post-fledging dependence period using radio-telemetry, and a case of three orphaned siblings (one nestling and two fledglings) originally from one nestbox successfully fostered to another one. A possible evolutionary context of the brood-switching is discussed.

Human scent is a complex combination of many chemical substances. Skin is supposed to be one of sources of scent traces. The values of the boiling points of human scent compounds were supposed to be lower than 300°C. The purpose of the study was to determine the temperature at which the human scent is degraded so that a dog would not be able to identify it. In contrast to expectations, eight dogs used in the experiment almost flawlessly identified human scents from five scent donors exposed to temperatures of 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C, and 800°C. Only two of the dogs were able to identify 5 of 15 scent samples exposed to 900°C. No dog identified a scent exposed to 1000°C. Our study verified heat survivabil- ity of human scent far beyond existing expectations. There may be an extremely heat resistant, previously undetected, compound of human scent, unsusceptible to heat which exceeds standard temperatures used for sterilization. We anticipate our results to be a starting point for cardinal change of our view of factors affecting the vulnerability of human scent, resulting in the need to alter the approach of forensic methodology dealing with identification of human scent.

Out of rut, male red deer (Cervus elaphus) associate themselves in bachelor groups where animals compete for rank position via agonistic interactions. In a previous study on red deer, males were recognized either as “Non-Fighters” (NF, low frequency of attacks) or “Fighters” (F, high frequency of attacks). This study, therefore, aims to verify the consistency of the inter-individual differences in fighting attitude across different social contexts and investigate whether they could be considered an individual characteristic. Behavioral consistency was presumed across three different sampling seasons, assuming that NF would have lower cortisol (C) and testosterone (T) concentrations than the F males. In 2015 the males were kept in one large group and labelled NF and F. In 2016, the herd was divided into two subgroups (“NF” and “F”) based on the frequency of attacks. Finally, in 2017, the males were divided into two randomly composed subgroups. Data about agonistic behavior and concentration of C and T were collected during each season. In 2015 the individuals differed only for the fighting attitude. After the division, the frequency of the attacks always increased, being consistently lower in NF than in F. Unexpectedly, a slight increase in the concentration of C was detected in the NF in 2016, compared to the F who experienced no difference neither in 2015 nor 2017. No significant differences were found in T. We concluded that, even though the males had shown behavioral plasticity, their diversified interaction-prone attitude had been maintained despite the modifications of the social environment.

The period of early ontogeny constitutes a time when the physical immaturity of an organism is highly susceptible to external stimuli. Thus, early development plays a major role in shaping later adult behavior. The aim of the study was to check whether stimulating puppies at this early stage in life with sound would improve their responsiveness towards unfamiliar noises during the selection process of the police behavioral test for puppies. The cohort comprised 37 puppies from the litters of three mothers. At the commencement of the experiment the dogs were aged 16 days, rising to the age of 32 days at its close. The mothers and litters of the treatment group were either exposed to radio broadcasts, (see below; three litters totaling 19 puppies), while the control group was not exposed to any radio programs (eight litters totaling 18 puppies). All three mothers had previously experienced both auditory circumstances, as described herein. Ordinary radio broadcasts were played to the puppies in the treatment group three times a day for 20 minute periods, always during feeding time. The cohort was subjected to the so-called Puppy Test, i.e. analysis of the potential of each animal, once the dogs had reached the age of 7 weeks. Such tests included exposure to a sudden noise caused by a shovel (100 dB), noise when alone in a room, and response to loud distracting stimuli (the latter two at 70 dB). Said tasks were rated by the same analyst on a scale of 0-5 points; the better the response of the dog, the higher the score given. The differences between the treatment and control groups were analyzed via Mixed Models (PROC MIXED) in SAS. The animals comprising the treatment group responded with a higher score to the sudden noise caused by the shovel than the control dogs (P

Social deprivation early in life affects further individual development and leads to irreversible behavioural alterations later in life. Although the syndrome is well-studied in vertebrates including humans, its presence in invertebrates has been described only in eusocial insects and cockroaches. Here we show the first evidence of social deprivation in subsocial decapod crustaceans, based on analysis of video-recorded agonistic encounters of juvenile red swamp crayfish (Procambarus clarkii, Girard). In comparison with maternally incubated juveniles, isolated crayfish had altered repertoires, numbers and frequency of agonistic interactions similar to those described in vertebrates. Our results support the view on the syndrome of social deprivation as a ubiquitous trait in species with developed maternal care across diverse taxa.

In a previous study, we suggested that the common practice of transporting a mare for mating and then bringing her back to an environment that also contains males that did not sire the fetus may be a major cause of high percentages of pregnancy disruption in domestic horses. In this study, we tested whether disruption of pregnancies induced by AI occurs as frequently as after mating with a strange stallion away from home and is affected by the same factors in the home social environment. Based on 77 records, the probability of pregnancy disruption after AI depended on the social environment in which the mare was maintained after mating and the number of foals the mare had delivered in the past. Also after AI, as with natural matings away from home, the probability of pregnancy disruption was higher when the mare had no male company in her enclosure but stallions or geldings were present in an adjacent enclosure than when the mare was sharing the enclosure with geldings (generalized linear mixed model = 8.68, = 0.007, odds ratio = 8.17). These data support the prediction that the mare perceives conception after AI equally to natural mating with a strange stallion. The results suggested pregnancy disruption may be stimulated by the social circumstances of the home environment in mares artificially inseminated as in mares mated naturally away from home. The practical implications of this result is that after AI, to reduce risk of pregnancy disruption and improve welfare, horse breeders should place the pregnant mare into an environment with no stallion or stallions/gelding or geldings or to an enclosure together with the male or males.

Reviews summarizing the literature on heritability of behavioural traits in dogs have been published repeatedly over the last four decades. The conclusions of these reviews vary to some extent. We applied meta-analysis and re-evaluated the literature available collecting 48 references dealing with heritability of behavioural traits in domestic dogs. For each study included, data was extracted for individual behavioural traits. Each of these traits was entered into the analysis as a separate unit of measure, giving a total of 1763 measures. We classified the traits measured in each study into five functional categories (Environment, Herding, Hunting, Play, and Psychical characteristic). The meta-analysis has shown low general heritability of the categorised behavioural traits analysed. Thus, the commonly used behaviour tests for many breeds, to determine the dog's eligibility for reproducing, traditionally required by many associations, is not supported by the present results of the meta-analysis.

Counting of calling males during territorial or nuptial displays is a method widely used for census of populations of wild vertebrates during the pre-breeding and breeding periods, particularly in relation to census of populations of wild birds. In principle, a similar method could be used for assessing numbers of surviving offspring, by monitoring of begging calls, but is used only rarely. We explored the possibility of assessing post-fledging survival of Tengmalm's Owl young by counting the number of individuals begging for food. This method did not however deliver satisfactory estimates of numbers of surviving fledglings and its accuracy depended on time of night, distance from the natal nestbox, and presence or absence of begging calls. We suggest that this method can be used in Tengmalm's Owls for rough estimates only and our finding could be applicable also for other, generally smaller, owl species whose fledglings exhibit quick dispersion from the nest site after the fledging.

Litter size is one of the most reliable state-dependent life-history traits that indicate parental investment in polytocous (litter-bearing) mammals. The tendency to optimize litter size typically increases with decreasing availability of resources during the period of parental investment. To determine whether this tactic is also influenced by resource limitations prior to reproduction, we examined the effect of experimental, pre-breeding food restriction on the optimization of parental investment in lactating mice. First, we investigated the optimization of litter size in 65 experimental and 72 control families (mothers and their dependent offspring). Further, we evaluated pre-weaning offspring mortality, and the relationships between maternal and offspring condition (body weight), as well as offspring mortality, in 24 experimental and 19 control families with litter reduction (the death of one or more offspring). Assuming that pre-breeding food restriction would signal unpredictable food availability, we hypothesized that the optimization of parental investment would be more effective in the experimental rather than in the control mice. In comparison to the controls, the experimental mice produced larger litters and had a more selective (size-dependent) offspring mortality and thus lower litter reduction (the proportion of offspring deaths). Selective litter reduction helped the experimental mothers to maintain their own optimum condition, thereby improving the condition and, indirectly, the survival of their remaining offspring. Hence, pre-breeding resource limitations may have facilitated the mice to optimize their inclusive fitness. On the other hand, in the control females, the absence of environmental cues indicating a risky environment led to "maternal optimism" (overemphasizing good conditions at the time of breeding), which resulted in the production of litters of super-optimal size and consequently higher reproductive costs during lactation, including higher offspring mortality. Our study therefore provides the first evidence that pre-breeding food restriction promotes the optimization of parental investment, including offspring number and developmental success.

Litter size is one of the most reliable state-dependent life-history traits that indicate parental investment in polytocous (litter-bearing) mammals. The tendency to optimize litter size typically increases with decreasing availability of resources during the period of parental investment. To determine whether this tactic is also influenced by resource limitations prior to reproduction, we examined the effect of experimental, pre-breeding food restriction on the optimization of parental investment in lactating mice. First, we investigated the optimization of litter size in 65 experimental and 72 control families (mothers and their dependent offspring). Further, we evaluated pre-weaning offspring mortality, and the relationships between maternal and offspring condition (body weight), as well as offspring mortality, in 24 experimental and 19 control families with litter reduction (the death of one or more offspring). Assuming that pre-breeding food restriction would signal unpredictable food availability, we hypothesized that the optimization of parental investment would be more effective in the experimental rather than in the control mice. In comparison to the controls, the experimental mice produced larger litters and had a more selective (size-dependent) offspring mortality and thus lower litter reduction (the proportion of offspring deaths). Selective litter reduction helped the experimental mothers to maintain their own optimum condition, thereby improving the condition and, indirectly, the survival of their remaining offspring. Hence, pre-breeding resource limitations may have facilitated the mice to optimize their inclusive fitness. On the other hand, in the control females, the absence of environmental cues indicating a risky environment led to “maternal optimism” (overemphasizing good conditions at the time of breeding), which resulted in the production of litters of super-optimal size and consequently higher reproductive costs during lactation, including higher offspring mortality. Our study therefore provides the first evidence that pre-breeding food restriction promotes the optimization of parental investment, including offspring number and developmental success.

Animal home ranges typically characterized by their size, shape and a given time interval can be affected by many different biotic and abiotic factors. However, despite the fact that many studies have addressed home ranges, our knowledge of the factors influencing the size of area occupied by different animals is, in many cases, still quite poor, especially among raptors. Using radio-telemetry (VHF; 2.1 g tail-mounted tags) we studied movements of 20 Tengmalm’s owl (Aegolius funereus) males during the breeding season in a mountain area of Central Europe (the Czech Republic, the Ore Mountains: 50° 40’ N, 13° 35’ E) between years 2006–2010, determined their average hunting home range size and explored what factors affected the size of home range utilised. The mean breeding home range size calculated according to 95% fixed kernel density estimator was 190.7 ± 65.7 ha (± SD) with a median value of 187.1 ha. Home range size was affected by prey abundance, presence or absence of polygyny, the number of fledglings, and weather conditions. Home range size increased with decreasing prey abundance. Polygynously mated males had overall larger home range than those mated monogamously, and individuals with more fledged young possessed larger home range compared to those with fewer raised fledglings. Finally, we found that home ranges recorded during harsh weather (nights with strong wind speed and/or heavy rain) were smaller in size than those registered during better weather. Overall, the results provide novel insights into what factors may influence home range size and emphasize the prey abundance as a key factor for breeding dynamics in Tengmalm’s owl.

Suckling bout duration and frequency were used in the past as an indicator of milk intake. However, later studies found no significant relationship between suckling bout duration and frequency and milk or energy intake. On the other hand recent studies are in line with the suggestion that suckling bout duration and frequency may express intensity of maternal care. The three extant zebra species differ in their ecology and social system. Mountain Equus zebra and Grevy's zebra E. grevyi live in an arid environment, whereas plains zebras E. quagga are found in savannah. Mountain and plains zebra mares form stable herds associated with high aggression and low aggression, respectively. Female Grevy's zebras form loose associations with the lowest level of aggression. The aim of this study was to re-evaluate the suggestion that suckling bout duration and frequency are affected by social system. We observed suckling behaviour of 30 foals (16 plains zebras, 8 Grevy's zebras and 6 mountain zebras) at the Dvůr Kralove Zoo, Czech Republic. We found that suckling bout duration was longest in mountain zebras, followed by plains and Grevy's zebras. Similar results were found for suckling frequency. These results coincide with the rate of aggression among mares; foals spent more time by suckling in species, where more aggression among adults occurred. Thus, the results of our study support the suggestion that suckling bout duration reflects social needs of the foal rather than milk intake requirements.

Knowledge about vocal ontogeny and vocal plasticity during ontogeny in primate species is central to understanding the evolution of human speech. Vocalizations in gibbons (Hominoidea) are very interesting and contain complex species- and sex-specific patterns. However, ontogeny of gibbon songs is little studied. Here, we document regular production and ontogenetic changes of female-specific "great call" in 4 immature (2 juvenile-c.a. 3 years old; and 2 adolescent-c.a. 5 years old) males of southern yellow-cheeked gibbon (N. gabriellae) over nine months. None of the males produced fully developed adult-like "great call" and little ontogenetic changes to "great calls" occurred. "Great calls" of sons were shorter, started higher and ended lower than those of their mothers. Regular production of twitter part of great call likely appears around 4th year as it was observed in adolescent but not in juvenile males.

Among domestic dog breeders it is common practice to transfer a domestic dog bitch out of her home environment for mating, bringing her back after the mating. If the home environment contains a male, who is not the father of the foetuses, there is a potential risk of future infanticide. We collected 621 records on mating of 249 healthy bitches of 11 breed-types. The highest proportion of successful pregnancies following mating occurred in bitches mated within their home pack and remaining there. Bitches mated elsewhere and then returned to a home containing at least one male had substantially lower incidence of maintained pregnancy in comparison with bitches mated by a home male. After returning home, housing affected strongly the frequency of pregnancy success. Bitches mated elsewhere but released into a home pack containing a home male were four times more likely to maintain pregnancy than bitches which were housed individually after returning home. Suppression of pregnancy in situations where a bitch is unable to confuse a home male about parentage may be seen as an adaptation to avoid any seemingly unavoidable future loss of her progeny to infanticide after birth and thus to save energy.

The three existing zebra species differ in their ecology: in the wild, mountain (Equus zebra) and Grevy’s zebra (Equus grevyi) live in an arid environment while plains zebra (Equus quagga) inhabit savannah. Interspecific differences in maternal care in terms of suckling bout duration and frequency are thought to be based on the ecological adaptations of equid species. However, other studies showed that suckling bout duration and frequency cannot reflect maternal investment. The aim of this study was to re-evaluate the suggestion of previous studies that suckling behaviour is influenced by environmental adaptations in equids using rejection and termination of suckling bouts in three captive zebra species kept in the same facility. Suckling behaviour of all three zebra species was observed over a period of 31 months at the Dvůr Kralove Zoo, Czech Republic. We found that Grevy’s and mountain zebra showed a lower rate of rejection and termination of suckling bouts by the mother than plains zebra. Therefore, mothers of species that evolved in a more arid habitat were more tolerant towards their offspring than those of species that evolved in a mesic habitat. Thus, our results confirmed that parent–offspring conflict in terms of suckling bout termination and rejection seems to be affected by ecological adaptation.

Sex differences in suckling behaviour could be explained either by different maternal investment or by different behaviour of young. Previously, we found sex differences in rejection and termination of suckling bouts in captive plains zebras (Equus burchellii). In this study, we analysed the length of suckling bout interruptions and unsuccessful subsequent attempts which followed a successful suckling bout in plains zebra foals at Dvůr Kralove Zoo. When a suckling bout was interrupted, male foals resumed the bout sooner than female foals. The probability of a subsequent attempt decreased with increasing age in female foals but did not change in male foals. These results demonstrate higher effort in suckling interest by male foals, who tried to suckle more than female foals. Although we found sex bias in the effort to suckle, which suggested higher parent–offspring conflict in male offspring, we cannot omit a sex bias in milk supply by the mother.

Based on questionnaires from horse breeders, we found that bringing a pregnant mare which had been mated away from home into a vicinity of a familiar male who was not the father of her foetus increased probability of pregnancy disruption. These mares aborted in 31% of cases, while none of those mated within the home stable aborted. Repeated sexual activity either by a stallion or dominant gelding from the normal home group was observed shortly after the mare came from away-mating. Pregnant mares isolated from home males by a fence were even seen soliciting them over the fence. We speculate that, once returned to the home “herd”, and introduced to familiar males, mares were more likely to terminate their pregnancy to save energy and avoid likely future infanticidal loss of their progeny by dominant male(s) of the home social group. This is a newly discovered phenomenon where a mare manipulates the male’s paternity assessment by promiscuous mating. It may explain a common increased incidence of foetal loss in domestic horses occurring in nearly 40% of pregnancies. We conclude that the common practice of transporting the mare for mating and then bringing her back to an environment with males, stallions or geldings, which did not sire the foetus, is the main cause of high percentages of pregnancy disruption in domestic horses.

Although allonursing (allowing non-filial offspring to suckle) can be a costly behaviour, it has been reported for many mammals including ungulate species. However, such behaviour is very rare in equids. This is the first report on adoption and allonursing in captive plains zebra (Equus burchellii), recorded in the Dvůr Králové Zoo, Czech Republic. We observed a case of adoption of an orphaned foal by a lactating mare, who then regularly nursed two foals (filial and non-filial). The allonursing mare rejected more suckling attempts, terminated suckling bouts more often, and had a shorter suckling bout duration than other mares. When nursing both foals at the same time, the suckling bout lasted for less time than when nursing a single foal, regardless of whether it was filial or non-filial. The allonursing mare apparently did not discriminate between the filial and non-filial foal.

Equids spend more than half of the day feeding. Lactation is a very demanding form of maternal investment. In an environment such as a zoo, where no grass but several feeding sites are present, conflict between suckling behaviour of the foal and feeding behaviour of the lactating mother should occur. We observed 20 foals of captive plains zebra, Equus burchellii , at the Dvůr Kralove Zoo, Czech Republic, and collected data concerning suckling events during 17 months of observation. First, we examined whether feeding by the mother while nursing affected suckling behaviour. We found that when the mother was feeding, the proportion of suckling bouts she terminated decreased with increasing age of the foal, whereas it did not change when she was not feeding. This result supported the trade-off between suckling and feeding behaviour which has been reported in other ungulates. Second, we examined what affected interruptions of feeding behaviour of the mother during the suckling bout. The proportion of interruptions of feeding by the mother during nursing increased with increasing age of her foal. This coincides with declining time spent nursing. In addition, younger mothers interrupted their feeding behaviour during suckling bouts more often than older ones. Mothers interrupted feeding during the suckling bout more often when they nursed a daughter than when they nursed a son. The results of our study show that feeding while suckling could reduce parent–offspring conflict and improve welfare of captive foals and mares.

Prenatal androgens are generally assumed to permanently affect the morphology of external genitalia. In laboratory rodents, the ano-genital distance index (AGDI) has become widely used as a marker of natural prenatal masculinization. A greater value should indicate a greater masculinization. The aim of this study was to assess the developmental stability of the AGDI in female mice during pre- (Days 1-21) and postweaning (Days 21-61) periods. Presuming that the AGDI reflects a permanent effect of prenatal masculinization, we hypothesized that the AGDI will be a developmentally stable morphometric measurement (interindividual differences in the AGDI measurement should persist over time). In contrast to our prediction, the AGDI showed poor repeatability both during pre- (.15) and postweaning (.22) periods, indicating developmental instability. (A value of 1 indicates perfect repeatability and a value of 0 indicates no repeatability.) The AGDI thus does not seem to be a reliable marker of prenatal female masculinization. 2010 Wiley Periodicals, Inc. Dev Psychobiol 52: 568- 573, 2010.

Eleven hinds and their calves were observed on a deer farm in order to study their vocal communication. Red deer calves are ‘hiders’, and therefore it was believed that they would need to recognize their mother's voice, but the hinds would not need to recognize the voice of their offspring. The following predictions were tested. First, the calf can recognize its mother by voice. Second, the hind's ability to recognize her calf by voice is less pronounced. The study had two parts. Part I was focused on spontaneous behaviour of the animals. Part II involved experiments with audio recordings. It was observed that the hinds vocalized more frequently than the calves, and it appeared that the vocalization served primarily a contact function. The calves seemed to recognize their mothers' voice better than vice versa. For the hinds, vision was more important than hearing. Thus, the predictions were confirmed.

We predicted that the proportion of suckling attempts rejected and terminated by the mother would be greater for female foals than male foals, based on parent offspring conflict theory and on the assumption that throughout the study, all zebra mothers were in good condition because of captivity. We presumed that an increasing rate of suckling terminated or rejected by a mother would indicate a decreasing effort by the mother to invest in her offspring. We observed foals of captive plains zebras at the Dvůr Kralove Zoo, Czech Republic. We found that the probability of successful suckling tended (slope = 0.0016; Z = 1.78; P = 0.074) to increase with increasing age of the female foals, but decreased (slope = -0.0018; Z = -2.51; P = 0.012) with increasing age of the male foals. The proportion of suckling bouts terminated by the mother decreased (slope = -0.0077; Z = -4.27; P < 0.0001) with increasing age of the female foals, but not the male foals (slope = -0.0005; Z = -0.34; P = 0.732). Our results indicate that conflict between mothers and female foals was less than that between mothers and male foals. The observed sex differences in termination and rejection of suckling bouts could be explained by the different behavior of the male and female foals, or by the selective maternal investment. Finally, we revealed no significant effect of herdmates on suckling behavior.

Recently, a lack of any significant relationship between suckling bout duration and milk or energy intake has been revealed in several mammal species. However, a short suckling bout duration could be taken as an indicator of shortage of milk and lack of maternal care, and could therefore be used to test the parent–offspring conflict hypothesis. We examined suckling bout duration of 20 plains zebra ( Equus burchellii ) foals, at the Dvůr Kralove Zoo, and collected data on suckling events during 19 months of observation. In total, we recorded 3252 suckling bouts during 831 h of observation. As expected, suckling bout duration decreased with increasing age of the foal. The suckling bouts differed in duration when terminated by the foal, mother or any other adult mare (foal > mother > herdmate). Thus, bouts terminated by the mother should indicate that demands of the foal were not satisfied. The shortest bouts were those terminated by a herdmate; however, herdmates terminated few suckling bouts. Moreover, since the foal was able to resume suckling after interruption, the effect of a herdmate on suckling behaviour was very limited. Finally, we found that suckling bout duration was shorter in pregnant mothers than in non-pregnant ones, suggesting higher mother–offspring conflict when the mother was pregnant. In conclusion, this study demonstrates the importance of the termination of suckling bouts and the mother's pregnancy when interpreting suckling bout duration of equids, which has received little attention in previous studies. Our study showed that environmental condition can affect the suckling behaviour of captive equids.

To analyse the relationship between spawning migrations and flow, cyprinids from ten fish ladders of the Elbe River (Czech Republic) were collected during the period of spawning migrations (April–June) in 1996, 2000 and 2001. Number of species and individuals in the fish ladders increased with increasing flow up to medium values, followed by further decrease during high flows, whilst length of individuals increased with increasing flow. Moreover, occurrence of four the most numerous species (bleak, roach, silver bream and barbel) showed species specific differences in response to flow variability. In early spring, the highest number of bleak in fish ladders occurred during the low flow, whilst later increased with increasing flow. Occurrence of roach and silver bream achieved the maximum during the medium flow values across the whole studied period. In opposite, occurrence of barbel increased with increasing flows during the whole period. Furthermore, it can be assumed that occurrence of fish in ladders was associated not only with spawning migrations but also reflected shifts in local fish distribution in response to flow variability in the main channel.

Summary The movement pattern of brown trout Salmo trutta (L.) in a fish ladder on the heavily fragmented Ohře River, Czech Republic was observed for 16 months. Some individually-tagged fish repeatedly occurred in the ladder. A total of 1640 fish represented captures of 595 S. trutta in the fish ladder; 247 fish were caught once and 348 individuals were caught repeatedly. Repeatedly-caught (348) individuals represented 1393 (84.9%) of the 1640 captures. The likelihood of repetitive occurrence decreased with the increase in fish body length. The number of individuals in the ladder was inversely related to temperature, and positively correlated with increasing water flow in the main channel. Fish abundance in the ladder was density-dependent, as the number of individuals was inversely related to fish size and time of residency in the ladder. Spawning migrations were not the best predictor of maximum fish occurrence in the ladder, suggesting that repetitive capture of individuals in the ladder was significantly affected by other factors influencing fish behaviour. Repetitive fish occurrence in ladders can be expected, particularly in rivers with numerous lateral obstructions.

Behavioral activity of 7-week-old German shepherd puppies was tested and the activities analyzed if they could be used for predicting police efficiency of the individual. In total 206 individuals sired by 42 sires and 44 dams were used. The activities were divided into 10 tasks in which reactions and behavior of pups were scored from 0 to 5 points. All pups were tested separately from other conspecifics. Probability that the puppy will pass the certification was tested by a logistic regression. Of the 206 puppies, 148 passed the certification while 58 failed. Some tested behavioral variables were moderately to highly correlated with one another. Therefore we applied a factor analysis. Three factors were retained accounting for 100% of the shared variance. After inspection of the rotated factor pattern matrix and its confidence intervals, it appeared that variables “Independent movement and interactions with the tester”, “Negotiating obstacles”, “Entering a room”, “Behavior toward a person”, and “Behavior in new environments” loaded on Factor 1 (“Factor for movement”), while variables “Response to distracting stimuli caused by a shovel”, “Response to a distracting noise while left alone in a room”, and “Response to loud distracting stimuli” on Factor 2 (“Factor for responding to noise”) and variables “Retrieval” and “Tug of war” on Factor 3 (“Factor for attitude to predation”). In the final logistic regression model, the probability that the puppy will pass the certification depended on the higher weight at the time of testing ( χ ( 1 ) 2 = 12.00 , P = 0.0005), on the “Factor for attitude to predation” ( χ ( 1 ) 2 = 11.63 , P = 0.0007), on the “Factor for responding to noise”, where the higher the score, the weaker was the response ( χ ( 1 ) 2 = 5.16 , P = 0.0232), and on the “Factor for movement” showing an increasing probability with decreasing score ( χ ( 1 ) 2 = 5.25 , P = 0.0219). The tests in our study seem to be a good base which might enable selection for suitable dogs as early as 7 weeks of age. The puppies having high probability to pass certification in adulthood were heavy individuals willing to chase, catch, and fetch a tennis ball, and follow a rag drawn away from them, while weakly responding to a distracting noise in various situations and showing low activity while negotiating obstacles and moving and interacting with the tester. To conclude, contrary to skeptical assumptions expressed by various authors, the specific puppy tests for police dogs provide a reliable tool for predicting future service ability of a puppy. Differences in methodology are likely to contribute to a lack of consensus among various studies.

Sucking duration in ungulates does not only mean milk transfer, but is also associated with maternal care in general. It seems to be a reflection of offspring demand rather than solely milk transfer rate. Thus, the objective of this study was to discriminate between sucking and allosucking (i.e. sucking non-maternal hind) behaviour in red deer according to the sucking duration. We hypothesized that: (1) calves should suck longer from their mothers than allosuck from non-maternal hinds; (2) sucking duration of calves frequently nursed by a particular non-maternal hind should be longer than that of calves occasionally allonursed; (3) sucking duration should be longer for bouts including one calf than two or more calves sucking simultaneously; (4) male calves should suck and allosuck longer than female calves; and (5) primiparous hinds should nurse and allonurse longer than multiparous hinds. We observed sucking behaviour of 25 hinds and their 38 calves (from birth until the youngest calf reached one month of age) in two seasons. We recorded 1730 sucking bouts, of which 11.62% in the first season and 4.37% in the second season were non-filial. The duration of filial sucking was significantly longer than non-filial sucking. A large individual variance in the incidence of non-filial sucking in both the calves and hinds was found. Therefore, the non-filial hind–calf pairs were categorized in two clusters according to the frequency of nursing non-filial calves for one hind in relationship to all nursing events for this hind by a cluster analysis (PROC CLUSTER, SAS). We used a general linear mixed model, GLMM (PROC MIXED, SAS) to test the influence of hind relationship to the nursed calf (filial, frequently allosucking non-filial, or occasionally allosucking non-filial pair). Sucking duration of occasionally allosucking non-filial calves was only marginally different from that of filial calves. There was no difference between the two groups of non-filial calves. Multiple sucking bouts were shorter than those with one calf. Male calves sucked longer than female calves; however, the greatest difference was recorded between frequently allosucking non-filial pairs of both sexes. Frequently allosucking non-filial males sucked the longest and differently from occasionally allosucking non-filial males. Frequently allosucking non-filial females sucked the shortest and differently from filial calves of both sexes. It is more likely that allosucking seems to be more important for male rather than female calves. Therefore, it is concluded that allosucking calves differ in their sucking behaviour and two types of allosuckers (frequent and occasional) should be taken into account when analyzing allosuckling behaviour.

Summary Changes in the behaviour of cyprinids belonging to different ecology groups were observed below a weir that was restricting their upstream migrations during the spawning period May–July. Positions of chub Leuciscus cephalus (L.), Prussian carp Carrasius auratus gibelio (Bloch 1783), bream Abramis brama (L.) and white bream Blicca bjoerkna (L.) were recorded every 12 min over a 24-h period using an automatic data logger (ALS) in the upper Elbe River, Czech Republic. For all observed species, two activity peaks occurred; however, the interspecies timing of these peaks differed. Peak times for chub, bream and white bream occurred at night and during daylight, whereas Prussian carp was active mostly at night. Specimens belonging to the rheophilous group suggested more efficient behavioural tactics in passing the weir, staying below the obstacle one month longer than did eurytopic species.

The Indian rhinoceros (Rhinoceros unicornis) is a highly endangered species that inhabits only three political states. Recently, Zschokke and Baur [Zschokke, S., Baur, B., 2002. Inbreeding, outbreeding, infant growth, and size dimorphism in captive Indian rhinoceros (Rhinoceros unicornis). Canadian Journal of Zoology 80, 2014–2023] found that the offspring of matings between captive Indian rhinoceros individuals from the Kaziranga and Chitwan populations had high mortality rates. These authors suggested that these two populations are partially genetically incompatible and, thus, they proposed that these would be separated into two subspecies. In this study we compiled data from a captive population with data from Dudhwa National Park (India), where rhinoceroses were successfully reintroduced in 1984. In Dudhwa, the breeding male came from the Kaziranga population and four out of the five breeding females came from the Chitwan population. In spite of these different origins, the Dudhwa population has bred very well. We analyzed, the factors influencing infant mortality of 22 Dudhwa and 181 captive calves. Outbreeding (matings between animals from Kaziranga and Chitwan) did not play any role in infant mortality. From our data, we can conclude that parity, not outbreeding, is responsible for infant mortality in the Indian rhinoceros. Thus, we are unable to agree with Zschokke and Baur’s suggestion that the Chitwan and Kaziranga populations belong to separate subspecies. Rather, we propose that the hybridization of captive animals from Chitwan and Kaziranga, as well as those in the wild, should help save the genetic diversity of this highly endangered species.

Little is known about the thermoregulatory response of the eland, a tropical animal often raised in temperate climate. We compared the surface temperature (Ts) of the eland with that of similarly sized Holstein–Friesian dairy cattle at three different ambient temperatures (Ta) to get better evidence about thermal response. The Ts of all body areas (neck, dewlap, trunk, body forepart, barrel, body hind part, forelimb and rear limb) did not differ at Ta 29.2 °C, but at Ta 12.5 °C all the areas of the eland (except the neck) had lower mean Ts than those areas in cattle. At Ta 0.4 °C, only the eland dewlap had a lower Ts and the eland neck had a higher Ts than that in cattle.

The first telemetry study analysing behaviour of the largest freshwater predator in European rivers, Silurus glanis, was performed bimonthly during the years 2002–2004. Movement of juveniles and adults occurred mostly in the same time intervals. The only statistical differences occurred for nocturnal activity in spring and autumn. In spring and winter, activity was low with the peaks during daylight, and in autumn, maximal movement was recorded during dusk. In summer, the European catfish were active across the whole 24 h even during high-flow conditions. During all other seasons, movement was inversely related to flow rate. Maximal home ranges occurred in summer, being larger for adults. Juveniles and adults were spatially segregated. With increasing flow, fish were displaced, and individuals from both groups got closer to each other. Only juveniles migrated downstream from the upstream isolated river stretch suggesting a negative impact of lateral obstructions on the fish population structure.