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The power of repetition: to repeat determines the dominance status of male reed warblers

The way birds sing is important in mate choice. This is well-known from behavioural research. But what characteristics of birdsong are important for competition between male birds? An international study led by the University of Veterinary Medicine Vienna used a playback experiment to investigate this question using reed warblers (Acrocephalus scirpaceus) - a native songbird that overwinters in sub-Saharan Africa. According to the study, monotonous repetitions of bird song syllables convey dominance. So, do stereotypical singers have an advantage?

In behavioural research, the virtuosity (complexity) with which a male bird performs his song has long been identified as an important criterion in female mate choice. In contrast, the role of song in interactions between rivals is less clear - and very little is known about which song characteristics are particularly important in territory defence and confrontations between males.

One way of getting your point of view and opinions across to the ‘man’ (addressee) clearly and emphatically is to repeat the ‘message’ to be conveyed. We humans also use repetition to emphasise statements and make them more credible. In reed warblers, males increase their song complexity to impress females, while they reduce it in territorial disputes. One way to reduce song complexity is by repeating individual syllables. In their recently published study, the team of scientists therefore investigated the importance of repeating syllables during territorial disputes with rivals.

Playback experiment with different frequencies of syllable repetition

The researchers hypothesised that the repetition of syllables signals a male's general fighting ability, aggressive status, or willingness to attack. Study lead author Herbert Hoi from the Konrad-Lorenz Institute of Ethology (KLIVV) at Vetmeduni explains: ‘In a playback experiment, we investigated the behavioural response of unmated, territorial reed warbler males to two intruders singing at the same time, whereby the song of the two intruders simulated by playbacks differed in the extent of syllable repetition.’

A clear behavioural response: those who repeat themselves demonstrate dominance

The reaction of the territory holder was determined using several behavioural parameters. The results showed that the complexity of the song does not play a role in whether the males dare to approach the playback or how close they come. However, it turned out that territory holders approached more quickly and stayed significantly longer in the vicinity of the complex playback song, i.e. the one with few repetitions.

‘This weaker response to the song with many repeated syllables suggests that territorial males are more intimidated by the aggressive nature of this type of song,’ says Herbert Hoi. However, as the other differences in response were rather weak in relation to the extremely divergent song characteristics in the playback experiment, Hoi believes that it would be interesting for future studies to investigate the social status and motivation of those males that seek the proximity of a conspecific that embodies one or the other song type.

The article „Is syllable repetitions a song parameter important for male-male interactions in Eurasian reed warbler (Acrocephalus scirpaceus)?“ by Alžbeta Darolová, Ján Krištofík, Lucia Rubáčová, Felix Knauer and Herbert Hoi was published in „Biologia“ .

Scientific article


Community project StadtWildTiere provides unknown insights into the world of urban wildlife

Starting in Zurich (Switzerland), the StadtWildTiere project has since been expanded to a total of 13 cities in Austria, Germany and Switzerland, including Vienna and Berlin. Observations of random encounters with wild animals in urban neighbourhoods are collected on a joint online platform. In Austria, reports can be submitted via the website  A recently published international study involving the University of Veterinary Medicine Vienna has now analysed the benefits of this transnational initiative.

StadtWildTiere collects sightings of wildlife in cities to raise awareness of biodiversity in urban areas throughout Central Europe. The collection of data also serves as a basis for scientific analyses. Furthermore, the knowledge collected by the citizens is used to promote nature and biodiversity in urban areas.

Climate change, interactions:
Community project uncovers the unknown for the first time

Urban ecology is still a young field and urban wildlife populations have not yet been the focus of many studies. "StadtWildTiere enables us to recognise previously hidden patterns and temporal trends, e.g. in the context of urban densification and the heat island effect, particularly with regard to climate change. The initiative can therefore also serve as a sensor for future interactions between humans and wildlife," explains study co-author Theresa Walter from the Research Institute of Wildlife Ecology at Vetmeduni.

Important basis for decisions at political level

In the long term, the scientists suggest that projects such as StadtWildTiere should create a basis for comparative, international monitoring in order to close the existing gaps in knowledge about urban wildlife populations. According to study co-author Richard Zink from the Konrad Lorenz Institute for Comparative Behavioural Research (KLIVV) at Vetmeduni, the data obtained from the study goes far beyond science: "This knowledge is also of crucial importance for political decision-makers and wildlife managers in order to establish the right strategies and measures. In particular, this also concerns the question of how to effectively improve biodiversity in cities."

The article „StadtWildTiere – added value and impact of transnational urban wildlife community science projects“ by Madeleine Geiger, Anouk Lisa Taucher, Sandra Gloor, Mirco Lauper, Sarah Kiefer, Sophia E. Kimmig, Janette Siebert, Theresa Walter, Richard Zink, Fabio Bontadina and Daniel Hegglin was published in „Frontiers in Ecology and Evolution“.

Scientific article

StadtWildTiere Österreich

EUFLYNET: a COST Action for the research and conservation of migratory landbirds

Migratory landbirds, particularly those bound for sub-Saharan Africa, are experiencing a decline across their range. The conservation of these species presents a formidable challenge due to the vast geographic span of their habitats. To effectively safeguard these birds, it is crucial to understand the obstacles they encounter not only within their breeding territories but also along their migratory paths and in their wintering locales. Regrettably, our knowledge is often limited by insufficient research capabilities throughout much of their range. Addressing this gap necessitates the establishment of a robust network of collaborative research efforts along the migratory flyways and the enhancement of research capacity in areas where it is currently lacking. Subsequently, key stakeholders must be engaged to actualize conservation measures.

A significant stride has been made with the initiation of the EUFLYNET COST Action, spearheaded by Dr. Ivan Maggini from the Konrad-Lorenz Institute of Ethology at the Vetmeduni. Funded by the EU, COST (Collaboration for Science & Technology) aims to foster networking and knowledge transfer. Launched in October 2023, EUFLYNET will span four years, orchestrating research coordination and facilitating knowledge exchange among scientists studying a broad spectrum of European migratory bird species. The network already boasts 160 members from 37 nations and is poised for further expansion. The inaugural in-person EUFLYNET assembly took place in Jastarnia, Poland, from February 28th to March 1st, 2024, convening approximately 100 participants who deliberated on collaborative ventures and received training on pertinent subjects such as statistical modeling, radiotracking, and tracking data analysis. We eagerly anticipate the forthcoming endeavors of this pivotal Action! For more information, please visit the Action website here:

Viennese research team develops new test to measure cognitive abilities of fish

The East African Lake Tanganyika is known worldwide for its colorful ornamental fish. The Princess of Lake Tanganyika (Neolamprologus pulcher), one of the most popular of these small cichlids, has now been studied by a team of scientists from the University of Veterinary Medicine, Vienna. The aim was to develop for the first time a simple test to investigate cognitive abilities of a wide range of fish in their natural habitat.

Cognitive abilities vary within and between species. Scientists propose several hypotheses to explain this variation. Two of the best-known hypotheses on the evolution of cognition relate an increased social complexity on the one hand and habitat complexity on the other to higher cognitive abilities.

Several studies have tested predictions derived from these two hypotheses, but only rarely under natural conditions with wild animals and not at all using free-living fish. "However, this is of particular importance if we want to link cognitive abilities with fitness-relevant factors in order to better understand the evolution of cognition," says study first author Arne Jungwirth from the Konrad Lorenz Institute of Ethology (KLIVV) at the University of Veterinary Medicine, Vienna.

First test to investigate cognitive abilities of fish in their natural habitat

According to the researchers, the biggest hurdle in assessing cognitive abilities in the wild has so far been finding a suitable set-up that is easy to use under field conditions. The research team set itself the goal of creating a test that was as simple as possible and could also be used with a variety of fish in their natural habitat.

Stefan Fischer from KLIVV, last author of the study, explains how this was achieved: "We developed a detour test in which the fish had to swim around an obstacle in order to reach a food reward." By altering the difficulty of the task, the behavioural researchers confirmed that this set up is a valid test for investigating the cognitive abilities of wild groups of Neolamprologus pulcher.

Hypothesis testing yields inconsistent results

They then tested specific predictions of the two main hypotheses on cognitive evolution using the most difficult test configuration. "In particular, we examined the differences in cognitive abilities between groups of different sizes inhabiting habitats of different complexity. However, neither hypothesis could be clearly verified in this first pilot study," says Arne Jungwirth. However, the scientists emphasise that the experimental set-up they have developed opens up the possibility of answering a whole range of research questions. Stefan Fischer comments: "We expect that the test we have developed will contribute to a better understanding of the evolution of cognitive abilities in the wild."

The article „Estimating Cognitive Ability in the Wild: Validation of a Detour Test Paradigm Using a Cichlid Fish (Neolamprologus pulcher)“ by Arne Jungwirth, Anna Horsfield, Paul Nührenberg and Stefan Fischer was published in „Fishes“.

Scientific article



Mercury poses a threat to poison frog offspring in the Amazon

Mercury is an environmental pollutant that raises concerns worldwide due to its toxicity and risks to both wildlife and human health – a point emphasized by the World Health Organization (WHO). This environmental toxin is found even in remote, untouched areas such as the Amazon, endangering the local wildlife. This is revealed in a recently published international study led by the Konrad Lorenz Institute for Comparative Behavioral Research (KLIVV) at the University of Veterinary Medicine Vienna, focusing on the poison frog Dendrobates tinctorius.

Artisanal and small-scale gold mining (ASGM) has become a major threat to South American forests. This method of gold extraction is a significant cause of small-scale deforestation and the largest contributor to mercury emissions into the atmosphere and freshwater systems worldwide. Previous studies have already highlighted the effects of mercury accumulation on various aquatic ecosystems and organisms. However, the consequences for other systems, such as small water-retaining plant structures (phytotelmata) and the organisms living within them, have gone unnoticed until now.

Focus on aquatic nurseries of Dendrobates tinctorius

A research team led by KLIVV at Vetmeduni (study's first author Lia Schlippe-Justicia; study's last author Bibiana Rojas) investigated this issue in French Guiana, focusing on the native poison frog Dendrobates tinctorius. The researchers focused on phytotelmata, small pools, for example, in the root area of plants, and other aquatic microenvironments, such as water in discarded containers.

High mercury levels from an early stage

In these typical breeding sites for Dendrobates tinctorius tadpoles, the researchers found high mercury concentrations. "In 17% of cases, we were able to detect very high mercury concentrations, particularly near known ASGM sites. However, we could not observe any influence of mercury concentration on the number of tadpoles in a given pool," says Lia Schlippe-Justicia. Tadpoles were also found in pools with extremely high concentrations, up to 8.68 ppm, suggesting that "D. tinctorius fathers do not seem to avoid pools with high mercury concentrations for tadpole deposition," according to Schlippe.

Negative effects on physical development

The research team also documented a significantly negative impact on amphibians, as reported by Bibiana Rojas: "Tadpoles in later developmental stages exhibited poorer body condition when growing up in pools with higher mercury concentrations. This underscores the need for further field and experimental studies examining the effects of mercury contamination on tadpole development and behavior, as well as the overall preservation of biodiversity in the Amazon."

The article „Poison in the nursery: Mercury contamination in the tadpole-rearing sites of an Amazonian frog“ by Lia Schlippe-Justicia, Jérémy Lemaire, Carolin Dittrich, Martin Mayer, Paco Bustamante and Bibiana Rojas was published in „Science of the Total Environment“.

Scientific Article

Naked mole rats and their molecular tricks to slow down aging and cancer

Due to their long life expectancy, naked mole rats are particularly suitable for researching mechanisms that maintain cellular function and slow aging. If these mechanisms could be solved, then the results could be relevant for humans aging and the development of cancer. An international study involving the University of Veterinary Medicine Vienna (Konrad Lorenz Institute for Ethology; KLIVV) is now providing important new insights into how adult stem cells affect long-term tissue maintenance using naked mole rats and their intestinal tract.

Naked mole rats (Heterocephalus glaber) are very special mammals. The animals, which are a maximum of 15 centimeters in size, live in large underground burrows and colonies of up to 300 animals in the semi-deserts of East Africa and are the only species of the genus Heterocephalus. Not only are they extremely social, their life expectancy is also unusually long and significantly exceeds that of other rodents. Because of this property, they offer scientists a unique opportunity to explore how evolution has influenced adult stem cell (ASC) activity and tissue function as life expectancy increases.

In mammals and other multicellular organisms, long-term maintenance of tissue homeostasis requires strict regulation of adult stem cell activity to ensure efficient repair and regeneration. In high-turnover mammalian tissues such as the intestine, the balance is controlled primarily by the continuous division and differentiation of the ASC and the subsequent cell death (apoptosis) of the mature cells. The longer survival of ASCs puts them at increased risk of mutations and reduces their fitness, which is evident in aging and in diseases such as cancer.

Intestinal tract with numerous cellular peculiarities

With this in mind, the scientific team examined the intestinal tract of naked mole rats and compared their intestinal ASCs (Lgr5+) with those of mice and humans. Study co-author Dustin J. Penn from the Vetmeduni's KLIVV said: “In vivo, we found an expanded pool of Lgr5+ cells in naked mole-rats. These cells exhibit slower division rates compared to those of wild house mice, specifically at the crypt base (Lgr5+CBC), but have a similar turnover to human Lgr5+CBC cells. Instead of entering quiescence (G0), naked mole rat Lgr5+CBC cells reduce their division rates by prolonging the G1 and/or G2 phases of the cell cycle.”

In addition, the researchers observed a higher proportion of differentiated cells in naked mole rats, which provide the intestinal mucosa with better protection and function. “The intestinal mucosa of naked mole rats is able to efficiently detect any chemical imbalance in the intestinal environment and trigger a robust pro-apoptotic, anti-proliferative response within the stem/progenitor cell zone,” explains study co-author Dustin J. Penn from the KLIVV at the Vetmeduni.

Less cancer: Evolutionary adaptations reduce the incidence of age-related diseases

Their study characterizing the intestinal tract of naked mole rats adds to the growing body of evidence that these remarkable animals have evolved unique adaptations that enable long-term maintenance of tissue homeostasis and, as a secondary consequence, reduce the incidence of age-related diseases such as cancer. The development of a greater reserve of ASC in all tissue types in naked mole rats facilitates efficient maintenance of the tissue in an environment of high oxidative and mechanical stress, reduces the likelihood of fixation of deleterious mutations due to increased selection against deleterious variants, and slows the clonal expansion that occurs in aging can be observed. The lower ASC division rates in the gut of naked mole-rats – as in humans – also likely prevent proliferative exhaustion of ASCs, which is necessary for a longer life expectancy.

The article “Adult stem cell activity in naked mole rats for long-term tissue maintenance” by Shamir Montazid, Sheila Bandyopadhyay, Daniel W. Hart, NanGao, Brian Johnson, Sri G. Thrumurthy, Dustin J. Penn, Bettina Wernisch, Mukesh Bansal , Philipp M. Altrock, Fabian Rost, Patrycja Gazinska, Piotr Ziolkowski, Bu'Hussain Hayee, Yue Liu, Jiangmeng Han, Annamaria Tessitore, Jana Koth, Walter F. Bodmer, James E. East, Nigel C. Bennett, Ian Tomlinson and Shazia Irshad was published in Nature Communications.

Scientific Article



Tail wagging - a clear sign with an unclear origin

Dogs often show sympathy and joy by wagging their tails. But how did the rhythmic back and forth of the dog's tail develop? And is tail wagging really always a synonym of joy?  The answer is anything but clear. Tail wagging is a conspicuous but scientifically elusive behaviour. Until now, different scientific meanings have been attributed to it, leading to fragmentary and contradictory answers. An international review study just published in the journal Biology Letters with the participation of the Konrad Lorenz Institute of Ethology (KLIVV) at the University of Veterinary Medicine Vienna highlights this problem - and at the same time provides new explanatory approaches to finally develop a structured theoretical framework.

In their review, the study authors summarise the existing research on the mechanisms, development, evolution and function of tail wagging in domestic dogs (Canis familiaris) and show where the results converge or diverge. As a solution to this discrepancy, the scientists suggest investigating this behaviour from its evolutionary roots.

Two new hypotheses to explain how tail-wagging evolved

The researchers put forward two hypotheses to explain its more frequent occurrence compared to other closely related dog species (canids) such as wolves. According to this hypothesis, tail wagging could have evolved in two ways during the domestication process: either as a by-product of selection for other traits, such as docility, or as a trait directly selected for by humans who are attracted to repetitive and rhythmic movements.

Giulia Cimarelli from the Domestication Lab (KLIVV) at Vetmeduni and her colleagues see this as an important starting point for new studies: "We propose to test these hypotheses through neurocognitive studies in both dogs and humans and thus shed light not only on a key behaviour of dogs, but also on the evolutionary history of characteristic human traits, such as our ability to perceive and produce rhythmic behaviours.."

A prime example of dog-human communication

Domestic dogs are the most widespread carnivores in the world: with an estimated population of one billion, they are present almost everywhere humans live. Due to their close cohabitation, humans interact directly with dogs in many contexts and must use various signals to communicate effectively. In particular, the position and wagging of the tail provide easily observable information that humans use to understand the internal state of the dog. "Tail wagging is probably one of the most distinctive animal behaviours that humans can observe," says Giulia Cimarelli.

The article "Why do dogs wag their tails?" by Silvia Leonetti, Giulia Cimarelli, Taylor A. Hersh and Andrea Ravignani was published in "Biology letters". 

Wissenschaftlicher Artikel

Successful avian flirtation: less is more

Successful courtship is a question of practice, and the most successful aren’t necessarily the biggest show-offs – alternative flirting strategies are just as promising. Subtle, demure behaviour, such as coyness, arouses curiosity and can increase the interest in a potential sexual partner. This sounds very human, but a recent study conducted by the Konrad Lorenz Institute for Ethology at the University of Veterinary Medicine Vienna analysed this behaviour in avian courtship. The review was published in the British scientific journal Proceedings of the Royal Society B.

The three researchers analysed previously published studies on avian courtship and suggest that sexual selection research has been dominated by the notion that the strongest, most impressive and most extravagant courtship displays will lead to the highest success in mate selection – in other words, that the displays best reflect the quality of the courter.

Subtle trumps vigorous

However, as the researchers note, courtship displays are often structured temporally and contain different elements with varying degrees of intensity and conspicuousness. “For example, highly intense movements are often coupled with more subtle components such as static postures or hiding displays,” as Thomas MacGillavry explains. The researchers refer to such subtle display traits as “coy”, as they involve the withholding of information about maximal display capabilities.

Three hypotheses for the success of coy courtship behaviour

The researchers examined the role of intensity variation within temporally dynamic displays and discuss three hypotheses for the evolution of coy courtship behaviours. Giovanni Spezie explains: “We first review the threat reduction hypothesis, which points to sexual coercion and sexual autonomy as important facets of sexual selection. We then suggest that variation in display magnitude exploits pre-existing perceptual biases for temporal contrast.” As a third hypothesis, the researchers propose that withholding information may leverage the receivers’ predisposition for filling in the missing gaps – a phenomenon they call “curiosity bias” – with the goal of arousing curiosity in potential sexual partners.

New insights for a better understanding of courtship behaviour

“Much like human music or theatre, courtship displays may constitute true performances in their own right, where different elements interact to entice, build suspense, surprise and excite the intended audience. The way in which such performances unfold over time represents a promising and novel direction for studies of courtship behaviour,” says Leonida Fusani. The underrepresentation of such aspects is due to the fact that behavioural research tends to break down behaviour into its components and does not look at it as a whole, the researchers say. Such an analysis, however, may not correspond to the actual interactions that occur during these kinds of courtship displays.

The article “When less is more: coy display behaviours and the temporal dynamics of animal courtship” by Thomas MacGillavry, Giovanni Spezie and Leonida Fusani was published in Proceedings of the Royal Society B.

Scientific article

Photos: Dominic Chaplin

Social experience enhances female attraction to male courtship songs

Male house mice produce complex ultrasonic vocalisations (USVs), especially during courtship and mating. Their calls are similar to birdsong, although they are inaudible to us because they are above the frequency range of human hearing (>20 kHz). Male courtship songs are attractive to females, but it depends on their social experience, as shown in a recent study conducted by Vetmeduni’s Konrad Lorenz Institute of Ethology.

In their study, the researchers conducted a playback experiment with wild female house mice (Mus musculus musculus) in which each subject was simultaneously presented with entering an area with recordings of male USVs versus another area playing a control recording with no male USVs. allowed to choose between an area with a speaker playing

The experiment aimed to test whether the females’ attraction to male USVs was influenced by any of the three factors, social experience (comparing females housed individually or socially with another female), sexual receptivity (comparing females were in oestrus or not), or neonatal paternal exposure (comparing females that were reared with or without their father). Previous studies suggested that these factors influence the attraction of female mice to male USVs, but the results were contrary to expectations and limited to inbred strains of laboratory mice.

Social experience has a positive effect, paternal exposure does not play a role

Overall, the females showed no attraction to the males' USVs, but it turned out to depend upon their housing. "We found that the females were attracted to male USVs if they were housed with another female, whereas females that were housed individually, showed the opposite response and avoided the male USVs,” says Sarah Zala from the Konrad Lorenz Institute for Ethology. "It is unclear why individual housing reversed females' attraction towards male courtship songs", she explains, "but living alone might make them more cautious about approaching an unfamiliar male."

“We also found that females showed more attraction towards male USVs when they were not in oestrus, and especially if they were not in oestrus and socially housed,” says co-author, Dustin Penn also from the Konrad Lorenz Institute for Ethology. "This oestrous effect is consistent with a previous study on laboratory mice, he points out, "but we have no explanation." Finally, early exposure to a father had no effect on the females’ preference for male USVs.

Social experience and sexual cycle make all the difference

In summary, this recent study shows that the attraction of wild female mice towards male courtship songs depended upon their social experience (housing) and oestrous stage. These results should facilitate research on the genetic control of hearing loss, often conducted with laboratory mice. The researchers emphasize how their findings show how seemingly unimportant factors, such as social housing and sexual cycle, can influence the behaviour of mice, despite that these and many other such variables are not usually reported in scientific papers. These results thus raise concerns that unreported variables potentially contribute to the "replication crisis" in science.

The article “Attraction of female house mice to male ultrasonic courtship vocalizations depends on their social experience and estrous stage” by Jakob Beck, Bettina Wernisch, Teresa Klaus, Dustin J. Penn and Sarah M. Zala was published in PLOS ONE.

Scientific article


Plastic instead of straw: Storks use human waste to build nests

Human-induced environmental pollution has a significant impact and even influences the nestbuilding of birds. This is shown by a recent European study led by the Konrad Lorenz Institute of Ethology at Vetmeduni using storks. However, the use of human waste differs significantly between individual stork populations.

Two major consequences of the ever-increasing human expansion are the conversion of natural habitats into agricultural land and the expansion of built-up areas. Related to this, human waste is also found just about everywhere. This has serious implications: Plastic pollution, in particular, is impacting wildlife worldwide. Discarded plastic is ubiquitous and increasingly a material for birds to incorporate into their nest structure - as now shown by a European research team from Spain, Poland and Austria using the white stork (Ciconia ciconia) as an example. In their study, the scientists describe the type, frequency and amount of anthropogenic nesting materials in two populations of the white stork in two geographically distant breeding areas, namely in Poland and in Spain.

Poland is not Spain: Significant differences in the use of plastic

In the total of 303 nests of the two populations, the researchers found significant differences in the use of anthropogenic nesting materials. To explain the reason of this, the scientist:in used remote sensing data from the Human Footprint Index (HFI) and the proportion of Impervious Surface Areas (ISA) - covered by buildings, roads and similar man-made structures. "We found that both ISA and HFI were positively related to the amount of anthropogenic nesting materials in the Spanish population. In contrast, there were no statistically significant correlations in the Polish population," said study final author Marcin Tobółka of the Vetmeduni's Konrad Lorenz Institute of Ethology. In addition, the researchers:in were able to demonstrate that the use of anthropogenic nesting material in Spain was twice as high as in the Polish white stork population.

Habitats: Variation in human footprint as a major factor

According to the study, the different human footprint HFI values for the Spanish and Polish study sites reflect different levels of human pressure on natural habitats. As a result, the Spanish white stork population inhabits more urbanized areas. In contrast, the Polish population remains a farmland bird and inhabits mainly areas with semi-natural meadows and pastures.

The article "The prevalence of anthropogenic nest materials differs between two distinct populations of migratory birds in Europe" by Zuzanna Jagiello, Łukasz Dylewski, José I. Aguirre, Joanna T. Białas, Andrzej Dylik, Alejandro López-García, Ireneusz Kaługa, Adam Olszewski, Joachim Siekiera and Marcin Tobółka was published in Environmental Science and Pollution Research.

Scientific article


Climate change alters bird clutches

A worldwide study with the participation of the University of Veterinary Medicine Vienna shows: Climate change has far-reaching consequences and also affects the offspring of birds - in very different ways.

Climate change influences the timing of reproduction in many bird species, but little is known about the impact on annual reproductive output. A recently published global study with the participation of the Vetmeduni now provides important new data based on a meta-analysis.

Broods become smaller on average

The research team examined long-term breeding data for the period from 1970 to 2019. A total of 201 populations of 104 bird species with 745,962 clutches on all continents were included in the study. On average, the number of offspring decreased over the last decades, but the researchers found significant differences between individual species and populations: 56.7% of the populations (significant at 17.4%) produced fewer offspring, whereas 43.3% (significant at 10.4%) had larger broods.

Some species benefit from climate change

"The results show that climatic changes influence offspring production," says co-author Marcin Tobółka from the Konrad Lorenz Institute of Ethology at Vetmeduni. In detail, the analyses indicate that rising temperatures have a negative effect especially on migratory, larger species, while sedentary species with smaller bodies might benefit from a warmer climate.

Declining number of birds is not due to smaller clutches

Since the trend towards smaller clutches is not very pronounced and is also inconsistent, the researchers assume that the rapid decline in bird populations worldwide is only to a small extent due to changes in the number of young.

The article „The effect of climate change on avian offspring production: A global meta-analysis“ by Lucyna Halupkaa, Marcin Tobółka, Konrad Halupkagg et al. was published in „PNAS“.

Scientific article


Poor visibility makes tadpoles more cautious

Low light and cloudy water are bad for vision. But how do such environmental conditions affect the behaviour of aquatic animals? A recently published study by the University of Veterinary Medicine in Vienna investigated this question using tadpoles. According to this, changing environmental conditions influence the behaviour of frog larvae - an important finding, especially because of the disturbance of many natural habitats by humans.

In their study, the international research team examined the behaviour of tadpoles of two poison dart frog species. The aim was to investigate the connection between environments with restricted vision and the individual reaction to perceived risks.

The poison dart frog species Dendrobates tinctorius - a frog with facultatively cannibalistic tadpoles - and Oophaga pumilio - whose tadpoles depend on their mother's food supply - were tested in different experimental settings. First, the general activity and space utilization of the tadpoles was measured on a black and white background, and then on either a black or white background where the tadpoles were exposed to visual cues from potential predators.

Clear and less clear effects

The effects of the original environment on the tadpoles of Dendrobates tinctorius were clear, according to study co-author Bibiana Rojas from the Konrad Lorenz Institute of Ethology at Vetmeduni: "Tadpoles that grew up in a darker original habitat were less active than tadpoles from lighter original habitats and did not respond to either of the two visual predators with increased activity. In contrast, tadpoles from a brighter source environment swam more when in the presence of potentially hostile conspecifics.” According to Rojas, this suggests that tadpoles can visually distinguish between predators. This hypothesis is also supported by the results with Oophaga pumilio: Their reactions to the two visual stimuli did not differ.

Clear proof of the influence of environmental disturbances on growing animals

A key finding of the study is that risk perception in animals is situation-dependent. In addition, the quality of light during adolescence has a significant impact on how animals respond to risk in novel contexts. "As animals are increasingly exposed to disturbed habitats, our results underscore how sensitively animals that rely on their vision respond to sudden environmental disturbances," Bibiana Rojas stresses.

Scientific article


Female scent – accelerated growth in juvenile male mice

Exposing female house mice (Mus musculus) to the scent of male urine is known to accelerate their sexual development in what scientists call the Vandenbergh effect. A recently published study led by the University of Veterinary Medicine Vienna now shows that this effect works both ways. The study found that juvenile male mice grew significantly faster when exposed to female urinary scent.

In their study, the research team tested whether exposing juvenile male mice to female urine influences their growth and the size of their sexual organs. Three-week-old male house mice were exposed to female urine daily 5x/week for about 30 minutes over a period of three months. A control group was exposed to normal water only.

Faster growth, but no influence on muscle mass or sexual organs

“We found that males exposed to females grew significantly faster and gained more body mass than control animals, despite all males being reared on the same amount of diet,” says the study’s first author, Sarah M. Zala of Vetmeduni’s Konrad Lorenz Institute of Ethology, “but we detected no differences in males’ muscle mass or sexual organs.” Exposing juvenile males to male urine had no effect on their growth. Last author Dustin J. Penn, also from the Konrad Lorenz Institute of Ethology, highlights the importance of the study: “Our results provide the first evidence to our knowledge that juvenile male mice accelerate their growth when exposed to the urine of adult females.”

Benefit without compromise: no change in immune resistance

The researchers also tested whether the males’ accelerated growth involved any functional trade-offs, where one benefit is given up in exchange for another, regarding the males’ immune resistance to an experimental infection. “We exposed juvenile male mice to a bacterial pathogen (Salmonella enterica) but found no evidence that increased growth had negative trade-offs on immune resistance to infectious disease,” says Dustin J. Penn. “Bacterial clearance, body mass or survival during infection were no different when compared to the animals from the control group.”

Underlying mechanisms still unclear

The exact mechanisms through which female urine triggers the accelerated growth response in males remains unclear, but an endocrine-mediated puberty acceleration seems conceivable. The new findings could prove useful for future studies aimed at influencing the growth or sexual development of male animals using more natural methods. According to the researchers, further studies are now needed to learn more about the mechanisms behind this effect. This would, for example, help to determine whether and how female urine exposure affects male growth and sexual development in a natural context.

The article "Female scent accelerates growth of juvenile male mice" by Sarah M. Zala, Brian Church, Wayne K. Potts, Felix Knauer and Dustin J. Penn was published in „Scientific Reports“.

Scientific article


Sexual selection alters dance moves of birds during courtship display

All dressed up and a god on the dance floor – in Saturday Night Fever, John Travolta made an impression both on the big screen and with the audience. Birds do it in a similar way, combining an attractive plumage with an acrobatic performance. The evolution of avian courtship displays was the focus of an international study conducted with the participation of researchers from the University of Veterinary Medicine Vienna using manakins, a group of birds found throughout the American tropics.

For their study, the researchers compared the elaborate courtship behaviour of two closely related species, golden-collared manakins (Manacus vitellinus) and white-collared manakins (Manacus candei), and their hybrids, focusing on a small island population of hybrids off the coast of Panama.

Courtship dance beats genetic similarity

The study confirmed that the island birds were genetically similar to the mainland hybrids, which in turn were more similar genetically to the white-collared manakin parental species. The research team then analysed the courtship dance, which is performed within an area demarcated by small saplings, which the courtship male cleans before his courtship dance (jump-snap routine).

The researchers were surprised to find that hybrid males, despite their genetic similarity to white-collared manakins, performed key dance manoeuvres like golden-collared manakins. Other elements of the hybrids’ dance performance either did not differ from that of the white-collared parents or was a mix of the courtship dance of both parental species.

Modular evolution in response to sexual selection

But why does the courtship dance of hybrid males resemble that of golden-collared manakins when the genetic background of the hybrids is more consistent with white-collared manakins? The researchers suspect that selected components of the dance routines of golden-collared manakins have been adopted by white-collared manakins through sexual selection.

Leonida Fusani, the study’s last author and head of the Konrad Lorenz Institute of Ethology at Vetmeduni Vienna, explains this process in evolutionary terms: “We hypothesise that such modular evolution occurs in response to sexual selection, whereby specific components of the bird’s dance routine shift to yield a broader change in its functional appearance.”

The article "Beyond plumage: acrobati c courtship displays show intermediate patt erns in manakin hybrids" by  Julia Barske, Matthew J. Fuxjager, Claudio Ciofi, Chiara Natali, Barney A. Schlinger, Tim Billo and Leonida Fusani was published in „Animal Behaviour“.

Video vom Balzritual

Wissenschaftlicher Artikel


Birds and biologgers – shape and position matter

Biologging devices are often attached to birds for research purposes and to collect important data. Now a team of researchers led by the University of Veterinary Medicine Vienna has investigated the aerodynamic effect of biologgers with northern bald ibis, an endangered species of bird, in a wind tunnel. The results showed that biologging devices significantly influence energy expenditure and flight distances, and that aerodynamic optimizations and proper positioning on the birds’ bodies can significantly reduce the detrimental effects.

There has been little scientific research to date regarding the impact of biologgers on animal aerodynamics and hydrodynamics. This stands in marked contrast to the increasingly extensive use of such technologies in wild-living animals. Recently, there have been growing concerns about the detrimental effects that these devices may have on the animals involved.

While the focus in biologging has long been solely on reducing weight, the researchers in this study investigated the aerodynamic effects of the devices. For this purpose, the northern bald ibises (Geronticus eremita) were trained to fly in a wind tunnel where heart rate and dynamic body acceleration (VeDBA) were measured as parameters for energy expenditure in relation to different logger shapes and wind flow directions.

The perfect biologger: attached to the back of the body and aerodynamically shaped

“Our data demonstrates that the position of biologging devices significantly influences the flight distances, and that shape has a considerable effect on energy expenditure. Unfavourable shape and positioning not merely affect the amount of energy expended during flapping flight; the energetically probably more important effect is that the devices impair the bird’s ability to glide or soar, which forces them to perform the energetically much more demanding flapping flight more frequently,” says the study’s first author, Ortal Mizrahy-Rewald from the Research Institute of Wildlife Ecology at Vetmeduni, summarizing the key findings of the study.

A complementary study with wild-living northern bald ibis during spring migration demonstrates that the position of the devices on the birds’ backs affects the length of the flight stages. “Birds that carried the devices on the upper back had significantly shorter flight stages compared to birds with a device positioned further towards the tail,” as Mizrahy-Rewald explains.

Little effort required to reduce detrimental effects

According to the researchers, the detrimental effects can be reduced with relatively little effort through a strictly aerodynamic design of the housing and increased consideration of aerodynamics when attaching the device to the animal’s body. In birds, the attachment of biologging devices via leg loops to the lower back is clearly preferable to the common attachment method via wing loops on the upper back. Nevertheless, the importance of drag reduction may vary between systems, as the benefits of having a biologging device close to the centre of gravity may outweigh the increase in drag that this involves.

The article “The impact of shape and attachment position of biologging devices in Northern bald ibises” by Ortal Mizrahy‑Rewald, Natalie Winkler, Frederik Amann, Katharina Neugebauer, Bernhard Voelkl, Herwig A. Grogger, Thomas Ruf, and Johannes Fritz was published in Animal Biotelemetry.

Scientific article


Drones and bird protection - a double-edged sword

A current international study led by the Konrad Lorenz Institute of Ethology at the Vetmeduni examined the effects of drone flights for research purposes on vultures. The researchers come to the conclusion that unmanned aerial systems offer significant advantages over other investigation methods. On the other hand, there are risks from potential disruptive effects at the breeding site of the birds of prey. The scientists therefore recommend using drones with a sense of proportion.

Vultures are among the world's most threatened bird species and play a unique role at the bottom of the food chain in ecosystems. They are therefore of great interest to science. The use of drones for research on them is developing rapidly. Reasons are technological advances, affordability and easy accessibility. However, there are a number of factors that must be taken into account when using unmanned aerial systems in order not to disturb the sensitive phase of the birds' reproduction.

An urgen need to close dangerous knowledge gaps

“The reduced disturbance of wildlife is the main argument for using modern observation and photo techniques with drones. The big unknown, however, is how animals will react and the potential for long-term negative consequences. To fill this dangerous gap, we strongly recommend documenting the use of drones with animals in captivity and in the wild. In addition, we need uniform guidelines for the use of drones in order to be able to scientifically interpret disturbances and bird reactions," says study lead author Richard Zink from the Konrad Lorenz Institute of Ethology at Vetmeduni, summarizing the most important results.

Better safe than sorry: use drones with care

Richard Zink also advocates a controlled use of drones: "Due to the lack of data on long-term disruptive effects, we advocate the precautionary principle. By following a set of species-specific recommendations, the potential negative impacts of drones can be limited and their value for conservation management maximized. In particular, the physiological and long-term effects on vulture health and reproductive success should be considered.”

Concrete recommendations to the international scientific community

According to the scientists, the high sensitivity and territorial behavior of most vulture species in particular pose considerable challenges to the use of drones. In general, the experts advise against the regular use of drones for nest inspections during the most sensitive breeding phases and in bad weather or when potential predators of the chicks are nearby. "We are not calling for a ban on the use of unmanned aerial vehicles for vulture researchers, but we expressly advocate careful examination of the circumstances and careful documentation of the effects," emphasizes Richard Zink, who is responsible for the study and together with his co-authors analyzed scientific research on the responses of European vultures and other similar species to drones.

The article "Assessing the potential disturbance effects on the use of Unmanned Aircraft Systems (UASs) for European vultures research: a review and conservation recommendations“ by Richard Zink, Elena Kmetova-Biro, Stefan Agnezy, Ivaylo Klisurov and Antoni Margalida was published in „Bird Conservation International“.

Wissenschaftlicher Artikel


Stress in salmon farming, and how to prevent it

Stefan Fischer of the  Konrad Lorenz Institute of Ethology is researching behavioural ecology and is especially interested in environmental factors that limit or facilitate social behaviour und behavioural plasticity in highly social species.  In a new project financed by the Vienna Science and Technology Fund  - WWTF, "Implementing novel feeding strategies to improve animal welfare and the release success of commercial fish farms" he will research stress in farmed salmon.

Fish farming involves the commercial breeding of fish for food production purposes or for the rehabilitation of declining natural fish populations. Thus, improving the yield and success of commercial fish farms is not only of major economic concern, but is highly relevant to the success of conservation programs. One of the most important species produced in fish farms is the Atlantic salmon, which is highly threatened in their natural habitat.

For many species bred in captivity, including fish, the availability of an unlimited supply of food is known to negatively impact the capacity to cope with stress. The success of fish farms largely depends on the production of unstressed individuals, in perfect condition to become either, high-quality food or successful re-introductions into the wild. Fish products derived from stressed individuals have a shorter shelf life, and higher levels of stress leads to low reintroduction success rates. Surprisingly, this fact is rarely considered during the commercial production of fish and very often, individuals are reared under an unlimited food supply.

In this project scientists are proposing to raise awareness of stakeholders of fish farms, to implement novel feeding strategies that consider the consequences of overfeeding. Our project has two main aims:

  1. to experimentally investigate the consequences of different feeding strategies on individual stress responses; and
  2. to improve awareness in fish farms across Sweden and Austria, that overfeeding leads to economic losses and issues in conservation programs.