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

2023-06-26

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

2023-06-21

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

2023-06-13

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

2023-06-01

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

2023-05-11

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

2023-05-08

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

2023-04-12

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.

2023-03-30

Aposematism is a way animals protect themselves from predators by warning them of their dangerous defenses. These warning signals can be in the form of bright colours or patterns, which often inform about the chemicals, such as alkaloids, that animals have stored in their bodies. Some animals get these chemicals from their food, so the amount and type of defense can vary depending on what they eat and where they live. Examples of animals that use aposematism include colourful frogs and some butterflies. While alkaloid defenses have been the subject of scientific inquiry for decades, their relationship to aposematic signal variation in the colours they are advertised with is less understood. 

An international team of researchers, including Bibiana Rojas from the Konrad Lorenz Institute of Ethology and her team, have studied different populations of the Dyeing Poison Frog in northeastern French Guiana. The Dyeing Poison Frog, is a type of frog species that lives in northern South America. It has many different colours and patterns, and these can vary depending on where the frog lives. Sometimes, even frogs living in the same area can look different from each other. These frogs have distinct alkaloid profiles and varying unpalatability to predators.

In a study conducted with Blue Tits as model predators, the researchers identified 15 alkaloids that are correlated with predator response in one frog population, including three previously undescribed. The study looked at two populations of frogs and found that even though the frogs had different warning signals, there were some key chemicals that were always present and helped to protect the frogs. The researchers hope that by understanding more about how predators respond to these chemicals, they can learn more about the evolution of chemical defenses.

The study provides a novel method for linking unpalatability of skin secretions with the toxins which may contribute to the predator response. This could help explain how varying alkaloid combinations are capable of eliciting consistent behavioural responses, and eventually driving evolutionary change in the characteristics of  aposematic animals.

The article "Linking Predator Responses to Alkaloid Variability in Poison Frogs" by J. P. Lawrence, Bibiana Rojas, Annelise Blanchette, Ralph A. Saporito, Johanna Mappes, Antoine Fouquet, and Brice P. Noonan was published in the Journal of Chemical Ecology.

Scientific article

2023-03-13

Neolamprologus pulcher (N. pulcher) is a species of cichlid found on rocky coasts in East Africa. They are one of only a handful of highly social fish species in the world. Instead of dispersing, they often prefer to stay at home. A research team from the Konrad Lorenz Institute of Ethology at the University of Veterinary Medicine, Vienna, has now investigated the reasons for this unusual social behaviour – and thus complements scientific theories explanations for the evolution of complex sociality in fishes. The long-term study has just been published in the top journal "Science Advances".

Extreme pressure from predators has previously been seen by scientists as the main reason for the unusual social behavior of N. pulcher: This is because a fish that wants to leave its home range is likely to be eaten. So it pays to stay at home.

Only particularly strong and fit individuals in good condition can overcome these “ecological constraints” (the name of the corresponding well-known theory). Weaker animals, however, are forced to guard the home and have very little room for self-realization “under their parents´ fins” - the chance of having their own offspring is thus extremely low.

First such long-term study on the cichlid species N. pulcher.

To confirm this common hypothesis, however, measurements of actual reproductive success have been lacking until now. In the world's first long-term study of this kind, a research team from Vetmeduni therefore examined N. pulcher under natural conditions. First author Arne Jungwirth of the Konrad Lorenz Institute of Ethology at the Vetmeduni said: "We measured the lifespan, reproductive success and social status of nearly 500 tagged fish over a period of up to five years.

Both sexes benefit from sedentariness

It turned out that both sexes benefit from staying at home, as survival probability and reproductive success increase. This is not consistent with the predictions of "ecological constraints," but rather with another classic theory - the benefits of sedentariness (benefits of philopatry).

"That both sexes benefit equally from sedentariness is surprising in that they differ both in dispersal behavior - males move around more - and in other aspects of their life history strategies. Females, for example, grow more slowly and to a smaller maximum size, but then live much longer," says Arne Jungwirth.

Polygyny with consequences: Males fight more and therefore have to relocate

According to Arne Jungwirth, the scientists found the following explanation for the fact that males have to move more often: "Competition between males prevents them from settling down more often than females - male cichlids fight more because there are fewer territories for them: There is only about one breeding male for every two breeding females, because the species practices polygyny."         

The article "Philopatry yields higher fitness than dispersal in a cooperative breeder with sex-specific life history trajectories" by Arne Jungwirth, Markus Zöttl, Danielle Bonfils, Dario Josi, Joachim G. Frommen, and Michael Taborsky was published in Science Advances.

Scientific article

2023-03-07

The Department for Interdisciplinary Life Sicences has a new Department Speaker: Univ.-Prof. Dr.rer.nat. Ludwig Huber takes over this function from Univ.-Prof. Leonida Fusani, PhD, who held it for three years. Ludwig Huber was suggested by the Department's professors and has now been appointed by the Rector. The term of office is 3 years: March 1, 2023 to February 28, 2026. As his deputies we now have KLIVV head  Leonida Fusani (1st) and FIWI head  Claudia Bieber (2nd). With a planned restructuring of the Vetmeduni, we are facing challenging times. Important groundwork will be laid as early as during the preparation of the development plan (in the summer) and the research priorities and fields defined therein as well as the profile lines. Ludwig Huber plans not only to hold the quarterly department conferences of the professors at the Department, but also to organize an annual Department meeting to which all members of the Department will be invited. These meetings will aim to make structural decisions for the Department and to coordinate between Departments, as well as to inform Department members and decide general matters affecting the Department.

We warmly welcome our new Department Speaker Ludwig Huber and at the same time thank Leonida Fusani for his wonderful services in this function.

Über Ludwig Huber

2023-03-01

Animals often produce honest signals, which is puzzling from an evolutionary perspective. A recent paper provides a new method for constructing mathematical models sufficiently complex to investigate and test theories about the evolution of honest signals. Moreover, this model confirms the authors' argument that the Handicap Principle – the textbook explanation for honest signalling – can be fully rejected.

Animals produce an amazing diversity of signals, which include the colourful plumage of peacocks, the roars of rutting stags, loud begging calls of chicks, stotting of gazelles, and scent marks and pheromones of male mice. These signals are often honest or reliable, which is surprising, because deception can be beneficial. If deception spreads and becomes common, then the signals will be ignored and communication breaks down. So, how does natural selection maintain honesty; what prevents the spread of dishonest signals?

Zahavi argued that signals are honest because they are costly to produce. It is the costs or wastefulness of a signal that makes it impossible to produce a fake signal. He called this idea the "Handicap Principle", and his proposal became widely accepted after Grafen published his 'strategic handicap' model, which he claimed confirmed the Handicap Principle.

Dustin Penn (Konrad Lorenz Institute of Ethology, Vetmeduni Vienna) and Szabolcs Számadó (Budapest University of Technology and Economics) have been collaborating on this theoretical problem for several years. They have previously shown why Grafen's and other previous models have been misinterpreted. They recently teamed up with two other theoreticians to construct a new model to analyze the surprising complexities of signalling games. In addition to providing a new method for constructing more complex and general models, their analyses show why the signal costs are irrelevant to explaining honesty.

Mathematical signalling games were originally adopted from economics, and they have often been used to model the evolution of animal signals and plant-pollinator interactions. These signalling games were far too simple, however, because they only considered the evolution of the sender, who produces the signal; they ignored the receiver, who can evolve decisions for how to respond to the signal. Thus, models are needed to investigate more complex signalling games and include this double-optimization problem.

The new model by Szamado and colleagues provides a novel and general approach for calculating cost functions and for determining how a signal will evolve and reach a stable evolutionary equilibrium. The authors then used their model to re-examine overly simplified signalling games, previously used for studying honesty in sexual signals and offspring begging calls. These are asymmetric signalling models, as the sender has more information about their condition than the receiver (similar to purchasing a used car of unknown quality; which is known as the 'lemon problem' in economics). The results show that an infinite number of signals can evolve that are honest, including signals that have no costs and only benefits. This new model shows that signals do not need to be costly in order to be honest, contrary to the Handicap Principle. This result confirms Penn and Szamado's argument that Grafen's model has been misinterpreted; it is not a model of the Handicap Principle. Honest signals evolve in this model, not because of the costs of the signal, but because of a particular tradeoff, a constraint that makes deceptive signals costly and honesty beneficial.

Thus, this new theoretical model confirms that the Handicap Principle can be fully rejected. Moreover, it provides a new method for testing ideas about the evolution of honest signals. The authors point out that this has become a rather timely topic, given the increasing spread of misinformation, which has become "one of the most important problem facing our species".

The article "Honesty in signalling games is maintained by trade-offs rather than costs" by Szabolcs Számadó, István Zachar, Dániel Czégel, and Dustin J. Penn was published in BMC Biology.

Scientific article

Also see the commentary in Proceedings of the National Academy of Sciences (PNAS): "The peacock’s tail and other flashy ornaments don’t have to come at a cost"

2023-01-30

Chemical defences often vary within and between populations both in quantity and quality, which is puzzling if prey survival is dependent on the strength of the defence.

An international team of researchers led by Cristina Ottocento from the Department of Biology and Environmental Science, University of Jyväskylä, Finland, with participation of Bibiana Rojas from the Konrad Lorenz Institute of Ethology and others, studied the within- and between-population variability in chemical defence of the wood tiger moth (Arctia plantaginis). The major components of its defences, SBMP (2-sec-butyl-3-methoxypyrazine) and IBMP (2-isobutyl-3-methoxypyrazine), are volatiles that deter bird attacks.

They hypothesized that (1) variation in the chemical defences of male wood tiger moths reflects the local predation pressure; (2) observed differences in quantity and quality of defence among populations have a genetic basis; and (3) increasing concentrations of SBMP and IBMP will elicit greater aversive reactions in predators, with the two pyrazines having an additive effect on predators' avoidance.

They found that the chemical defence of wild moths partly reflects local predator selection: high predation pressure populations (Scotland and Georgia) had stronger chemical defences, but not lower variance, than the low-predation populations (Estonia and Finland). Based on the common garden results, both genetic and environmental components seem to influence the strength of chemical defence in moth populations. Furthermore, they found that IBMP alone did not provide protection against bird predators, but worked against bird attacks only when combined with SBMP, and while SBMP was more effective at higher concentrations, IBMP was not.

Altogether this suggests that, when it comes to pyrazine concentration, more is not always better, highlighting the importance of testing the efficacy of chemical defence and its components with relevant predators, as extrapolating from chemical data may be less than straightforward.

The article "Not just the sum of its parts: Geographic variation and nonadditive effects of pyrazines in the chemical defence of an aposematic moth" by Cristina Ottocento, Anne E. Winters, Bibiana Rojas, Johanna Mappes, and Emily Burdfield-Steel was published in the Journal of Evolutionary Biology.

Scientific article

2023-01-17

The long seasonal travels of migratory birds are a well-known phenomenon. But what hormonal processes are involved? A recent study by the Konrad Lorenz Institute of Ethology at the University of Veterinary Medicine Vienna identifies sharply rising levels of the hormone ghrelin as a key trigger of migratory restlessness. The recently published research could not, however, confirm a connection with the hormone corticosterone as shown in other studies.

Migratory birds have spectacular physiological adaptations to accommodate the long-distance flights between their breeding and wintering grounds. The animals use fat reserves built up prior to migration as their main source of energy. In both captive and free-flying birds, the migratory phenotype – the physical changes that occur prior to and during migration – is signalled by rapid and marked increases in food and energy intake as well as by changes in nocturnal activity and by migratory restlessness. However, there has been little scientific evidence to date on the exact hormonal mechanisms underlying this process.

Hormone ghrelin makes quail fit for long flights

An international research team led by the Konrad Lorenz Institute of Ethology at the University of Veterinary Medicine used common quails (Coturnix coturnix) to assess if  the hormone corticosterone and the gut-derived hormone ghrelin play a role in the seasonal expression of migratory behaviour. For their experiment, the researchers exposed quails to controlled changes in day length  to simulate autumn migration, followed by a wintering period. The researchers then compared corticosterone and ghrelin concentrations and assessed whether these two metabolic hormones varied between migratory states.

“In accordance with our predictions, we found that the emergence of the migratory phenotype was associated with higher concentrations of ghrelin. In addition, ghrelin correlated with changes in body mass of birds as they transitioned into their autumnal migratory state and as they entered the wintering state,” explains the study’s first author, Valeria Marasco from the Konrad Lorenz Institute of Ethology at Vetmeduni.

No correlation between corticosterone levels and migratory restlessness

Contrary to their predictions, however, the researchers observed no correlation between circulating levels of ghrelin and corticosterone. The scientists were also unable to detect elevated levels of corticosterone in the migratory phenotype. “There was no significant correlation between baseline corticosterone levels and changes in body mass, levels of food intake or migratory restlessness (the urge of captive birds to migrate at night)” says the study’s senior author Leonida Fusani, head of the Unit of Ornithology at the Konrad Lorenz Institute of Ethology.

The article "Ghrelin, not corticosterone, is associated with transitioning of phenotypic states in a migratory Galliform“ von Valeria Marasco, Hiroyuki Kaiya, Gianni Pola, and Leonida Fusani was publised in „frontiers“.

Scientific article

2023-01-11