Audience effects in the Atlantic molly (Poecilia mexicana)–prudent male mate choice in response to perceived sperm competition risk?

Background Multidirectional interactions in social (or communication) networks can have a profound effect on mate choice behavior. For example, Poecilia mexicana males show weaker expression of mating preferences when being observed by an audience male. It was suggested that this behavior is an adaptation to reduce sperm competition risk, which arises because commonly preferred female phenotypes will receive attention also by surrounding males, and/or because the audience male can copy the focal male's mate choice. Do P. mexicana males indeed respond to perceived sperm competition risk? We gave males a choice between two females and repeated the tests under one of the following conditions: (1) during the 2nd part of the tests an empty transparent cylinder was presented (control); (2) an audience male inside the cylinder observed the focal male throughout the 2nd part, or (3) the audience male was presented only before the tests, but could not eavesdrop during the actual choice tests (non-specific sperm competition risk treatments); (4) the focal male could see a rival male sexually interacting with the previously preferred, or (5) with the non-preferred female before the 2nd part of the tests (specific sperm competition risk treatments). Results When comparing the strength of individual male preferences between the 1st and 2nd part of the tests (before and after presentation of an audience), male preferences declined slightly also during the control treatment (1). However, the decrease in strength of male preferences was more than two-fold stronger in audience treatment (2), i.e., with non-specific sperm competition risk including the possibility for visual eavesdropping by the audience male. No audience effect was found in treatments (3) and (5), but a weak effect was also seen when the focal male had seen the previously preferred female sexually interact with a rival male (treatment 4; specific sperm competition risk). Conclusions When comparing the two 'non-specific sperm competition risk' treatments (2 and 3), a very strong effect was found only when the audience male could actually observe the focal male during mate choice in treatment (2). This suggests that focal males indeed attempt to conceal their mating preferences in the visual presence of other males so as to avoid mate choice copying. When there is no potential for eavesdropping [treatment (3)], non-specific specific sperm competition risk seems to play a minor or no role. Congruent with studies on other poeciliid species, our results also show that P. mexicana males respond to perceived specific sperm competition risk, and tend to share their mating effort more equally among females when the resource value of their previously preferred mate decreases (after mating with a rival male). However, this effect is comparatively weak

Predator-induced changes of female mating preferences: innate and experiential effects

Background: In many species males face a higher predation risk than females because males display elaborate traits that evolved under sexual selection, which may attract not only females but also predators. Females are, therefore, predicted to avoid such conspicuous males under predation risk. The present study was designed to investigate predator-induced changes of female mating preferences in Atlantic mollies (Poecilia mexicana). Males of this species show a pronounced polymorphism in body size and coloration, and females prefer large, colorful males in the absence of predators. Results: In dichotomous choice tests predator-naïve (lab-reared) females altered their initial preference for larger males in the presence of the cichlid Cichlasoma salvini, a natural predator of P. mexicana, and preferred small males instead. This effect was considerably weaker when females were confronted visually with the non-piscivorous cichlid Vieja bifasciata or the introduced non-piscivorous Nile tilapia (Oreochromis niloticus). In contrast, predator experienced (wild-caught) females did not respond to the same extent to the presence of a predator, most likely due to a learned ability to evaluate their predators' motivation to prey. Conclusions: Our study highlights that (a) predatory fish can have a profound influence on the expression of mating preferences of their prey (thus potentially affecting the strength of sexual selection), and females may alter their mate choice behavior strategically to reduce their own exposure to predators. (b) Prey species can evolve visual predator recognition mechanisms and alter their mate choice only when a natural predator is present. (c) Finally, experiential effects can play an important role, and prey species may learn to evaluate the motivational state of their predators. Keywords: Sexual selection; female choice; non-independent mate choice; predator recognition; Poecilia mexican

Ziege et al. 2016 Field data latrine survey

Sheet 1 (Latrine data): Data gained from systematically mapping latrines by two persons walking line transects (app. 5 m apart) across the entire study area within 15 different study sites. Data was collected in the early morning during the reproductive season of rabbits in 2011 (April to September). Sheet 2 (Calculation degree of urbanity): Data stemming from transect counts within study sites (visitors per min and ha), the Einwohnermeldeamt of Frankfurt (residents within 500 m) and the use of ArcGis and map material provided by the city of Frankfurt (percent sealed surface and numbers of anthropogenic objects). Data on rabbit/burrow densities and group sizes respectively have been gained through observation at burrows and the use of ferrets that chased rabbits out of their burrow

Effects of gradual anthropogenic habitat alteration on the ecology and behavior of European rabbits (Oryctolagus cuniculus) in and around Frankfurt am Main

The process of urbanization is one of the major causes of the global loss of biodiversity; however, cities nowadays also have the potential to serve as new habitats for wildlife. The European rabbit (Oryctolagus cuniculus, L. 1758) is a typical example of a wildlife species that reaches stable population densities in cities. Due to intense plant and soil damages, German city authorities aim to control high rabbit densities through the application of a yearly hunting regime (e. g., in Munich, Berlin or Frankfurt am Main). In contrast, population densities of O. cuniculus are on decline in German rural areas, i. e., numbers of yearly hunting bags decreased. The aim of my doctoral thesis was to answer the following research questions: Do population densities of the European rabbit correlate with the intensity of urbanization in and around Frankfurt am Main and if so, which factors play a role in varying densities? How are burrow construction behaviors and group sizes, daytime activity patterns and anti-predator behaviors as well as communication behaviors of this mammal affected by urbanization? In my first study, I focused on population dynamics across 17 different study sites in and around Frankfurt. As one of yet few studies, I invented an approach that quantified the intensity of urbanization (degree of urbanity) of each study site base on four variables: (1) intensity of anthropogenic disturbance per min and ha, (2) number of residents within a radius of 500 m, (3) proportion of artificial ground cover and (4) numbers of anthropogenic objects per ha. Spearman rank correlations confirmed that with increasing degree of urbanity also rabbit and burrow densities increased. The access to dense shrubs, bushes etc. as suitable sites for burrow construction is the most determining factor for rabbit abundances, and therefore I presumed different densities along the rural-to-urban gradient to be driven by shifts in the availability of thick vegetation. In the second study, I calculated two indices that in both cases classified burrows to be either accumulated, evenly or randomly distributed within study sites. Additionally, in cooperation with local hunters the number of burrow entrances and animals that occupy the same burrow had been determined during the hunting season. With increasing degree of urbanity burrow distribution patterns shifted from accumulated in rural areas towards more evenly distributed within the city center of Frankfurt. This is a clear sign for an increasing access to sites suitable for burrow construction along the rural to-urban gradient. Additional Spearman rank correlations revealed that the external dimensions of burrows decreased (shorter distances between entrances) and that burrows became less complex (fewer entrances) along the rural-to-urban gradient. In accordance, the number of rabbits that commonly shared the same burrow system was highest within rural areas, whereas I found mainly pairs and single individuals within highly urbanized study sites. In the last study I compared activity patterns, burrow use and percentages of anti-predator behaviors from one hour before sunrise until one hour after sunset of rural, suburban and urban rabbit groups. A linear mixed model (LMM) and Spearman rank correlations confirmed that rabbits located at urban and suburban sites spent more time outside their protective burrows compared to their rural conspecifics. At suburban sites, individuals invested the least amount of time in anti-predator behavior. Results of this third study gave evidence that suburban rabbit populations on one hand benefit from less predation pressure by natural predators in comparison to rural sites, whereas on the other hand are exposed to less intense disturbance by humans compared to urban study sites. The last study focused on the effects that urbanization had on the latrine-based communication behavior of rabbits. As many other mammals, O. cuniculus exchange information via the deposition of excreta in latrines, and depending on the intended receiver(s), latrines are either formed in central areas for within-group communication or at territorial boundaries, e. g., for between-group communication. The relative importance of within- vs. between-group communication depends on, amongst other factors, population densities and group sizes which I proved both to shift along the considered rural-to-urban gradient. I determined latrine sizes, latrine densities and latrine utilization frequencies relative to their distance to the nearest burrow at 15 different study sites. Latrine densities and utilization frequencies increased with increasing distance from the burrow in suburban and urban populations whereas at rural sites, largest latrines and those containing the most fecal pellets were close to the burrow, suggesting that within-group communication prevailed. To sum up, for the first time, I was able to relate shifts in the ecology and behavior of the European rabbit as adaptations to a gradual anthropogenic habitat alteration that are typical for “urban exploiters”. Especially the suburban habitat provides high landscape heterogeneity (“edge habitat“) which is essential for high and stable rabbit populations. Moreover, here, comparably low human disturbance and predation pressure are given in contrast to the agriculturally transformed, open landscapes which are nowadays typical for most rural areas in central Europe. I argue that this mainly leads to the observed behavioral changes along the rural-to-urban gradient. Future plans for rural land management actions should aim to increase refuge availability by generating networks of ecotones. This would also benefit species that depend on similar ecosystem structures as the European rabbit and are on decline in Germany.Die Zerstörung natürlicher Lebensräume während des Prozesses der Urbanisierung gilt als einer der Hauptgründe für den Verlust der globalen Artenvielfalt. Dem gegenüber steht die Beobachtung, dass moderne Städte durchaus alternative Lebensräume für Tier- und Pflanzenarten bieten. Das Europäische Wildkaninchen (Oryctolagus cuniculus, L. 1758) ist ein typisches Beispiel für eine Wildtierart, die hohe Populationsdichten in städtischen Arealen wie Parkanlagen oder Friedhöfen erreicht. Häufig kommt es daher insbesondere in Großstädten wie Berlin, München oder Frankfurt am Main zu Konflikten mit der urbanen Bevölkerung, so dass Jagdmaßnahmen zur Dezimierung der Kaninchenbestände ergriffen werden. Im Gegensatz dazu ist eine deutliche Abnahme der Bestände in einigen ländlichen Gegenden Deutschlands zu beobachten. Ziel meiner publikationsbasierten Doktorarbeit war es am Beispiel von Frankfurt am Main und Umgebung den Zusammenhang zwischen dem Grad der Urbanisierung und den Populationsdynamiken von O. cuniculus zu untersuchen sowie folgende Frage zu klären: Welchen direkten und indirekten Einfluss hat der Grad der Urbanisierung auf die Bautenanlage und Gruppengröße, die Tagesaktivität und das Anti-Prädator-Verhalten sowie das Kommunikationsverhalten dieser Säugetierart hat? In meiner ersten Studie wurden die Populations- und Bautendichten von Wildkaninchenpopulationen in insgesamt 17 verschiedenen Studiengebieten in und um Frankfurt am Main bestimmt. Weiterhin wurde für jedes Gebiet ein Urbanitätsindex berechnet, der auf folgenden Variablen basiert: (1) die Störungsintensität durch den Menschen pro ha und min, (2) die Einwohnerdichte in 500 m Umkreis vom Studiengebiet, (3) dem prozentualen Anteil versiegelter Oberflächen (Gebäude, Straßen etc.) sowie (4) die Anzahl anthropogener Gegenstände pro ha. Mittels einer Spearman-Rangkorrelation konnte gezeigt werden, dass die Populations- sowie Bautendichten mit steigendem Grad an Urbanität signifikant zunahmen. In meiner zweiten Studie untersuchte ich die Anzahl der Bautenöffnungen bzw. der Kaninchen pro Bau während der Jagdsaison in Kooperation mit Stadtjägern. Mit zunehmendem Grad der Urbanisierung konnte eine gleichmäßigere Verteilung der Kaninchenbauten beobachtet werden – ein eindeutiger Hinweis dafür, dass entlang des rural-urbanen Gradienten die Anzahl an Strukturen zur Anlage von Bauten zunimmt. Weiterhin nahm die Anzahl der Ein- und Ausgänge sowie die oberirdische Ausdehnung der Bauten mit zunehmendem Grad der Urbanisierung signifikant ab. So dominierten in der Frankfurter Innenstadt kleine Bauten mit wenigen Ein- und Ausgängen die wiederum von nur wenigen Tieren bewohnt waren. In Städten ist die Störung durch den Menschen besonders intensiv während die Häufigkeit der Prädation durch natürliche Beutegreifer oft geringer ist. Meine dritte Studie bestätigte, dass sich Wildkaninchen in den urbanen und suburbanen Studiengebieten signifikant öfter außerhalb des Baues aufhielten als ihre ruralen Artgenossen. Weiterhin ergab die Studie, dass ländliche Wildkaninchen 40% ihrer Zeit darin investierten, nach Fressfeinden Ausschau zu halten sobald sie den Bau verließen. In den urbanen und suburbanen Studiengebieten nahm diese Verhaltensweise nur 20% der Tagesaktivität der Tiere ein. Statt der „Überwachung“ ihrer Umgebung verbrachten städtische Wildkaninchen mehr Zeit damit, Nahrung aufzunehmen oder sich auszuruhen. Wie bei vielen anderen Säugetierarten spielt auch bei O. cuniculus die Anlage von Kotanhäufungen (Latrinen) als olfaktorische und visuelle Signale für die Kommunikation eine große Rolle. Latrinen, die in nächster Nähe des Kaninchenbaus angelegt werden dienen dem Informationsaustausch innerhalb derselben sozialen Gruppe. Latrinen hingegen, die in einiger Entfernung vom Kaninchenbau an den Grenzen des Territoriums angelegt werden, bilden einen olfaktorischen „Zaun“ zu benachbarten sozialen Gruppen. Die Analyse der Latrinenverteilungen bzw. Latrineneigenschaften (z. B. Anzahl Pellets, Dichte, Distanz zur nächsten Vegetation) entlang des rural-urbanen Gradienten zeigte in meiner letzten Studie, dass Wildkaninchen in der Frankfurter Innenstadt nicht nur besonders viele Latrinen an den Territoriumsgrenzen in einigen Metern entfernt vom Bau anlegten, sondern diese Latrinen auch häufiger Anzeichen einer regelmäßigen Nutzung zeigten als solche direkt am Bau. Die Anlage von Latrinen zur Kommunikation zwischen benachbarten sozialen Gruppen, z. B. um das Territorium eindeutig abzugrenzen, scheint somit bei Tieren in der Innenstadt besonders wichtig zu sein. Zusammenfassend trugen die Erkenntnisse aus meiner Forschungsarbeit zu einem besseren Verständnis bei, welchen direkten und indirekten Einfluss Urbanisierung auf die Ökologie und das Verhalten eines Wildtieres haben kann. Während sich rurale Lebensräume im Zuge der modernen agrarwirtschaftlichen Nutzung überwiegend durch Offenlandschaften auszeichnen bieten suburbane und urbane Studiengebiete eine vielfältigere Habitatnutzung. Der bessere Zugang zu schützender Vegetation und Nahrung in nächster Nähe zueinander in der Stadt führt direkt zu höheren Populationsdichten und indirekt zu kleineren Bauten bzw. sozialen Gruppengrößen. Im Gegensatz zu den ländlichen Gebieten begünstigt ein niedriger Prädationsdruck sowie ein wärmeres Mikroklima weiterhin hohe Dichten in der Stadt. Wärmere Temperaturen und weniger Prädation erklären auch die beobachteten Unterschiede in der Bautenanlage und Gruppengröße, der Tagesaktivität, dem Anti-Prädator-Verhalten sowie dem Kommunikationsverhalten. Diese Beobachtungen sind auch für das Populationsmanagement von Arten von Bedeutung, die ähnliche Habitatansprüche wie das Wildkaninchen haben und in ländlichen Gebieten Deutschlands zunehmend seltener vorkommen

»Single-Kaninchen in der Großstadt« : die Geschichte einer Pressemeldung. Fragen an die Biologin Madlen Ziege

Anfang Februar veröffentlichte die Pressestelle der Goethe-Universität die Meldung „In der Stadt bauen Kaninchen dichter: Große Bauten für die ländliche Großfamilie, kleine Bauten für das städtische Pärchen.“ Die Meldung beruhte auf einem Fachartikel der Arbeitsgruppe Ökologie und Evolution im Journal of Zoology. Rasend schnell verbreitete sich die Meldung in den Medien – wir haben Madlen Ziege, Doktorandin in der Arbeitsgruppe Ökologie und Evolution einmal danach befragt, wie die Forschung mit populären oder besser: popularisierten Meldungen umgeht

Den Wandel in ein emissionsfreies Frankfurt gestalten : GRADE Sustain bietet der Climate-KIC Summer School den Rahmen für ein innovatives Brainstorming

Unter ökonomischen Gesichtspunkten ist die Mainmetropole ein etablierter Global Player, nun will sie auch in Sachen Klimaschutz eine Vorreiterrolle einnehmen. Ziel ist es, die städtische Energieversorgung in den nächsten vier Jahrzehnten komplett aus erneuerbaren Ressourcen sicherzustellen. Dabei ist Frankfurt bereits jetzt auf einem guten Weg. Neben Kopenhagen und Bristol schaffte es die größte Stadt Hessens in die Finalrunde um den Titel „Europäische Grüne Hauptstadt 2014“

A comparison of two methods to assess audience-induced changes in male mate choice

Multidirectional communicative interactions in social networks can have a profound effect on mate choice behavior. Male Atlantic molly Poecilia mexicana exhibit weaker mating preferences when an audience male is presented. This could be a male strategy to reduce sperm competition risk: interacting more equally with different females may be advantageous because rivals might copy mate choice decisions. In line with this hypothesis, a previous study found males to show a strong audience effect when being observed while exercising mate choice, but not when the rival was presented only before the choice tests. Audience effects on mate choice decisions have been quantified in poeciliid fishes using association preference designs, but it remains unknown if patterns found from measuring association times translate into actual mating behavior. Thus, we created five audience treatments simulating different forms of perceived sperm competition risk and determined focal males’ mating preferences by scoring pre-mating (nipping) and mating behavior (gonopodial thrusting). Nipping did not reflect the pattern that was found when association preferences were measured, while a very similar pattern was uncovered in thrusting behavior. The strongest response was observed when the audience could eavesdrop on the focal male’s behavior. A reduction in the strength of focal males’ preferences was also seen after the rival male had an opportunity to mate with the focal male’s preferred mate. In comparison, the reduction of mating preferences in response to an audience was greater when measuring association times than actual mating behavior. While measuring direct sexual interactions between the focal male and both stimulus females not only the male’s motivational state is reflected but also females’ behavior such as avoidance of male sexual harassment [Current Zoology 58 (1): 84–94, 2012]

Data from: Importance of latrine communication in European rabbits shifts along a rural–to–urban gradient

BACKGROUND: Information transfer in mammalian communication networks is often based on the deposition of excreta in latrines. Depending on the intended receiver(s), latrines are either formed at territorial boundaries (between-group communication) or in core areas of home ranges (within-group communication). The relative importance of both types of marking behavior should depend, amongst other factors, on population densities and social group sizes, which tend to differ between urban and rural wildlife populations. Our study is the first to assess (direct and indirect) anthropogenic influences on mammalian latrine-based communication networks along a rural-to-urban gradient in European rabbits (Oryctolagus cuniculus) living in urban, suburban and rural areas in and around Frankfurt am Main (Germany). RESULTS: The proportion of latrines located in close proximity to the burrow was higher at rural study sites compared to urban and suburban ones. At rural sites, we found the largest latrines and highest latrine densities close to the burrow, suggesting that core marking prevailed. By contrast, latrine dimensions and densities increased with increasing distance from the burrow in urban and suburban populations, suggesting a higher importance of peripheral marking. CONCLUSIONS: Increased population densities, but smaller social group sizes in urban rabbit populations may lead to an increased importance of between-group communication and thus, favor peripheral over core marking. Our study provides novel insights into the manifold ways by which man-made habitat alterations along a rural-to-urban gradient directly and indirectly affect wildlife populations, including latrine-based communication networks