Klaudia Witte

Sexual imprinting on a novel trait in the dimorphic zebra finch: sexes differ

We investigated the effect of a novel trait, a red feather on the forehead, on sexual imprinting in the dimorphic zebra finch, Taeniopygia guttata. Parents reared young in one of four imprinting groups: (1) both parents adorned with the red feather; (2) the father only adorned; (3) the mother only adorned; (4) both parents unadorned. After the young matured, we tested their preference for adorned and unadorned conspecifics of the opposite sex in simultaneous double-choice tests. Females but not males sexually imprinted on the red feather when their parents or father were adorned. In further tests, females that had sexually imprinted on the red feather did not generalize from the learned preference for a red feather to a preference for an orange or blue feather. Neither males nor females reared by unadorned parents showed a latent preference for potential mates adorned with a red, orange, or blue feather. Our results show that in the dimorphic zebra finch, only females sexually imprint on a novel trait. Sexual imprinting can support the evolution of novel male traits and would enhance the dimorphism in this species.

Sexual imprinting on a novel blue ornament in zebra finches

Sexual imprinting plays an important role for the development of mate preferences in birds. We tested whether male and female zebra finches Taeniopygia guttata sexually imprinted on an evolutionary novel trait, a blue feather on the forehead in parents. Additionally, we tested whether males and females would transfer a learned preference for the blue feather to a preference for blue leg bands, and whether a potential mate with two novel blue traits can amplify its attractiveness. Offspring were raised by parents in four different imprinting groups: (1) both parents unadorned; (2) the mother adorned only; (3) the father adorned only; (4) both parents adorned with the blue feather. After young reached maturity, we tested their mate preference for adorned and unadorned conspecifics of the opposite sex in binary choice tests. Females of the father adorned imprinting group sexually imprinted on the blue feather, and females reared by adorned parents showed a tendency to prefer adorned males. None of the males sexually imprinted on the blue feather. Our study replicates the results of a previous study on sexual imprinting on a red feather in zebra finches. We, therefore, propose a sex difference in the learning process of sexual imprinting. Females sexually imprinted on the blue feather did not transfer the learned preference to males with blue leg bands, and two novel blue traits could not amplify the attractiveness in males and females for the opposite sex. Our study emphasizes the role of sexual imprinting for the cultural evolution in mate preferences in zebra finches.

Technical and conceptual considerations for using animated stimuli in studies of animal behavior

Abstract Rapid technical advances in the field of computer animation (CA) and virtual reality (VR) have opened new avenues in animal behavior research. Animated stimuli are powerful tools as they offer standardization, repeatability, and complete control over the stimulus presented, thereby “reducing” and “replacing” the animals used, and “refining” the experimental design in line with the 3Rs. However, appropriate use of these technologies raises conceptual and technical questions. In this review, we offer guidelines for common technical and conceptual considerations related to the use of animated stimuli in animal behavior research. Following the steps required to create an animated stimulus, we discuss (I) the creation, (II) the presentation, and (III) the validation of CAs and VRs. Although our review is geared toward computer-graphically designed stimuli, considerations on presentation and validation also apply to video playbacks. CA and VR allow both new behavioral questions to be addressed and existing questions to be addressed in new ways, thus we expect a rich future for these methods in both ultimate and proximate studies of animal behavior.

No pre-existing bias in sailfin molly females, Poecilia latipinna, for a sword in males

The origination of female mate preference is still not well known and may depend on genetic predispositions, social environment and sensory stimuli in the environment. Females of different populations, which live in different environments, may therefore differ in a pre-existing bias for male traits. Previous studies within the genus Xiphophorus and Priapella (Poeciliidae) have indicated that females have a latent preference for a sword in males, even though conspecific males do not express a sword. In a recent study Basolo (2002a) found such a pre-existing bias for artificially sworded males in sailfin molly females from a Louisiana population. To investigate whether Poecilia latipinna females exhibit in general a pre-existing bias for sworded males or whether populations differ in a pre-existing female preference for sworded males, we tested P. latipinna females from a Texas population for a latent preference for sworded males. We tested in video playback experiments whether sailfin molly females P. latipinna have a latent preference for males with an artificial coloured plastic sword on TV monitors. Using video playbacks we first showed in a conditioning experiment that females perceived yellow plastic swords. Females preferred to associate with conspecific males to conspecific females on TV monitors. Females, however, did not exhibit a preference for males with a coloured sword over males with a transparent sword. Our result contradicts results of a previous study showing that sailfin molly females from a different population exhibited a preference for live males with an artificial sword. Pre-existing biases for novel male traits in females may differ between populations within a species. Thus, environmental factors may influence the development of pre-existing biases and might, therefore, drive the evolution of latent preferences in different populations differently.

SEXUAL IMPRINTING SUPPORTS THE EVOLUTION OF NOVEL MALE TRAITS BY TRANSFERENCE OF A PREFERENCE FOR THE COLOUR RED

We investigated if sexual imprinting on birds with a red artificial trait can influence female preference for mates bearing other novel, i.e. not-imprinted traits in male Javanese mannikins (Lonchura leucogastroides). We tested two groups of females in mate choice tests. One group of females was sexually imprinted on parent birds adorned with a red feather on the forehead. The other group was raised by normal unadorned birds and was assumed to be sexually imprinted on the normal unadorned phenotype. Females could choose between unadorned and adorned males in simultaneous double choice tests. The adorned males were ornamented with three different kinds of artificial ornament, which differed from the learned red feather on the forehead in a specific manner. The novel traits were a blue feather which differed from the familiar red feather in colour only, red stripes at the tail which had the same colour as the red feather but differed in shape and position at the body, and blue stripes at the tail (same colour as the blue forehead feather), which were different from the red feather in all three qualities. Females which were sexually imprinted on the red feather showed a similar strong preference for the red stripes at the tail as for the learned red feather. These same females showed no preference for males bearing a blue feather on the forehead or for males bearing blue stripes at the tail. This shows that sexual imprinting on a red trait leads to a preference only for another novel red trait due to transference of a preference for the colour red. The control females which were raised by unadorned birds responded on average indifferently to males bearing any of the artificial traits, i.e. some females rejected adorned males, some females preferred adorned males. To latter females it seems that a novel male ornament is somewhat attractive independent of any previous learning. Sexual imprinting on the red feather can influence female mate preferences for mates bearing other novel artificial traits due to transference of a preference for the colour red. Transference of colour preference makes it possible to react to a stimulus that differs from the imprinting stimulus in size, shape or position and therefore might play an important role in the evolution of conspicuous male traits.

Public Information Influences Sperm Transfer to Females in Sailfin Molly Males

In animals, including humans, the social environment can serve as a public information network in which individuals can gather public information about the quality of potential mates by observing conspecifics during sexual interactions. The observing individual itself is also a part of this information network. When recognized by the observed conspecifics as an audience, his/her presence could influence the sexual interaction between those individuals, because the observer might be considered as a potential mate or competitor. One of the most challenging questions in sexual selection to date is how the use of public information in the context of mate choice is linked to the fitness of individuals. Here, we could show that public information influences mate-choice behaviour in sailfin molly males, Poecilia latipinna, and influences the amount of sperm males transfer to a female partner. In the presence of an audience male, males spent less time with the previously preferred, larger of two females and significantly more time with the previously non-preferred, smaller female. When males could physically interact with a female and were faced with an audience male, three audience females or no audience, males transferred significantly more sperm to a female partner in the presence of an audience male than with female audience or no audience and spent less time courting his female partner. This is the first study showing that public information use turns into fitness investment, which is the crucial factor to understand the role of public information in the dynamic processes in sexual selection.

The virtual lover: variable and easily guided 3D fish animations as an innovative tool in mate-choice experiments with sailfin mollies-II. Validation

Abstract The use of computer animation in behavioral research is a state-of-the-art method for designing and presenting animated animals to live test animals. The major advantages of computer animations are: (1) the creation of animated animal stimuli with high variability of morphology and even behavior; (2) animated stimuli provide highly standardized, controlled and repeatable testing procedures; and (3) they allow a reduction in the number of live test animals regarding the 3Rs principle. But the use of animated animals should be attended by a thorough validation for each test species to verify that behavior measured with live animals toward virtual animals can also be expected with natural stimuli. Here we present results on the validation of a custom-made simulation for animated 3D sailfin mollies Poecilia latipinna and show that responses of live test females were as strong to an animated fish as to a video or a live male fish. Movement of an animated stimulus was important but female response was stronger toward a swimming 3D fish stimulus than to a “swimming” box. Moreover, male test fish were able to discriminate between animated male and female stimuli; hence, rendering the animated 3D fish a useful tool in mate-choice experiments with sailfin mollies.

Holding tight on feathers - structural specializations and attachment properties of the avian ectoparasite Crataerina pallida (Diptera, Hippoboscidae)

ABSTRACT The louse fly Crataerina pallida is an obligate blood-sucking ectoparasite of the common swift Apus apus. As a result of reduction of the wings, C. pallida is unable to fly; thus, an effective and reliable attachment to their hosts plumage is of utmost importance. The attachment system of C. pallida shows several modifications in comparison to that of other calyptrate flies, notably the large tridentate claws and the dichotomously shaped setae located on the pulvilli. Based on data from morphological analysis, confocal laser scanning microscopy, cryo-scanning electron microscopy and attachment force experiments performed on native (feathers) as well as artificial substrates (glass, epoxy resin and silicone rubber), we showed that the entire attachment system is highly adapted to the flys lifestyle as an ectoparasite. The claws in particular are the main contributor to strong attachment to the host. Resulting attachment forces on feathers make it impossible to detach C. pallida without damage to the feathers or to the legs of the louse fly itself. Well-developed pulvilli are responsible for the attachment to smooth surfaces. Both dichotomously shaped setae and high setal density explain high attachment forces observed on smooth substrates. For the first time, we demonstrate a material gradient within the setae, with soft, resilin-dominated apical tips and stiff, more sclerotized bases in Diptera. The empodium seems not to be directly involved in the attachment process, but it might operate as a cleaning device and may be essential to maintain the functionality of the entire attachment system. Highlighted Article: The avian ectoparasitic fly Crataerina pallida (Diptera, Hippoboscidae) can stay attached to its flying host, the common swift, by using a strongly modified tarsal attachment system, which provides exceptionally high attachment forces on various surfaces.

No sexual imprinting on a red bill as a novel trait

Sexual imprinting is one of several known non - genetical, yet social factors which influence mate preferences and might play a role in the evolution of novel traits. We introduced a red bill as a novel trait in a monomorphic estrildid finch, the Javanese mannikin Lonchura leucogastroides . We established three different imprinting groups in which the father only, the mother only or none of the parents had a red bill. After reaching maturity we tested the offspring in double choice tests for a response to birds of the opposite sex with a naturally coloured black bill or with an artificially coloured red bill. Neither males nor females showed a preference for potential mates with a red bill. Males and females raised by a red bill father showed even a strong rejection to conspecifics of the opposite sex with a red bill. This is in contrast to a previous imprinting study in the Javanese mannikin under similar conditions (Witte et al ., 2000) in which males and females became sexually imprinted on conspecifics adorned with a red feather on the forehead. It seems that not all kinds of novel traits birds can be sexually imprinted on. We could show in the present study that the red bill is a meaningful trait in female mate choice, i.e. females responded to males with and without a red bill in a similar way as do females imprinted on natural type parents to males with and without other artificial adornments (Witte & Curio, 1999). We could confirm an interaction between the red bill and the natural attractiveness of males as found in a previous study (Witte & Curio, 1999). Our study opens up questions about what traits are really learned and why some traits are not learned during imprinting.

Sex-Specific Audience Effect in the Context of Mate Choice in Zebra Finches.

Animals observing conspecifics during mate choice can gain additional information about potential mates. However, the presence of an observer, if detected by the observed individuals, can influence the nature of the behavior of the observed individuals, called audience effect. In zebra finches (Taeniopygia guttata castanotis), domesticated males show an audience effect during mate choice. However, whether male and female descendants of the wild form show an audience effect during mate choice is unknown. Therefore, we conducted an experiment where male and female focal birds could choose between two distinctive phenotypes of the opposite sex, an artificially adorned stimulus bird with a red feather on the forehead and an unadorned stimulus bird, two times consecutively, once without an audience and once with an audience bird (same sex as test bird). Males showed an audience effect when an audience male was present and spent more time with adorned and less time with unadorned females compared to when there was no audience present. The change in time spent with the respective stimulus females was positively correlated with the time that the audience male spent in front of its cage close to the focal male. Females showed no change in mate choice when an audience female was present, but their motivation to associate with both stimulus males decreased. In a control for mate-choice consistency there was no audience in either test. Here, both focal females and focal males chose consistently without a change in choosing motivation. Our results showed that there is an audience effect on mate choice in zebra finches and that the response to a same-sex audience was sex-specific.