Deborah L. Duffy

Seasonal Changes in Courtship Song and the Medial Preoptic Area in Male European Starlings (Sturnus vulgaris)

In male starlings (Sturnus vulgaris) courtship song plays a critical role in mate attraction. During the breeding season courtship song occurs prior to copulation and appears to reflect male sexual arousal. Outside the breeding season starlings sing, but song appears unrelated to reproduction. The aromatization of testosterone (T), likely within the medial preoptic nucleus (POM), is critical for the expression of male sexual arousal. The present study was performed to determine whether seasonal changes in the POM might relate to seasonal changes in courtship singing behavior in male starlings. T concentrations, the volume of the POM, and aromatase within the POM were examined both during and outside of the breeding season in male starlings. Song was also recorded at these times both with and without a female present. The POM was largest and contained dense aromatase immunostaining only during the spring breeding season, when T concentrations were highest and males responded to a female with an increase in courtship song. Outside the breeding season the volume of the POM was small, T concentrations were low, and males displayed no changes in song expression in response to female conspecifics. Song bout length was positively related to POM volume, and males sang longer songs in spring. Only males with nestboxes in spring responded to a female, and the POM tended to be larger in these males, suggesting that nestbox possession might influence neuroplasticity within the POM. Overall, the findings suggest that T-dependent plasticity and aromatase activity within the POM might regulate courtship singing in a wild songbird.

Response biases in auditory forebrain regions of female songbirds following exposure to sexually relevant variation in male song

In many species of songbirds, individual variation between the songs of competing males is correlated with female behavioral preferences. The neural mechanisms of song based female preference in songbirds are not known. Working with female European starlings (Sturnus vulgaris), we used immunocytochemistry for ZENK protein to localize forebrain regions that respond to sexually relevant variation in conspecific male song. The number of ZENK-ir cells in ventral caudo-medial neostriatum [NCMv] was significantly higher in females exposed to longer songs than in those exposed to shorter songs, whereas variation in the total duration of song exposure yielded no significant differences in ZENK expression. ZENK expression in caudo-medial ventral hyperstriatum [cmHV] was uniformly high in all subjects, and did not vary significantly among the three groups. These results suggest that subregions of NCM in female starlings are tuned to variation in male song length, or to song features correlated therewith. Female starlings exhibit robust behavioral preferences for longer over shorter male songs (Gentner and Hulse; Anim Behav 59:443-458, 2000). Therefore, the results of this study strongly implicate NCM in at least a portion of the perceptual processes underlying the complex natural behavior of female choice.

Consequences of elevating plasma testosterone in females of a socially monogamous songbird: evidence of constraints on male evolution?

To explore whether selection for testosterone-mediated traits in males might be constrained by costs of higher testosterone to females, we examined the effects of experimental elevation of plasma testosterone on physiological, reproductive, and behavioral parameters in a female songbird, the dark-eyed junco (Junco hyemalis). We used subcutaneous implants to elevate testosterone (T) in captive and free-living female juncos. In captive birds, we measured the effects of high T on body mass, feather molt, and brood patch formation. In the field, we monitored its effects on the timing of egg laying, clutch size, egg size, egg steroid levels, incubation, and nest-defense behavior. Females implanted with testosterone (T-females) had significantly higher circulating levels of testosterone than did control females (C-females). Captive T-females had lower body mass, were less likely to develop brood patches, and delayed feather molt relative to C-females. Among free-living females, the interval between nest completion and appearance of the first egg was longer for T-females than for C-females and egg yolk concentrations of testosterone were higher, but there were no significant differences in estradiol levels, clutch size, or egg size. Incubation and nest defense behavior were also similar between T- and C-females. Our results suggest that selection on males for higher testosterone might initially lead to a correlated response in females producing changes in body mass and feather molt, both of which could be detrimental. Other possible female responses would be delayed onset of reproduction, which might reduce reproductive success, and higher yolk testosterone, which might have either positive or negative effects on offspring development. We found no reason to expect reduced parental behavior by females as a negative fitness consequence of selection for higher testosterone in males.

Diet quality affects an attractive white plumage pattern in dark-eyed juncos (Junco hyemalis)

Sexually selected traits that act as signals of quality often display some degree of condition dependence. In birds, condition dependence of ornamental plumage is often mediated by production costs related to acquisition or allocation of dietary resources. White plumage ornaments, however, have often been assumed to be inexpensive because their production requires neither pigment nor specialized feather structure. In male dark-eyed juncos (Junco hyemalis), the size of a white patch on the tail contributes to attractiveness and mating success. Using captive males, we examined the effects of diet quality on the size and brightness of the tail-white patch. After removing four tail feathers to induce replacement, we maintained subjects on a subsistence (low-protein) or enriched (high-protein) diet while induced feathers grew. Birds that received an enriched diet grew their feathers more quickly and grew larger, brighter white patches. Feather growth rate was positively correlated with the increase in the size of the tail-white patch, a relationship that was stronger in the subsistence diet group. However, within diet treatments, faster-grown feathers were slightly duller. Taken together, these results suggest that variation in diet quality may lead to condition-dependent expression of tail white and that condition dependence may be stronger in more stressful environments. We suggest a mechanism by which increased feather growth rate may lead to an increase in the size of the tail-white patch and discuss potential trade-offs between signal size and brightness.

Does sex or photoperiodic condition influence ZENK induction in response to song in European starlings

Variables such as the photoperiod a bird experiences, or its sex, affect behavioral responses to song. The present experiment investigated whether song-induced expression of the immediate-early gene ZENK is also influenced by sex or photoperiod. We examined the expression of the protein product of ZENK in wild-caught male and female European starlings (Sturnus vulgaris) in different photoperiodic conditions. In the first experiment, adult reproductively active male and female starlings were presented with either conspecific male song or no song in experimental chambers. In the second experiment, conspecific male song was presented to reproductively active and reproductively inactive adult female starlings. Localization of the ZENK protein product revealed that song stimulation resulted in a significant increase in the number of ZENK immunoreactive (-ir) cells in the caudomedial neostriatum (NCM) and the caudomedial hyperstriatum ventrale (cmHV) compared with unstimulated birds. No differences in the number of ZENK-ir neurons were observed between males and females or between reproductively active and inactive females. Thus, the present data indicate that the number of cells expressing ZENK in NCM and cmHV following song playback does not vary with sex or photoperiod in starlings.

Dog Breeds and Their Behavior

Domestic dogs display an extraordinary level of phenotypic diversity in morphology and behavior. Furthermore, due to breeding practices introduced during the nineteenth century, these phenotypic traits have become relatively ‘fixed’ within breeds, allowing biologists to obtain unique insights regarding the genetic bases of behavioral diversity, and the effects of domestication and artificial selection on temperament. Here we explore differences in behavior among the 30 most popular dog breeds registered with the American Kennel Club based on owner responses to a standardized and validated behavioral questionnaire (C-BARQ©). The findings indicate that some breed-associated temperament traits (e.g. fear/anxiety) may be linked to specific gene mutations, while others may represent more general behavioral legacies of ‘ancient’ ancestry, physical deformity, and/or human selection for specific functional abilities. They also suggest that previous efforts to relate dog breed popularity to behavior may have failed due to the confounding effects of body size.

A Neuroethological Approach to Song Behavior and Perception in European Starlings: Interrelationships Among Testosterone, Neuroanatomy, Immediate Early Gene Expression, and Immune Function

Publisher Summary The purpose of this chapter is to review studies on the interrelationships among endocrine state, brain mechanisms for song perception and production, and immunocompetence and relate these to the question of female choice based on male song in European starlings (Sturnus vulgaris). The chapter illustrates how by studying a single species from multiple viewpoints one can start to make connections among the major physiological communications systems—namely, the nervous system, the endocrine system, and the immune system. This approach is needed to address how behavior is controlled and concomitantly how these physiological systems that regulate behavioral output have themselves been shaped by natural and sexual selection. Song in European starlings is long and complex and can include imitations of sounds from other species. Several lines of evidence support the contention that male starling song is important for female mate choice. European starlings and other members of the songbirds (suborder Passeres or Oscines) have evolved a suite of neural specializations in association with their sophisticated vocal abilities, which facilitate the learning, production, and perception of song. One can consider starling song as a sequence of phrases or motifs, where each motif is an acoustically complex event. The primary adaptive function of male starling song is in attracting and obtaining mates. Male European star lings produce a long complex song that is used by females to choose mates in a breeding context. Females tend to prefer males that produce songs organized into long bouts. These studies illustrate how behavioral investigations of functional significance can provide tools to implement a neuroethological investigation of behavioral mechanisms.

Behavioral and psychological characteristics of canine victims of abuse.

Abuse is an intentional act that causes harm to an individual. Dogs (Canis familiaris) with a known or suspected history of abuse were solicited for the study. A panel of 5 experts in canine behavior and abuse selected the dogs judged as having a certain or near certain history of being abused for inclusion in the study. Behavioral evaluations of the dogs were obtained using the Canine Behavioral Assessment and Research Questionnaire, which utilizes ordinal scales to rate either the intensity or frequency of the dogs behaviors. Sixty-nine dogs ultimately met the criteria for inclusion in the study. When compared with a convenience sample of 5,239 companion dogs, abused dogs were reported as displaying significantly higher rates of aggression and fear directed toward unfamiliar humans and dogs, excitability, hyperactivity, attachment and attention-seeking behaviors, persistent barking, and miscellaneous strange or repetitive behaviors. Delineating the behavioral and psychological characteristics of abused dogs provides the first step in identifying and distinguishing the risk factors and sequelae associated with abuse, which may inform the development of preventive and therapeutic programs for nonhuman animal abuse.

Aspects of Juvenile and Adolescent Environment Predict Aggression and Fear in 12-Month-Old Guide Dogs

Maturational changes in behavior, and the possible influence of the puppy-raising environment on behavioral development, were investigated in a total sample of 978 prospective guide dogs belonging to four different breeds/crosses. All dogs belonged to the same guide dog organization, and had been exposed to similar early environmental influences prior to being assigned to puppy-raising households at 7–8 weeks of age. Behavioral data were collected from puppy raisers when the dogs were 6 and 12 months old using the C-BARQ©, a standardized, validated, and widely used survey instrument that measures the frequency and/or severity of most common behavior problems in dogs. Information about the puppy-raising environment was obtained from puppy raisers using a standardized questionnaire shortly before the dogs were returned to the guide dog organization for training. Data were analyzed using both univariate and multivariate statistics (binary logistic generalized estimating equations modeling and generalized linear modeling). The findings demonstrated specific maturational changes in behavior between 6 and 12 months of age. In particular, German Shepherd dogs displayed an increase in stranger-directed aggression compared with the other breeds/crosses between 6 and 12 months of age. Several aspects of the puppy-raising environment were associated with puppies’ C-BARQ scores at 12 months of age. In particular, growing up in households with more experienced puppy raisers, and in the company of at least one other dog, were both associated with positive effects on a number of puppy behaviors. By contrast, puppies that had been frightened by a person or threatened by another unfamiliar dog showed significantly worse scores for fear of strangers and dogs, respectively. Being frightened by a person, being reared by less experienced puppy raisers, and/or in households without other pets were associated with less successful training outcomes. The relevance of these findings to current guide dog breeding and husbandry practices is discussed.