scholarly journals Testosterone induces plumage ornamentation followed by enhanced territoriality in a female songbird

2020 ◽  
Vol 31 (5) ◽  
pp. 1233-1241 ◽  
Author(s):  
Jordan Boersma ◽  
Erik D Enbody ◽  
John Anthony Jones ◽  
Doka Nason ◽  
Elisa Lopez-Contreras ◽  
...  
Keyword(s):  
Territorial Behavior ◽  
Free Living ◽  
Territory Defense ◽  
Testosterone Treatment ◽  
Territorial Aggression ◽  
Proximate Mechanisms ◽  
Active Life ◽  
Pretreatment Period ◽  
Territorial Behaviors ◽  
Partial Acquisition

Abstract We know little of the proximate mechanisms underlying the expression of signaling traits in female vertebrates. Across males, the expression of sexual and competitive traits, including ornamentation and aggressive behavior, is often mediated by testosterone. In the white-shouldered fairywren (Malurus alboscapulatus) of New Guinea, females of different subspecies differ in the presence or absence of white shoulder patches and melanic plumage, whereas males are uniformly ornamented. Previous work has shown that ornamented females circulate more testosterone and exhibit more territorial aggression than do unornamented females. We investigated the degree to which testosterone regulates the expression of ornamental plumage and territorial behavior by implanting free-living unornamented females with testosterone. Every testosterone-treated female produced a male-like cloacal protuberance, and 15 of 20 replaced experimentally plucked brown with white shoulder patch feathers but did not typically produce melanic plumage characteristic of ornamented females. Testosterone treatment did not elevate territorial behavior prior to the production of the plumage ornament or during the active life of the implant. However, females with experimentally induced ornamentation, but exhausted implants, increased the vocal components of territory defense relative to the pretreatment period and also to testosterone-implanted females that did not produce ornamentation. Our results suggest that testosterone induces partial acquisition of the ornamental female plumage phenotype and that ornament expression, rather than testosterone alone, results in elevations of some territorial behaviors.

scholarly journals Testosterone induces a female ornament followed by enhanced territoriality in a tropical songbird

2020 ◽  
Author(s):  
Jordan Boersma ◽  
Erik D. Enbody ◽  
John Anthony Jones ◽  
Doka Nason ◽  
Elisa Lopez-Contreras ◽  
...  
Keyword(s):  
Territorial Behavior ◽  
Similar Function ◽  
Free Living ◽  
Territory Defense ◽  
Territorial Aggression ◽  
Proximate Mechanisms ◽  
Naturally Occurring ◽  
Female Ornament ◽  
Empirical Tests ◽  
Partial Acquisition

ABSTRACTWe know little of the proximate mechanisms underlying expression of signaling traits in female vertebrates. Across males the expression of sexual and competitive traits, including ornamentation and aggressive behavior, is often mediated by testosterone. In the White-shouldered Fairywren (Malurus alboscapulatus) of New Guinea, females of different subspecies differ in presence or absence of white shoulder patches and melanic plumage, while males are uniformly ornamented. Previous work has shown that ornamented females circulate more testosterone and exhibit more territorial aggression than do unornamented females. We investigated the degree to which testosterone regulates expression of ornamental plumage and territorial behavior by implanting free-living unornamented females with testosterone. Every testosterone-treated female produced a male-like cloacal protuberance, and 15 of 20 replaced plucked brown feathers with white shoulder patch feathers, but did not produce melanic plumage characteristic of ornamented females. Testosterone treatment did not elevate territorial behavior prior to production of the plumage ornament and exhaustion of the implant. However, females with experimentally induced ornamentation, but exhausted implants, increased the vocal components of territory defense relative to fully unornamented control and also to testosterone-implanted females. Our results suggest that testosterone induces partial acquisition of the ornamental plumage phenotype, and that ornament expression, rather than testosterone alone, results in elevated territorial behavior.Lay SummaryTestosterone regulates expression of a suite of competitive traits in male organisms and could have similar function in females. Empirical tests are needed to determine the extent to which testosterone promotes production of ornamentation and competitive behaviors in female animals. We supplemented testosterone in unornamented females of a species where naturally occurring ornamented females circulate higher testosterone and are more territorially aggressive. Implanted females produced partial ornamentation, which was followed by increased territoriality that was apparently unrelated to testosterone circulation itself.

scholarly journals Characterizing territoriality and the mechanisms that mediate it in female Anolis gundlachi lizards

2019 ◽  
Author(s):  
◽  
Ellee G. Cook
Keyword(s):  
Body Condition ◽  
Morphological Characteristics ◽  
Parasite Load ◽  
Field Studies ◽  
Territorial Behavior ◽  
Territory Size ◽  
Free Living ◽  
The Subject ◽  
Males And Females ◽  
Territorial Behaviors

Territoriality is a suite of behaviors through which animals secure access to particular areas or resources. It is prevalent across animal groups and has the potential to exert substantial influence on fitness by mediating how individuals are distributed across the landscape, which individuals interact socially, and those that have access to resources. Territoriality has been the subject of extensive research on animal behavior over the last century and has influenced our understanding of other aspects of species ecology, such as mating systems. However, a substantial portion of research on territoriality has focused primarily on males, despite the fact that females of many species are also observed to exhibit territoriality. This is particularly true of studies investigating the mechanisms that modulate territoriality, such as circulating hormones and morphological characteristics including body condition. As such, two important questions remain open for many territorial taxa--within territorial species, do both sexes use similar repertoires of territorial behavior, and if so, are these behaviors mediated by the same mechanisms in both females? The aim of this dissertation has been to pursue these two questions in the lizard Anolis gundlachi. Anolis have figured prominently in territorial research over the last century but are plagued with the same pitfall of lack of studies of females, which is a common problem across many groups, as is observed in other species. Integrating field studies and laboratory techniques, I characterized the behavior and space use of free-living female A. gundlachi in Puerto Rico to assess whether females exhibit similar behavioral patterns as males. As part of this research, I assessed the potential for individual variation in body condition to mediate differences in territory size. I also characterized the testosterone and corticosterone profiles of free-living male and female A. gundlachi, and staged territorial intrusions among females to evaluate the potential for these hormones to mediate differences in territorial behavior across the sexes and among females. Finally, I evaluated the potential for a tradeoff between testosterone, corticosterone, and parasite load by measuring parasite loads of Plasmodium sp. in the same free-living population. Together, the results presented in this dissertation demonstrate that female A. gundlachi exhibit territorial behaviors that highly resemble those observed in male A. gundlachi and other species of Anolis. However, two mechanisms commonly implicated in the control of territoriality in males--metrics of body size and circulating hormones concentrations--did not explain similar patterns in females. In addition, we found no evidence of a tradeoff between hormone concentration and parasite load. Taken together, these results demonstrate that different mechanisms may influence similar behaviors exhibited by males and females of the same species. In combination with a growing body of work investigating the evolution of territorial and other aggressive behaviors in females, our findings demonstrate the need for more direct studies of females to more clearly understand why these behaviors have arisen in both sexes and to identify the mechanisms that mediate them in females.

Individual Variation in the Strength of Territory Defense in Male Song Sparrows: Correlates of Age, Territory Tenure, and Neighbor Aggressiveness

Behaviour ◽  
2004 ◽  
Vol 141 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Jeremy Hyman ◽  
Melissa Hughes ◽  
Stephen Nowicki ◽  
William Searcy
Keyword(s):  
Individual Differences ◽  
Reproductive Success ◽  
Extrinsic Factors ◽  
Territory Defense ◽  
Intrinsic Factors ◽  
Territorial Aggression ◽  
Male Song ◽  
Song Sparrows ◽  
Territory Owner ◽  
Older Males

AbstractIn many species, the ability to defend a territory is essential for a male to obtain any reproductive success at all, and even among territorial individuals, variation in the strength of territory defense could have a significant impact on how much reproductive success is obtained. Previous studies have documented consistent individual differences in the vigor with which male song sparrows (Melospiza melodia) defend their territories, as measured by the strength of their reactions to territorial intrusions simulated through song playback. Variation in the strength of defense could reflect intrinsic differences among individuals in their resource holding potential (RHP), or variation in extrinsic factors. In this study, we examined whether variation in the strength of territory defense corresponds to differences in intrinsic factors such as the age or experience of the territory owner, the extrinsic factor of the level of aggression shown by neighbours, or both. Results indicate that males that previously held territories on the study site, regardless of whether they were holding the same territory as the previous year, show higher levels of territory defense than males that are new to the study site, and, assuming that returning males are older males, suggest that age is more important than experience on a specific territory in determining strength of territory defense. In addition, we found evidence that males with high levels of territorial aggression tend to be spatially clustered. The pattern observed suggests that a combination of intrinsic and extrinsic factors contribute to the expression of individual differences in territorial aggression.

scholarly journals Progesterone modulates aggression in sex-role reversed female African black coucals

2008 ◽  
Vol 275 (1638) ◽  
pp. 1053-1060 ◽  
Author(s):  
Wolfgang Goymann ◽  
Andrea Wittenzellner ◽  
Ingrid Schwabl ◽  
Musa Makomba
Keyword(s):  
Aggressive Behaviour ◽  
Sex Role ◽  
Bird Species ◽  
General Mechanism ◽  
Hormonal Changes ◽  
Free Living ◽  
Experimental Conditions ◽  
Resource Defence ◽  
Territorial Aggression ◽  
African Black

Testosterone is assumed to be the key hormone related to resource-defence aggression. While this role has been confirmed mostly in the context of reproduction in male vertebrates, the effect of testosterone on the expression of resource-defence aggression in female vertebrates is not so well established. Furthermore, laboratory work suggests that progesterone inhibits aggressive behaviour in females. In this study, we investigated the hormonal changes underlying territorial aggression in free-living female African black coucals, Centropus grillii (Aves; Cuculidae). Females of this sex-role reversed polyandrous bird species should be particularly prone to be affected by testosterone because they aggressively defend territories similar to males of other species. We show, however, that territorial aggression in female black coucals is modulated by progesterone. After aggressive territorial challenges female black coucals expressed lower levels of progesterone than unchallenged territorial females and females without territories, suggesting that progesterone may suppress territorial aggression and is downregulated during aggressive encounters. Indeed, females treated with physiological concentrations of progesterone were less aggressive than females with placebo implants. This is one of the first demonstrations of a corresponding hormone–behaviour interaction under challenged and experimental conditions in free-living females. We anticipate that our observation in a sex-role reversed species may provide a more general mechanism, by which progesterone—in interaction with testosterone—may regulate resource-defence aggression in female vertebrates.

scholarly journals Covariation of Clutch Size, Laying Date, and Incubation Tendency in the American Kestrel

The Condor ◽  
2001 ◽  
Vol 103 (3) ◽  
pp. 570-578 ◽  
Author(s):  
Keith W. Sockman ◽  
Hubert Schwabl
Keyword(s):  
Environmental Factors ◽  
Clutch Size ◽  
Egg Production ◽  
Laying Date ◽  
Falco Sparverius ◽  
Free Living ◽  
American Kestrel ◽  
Proximate Mechanisms ◽  
American Kestrels ◽  
Seasonal Decline

Abstract Seasonal decline in clutch size is common in birds, but the proximate mechanisms for this phenomenon have not been elucidated. The most credible model to date posits that late-laying females lay fewer eggs due to a seasonal increase in the tendency to incubate during laying, which inhibits egg production. We tested this model with free-living and laboratory American Kestrels (Falco sparverius) by quantifying changes in clutch size and incubation tendency during laying over the course of the breeding phase. Consistent with the model, clutch size in free-living kestrels decreased while incubation increased with progress of the 74-day breeding phase. Inconsistent with the model, variation in incubation tendency during laying was not associated with clutch size in either the field or the laboratory. In the laboratory, incubation increased but clutch size did not decrease over the course of the 77-day breeding phase. In the laboratory, females that nested early in one breeding phase renested more quickly and nested in a second breeding phase more quickly than females nesting late in the first breeding phase. This indicates that timing of laying is, in part, a property of individual females, independent of environmental factors. Together, our findings suggest that both clutch size and timing of laying are inherent, correlated properties of particular females. Although incubation tendency may influence clutch size, other factors appear to override its influence. Covariación del Tamaño de la Nidada, la Fecha de Postura y la Tendencia de Incubación en Falco sparverius Resumen. Aunque la disminución estacional en el tamaño de la nidada es común entre las aves, los mecanismos proximales para este fenómeno no han sido elucidados. El modelo de mayor credibilidad propuesto hasta el momento sugiere que las hembras que ovipositan tarde ponen menos huevos debido a un aumento estacional en la tendencia a incubar durante la postura que inhibe la producción de huevos. Pusimos a prueba este modelo con individuos de Falco sparverius en condiciones naturales y en cautiverio, cuantificando los cambios en el tamaño de la nidada y la tendencia a incubar durante la postura a lo largo de la época reproductiva. Tal como el modelo plantea, el tamaño de la nidada en individuos silvestres de F. sparverius disminuyó mientras que la incubación aumentó a medida que transcurrían los 74 días de la época de reproducción. Mientras tanto, en contraste con el modelo, la variación en la tendencia a incubar durante la postura no estuvo asociada con el tamaño de la nidada ni en el campo ni en el laboratorio. En el laboratorio, la incubación aumentó pero el tamaño de la nidada no disminuyó en el transcurso de la época reproductiva (77 días). En condiciones de laboratorio, las hembras que anidaron temprano en una fase reproductiva volvieron a anidar más rápidamente en una segunda fase que las hembras que anidaron tarde en la primera. Esto indica que el tiempo en que se hace la postura es en parte una propiedad de cada hembra y es independiente de factores ambientales. En conjunto, nuestros hallazgos sugieren que tanto el tamaño de la nidada como el momento de la postura son propiedades correlacionadas de cada hembra en particular. Aunque la tendencia a incubar podría influenciar el tamaño de la nidada, otros factores parecen anular su influencia.

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