Male Condition (male + condition)

Distribution by Scientific Domains


Selected Abstracts


Variation in Vocal Performance in the Songs of a Wood-Warbler: Evidence for the Function of Distinct Singing Modes

ETHOLOGY, Issue 7 2004
Martin D. Beebee
Male North American wood-warblers (family Parulidae) subdivide their song repertoires into two different categories, or modes, of singing (first and second category songs). These two modes are thought to be specialized for interacting with females and males, although the data are inconclusive. I conducted an acoustic analysis of the song types used by yellow warblers (Dendroica petechia) for type I (first category) and type II (second category) singing to ask whether there are consistent structural differences between them which could provide insight into how they might function as separate signals. I found that type I songs are performed closer to the upper boundary of a song performance limit, measured in terms of the difficulty of production, compared with type II songs. By contrast, the performance of specific song types did not depend on whether they were used for type I singing vs. type II singing by different males. In addition, type I songs had a greater amplitude increase across the first two syllables compared with type II songs. There was no relationship between the performance of type I or type II songs and male condition. These results suggest that wood-warblers might subdivide their song repertoire into distinct categories to highlight the relative vocal performance of their songs. [source]


Strophe Length in Spontaneous Songs Predicts Male Response to Playback in the Hoopoe Upupa epops

ETHOLOGY, Issue 5 2004
Manuel Martín-Vivaldi
Hoopoe (Upupa epops, Coraciformes) males produce a very simple song during the breeding season in order to attract females and repel intruders. Strophes vary in length (i.e. number of elements) both within and between males, and previous studies have shown that this song cue is positively correlated with male condition and breeding success. In the present study we tested whether strophe length of males influences male behaviour during intra-sexual contests, in a colour-ringed population in southeast Spain. Paired males were presented with a recorded song with long strophes during the pre-laying period, while they were near their mates, in order to provoke male mate-defence behaviour. Most males responded to the playback, but the strategy of defence adopted depended on their own strophe length in spontaneous songs recorded before the experiments. While singing responses were common to most of the males, only those using long strophes adopted the most risky strategy of approaching the loudspeaker. However, the males that approached produced abnormal songs during playback, that were shorter and with fewer strophes than those of males that did not approach, and used shorter strophes in comparison with spontaneous songs before the experiment. These differences in quality of the song produced in response to the playback suggest that long-strophe males were basing their response mainly on attacking rather than singing, while short-strophe males tried to resolve the contest at a distance by means of their song. These results show that strophe length reflects some component of the competitive ability of males (either physical strength or aggressiveness) in the hoopoe, which together with previous results regarding its role for female choice, show that it is a sexual signal with dual function. [source]


CONDITION DEPENDENCE OF SEXUAL ORNAMENT SIZE AND VARIATION IN THE STALK-EYED FLY CYRTODIOPSIS DALMANNI (DIPTERA: DIOPSIDAE)

EVOLUTION, Issue 5 2004
Samuel Cotton
Abstract We used the stalk-eyed fly Cyrtodiopsis dalmanni to examine predictions made by condition-dependent handicap models of sexual selection. Condition was experimentally varied by manipulation of larval food availability. Cyrtodiopsis dalmanni is a highly dimorphic species exhibiting strong sexual selection, and the male sexual ornament (exaggerated eyespan) showed strong condition-dependent expression relative to the homologous trait in females and nonsexual traits. Male eyespan also showed a great increase in standardized variance under stress, unlike nonsexual traits. The inflated variance of the male ornament was primarily attributable to condition-dependent (but body-size-independent) increase in variance. Thus, evaluation of male eyespan allows females to gain additional information about male condition over and above that given by body size. These findings accord well with condition-dependent handicap models of sexual selection. [source]


Territorial behaviour and immunity are mediated by juvenile hormone: the physiological basis of honest signalling?

FUNCTIONAL ECOLOGY, Issue 1 2009
Jorge Contreras-Garduño
Summary 1The role of the juvenile hormone (JH) as a potential mediator in the trade-off between male,male competition and immune response has not been tested, but its study could reveal a potential mechanism that mediates resource allocation between these two traits. 2Controlling for body size, we tested whether males of the territorial damselfly Calopteryx virgo administrated with methoprene acid, an analog of the JH (JHa), compared to control males, increased their aggression and occupation time on territories but decreased their phenoloxidase (PO) activity (a key enzyme used during immune response after a bacterial challenge). We found an increase in aggression in JHa treated males compared to control males, but the opposite was found for PO activity. 3As fat load and muscle mass are also important traits during a contest, we tested whether JHa males compared to control males showed more fat and muscle content 2 h after JHa administration. Our results did not show a significant difference between both male groups, suggesting that JHa only increased aggression. 4These results and a review of other published articles, which have documented an effect of JH on a variety of functions in insects, suggest that JH may be a target of sexual selection: this hormone not only promotes the expression of secondary sexual characters but also seems condition-dependent and so its titers may indicate male condition. [source]


Singing as a handicap: the effects of food availability and weather on song output in the Australian reed warbler Acrocephalus australis

JOURNAL OF AVIAN BIOLOGY, Issue 2 2005
Mathew L. Berg
Bird song is generally regarded as a sexually selected trait, and may represent a reliable handicap signal under at least certain conditions. Females may use the degree of male song production as a reliable cue to male condition or territory quality. We investigated the effect of supplementary feeding on song output in the migratory Australian reed warbler Acrocephalus australis. We experimentally increased the food availability on alternate days, and recorded several weather variables. We measured song rate and song length independently. Supplementary fed birds sang more on feeding days than on non-feeding days, while control birds did not show this effect. Song output was not significantly associated with any of the weather variables examined. Our results indicate that singing has the potential to serve as a reliable handicap signal to territorial food availability irrespective of the prevailing weather conditions. We discuss the role of energetic constraints and behavioural flexibility on the signaling function of song. [source]


,What should I do with a 60-year old man with a slightly low serum total testosterone concentration and normal levels of serum gonadotrophins'?

CLINICAL ENDOCRINOLOGY, Issue 5 2010
T. Hugh Jones
Summary The fundamental question in assessing an older man with a slightly low total testosterone and normal gonadotrophin levels is to determine whether or not he has clinical hypogonadism. Hypogonadism is defined as a clinical syndrome complex, which comprises both symptoms as well as biochemical testosterone deficiency. As symptoms are nonspecific and there are no clear cut-off values for testosterone levels this invariably leads to a clinical dilemma. International guidelines have been published which provide recommendations to aid the clinician in making a diagnosis. Late-onset hypogonadism, the preferred terminology for age-related hypogonadism, can only be made once other causes have been excluded. Evidence shows that low testosterone levels are associated with several common male conditions including erectile dysfunction, osteoporosis and diabetes. Short-term studies have shown benefits of testosterone replacement therapy (TRT) on body composition, bone metabolism, insulin resistance, sexual function and quality of life. Recommendations give clear advice on safety monitoring, specifically in relation to prostate health. If a diagnosis of hypogonadism is made with borderline testosterone levels then a 3-month trial of TRT can be considered. The diagnosis of hypogonadism associated with borderline testosterone levels and the decision to treat should only be made by an experienced clinician. [source]


Modulation of sexual signalling by immune challenged male mealworm beetles (Tenebrio molitor, L.): evidence for terminal investment and dishonesty

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2006
B. SADD
Abstract Organisms partition resources into life-history traits in order to maximise fitness over their expected lifespan. For the males of many species fitness is determined by qualitative and quantitative aspects of costly sexual signals: The notion that epigamic traits are costly forms the cornerstone of those theories that propose parasites drive sexual selection. Consequently studies examining this notion assume sexual signalling is honest (i.e. driven by cost) when they seek to identify correlations or causal links between male immune function and attractiveness. We demonstrate that immune challenged males of the mealworm beetle, Tenebrio molitor, increased their investment in epigamic pheromone signals: these males became significantly more attractive to females whilst increasing the activity of a key immune effector system. In other words males increase terminal reproductive effort (invest in attractiveness) in response to a survival threat (immune insult). Consequently the signal preferred by the female is dishonest when considering the male's condition. [source]