Males In Good Condition Research Articles

Paternity and parental care in the black-throated blue warbler, Dendroica caerulescens

Much debate surrounds the relationship between male parental care and paternity. We quantified parental care of yearling (second year: SY) and older (after second year: ASY) male black-throated blue warblers and determined parentage with microsatellites over four breeding seasons. ASY males that had sired all young in their broods fed 7-day-old nestlings at higher rates than ASY males that sired only some of the young in their broods. This relationship was not present in yearling males. A negative relationship between level of paternity and paternal care may arise if males facultatively adjust their care in response to cues of paternity, if poor-quality males are both more likely to be cuckolded and less able to provide parental care, or if males reduce both mate guarding and parental care to pursue extrapair matings. Parental care given by ASY males was not associated with additional mating opportunities during the nestling period. Thus, pursuit of extra matings is unlikely to account for the association between paternity and parental care. ASY males in better condition had higher levels of paternity, but did not guard their mates more closely nor feed their young at higher rates. These results suggest that ASY males may be able to assess their paternity, possibly by using cues related to levels of local synchrony during their females' fertile periods, and adjust their care accordingly. Paternity obtained by SY males was not associated with local synchrony, however, suggesting that the apparent lack of a facultative response by males of this age class may be due to a lack of reliable cues to paternity.

Strategic male mating effort and cryptic male choice in a scorpionfly.

In animal species with high male mating effort, males often find themselves in a dilemma: by increasing their mating effort, the gain from each copulation increases but simultaneously reduces available resources and, thus, the opportunity for future copulations. Therefore, we expect males to spend less reproductive resources on matings that provide low reproductive potential, thereby saving resources for future copulations, possibly with high-quality females, a sort of cryptic male choice. However, the strength of the trade-off between investment in a current mating and resources available for future matings must not be the same for all males. Males with relatively high mating costs should allocate their limited resources more cautiously than males with more plentiful resources. Here, we examine this prediction in the scorpionfly Panorpa cognata. Prior to copulation, males produce a large salivary mass on which females feed during copulation. We show that the production of larger salivary masses leads to longer copulations. Moreover, the size of the salivary gland and salivary mass increases with increasing male condition. However, males in poor condition make a relatively higher mating investment than males in good condition. We therefore expect male condition to influence cryptic male choice. In accordance with our hypothesis, only males in poor condition choose cryptically, producing larger salivary masses in copulations with females of high fecundity.

Effects of Hematozoan Parasites on Condition and Return Rates of American Kestrels

We evaluated the relationship between blood parasites and body condition of American Kestrels (Falco sparverius) during the breeding season. Females that were infected with at least one species of parasite were in poorer condition than those without parasites during incubation but not prior to egg laying. We suggest that the relationship between parasitism and condition was masked before laying because of large increases in body mass of females during egg formation. Reduced condition of males during incubation also was associated with higher intensity of infections by Haemoproteus in one of two years. The negative association between condition and intensity of infection suggests that blood parasites impose costs on kestrels owing to competition for nutrients or allocation of energy by hosts to immune function or tissue repair. Alternatively, kestrels in poor condition may be more likely to have relapses of chronic infections, or they may be less able to control new infections because of resource limitations. In contrast to results during incubation, during the prelaying period the prevalence of parasites tended to be higher, and in one year infections were more intense, among males in good condition. One possible explanation for these results is that body condition of males during courtship is an important determinant of the quality of mate they are able to obtain, and males may be accumulating body reserves at the expense of decreased immune function. Return rates of female kestrels to the study area declined as the intensity of their Haemoproteus infections increased, suggesting that blood parasitism is associated with reduced survival or increased dispersal probability.

Effects of Hematozoan Parasites on Condition and Return Rates of American Kestrels

Abstract We evaluated the relationship between blood parasites and body condition of American Kestrels (Falco sparverius) during the breeding season. Females that were infected with at least one species of parasite were in poorer condition than those without parasites during incubation but not prior to egg laying. We suggest that the relationship between parasitism and condition was masked before laying because of large increases in body mass of females during egg formation. Reduced condition of males during incubation also was associated with higher intensity of infections by Haemoproteus in one of two years. The negative association between condition and intensity of infection suggests that blood parasites impose costs on kestrels owing to competition for nutrients or allocation of energy by hosts to immune function or tissue repair. Alternatively, kestrels in poor condition may be more likely to have relapses of chronic infections, or they may be less able to control new infections because of resource limitations. In contrast to results during incubation, during the prelaying period the prevalence of parasites tended to be higher, and in one year infections were more intense, among males in good condition. One possible explanation for these results is that body condition of males during courtship is an important determinant of the quality of mate they are able to obtain, and males may be accumulating body reserves at the expense of decreased immune function. Return rates of female kestrels to the study area declined as the intensity of their Haemoproteus infections increased, suggesting that blood parasitism is associated with reduced survival or increased dispersal probability.

The relationship between signal quality and physical condition: is sexual signalling honest in the three-spined stickleback?

Honest sexual signalling requires that the level of advertisement reveals mate quality. In the three-spined stickleback, Gasterosteus aculeatus, females base their mate choice mainly on the intensity of the males' red breeding coloration. Different results have, however, been obtained on the relationship between red breeding coloration and physical condition. In this study, the relationship was curvilinear in a natural population, with males in good and poor condition (measured as lipid content) having larger red areas than males of intermediate condition. By manipulating food intake and thus male condition prior to breeding, I further show that poor condition can induce an increase in signalling effort. This effect was further strengthened when the predation cost of signalling was increased by exposing the males to predators. This suggests that the reason for the high signalling effort of males in poor condition is their low probability of future reproduction and thus lower cost of signalling in terms of loss of future reproductive opportunities. Males in poor condition signal as a terminal effort and take larger risks and invest more in current reproduction than males in good condition. Finally, I discuss whether an effect of decreasing residual reproductive value on signalling effort could result in the breakdown of the honesty of the signal.

Sexual selection, parasites and bower height skew in a bower-building cichlid fish

The good genes mechanism of sexual selection predicts that secondary sexual ornaments may reliably reveal a males resistance to parasites. We studied correlates of courtship and spawning success in a species ofCopadichromis, a lekking cichlid fish from Lake Malawi, Africa, which builds sand bowers. We present the first evidence of a negative relationship between the structure of an extended phenotypic character (height skew of sand bowers) and male parasite load. Males that spawned had significantly fewer dilepipid cestodes in their livers than males that did not spawn, never before demonstrated in a lekking species of fish. Furthermore, males that spawned had significantly heavier gonads than 'unsuccessful males. We also found significant correlations between relative liver weight and some measures of reproductive success. This may indicate females are choosing to mate with males in better condition.

Variation in the train morphology of peacocks (Pavo cristatus)

A sample of full‐trained adult male peacocks was collected and measured to determine whether or not there were any morphological correlates of train elaboration. Peacocks with longer or heavier trains are those with relatively large fat reserves for their overall body mass. The proportion of feathers in the train which have eyespots is also greater in peacocks with a relatively large muscle. These relationships indicate that train elaboration may be condition‐dependent. Females that prefer males with larger trains may therefore gain good condition males, which may reflect overall genetic quality. There is also a significant tendency for larger‐trained peacocks to have high louse loads, after controlling for body mass. It may be that larger‐trained males are older, and have accrued more lice than younger ones. Alternatively, long‐trained males may have acquired more lice through direct contact with more females than shorter‐trained birds.

Size of Testes and Scent Glands in Capybaras, Hydrochaeris hydrochaeris (Rodentia: Caviomorpha)

The volume of the morrillo (snout scent-gland) of adult capybara (Hydrochaeris hydrochaeris) males was found to correlate significantly with testes mass (r = 0.359, d.f. = 110, P < 0.0001). This was independent of body size. Males in better condition did not have larger testes or morrillos, whereas age did correlate with size of the morrillo and testes. These results were related to the higher rates of scent marking and reproductive success of dominant males reported in previous studies.

A test of the condition-bias hypothesis using Brown-headed Cowbirds trapped during the breeding season

We examined trap bias relative to body condition, age, and sex using data collected from Brown-headed Cowbirds (Molothrus ater) decoy trapped during the 1987 and 1988 breeding seasons. A condition bias was evident, as decoy-trapped birds were in poor condition relative to those caught by mist net in an adjacent roost. This occurred in both sexes and independently of study year and male age. Paradoxically, however, males in better condition when first trapped were more likely to be recaptured in the same season, possibly reflecting more widespread movement, and hence fewer encounters with traps, by birds in poor condition. Hatching-year birds were more likely than adults to be recaptured in the same season. Trapped samples were strongly male biased, which probably reflects a difference in nutritional requirements, and thus foraging strategies, between males and females during the breeding season. This study indicates that biases among birds trapped by methods that rely on a feeding response are likely to be widespread and difficult to predict, suggesting that interpretation of data from such samples always requires caution.

Announcing intent: the aggressive state of musth in African elephants

Predictions derived from game theory suggest that animals should not signal their intentions during conflict situations. However, during the period of musth, male elephants, Loxodonta africana, announce a state of heightened aggression with signals that are unbluffable. Since smaller musth males in poor condition are able to dominate larger, normally higher-ranking, non-musth males in good condition, musth provides a useful system with which to examine the possibility of honest signalling of motivation, rather than of fighting ability. Despite the highly aggressive state of males in musth, escalated contests are extremely rare. The behaviour of musth and non-musth males suggests that opponents are able to estimate their often rapidly changing roles in the asymmetries with relative accuracy. Since, unlike most other rutting mammals, elephants have asynchronous sexually active periods, resource value varies both with age and the fluctuating sexual state of a particular individual. It is suggested that musth may be a case where information about resource value is conveyed.

SOME NEW NOCTUIDÆ

Agrotis agilis, n. s.Two males in good condition received from Mr. James Fletcher, from Vancouver, belong to a decidely different species from my semiclarata, Essay, Plate 1, Fig 9, though allied,as also to Californian gravis, and our Eastern venerabilis. Antennæ brush-like. Gray, with a brown tinge. Lines obliterate.