UV plumage color is an honest signal of quality in male budgerigars

Elaborate and colorful feathers are important traits in female mate choice in birds. Plumage coloration can result from pigments deposited in feathers such as carotenoids and melanins, or can be caused by nano-scale reflective tissues (structurally based coloration), usually producing ultraviolet (UV) coloration. Structural colorations remain the least studied of the three most important feather colorations. Previous studies have found a female preference for UV color in the budgerigar, Melopsittacus undulatus, but it is not clear what information this ornament conveys, nor what is the possible cost associated with its production. We investigated possible correlations between immune response and plumage color of wild-type (green) male budgerigars. In particular we measured the wing web swelling resulting from injection of phytohaemagglutinin (PHA). We did not detect any correlation between the sedimentation rate and morphological and color variables. We found that UV chroma is the best predictor for the cutaneous immune activity. Indeed, male budgerigars with high UV reflectance in the breast feathers showed stronger immune responses. These results are consistent with the idea that UV colors are special signals conveying information about a bird’s condition.     

Resource-dependent nuptial feeding in Panorpa vulgaris: an honest signal for male quality

In mating systems that are characterized by resource-dependentmale behavior like nuptial feeding, food limitation obviouslyplays a major role in male performance. In Panorpa vulgaris(Mecoptera: Panorpidae), the ability to produce nuptial giftshas major fitness consequences as the number of gifts determinescopulation duration, which then determines the number of eggsfertilized by a given male. In the present study, we are ableto show that males of P. vulgaris were limited in their productionof salivary secretions. The number of saliva secretions maleswere able to produce declined in successive matings. Moreover,males of nutritionally high status produced more gifts thanthose of nutritionally low status. The proximate factor determiningmale saliva secretion was the development of the salivary gland,which in turn depended on the amount of food a male could access.The degree of male mating effort corresponded to the size ofthe salivary gland, yet while absolute investment increasedwith gland size, the relative investment decreased. Mating costsfor males thus depend on nutritional status.     

Structurally based plumage coloration is an honest signal of quality in male blue grosbeaks

We investigated the signaling function of blue plumage in maleblue grosbeaks (Guiraca caerulea) to determine if structurallybased coloration may act as a reliable signal of quality toconspecifics. Blue plumage results from the microstructureof feather barbules rather than from pigment granules, andthus it is possible that structurally based plumage ornamentsmay function differently from sexually selected ornamentalcoloration that is pigment based. The plumage of male blue grosbeaksreflects maximally in the blue-ultraviolet range, so most variationin plumage coloration among males is invisible to human observers.In previous research, we showed that increased area of blueplumage on the body is associated with a shift in the wavelengthof maximum feather reflectance toward the ultraviolet and withhigh intensity of light reflected at that maximum, and thatextreme expression of the male ornament is condition dependent.These observations suggest that blue plumage may be an honestadvertisement of male quality. We tested this hypothesis ina wild population of blue grosbeaks. We quantified male qualityin three broad categories. (1) Physical condition was assessedfrom subcutaneous fat deposits, ectoparasite load, and bodysize. (2) Territory quality was assessed from territory area,prey abundance, and predation risk. (3) Paternal investmentwas assessed from male feeding rate. We found that the bluestmales have the largest body size, maintain the largest territorieswith the greatest prey abundance, and feed nestlings in thefirst nest of the season at the highest rates. We conclude thatstructurally based plumage coloration functions as an honest,intraspecific signal of quality.     

Population density and phenotypic attributes influence the level of nematode parasitism in roe deer

The impact of parasites on population dynamics is well documented, but less is known on how host population density affects parasite spread. This relationship is difficult to assess because of confounding effects of social structure, population density, and environmental conditions that lead to biased among-population comparisons. Here, we analyzed the infestation by two groups of nematodes (gastro-intestinal (GI) strongyles and Trichuris) in the roe deer (Capreolus capreolus) population of Trois Fontaines (France) between 1997 and 2007. During this period, we experimentally manipulated population density through changes in removals. Using measures collected on 297 individuals, we quantified the impact of density on parasite spread after taking into account possible influences of date, age, sex, body mass, and weather conditions. The prevalence and abundance of eggs of both parasites in females were positively related to roe deer density, except Trichuris in adult females. We also found a negative relationship between parasitism and body mass, and strong age and sex-dependent patterns of parasitism. Prime-age adults were less often parasitized and had lower fecal egg counts than fawns or old individuals, and males were more heavily and more often infected than females. Trichuris parasites were not affected by weather, whereas GI strongyles were less present after dry and hot summers. In the range of observed densities, the observed effect of density likely involves a variation of the exposure rate, as opposed to variation in host susceptibility.     

Female goats use courtship display as an honest indicator of male quality

Due to the differential cost of reproduction in promiscuous species, like domesticated goat(s) (Capra hircus), it is expected that females should mate with higher quality males, while males should mate with a greater number of females. Females may use conspicuous secondary sexual characteristics of males such as courtship display to distinguish among high and low quality males. Testosterone (T) controls a large suite of secondary sexual characteristics and variation in T concentrations may account of differences in courtship rates. Two studies were conducted to examine the relationship between T concentrations and courtship rate and its role in mammalian female mate choice. Experiment 1 utilized bucks (intact males) and Experiment 2 utilized T-replaced wethers (castrated pre-pubertally). During the first year of Experiment 2, T-replaced wethers received either vehicle control (CON), 25 mg or 100 mg testosterone propionate (TP). During the second year of Experiment 2, T-replaced wethers were treated with either 5 mg, 15 mg or 25 mg TP. For all experiments, mean courtship rates and circulating T concentrations were measured, as well as female preference for males displaying different courtship frequencies. T concentrations and courtship rate were positively correlated for bucks and estrous females preferred high courting bucks. Males receiving 25 mg and 100 mg TP courted females at a similar rate, but both were significantly higher than courtship rates of the CON wethers. Courtship rates of the 25 mg, 15 mg and 5 mg TP-treated males were all significantly different. Females did not show a preference between the 100 mg or 25 mg TP-treated wethers, however both were preferred in comparison to the CON wethers. Females did not show preference between the 25 mg or 15 mg TP-treated wethers, however both were preferred in comparison to the 5 mg TP-treated wethers. Taken together, these studies suggest that courtship rate is T-dependent. Further, females can use courtship rate to distinguish among males.     

Dominance is not always an honest signal of male quality,but females may be able to detect the dishonesty

Females prefer dominant males as mating partners in numerous species. Male dominance rank is considered as an honest signal of male quality, because only healthy males in good condition are thought to be able to win fights with other males. Here, we tested whether activation of the immune system influences the success of males in male–male competition and mating in the field cricket, Gryllus integer. We activated the immune system of males with a nylon monofilament (to mimic a parasitoid larva), and arranged fights between male pairs to assess male dominance and associated mating success. Activation of the immune system with nylon monofilament substantially enhanced the fighting success of males during male–male competition but had no effect on mating success. However, sham-manipulation (a wound only) did not have any effect on fighting success although females mated more often with dominant males. Our study suggests that when male crickets meet an apparent survival threat they may behave more dominantly, probably owing to terminal investment. Male success during male–male competition is not always an honest signal of males’ quality, but females may be able to detect this dishonesty.     

A paretic condition in an Anaplasma phagocytophilum infected roe deer calf

This paper describes a case of Anaplasma phagocytophilum infection in a roe deer (Capreolus capreolus) calf in Norway. The calf was found deserted, paretic, and heavily infested with Ixodes ricinus ticks. It was euthanized and investigated postmortem. Anaplasma phagocytophilum was detected in several tissues by polymerase chain reaction (PCR) and 16S rRNA sequence analyses. Analyses for Borrelia burgdorferi sensu lato and tick-borne encephalitis (TBE) virus infections were negative. This is the first report of a possible paretic condition in A. phagocytophilum infected roe deer.     

Variation in cohort mandible size as an index of roe deer (Capredus capreolus) densities and population trends

This paper examines the effects of increasing population density on the skeletal development of roe deer as indexed by variation in the size of the mandible. We tested for density-dependence in total jaw length and minimum diastema height among cohorts in a single, intensively studied population in France. A strong relationship of average adult jaw length of both males and females with deer density in the year of birth of a given cohort was observed, and presumably reflects inadequate nutrition of juveniles at high population density. No such relationship was observed for the minimum diastema height which remained constant over the range of densities studied. This relationship was exploited to investigate population trends of roe deer in Britain. In nine populations, where equivalent data were available for between 16 and 28 separate cohorts, a consistent pattern of variation in cohort jaw size was observed, with a decrease in average total length, but not diastema height, towards the present. This trend is discussed in relation to changes in habitat structure in the coniferous forests of Britain. The utility of cohort jaw length as a management tool to index population trends of roe deer is highlighted.     

Courtship as an honest indicator of male parental quality in the bicolor damselfish, Stegastes partitus

Previous work on the bicolor damselfish, a species with exclusivemale parental care of eggs, suggested that female mate choicewas based on male characteristics. The aims of this study wereto determine whether females discriminate among potential mateson the basis of courtship and, if so, to determine whether courtshipserves as an indicator of male parental quality. Observationsmade over two reproductive cycles showed that courtship ratesand mating success of individual males are positively correlatedand that males begin courting several days before females beginlaying eggs. Experimental manipulations showed that a male'scourtship rate is indicative of the subsequent egg survivalfrom his nest. We suggest that observed differences betweenmales in their courtship rates and parental ability may be aresult of differences in their energy reserves. These resultsdemonstrate the operation of honest advertising and lend supportto adaptive models of sexual selection. [Behav Ecol 1991;2:295–300]     

Descriptive epidemiology of roe deer mortality in Sweden

A retrospective epidemiologic study was conducted to examine causes of mortality of 985 wild roe deer (Capreolus capreolus) submitted to the National Veterinary Institute (SVA; Uppsala, Sweden) from January 1986 to December 1995. Age, sex, body condition, and geographic distribution as related to disease conditions are reported herein. The most common causes of mortality in roe deer were trauma (19%), winter starvation (18%), gastritis/enteritis (15%), bacterial infections (11%), parasitic infection (11%), systemic diseases (11%), neoplasia (2%), congenital disorders (1%), and miscellaneous causes (6%). Cause of death was not determined in 6% of the cases. The distribution of causes of death reported in this study differ from previous works in Sweden in that infectious and parasitic diseases were more common than winter starvation. The pathologic findings in studies like this do not necessarily represent what is occurring in the natural environment, but they do provide a good indication of distribution of diseases over time as well as age and sex structure in relation to disease conditions. Further research and more detailed studies are in progress to better understand specific mortality factors as well as etiologies of certain described diseases in roe deer in Sweden.     

Inter-specific competition from fallow deer Dama dama reduces habitat quality for the Italian roe deer Capreolus capreolus italicus

The roe deer of Mediterranean habitats in the central and southern parts of Italy has recently been recognised as a distinct subspecies, Capreolus capreolus italicus . A population of this endangered subspecies has been monitored in the Preserve of Castelporziano, near Rome, since 1988. We observed an abrupt population decline in 2000, which may severely threaten the sustainability of this population. We evaluated the hypothesis that competition by fallow deer may be a principal cause of this decline. By a new and innovative methodology, we modelled the spatial distribution of fallow deer density (FDD) in the study area to show that 1) habitat quality for roe deer was an inverse function of FDD, 2) habitat apportionment between fallow and roe deer increased as a function of FDD and – by applying structural equation modelling – 3) FDD was superior to habitat composition in explaining observed variations in home range size and probably in habitat quality for roe deer. This analysis is the first to document that inter-specific competition may influence the spatial behaviour of a deer species leading to poor phenotypic performance in the inferior competitor. We conclude that the conservation of this relict population would benefit by reducing fallow deer numbers at Castelporziano and from other measures aimed to decrease the level of inter-specific competition.     

Polydactyly in roe deer (Capreolus capreolus)

Supernumerary digits on roe deer (Capreolus capreolus) have been recorded over many decades in Germany. The case described in this communication is believed to be only the second documented example from the UK. A right hind foot of a buck had three equally developed digits arising from a metatarsal that trifurcated.     

High red deer density depresses body mass of roe deer fawns

Many previous studies have pointed out that, when resources are limited, the potential for competition should be high among sympatric species that display overlaps in habitat and nutritional niches. However, reliable evidence of competition between red deer (Cervus elaphus) and roe deer (Capreolus capreolus) has not been yet reported for life history traits directly measuring performance such as body mass, reproduction, or survival. From long-term monitoring of deer populations in the reserve of La Petite Pierre (France), we measured the sex-specific responses of roe deer fawn body mass to changes in red deer density after accounting for possible confounding effects of date of shooting, climatic conditions, and roe deer density. As expected under the hypothesis of competition, red deer density in a given year had a marked negative influence on body mass of roe deer fawns born the same year and the following year. Fawn mass of roe deer males and females responded in similar ways to changes in red deer density. Our study provides the first evidence of a negative response of roe deer performance to high red deer density.