Marion Petrie

Peahens prefer peacocks with elaborate trains

Abstract Peacocks, Pavo cristatus, defend small display sites and aggregate to form leks. Observations of one lek, consisting of 10 males, showed that there was considerable variance in mating success. The most successful male copulated 12 times whilst the least successful males obtained no copulations. Over 50% of the variance in mating success could be attributed to variance in train morphology; there was a significant positive correlation between the number of eye-spots a male had in his train and the number of females he mated with. Furthermore, analysis of female behaviour provided good evidence that this non-random mating is a result of a female preference. On no occasion did a female mate with the first male that courted her and, on average, females visited three different males. Females thus always reject some potential mates. For 10 out of 11 sequences ending in a successful copulation, the male ‘chosen’ at the end of a sequence had the highest eye-spot number among the males visited. These data support Darwins hypothesis that the peacocks train has evolved, at least in part, as a result of a female preference.

Intraspecific variation in structures that display competitive ability: large animals invest relatively more

The benefits of possessing (or enlarging) a display structure used in competitor assessment will vary between individuals of a species. For some individuals the cost of developing such a feature could outweigh any benefits accrued. Animals whose competitive ability is high can benefit from display, but there is little advantage in advertising low competitive ability. Thus, since large animals generally win fights it can be predicted that large animals should have relatively large display features. This prediction was tested using data on the moorhen, Gallinula chloropus. Evidence is presented that in this species frontal shields are used in competitor assessment. The size of an individuals frontal shield varied seasonally. Maximum shield size corresponded with peak aggressive behaviour. Shield size was positively correlated with body weight, which is the best predictor of the outcome of agonistic encounters in this species, and the slope of the regression was significantly greater than one. Thus shield size proved to be positively allometric as predicted. It remains to be tested whether or not positive allometry is a feature of all structures used to display competitive ability.

Multiple mating in a lekking bird: why do peahens mate with more than one male and with the same male more than once?

SummaryApproximately 50% of marked peahens (Pavo cristatus) mate more than once with lek males. Some females mate with more than one male, others copulate repeatedly with the same male. The frequency of courtship also shows marked variation. Some females repeatedly engage males in courtship interactions after they have succesfully copulated with them. The likelihood of mating with more than one male increases if a female first mates with a non-preferred (unsuccessful male). There is a non-significant tendency for females to copulate with a more successful male when remating. Peahens may mate with a non-preferred male first if they do not encounter a successful male during their initial period of choice, perhaps because the most successful male on a lek was courting another female and/or was defended by another female. There are more aggressive interactions between females in front of preferred males. Preferred males receive more repetitive courtship behaviour and repeated matings. Dominant females are more likely to engage in repetitive courtship and matings. The number of times a female initiates courtship on any one day increases with the number of other females actively courting males at a lek site on that day. We suggest that there is competition amongst females for access to preferred males and that dominant females try to monopolise these males by repeatedly engaging them in courtship interactions. We discuss the implications of these observations for the idea that female may gain directly from mate choice in a species where males contribute nothing but gametes to their offspring.

Lekking in topi: a consequence of satellite behaviour by small males at hotspots

Abstract Male topi, Damaliscus lunatus , either defend large territoriescontaining food resources or join leks. In this study there was large variation in mating success on leks with a few males getting the majority of matings. Resource territories attracted more females than the territories of unsuccessful males on leks. All males on leks spent more time in contest behaviour than males in resource territories so that the majority of lek males that obtained few matings incurred high costs and low benefits. The reason that unsuccessful males stay on leks, rather than adopt the less costly alternative of resource defence, may be that they are smaller than males in resource territories and thus unable to win fights to acquire resource territories. Although scucessful territories were scattered through the study lek, two small territories near the centre consistently attracted many more females than any others. This pattern persisted regardless of which male was in residence; females even came to these territories when the owner was absent. The ability to hold a successful lek territory could be a more reliable indicator of competitive ability, and thus fitness, than any single phenotypic characteristic. Leks may develop from groups of successful resource territories. In the case of topi, the desirable feature of these territories is probably a resting area in open habitat where females concentrate for anti-predator advantage. It is proposed that leks appear when small, satellite males of low resource-holding potential cluster around the males in these successful territories.

Do peacock's trains advertise age?

Manning (1987 and 1989) found a positive correlation between several measured aspects of the males upper tail coverts and male age in a sample of males measured at several different sites. Here we test whether or not the trains of individuals from the same population increase between years. There is no evidence from the data presented that variation in the degree of train elaboration amongst male peacocks is age‐dependent beyond 4 years or that peahens always prefer to mate with older males; one young male in his first year of displaying achieved high mating success and was preferred by several females over other older males present. It therefore appears unlikely that the peacocks train acts as an age‐indicator.