Effects of migration distance and sex on stopover timing and refueling by Wilson's Warblers

Migration distance and sex are integral to avian migration strategies, yet these intrinsic factors are understudied with respect to their effects on stopover ecology and behavior. We investigated how individual variation in migration distance and sex affected body condition, refueling performance, and stopover durations of Wilson's Warblers (Cardellina pusilla) during spring and fall 2006 at a stopover site in southern Arizona. Migration distance of individuals was inferred using the hydrogen stable isotope ratio of feathers (δ²H_f) as an index of breeding latitude, refueling rate was assessed using plasma triglyceride and β‐OH‐butyrate, and minimum length of stay was estimated by re‐sighting color‐banded birds. In the spring, migration distance and sex were strong determinants of the timing of migration by Wilson's Warblers, with males and shorter‐distance migrants passing through the site earlier than females and longer‐distance migrants. Later‐arriving migrants also had higher fat scores and refueling rates. However, neither migration distance nor sex independently affected body condition (fat score or size‐corrected mass), refueling rate, or minimum length of stay. In a smaller sample of fall migrants, we found that longer‐distance migrants and males had higher refueling rates than shorter‐distance migrants and females. Our results show that differences in migration distance can, under some circumstances, affect how birds use stopover sites. Stable isotope analysis and other methods can provide information on migration distance, and should be integrated with measurements of timing, fuel stores, refueling performance, and departure behavior to gain a deeper understanding of bird migration.     

Latitudinal variation and coevolutionary diversification of sexually dimorphic traits in the false blister beetle Oedemera sexualis

Sexual traits are subject to evolutionary forces that maximize reproductive benefits and minimize survival costs, both of which can depend on environmental conditions. Latitude explains substantial variation in environmental conditions. However, little is known about the relationship between sexual trait variation and latitude, although body size often correlates with latitude. We examined latitudinal variation in male and female sexual traits in 22 populations of the false blister beetle Oedemera sexualis in the Japanese Archipelago. Males possess massive hind legs that function as a female‐grasping apparatus, while females possess slender hind legs that are used to dislodge mounting males. Morphometric analyses revealed that male and female body size (elytron length), length and width of the hind femur and tibia, and allometric slopes of these four hind leg dimensions differed significantly among populations. Of these, three traits showed latitudinal variation, namely, male hind femur was stouter; female hind tibia was slenderer, and female body was smaller at lower latitudes than at higher latitudes. Hind leg sizes and shapes, as measured by principal component analysis of these four hind leg dimensions in each sex, covaried significantly between sexes, suggesting coevolutionary diversification in sexual traits. Covariation between sexes was weaker when variation in these traits with latitude was removed. These results suggest that coevolutionary diversification between male and female sexual traits is mediated by environmental conditions that vary with latitude.     

Intraspecific acoustic communication and mechanical sensitivity of the tympanal ear of the gypsy moth Lymantria dispar

Tympanal ears of female gypsy moths Lymantria dispar dispar (L.) (Lepidoptera: Erebidae: Lymantriinae) are reportedly more sensitive than ears of conspecific males to sounds below 20 kHz. The hypothesis is tested that this differential sensitivity is a result of sex‐specific functional roles of sound during sexual communication, with males sending and females receiving acoustic signals. Analyses of sounds produced by flying males reveal a 33‐Hz wing beat frequency and 14‐kHz associated clicks, which remain unchanged in the presence of female sex pheromone. Females exposed to playback sounds of flying conspecific males respond with wing raising, fluttering and walking, generating distinctive visual signals that may be utilized by mate‐seeking males at close range. By contrast, females exposed to playback sounds of flying heterospecific males (Lymantria fumida Butler) do not exhibit the above behavioural responses. Laser Doppler vibrometry reveals that female tympana are particularly sensitive to frequencies in the range produced by flying conspecific males, including the 33‐Hz wing beat frequency, as well as the 7‐kHz fundamental frequency and 14‐kHz dominant frequency of associated clicks. These results support the hypothesis that the female L. dispar ear is tuned to sounds of flying conspecific males. Based on previous findings and the data of the present study, sexual communication in L. dispar appears to proceed as: (i) females emitting sex pheromone that attracts males; (ii) males flying toward calling females; and (iii) sound signals from flying males at close range inducing movement in females, which, in turn, provides visual signals that could orient males toward females.     

Sexual dimorphism and interpopulation differences in lizard hind limb length: locomotor performance or chemical signalling?

Intraspecific variation in morphology has often been related to fitness differences through its effects on performance. In lizards, variation in hind limb length can be shaped by natural selection for increased locomotor performance, sexual selection on the number or size of femoral pores involved in chemical signalling, or both. Here, we analyse the selective forces involved in sexual dimorphism and differences in hind limb length between two populations of Psammodromus algirus living at different elevation. Males were more robust and had longer hind limbs and limb segments than females, and low‐elevation lizards had longer limbs than high‐elevation lizards. However, differences in locomotor performance were small and non‐significant, making natural selection for faster runs an unlikely explanation for the observed pattern. On the other hand, males had more femoral pores than females, and lizards had more pores at lower elevation, although the difference was significant only for males (which invest more in chemical signalling). In males, the number of pores, which remains constant along a lizard's life, was not correlated with hind limb length. However, femur length was positively correlated with mean pore size, allowing low‐elevation males to have larger than expected pores, which could increase the effectiveness with which they spread their signals in a dry and warm habitat where chemicals become volatile rapidly. Also, saturation of the sexual coloration of the head was higher for low‐elevation males, suggesting that sexual selection pressures may be more intense. Overall, our results indicate that sexual selection plays a significant role in shaping intraspecific variation in hind limb length. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 318–329.     

Growth and mortality in mountain hares: the effect of sex and date of birth

Summary Current theory suggests that high juvenile growth effort, may result in higher mortality. This prediction is tested in mountain hares (Lepus timidus), by examination of post-weaning growth and mortality of males and females. Dates of birth were estimated from weight at first capture and growth in body weight and hind foot length was described by the logistic growth equation. Although adult female hares are on average larger than males, this results from a longer period of growth and not from a faster growth rate. There was no clear sex bias in mortality, a slight but not significantly greater proportion of males suffered mortality during the growth period. Predictions as to sex difference in mortality should specify which aspects of growth (rate or duration) are the agents of mortality, since the two parameters are not necessarily positively associated. Overall asymptotic body size decreased and rate of growth increased from early through to late-born young. Rate of growth in hind foot length was greater in late-born males but not in late-born females as compared with those born earlier. It is hypothesized that late-born males are more tightly constrained to complete growth and subsequent sexual maturation earlier than late-born females.     

Pellet morphometry as a tool to distinguish age and sex in the mule deer

By examining the morphometry (i.e., length, width, length‐to‐width ratio, and volume) of pellets in three different categories (adult males, adult females, and yearlings) mule deer (Odocoileus hemionus), we were able to distinguish via discriminant function and fuzzy clustering analyses the age and sex of these animals. To determine a priori the identity of the pellet samples and evaluate the accuracy of our methods, we obtained samples from individuals in captivity. The discriminant function allowed us to correctly assign 100% of adult males, 91.66% of adult females, and 75% of yearlings to an age class, using previous information. The fuzzy clustering method enabled us to correctly distinguish 100% of adult males, 83.3% of adult females, and 75% of yearlings. The methods are based upon different assumptions. An important assumption with the discriminant function method is that the membership of each pellet group must be established a priori. This may be a disadvantage in certain cases, such as when pellet samples are gathered for an indirect population assessment procedure. Despite this drawback, however, both methods appear to be highly accurate. Zoo Biol 23:139–146, 2004. © 2004 Wiley‐Liss, Inc.     

Fluctuating asymmetry,body size and sexual selection in the dung fly Sepsis cynipsea — testing the good genes assumptions and predictions

In the dung fly Sepsis cynipsea large and more symmetric males have been shown to enjoy a mating advantage, but we still do not know which mechanism of sexual selection is responsible. Here we test several assumptions and predictions relating to the hypothesis that either trait is indicative of ‘good genes’. We tested for good genes by regressing fitness in good and bad environments (no and high larval competition, respectively) on the family mean for size or asymmetry as expressed in the good environment, separately for both sexes. Body size (hind tibia length or head width) was positively correlated with female fecundity, growth rate of both sexes and larval survivorship for males, but only in the good environment. The corresponding evidence for asymmetry is more equivocal. Mean standardised asymmetry was weakly associated with lower survivorship in the good environment, while growth rates and female fecundity were not. As predicted by sexual selection theory, fore tibia length showed greater asymmetry than other, presumably not sexually selected traits, and asymmetry in fore tibia length was greater for males than females. However, a negative correlation between trait size and asymmetry was only evident for male seta length but not for fore tibia length, fore femur length, or any composite measure of asymmetry. Most crucially, asymmetry was heritable for some female morphological traits (hind tibia length: h² = 0.15; fore femur length: h² = 0.16; mean of all measured traits: h² = 0.27), but not for any male trait. Also, asymmetry of the various traits measured was not correlated within males and only weakly so within females. The crucial assumption that asymmetry of sexually selected traits reflects overall, heritable developmental stability of an individual is thus only partly substantiated by our data. In contrast, large body size is heritable, associated with high fitness and consequently could be indicative of good genes. Fore leg asymmetry may influence male mating success by simply mechanically constraining his ability to hold on to the female.     

Reproductive behavior of the dragonfly,Orthetrum japonicum (Odonata: Libellulidae)

The reproductive behavior of the dragonfly,Orthetrum japonicum, is described. Behavioral processes of turnover of territorial males, simultaneous guarding of 2 females by a male, and copulation by non-territorial males are described. The males with longer hind wings won the territorial conflicts more frequently. The total duration of territorial residence of a given male was correlated with the number of his matings, but not correlated with the length of his abdomen or hind wings. The territorial site with the lower degree of vegetation cover was occupied by males more consistently. Males in more consistently occupied territorial sites did not have longer abdomen and hind wings than males in less consistently occupied sites. The territorial site where the larger number of copulations was observed was not occupied more consistently. Selection episode analysis using the method of Arnold & Wade (1984a, b) showed that direct selection on the hind wing length favored the short wing and that direct selection on the abdomen length favored the long abdomen during mating.     

Morphological variation in adult chimpanzees (Pan troglodytes verus) of the Taï National Park, Côte d'Ivoire

Twenty five adult chimpanzee skeletons (Pan troglodytes verus) of known age and sex (15 females, 10 males) from a long‐term study site in Taï National Park, Cote d'Ivoire present new data on variation. These skeletons provide a rare opportunity to measure the cranium and postcranium from the same individuals. We compare measurements and indices of the Taï sample with those of relatively complete Pan troglodytes schweinfurthii skeletons from Gombe National Park, Tanzania. Measurements of Pan paniscus are included as an outside comparison. The Taï and Gombe samples are analyzed by sex; combined sex samples are compared between the two groups, and the two sexes to each other. Taï females and males do not differ in most long bone lengths or in pelvic dimensions, but do differ significantly in cranial capacity, facial measurements, clavicle length, scapular breadth, and femur length. Gombe females and males differ significantly in some facial measurements and in scapular breadth. In combined sex samples, Taï individuals have lower cranial capacity, longer palate and mandible, and greater dimensions in the trunk and limb lengths. Taï females account for most of the variation; males differ from each other only in greater length of humerus and femur. The Taï skeletons provide new data for assessing individual variation and sexual dimorphism within and between populations and species. The combination of cranial and postcranial data provides a clearer picture of chimpanzee intraspecific and interspecific variation than can be gained from either data set alone. Am J Phys Anthropol, 2008. © 2007 Wiley‐Liss, Inc.     

Sexual Selection of Zorion guttigerum Westwood (Coleoptera: Cerambycidae: Cerambycinae) in Relation to Body Size and Color

Zorion guttigerum is a flower-visiting longhorned beetle endemic to New Zealand. Sexual selection of this species in relation to the body size and color form of different sexes was investigated in the field. The population sex ratio, based on censuses of feeding and mating sites (flowers), is male-biased. Females are significantly larger than males. Both sexes have antennae of similar length but the antennal length relative to the elytral length is greater in males than in females, and the antennal length of males increases more with an increase in body size than that of females. Both sexes have dark blue (DB) and yellowish-brown (YB) individuals. Both pair-bonded and solitary males are similar in elytral and antennal length. In pair-bonded males, DB individuals are significantly more numerous than YB ones, but in solitary males, the number of both color forms is similar. Males tend to have territory protection behavior, fighting with and chasing away rival males from feeding and mating sites. Larger males usually win the fight but the size-dependent fighting advantage does not translate into mating success. Male color plays an important role in mating success, with DB males having a significantly better chance to mate than YB males. Furthermore, male body size and color also have interactions in mating success: males of DB color morph obtain a greater mating advantage according to body size. Pair-bonded females are significantly larger and have longer antennae than solitary females, suggesting that males prefer larger females for mating. In addition, females of DB color morph with longer antennae are also preferred by males for mating. The significance of these findings is discussed.     

Mating behavior ofPhytoecia rufiventris Gautier (Coleoptera: Cerambycidae)

Sexual behavior between males and females, as well as between males, is described and discussed for the cerambycid beetlePhytoecia rufiventris. The beetles' taxis toward plants taller than average height brings the sexes together from a distance. A male may mount another individual (male or female) and attempt copulation without sex discrimination. The male can discern the sex of another individual only when the terminal part of his abdomen touches the ventral surface of the fifth visible sternite of the latter. No evidence of a sex pheromone is found in this species. Within 1.5–5.5 cm the substrateborne vibrations produced by a moving individual may be the important factor which elicits males to approach a moving individual and attempt copulation. If a female is receptive when a male touches her, he can copulate with her without any courtship display. However, if the female runs away and appears unreceptive, the male will perform courtship displays. Copulation is usually terminated by males. Homosexual behavior between males is discussed.     

Sex,life history and morphology drive individual variation in flight performance of an insect parasitoid

1. The movement of organisms can be driven by multiple factors and has implications for fitness and the spatial distribution of populations. Insects spend a large proportion of their adult lives foraging by flying for resources; however, their capability and motivation to move can vary across individuals. 2. The aims of this study were to examine interindividual and sex differences in flight performance and flight characteristics, using a flight mill bioassay, in Megarhyssa nortoni (Hymenoptera; Ichneumonidae), a parasitoid of the invasive woodwasp Sirex noctilio (Hymenoptera: Siricidae), one of the most important pests of pine afforestation worldwide. We also assessed the influence of morphological traits in combination with sex on flight and explored the cost of flight on longevity and mass loss. 3. The results show a difference between sexes in flight characteristics and performance. Females show greater total distance flown than males, and have a better capacity to undergo sustained flight. Sexual size dimorphism was also found and it was noted that size positively affects distances travelled. Females have a longer life span than males, yet no differences were noted in longevity within sex between individuals that did not fly and those that flew. Age did not influence flight performance of females or impacted on post‐flight longevity. Females lost less body mass than males even after flying longer distances. 4. These results suggest that sex‐specific behaviours probably govern flight abilities together with (and not only because of) morphological traits. The paper discusses sex‐specific life‐history strategies in parasitoids and their implications for biocontrol programmes.     

Does ‘gliding while gravid’ explain Rensch's rule in flying lizards?

Among species with sexual size dimorphism (SSD), taxa in which males are the larger sex have increasing SSD with increasing body size, whereas in taxa in which females are the larger sex, SSD decreases with body size: Rensch's rule. We show in flying lizards, a clade of mostly female‐larger species, that SSD increases with body size, a pattern similar to that in clades with male‐biased SSD or more evenly mixed SSD. The observed pattern in Draco appears due to SSD increasing with evolutionary changes in male body size; specifically divergence in body size among species that are in sympatric congeneric assemblages. We suggest that increasing body size, resulting in decreased gliding performance, reduces the relative gliding cost of gravidity in females, and switches sexual selection in males away from a small‐male, gliding advantage and toward selection on large size and fighting ability as seen in many other lizards. Thus, selection for large females is likely greater than selection for large males at the smaller end of the body size continuum, whereas this relationship reverses for species at the larger end of the continuum. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 270–282.     

Sex roles in the ghost moth Hepialus humuli (L.) and a review of mating in the Hepialidae (Lepidoptera)

Recently it has been found that female Lepidoptera belonging to diverse families actively court their males, rather than play a merely passive role. Male and female Hepialus humuli have been reported to come together in three different ways: (1) females are attracted to groups or ‘leks’ of white, hovering males by visual stimuli; (2) females are attracted to the males by olfactory-substances produced on the hind-tibial brushes of the males; (3) males are attracted to sedentary females by olfactory stimuli. During my study I observed H. humili males flying on a total of 21 nights in two different parts of England. The males hovered in groups for about 20 min each evening, starting and stopping their flights in synchrony. Timing depended on light intensity, northern moths flying later in the summer evenings than southern moths. I observed a total of 18 matings. Normally, a female from outside a male lek flew into the group and up to one of the males. This male then usually followed her to a settling position, where mating took place. In a few cases females touched males; in one case a female struck a male in the air so that both fell to the ground and were copulating when examined. Photographs of hovering males show that their hind tibial brushes are fully everted in flight. The organs are folded against the body when the moth is mating, at rest or dead. Whilst hovering, the males are apparently emitting pheromones which function as primary attractants, rather than as the aphrodisiacs of many other lepidopteran males. The mating behaviour of hepialids is reviewed. It is concluded that all studied hepialids which have male brush organs (some Hepialus and Oncopera, Sthenopis, Zenophassus) exhibit similar flight and mating behaviour: males hover, sit or loop back and forth on the spot in leks; females fly into male aggregations and mate there (although some published observations suggest otherwise). In contrast, hepialids such as Fraus, Oxycanus and other Hepialus that lack male brush organs have mating behaviour in which the males are the active partner, a more standard lepidopteran method. In view of the controversies surrounding mating in hepialids, future systematic and behavioural work on Hepialidae throughout the world will be worthwhile.     

Sexually dimorphic male horns and their use in agonistic behaviors in the horn-headed cricket <Emphasis Type="Italic">Loxoblemmus doenitzi</Emphasis> (Orthoptera: Gryllidae)

Sexual dimorphism, the difference between the sexes in secondary sexual characters, is in general driven by processes of sexual selection. The horn-headed cricket, Loxoblemmus doenitzi, exhibits sexual dimorphism in head shape. Males have flat heads and triangular horns on both sides of their heads, whereas females have rounded heads and no horns. We hypothesized that male horns have evolved due to intra-sexual selection, in which males use these horns as weapons in aggressive interactions. We tested two predictions of this hypothesis by conducting agonistic trials with field-caught males of L. doenitzi: (1) the horns should be used in agonistic interactions between males, and (2) the asymmetry in horn size or horn use may determine contest outcome. Horn length was significantly correlated with thorax length and hind femur length. During agonistic interactions, males aggressively used their horns by beating the opponent’s horns with their own or by poking the opponent’s body. However, logistic regression analysis revealed that neither horn length nor horn use were significant factors for contest outcome. Instead, body size was significant for determining contest outcome. We discuss possible scenarios for evolution of male horns in L. doenitzi.     

Effects of inter-pond distance on the breeding ecology of tungara frogs

Habitat and resource distributions can influence the movement and aggregation of individuals and thus have important effects on breeding behavior and ecology. Though amphibians have been model systems for the study of breeding behavior and sexual selection, most studies have examined breeding behavior within a single pond. As a result, little is known about how inter-pond distance affects breeding amphibians. We studied the effects of inter-pond distance on the breeding ecology of the tungara frog, Physalaemus pustulosus, in replicated pond arrays in which distance was varied from 0 to 50 m. We predicted that male site fidelity and male aggregation within arrays would increase with inter-pond distance, and that the opportunity for mate choice and oviposition site selectivity by females would decrease with the distance between ponds. Male site fidelity did increase with inter-pond distance. However, male aggregation decreased with distance, such that males tended to be more evenly spaced among ponds when ponds were farther apart. The opportunity for mate choice by females, measured as the number of males within the phonotactic radius of females, also decreased with inter-pond distance. Each of these three responses was consistent with a threshold effect between 5 m and 10 m in inter-pond distance. This threshold corresponded to the maximum distance at which females in laboratory choice experiments exhibited phonotaxis toward the ”whine” call of a tungara male, suggesting that phonotactic limits may play an important role in tungara movements and spacing patterns. The distribution of egg masses among ponds, a potential correlate of oviposition site selectivity, did not vary with inter-pond distance. Multiple egg masses deposited on the same night were significantly overdispersed in all distance treatments, implying that females may select oviposition sites to avoid conspecific egg masses over distances of at least 50 m. Collectively, these results demonstrate that inter-pond distance may indeed affect amphibian breeding and movement behavior, and that consideration of multiple habitat patches and their spatial distributions can provide new insights into even the most well-understood mating systems. Received: 9 January 1999 / Accepted: 1 August 1999     

Mating behavior ofXylotrechus pyrrhoderus Bates (Coleoptera: Cerambycidae). VI mating system

Observations made in an outdoor cage showed that most pairings of the grape borerXylotrechus pyrrhoderus Bates were formed via inflight orientation of females towards pheromone-releasing males. The male sex pheromone induced orientation behavior in flying females, as well as walking approaches and prolonged lingering periods near the pheromone source in alighting females. When an approaching female failed to elicit any response in a male (e.g., when the male was copulating), she touched and sometimes mounted him. This behavior stimulated the males and often resulted in successful copulation. The male usually inseminated the second female, and the male's fitness increased when the second mating occurred more than 5 min after the start of the firt mating. These results suggest that male-like behavior in females (i.e., approaching and mounting behavior) has biological significance. The grape borer sometimes forms pairs via incidental encounters of the sexes. This is the same as the prevailing mating system of cerambycids. It is suggested that the male sex pheromonemediated mating system of the grape borer developed from the prevailing system of cerambycid groups.     

Indirect female choice mediated by sex pheromones in the hermit crab Pagurus filholi

Males of the hermit crab Pagurus filholi perform precopulatory guarding behavior, and solitary males often show aggressive behavior to take away guarded females. Males behave coercively while guarding females, so direct mate choice by females seems difficult in such a situation. By performing several experiments we examined possible indirect female choice of hermit crab. Males were attached to a shell by their left cheliped to look like guarding pairs (fake guarding pairs). The shells were filled with cotton containing either seawater or pheromone water. The fake guarding pair with only seawater caused male–male combat in 60% of trials whereas with pheromone water combats occurred in 88% of trials. Mean duration of male–male combat was significantly longer in trials with drops of seawater containing pheromones than in those without pheromones. These results suggest guarding pairs themselves cause male–male combat by visual stimulation, that female sex pheromones have further significant function in the recognition of guarding pairs and intensification of male–male combat, and that females release sex pheromones while they are guarded. As a result of the combat, the larger male ended up guarding a female. This strongly suggests that females choose males indirectly by exploiting male–male competition induced by sex pheromones under male coercive behavior.     

Scaling of the appendicular skeleton of the giraffe (Giraffa camelopardalis)

Giraffes have remarkably long and slender limb bones, but it is unknown how they grow with regard to body mass, sex, and neck length. In this study, we measured the length, mediolateral (ML) diameter, craniocaudal (CC) diameter and circumference of the humerus, radius, metacarpus, femur, tibia, and metatarsus in 10 fetuses, 21 females, and 23 males of known body masses. Allometric exponents were determined and compared. We found the average bone length increased from 340 ± 50 mm at birth to 700 ± 120 mm at maturity, while average diameters increased from 30 ± 3 to 70 ± 11 mm. Fetal bones increased with positive allometry in length (relative to body mass) and in diameter (relative to body mass and length). In postnatal giraffes bone lengths and diameters increased iso‐ or negatively allometric relative to increases in body mass, except for the humerus CC diameter which increased with positive allometry. Humerus circumference also increased with positive allometry, that of the radius and tibia isometrically and the femur and metapodials with negative allometry. Relative to increases in bone length, both the humerus and femur widened with positive allometry. In the distal limb bones, ML diameters increased isometrically (radius, metacarpus) or positively allometric (tibia, metatarsus) while the corresponding CC widths increased with negative allometry and isometrically, respectively. Except for the humerus and femur, exponents were not significantly different between corresponding front and hind limb segments. We concluded that the patterns of bone growth in males and females are identical. In fetuses, the growth of the appendicular skeleton is faster than it is after birth which is a pattern opposite to that reported for the neck. Allometric exponents seemed unremarkable compared to the few species described previously, and pointed to the importance of neck elongation rather than leg elongation during evolution. Nevertheless, the front limb bones and especially the humerus may show adaptation to behaviors such as drinking posture. J. Morphol. 276:503–516, 2015. © 2014 Wiley Periodicals, Inc.     

Vigilance behavior during the birth and lactation season in naturally occurring ring-tailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve,Madagascar

I examined the vigilance behavior of adult males and females in two groups of ring-tailed lemurs(Lemur catta)during the birth and lactation season at the Beza-Mahafaly Reserve, southwestern Madagascar. I found no sex difference with respect to the rates of overall vigilance, rates of vigilance toward a potential predator or unfamiliar sound, or rates of vigilance toward conspecifics from other social groups, nor were there sex differences in the percentage of time spent vigilant in any of the above categories. Higher-ranking females were vigilant significantly more often toward predators or potential predators than lower-ranking females were. I detected no relationship between vigilance behavior and dominance rank among adult males. The alpha female in each group exhibited significantly more vigilance behavior than all other members of her group. It was predicted that males should exhibit more vigilance behavior than females do, particularly during the birth and lactation season, when predator pressure is high, if they are benefiting females in this respect. I discuss the results in the context of this prediction and in terms of how ring-tailed lemur males benefit females, and why they may be tolerated in social groups.