Lek Breeding and Territorial Aggression in White-eared Kob

Territorial aggression in a lek breeding population of white-eared kob (Kobus kob leucotis) was investigated in the Boma National Park region, southern Sudan. The frequency of aggression on leks was positively related to the number of females present, but generally declined over the course of the breeding season. Males fought most strenuously for central territories that were preferred by females. Males with females in their territories were more frequently engaged in fights than unaccompanied males. Such fights often induced females to leave their original partners, especially when large groups of females were involved. Territorial aggression led to damaging injuries in several instances, and mortality of breeding age males was disproportionately high. These results suggest that the intensity of aggression exhibited by territorial males was scaled to potential reproductive benefits.     

The relative costs and benefits of territorial defense and the two conditional male mating tactics in the Comanche Springs pupfish (Cyprinodon elegans)

We examined the aggressive costs and reproductive benefits of territorial defense and its alternatives in a population of the Comanche Springs pupfish (Cyprinodon elegans). The breeding system was characterized by three different male mating tactics: territorial defense, satellite positioning, and sneak spawning. The mating tactic adopted by males reflected the males' sizes. Territorial residents were the largest, satellites were medium-sized, and sneakers were the smallest adult males observed. Consistent with the hypothesis that primary mating tactics are relatively high-cost, high-benefit strategies, we found that territorial males engaged in a number of aggressive encounters but had higher reproductive successes than any other males. However, our observations did not support the premise that conditionally breeding males engage in relatively low-benefit, low-cost tactics. Medium satellites and small sneakers acquired fewer spawns than did territorial males, but both satellites and sneakers were involved in as much aggression as territorials. That is, the data supported the prediction that satellite or sneaker males with the inability to compete for territories would attempt to accrue some reproductive opportunities in the presence of territorial males despite the high costs of spending time on the breeding grounds. Adopting conditional tactics appeared to allow satellites and sneakers to make the best of a bad situation. During a subsequent breeding season, large males were absent from the population, and medium-sized males established territories. The aggressive behavior exhibited by medium residents was similar to the previous year, but these males did not acquire higher reproductive successes than medium satellites had. The implications of switching tactics and the influence of operational sex ratios on the costs and benefits of the male tactics are briefly addressed. Electronic Publication     

Male reproductive strategy and the importance of maternal status in the Antarctic fur seal Arctocephalus gazella

Abstract. Although mammalian mating systems are classically characterized in terms of male competition and polygyny, it is becoming increasingly apparent that alternative male strategies and female choice may play important roles. For example, females who mate with males from a dominant dynasty risk producing inbred offspring. Many pinnipeds are highly polygynous, but in some species alternative male strategies such as aquatic mating appear to be important, even when behavioral observations suggest strong polygyny. Here, we analyze male reproductive success in the Antarctic fur seal Arctocephalus gazella , an otariid described behaviorally as being highly polygynous, by combining a microsatellite paternity analysis spanning seven consecutive breeding seasons with detailed behavioral data on both sexes. Territorial males fathered 59% of 660 pups analyzed from our study colony. Male reproductive skew was considerable, with a quarter of all paternities assigned to just 12 top individuals on a beach where mean annual pup production was 635. Most males were successful for only a single season, but those able to return over successive years enjoyed rapidly increasing success with each additional season of tenure. We found no evidence of alternative male reproductive tactics such as aquatic or sneaky terrestrial mating. However, paternity was strongly influenced by maternal status. Females observed on the beach without a pup were significantly less likely to conceive to a sampled territorial male than equivalent females that did pup. In addition, their pups carried combinations of paternal alleles that were less likely to be found on the study beach and exhibited lower levels of shared paternity. Thus, from a territorial male's perspective, not all females offer equal opportunities for fertilization.     

Resource attractiveness of the male beaugregory damselfish and his decision to court or defend

We examined the decisions territorial male beaugregory damselfish (Stegastes leucostictus) make when presented with mating and aggressive situations simultaneously. Specifically, we testedhow males responded to simultaneous and consecutive presentationsof conspecific males and females in bottles. We hypothesizedthat (1) territorial males would show lower levels of courtshiptoward females when a competing male is also present comparedto when only the female is present and (2) territorial maleswould show higher levels of aggression toward intruding maleswhen a female is also present on their territories than whenonly the intruder is present. We predicted that males withhigh-quality breeding sites would court females and attackcompetitors more vigorously than males with low-quality breedingsites. Males on low-quality breeding sites exhibited fewerconspicuous courtship displays toward bottled females and alower bite rate toward bottled males than did the males onhigh-quality breeding sites. We concluded that poor breeding-sitequality was responsible for the decline in the most conspicuous aspects of both courtship and aggression. When presented simultaneouslywith a bottled male and a bottled female, defenders of bothbreeding-site types drastically reduced the number of courtshipdisplays and the amount of time they spent near the female.Thus, all aspects of courtship were reduced in the presenceof a male intruder. Time spent near the bottled male also decreased in these simultaneous presentations; however, this decreasewas less dramatic than the reduction in time spent near bottledfemales. Habitat quality did not affect these trade-off decisions,but the bite rate exhibited toward the bottled male increasedin the simultaneous presentations compared to the single presentations.Due to this increase in a territorial male's defensive behaviorwhen a female is present, we conclude that the presence of afemale temporarily increased the value of a territory. We suggestthat the possible loss of a territory to an intruding maletakes priority over the potential benefits of successfullycourting a single female and that it is a male's future reproduction,as well as his current reproduction, by which he assesses hisbenefits.     

Daily activity of impala

The basic activity pattern of impala in the Serengeti is described quantitatively; seasonal variations and those related to social status are discussed. The adaptiveness of the basic pattern, especially in the preponderance of vulnerable and mobile activities in the daytime and of static activities at night, is discussed. The cost of various territorial activities is stressed; the presence of females in his territory disturbs the basic activity pattern of the territorial male, reducing his time spent on feeding and ruminating. The relationship between the occurrence of males in shade and some environmental factors is analysed.     

Context matters: female aggression and testosterone in a year-round territorial neotropical songbird (Thryothorus leucotis)

Testosterone promotes aggressive behaviour in male vertebrates during the breeding season, but the importance of testosterone in female aggression remains unclear. Testosterone has both beneficial and detrimental effects on behaviour and physiology, prompting the hypothesis that selection favours an association between aggression and testosterone only in certain contexts in which intense or persistent aggression may be beneficial. We tested this hypothesis in a year-round territorial female buff-breasted wrens (Thryothorus leucotis), by exposing free-living females to experimental intrusions in different social (either single female or male, or paired decoys) and seasonal (pre-breeding or breeding) contexts. Females responded more aggressively to intrusions by females and pairs than to males. However, female intrusions elicited stronger responses during pre-breeding, whereas responses to pair intrusions were more intense during breeding. Territorial females had elevated testosterone levels after female intrusions and intermediate levels after pair intrusions during pre-breeding, but the levels of testosterone remained low after these intrusions during breeding. These results demonstrate seasonal differences in circulating testosterone following territorial aggression in female buff-breasted wrens and are suggestive of differences according to social context as well. Context-dependent elevation of testosterone implies that selection acts directly on female vertebrates to shape patterns of testosterone secretion.     

Vigilance and group size in impala (Aepyceros melampus Lichtenstein): a study in Nairobi National Park, Kenya

One of the advantages of living in groups is that individuals may need to be less vigilant, allowing them more time for other important activities, such as foraging. This relationship between group size and per cent time spent being vigilant was investigated by observing impala in Nairobi National Park, Kenya. Three types of individual were observed: females, territorial males and bachelor males. Only females showed the predicted negative relationship between per cent vigilance and herd size. Both types of male showed no significant change of vigilance with increasing group size. There was no difference in levels of vigilance in open or closed habitats and no difference in vigilance between herds ‘alone’ and herds with other species that might have provided ‘extra eyes’.     

Seasonal Changes of Vocal Rates and Their Relation to Territorial Status in Male Galápagos Sea Lions (Zalophus wollebaeki)

Male vocal displays play an important role in sexual selection through both male–male competition and female choice. While this is supported by numerous studies in birds, much less attention has been paid to the role of such displays in mammals. We investigated the function of vocal displays in a polygynous mammal, the Galápagos sea lion (Zalophus wollebaeki). In our study population a large proportion of mature males are unable to establish a territory, providing the opportunity to compare the vocal behaviour between territorial and non‐territorial males. We examined how seasonal patterns of vocalizations differed between territorial and non‐territorial males and how the number of females present in a territory influenced behaviour of territorial males. We found that territorial males vocalized at higher rates than non‐territorial males, and territorial males vocalized more at the onset than towards the end of territory tenure. During the onset of territory‐tenure vocalizations of territorial males were directed more often towards other males than females. Furthermore, we found that vocalizations of territorial males were not only given in male–male interactions, but were also actively directed towards females. Territorial males vocalized at higher rates when more females were present in their territory. Our results suggest that vocalizations are important in male–male interactions, are relevant in territorial disputes and are used as a proxy for females to assess a male’s quality.     

Territorial aggression and hormones during the non-breeding season in a tropical bird

The hormonal control of territorial aggression in male and female vertebrates outside the breeding season is still unresolved. Most vertebrates have regressed gonads when not breeding and do not secrete high levels of sex steroids. However, recent studies implicate estrogens in the regulation of non-breeding territoriality in some bird species. One possible source of steroids during the non-breeding season could be the adrenal glands that are known to produce sex steroid precursors such as dehydroepiandrosterone (DHEA). We studied tropical, year-round territorial spotted antbirds (Hylophylax n. naevioides) and asked (1). whether both males and females are aggressive in the non-breeding season and (2). whether DHEA is detectable in the plasma at that time. We conducted simulated territorial intrusions (STIs) with live decoys to male and female free-living spotted antbirds in central Panama. Non-breeding males and females displayed robust aggressive responses to STIs, and responded more intensely to decoys of their own sex. In both sexes, plasma DHEA concentrations were detectable and higher than levels of testosterone (T) and 17beta-estradiol (E(2)). In males, plasma DHEA concentrations were positively correlated with STI duration. Next, we conducted STIs in captive non-breeding birds. Captive males and females displayed robust aggressive behavior. Plasma DHEA concentrations were detectable in both sexes, whereas T was non-detectable (E(2) was not measured). Plasma DHEA concentrations of males were positively correlated with aggressive vocalizations and appeared to increase with longer STI durations. We conclude that male and female spotted antbirds can produce DHEA during the non-breeding season and DHEA may serve as a precursor of sex steroids for the regulation of year-round territorial behavior in both sexes.     

Time, gender, and seasonality in vervet activity: A chronobiological approach

A chronobiological approach has been used to highlight the issue of how climatic factors and breeding seasonality may affect male and female diurnal activity budget. We investigated gender differences for vervet monkeys in the diurnal distribution of feeding, locomotion, inactivity, and social grooming within and between birth, pre-mating, and mating seasons. The main climatic traits were that days were shorter, drier, and cooler in the mating season. Non-parametric statistics showed that female activities changed with time of day to a greater extent than did male activities. When the constraints imposed by climatic factors and mate competition increased, from the birth to the mating season, male maintenance activities were more independent of the time of day whereas females continued to vary. Gender differences in timing were therefore greater in the mating season, except for social grooming; males and females were more coordinated in diurnal timing of their grooming in the mating season. It is argued that these changes may result in reduced levels of male-female contest competition, and may be related to higher levels of male-female socialization in the mating season. Finally, it is inferred that an out-of-phase synchronization between inactivity and feeding for males in the birth season, and for females in the mating season, may result from each sex investing more time feeding at the expense of resting in those periods.     

Grooming as a secondary behavior in the shrimp Macrobrachium rosenbergii (Crustacea,Decapoda, Caridea)

The giant freshwater prawn, Macrobrachium rosenbergii, is a large shrimp extensively used in aquaculture whose grooming behaviors were analyzed in this study. Macrobrachium rosenbergii exhibits three unique male morphotypes that differ in their behavior, morphology and physiology: small-clawed males (SM), orange-clawed males (OC) and blue-clawed males (BC). The largest and most dominant males, BC males, are predicted to have significantly different grooming behaviors compared to females and the other two male morphotypes. These BC males may be too large and bulky to efficiently groom and may dedicate more time to mating and agonistic interactions than grooming behaviors. Observations were conducted to look at the prevalence of grooming behaviors in the absence and presence of conspecifics and to determine if any differences in grooming behavior exist among the sexes and male morphotypes. Significant differences in the grooming behaviors of all individuals (females and male morphotypes) were found. BC males tended to have the highest grooming time budget (percent of time spent grooming) while SM males had a relatively low grooming time budget. The grooming behaviors of the male morphotypes differed, indicating while these males play distinct, separate roles in the social hierarchy, they also have different grooming priorities. The conditions in which Macrobrachium rosenbergii are cultured may result in increased body fouling, which may vary, depending on the grooming efficiencies and priorities of these male morphotypes. Overall, grooming behaviors were found to be a secondary behavior which only occurred when primary behaviors such as mating, feeding or fighting were not present.     

Territorial aggression and song of male European robins (Erithacus rubecula) in autumn and spring: effects of antiandrogen treatment

Male robins aggressively defending a feeding territory in winter have low levels of testosterone, while males defending a breeding territory in spring have elevated levels of testosterone. Song is an integrated part of territorial defense during both phases. We investigated whether testosterone is involved in the expression of these behaviors by treating free-living and captive male robins during both phases with the antiandrogen flutamide. Results suggest that, similar to species in which territoriality is restricted to the reproductive phase, aggressive defense of a breeding territory by male robins is facilitated by androgens. Territorial defense during the nonbreeding season, however, does not require androgenic activity. Singing frequency, on the other hand, was not significantly reduced during either phase by flutamide application. Since the quality of male song changes with season we suggest that the incorporation of sexual signals into male song during breeding depends on testosterone, but that the year-round production of territorial "keep out" signals is independent of testosterone.     

Alternative phenotypes of male mating behaviour in the two-spotted spider mite

Severe intraspecific competition for mates selects for aggressive individuals but may also lead to the evolution of alternative phenotypes that do not act aggressively, yet manage to acquire matings. The two-spotted spider mite, Tetranychus urticae, shows male mate-guarding behaviour and male–male combat for available females. This may provide opportunity for weaker males to avoid fighting by adopting alternative mating behaviour such as sneaker or satellite tactics as observed in other animals. We investigated male precopulatory behaviour in the two-spotted spider mite by means of video-techniques and found three types of male mating behaviour: territorial, sneaker and opportunistic. Territorial and sneaker males associate with female teleiochrysales and spend much time guarding them. Territorial males are easily disturbed by rival males and engage themselves in fights with them. However, sneaker males are not at all disturbed by rival males, never engage in fights and, strikingly, never face attack by territorial males. Opportunistic males wander around in search of females that are in the teleiochrysalis stage but very close to or at emergence. To quickly classify any given mate-guarding male as territorial or sneaker we developed a method based on the instantaneous response of males to disturbance by a live male mounted on top of a brush. We tested this method against the response of the same males to natural disturbance by two or three other males. Because this method proved to be successful, we used it to collect territorial and sneaker males, and subjected them to morphological analysis to assess whether the various behavioural phenotypes are associated with different morphological characters. However, we found no statistical differences between territorial and sneaker males, concerning the length of the first legs, the stylets, the pedipalps or the body.     

Contrasting Alternative Hypotheses to Explain Rut‐Induced Hypophagia in Territorial Male Chamois

Male ungulates in temperate environments often show a severe reduction in time spent foraging during the mating season. Several hypotheses have been put forward to explain this phenomenon but, so far, no study investigated the proximate mechanisms underlying rut‐induced hypophagia in ungulates using alternative mating tactics (AMTs). Between the pre‐rut and post‐rut of 2011 and 2012, we collected data on activity budgets, parasite burden and androgen levels of territorial and non‐territorial male Alpine chamois Rupicapra r. rupicapra in the Gran Paradiso National Park (Italy). We aimed to investigate whether AMTs showed similar reduction in time spent foraging during the mating period and to test the predictions underlying alternative hypotheses that may explain rut‐induced hypophagia. Only territorial males showed a significant reduction in time spent foraging during the rut; the lack of correlation between proportion of time spent foraging and androgen metabolites or parasite burden did not fully support the physiological and the parasite hypotheses, while the foraging constraint, the energy‐saving and the physical rest hypotheses could not be discounted. Territorial males decreased the time spent lying down from the pre‐rut to the rut, but not their foraging‐to‐lying‐down ratio. During the mating period, we found negative correlations between time spent foraging or lying down and time spent rutting. Our data suggest that territorial males’ behaviour is more consistent with the foraging constraint hypothesis than with the energy‐saving hypothesis previously suggested. Yet, during the rut territorial males did not maximise their foraging time, and the optimisation of their energy balance could rather depend upon feeding on relatively high‐quality plants. This suggestion – possibly named ‘forage quality hypothesis’ – now requires further investigations. This work showed that alternative mating behaviours may underlie different patterns of foraging strategies: we suggest that tests of alternative hypotheses to explain rut‐induced hypophagia within ungulate populations should not ignore the occurrence of AMTs.     

The Behavioral Ecology of Libellula luctuosa (Burmeister) (Anisoptera: Libellulidae): I. Temporal Changes in the Population Density and the Effects on Male Territorial Behavior

A single population of a common pond dragonfly, Libellula luctuosa, was studied at a site where the density of males increased dramatically during the breeding season. Early in the summer one active male was found on each territory on the pond. Satellite males were only occasionally found on the territories. Later in the season the number of males per territory increased so that two or more males simultaneously defended on many of the territories, and several satellite males occupied each of the territories. The number and rate of female visitations per day did not change over the summer. These factors resulted in a change in the operational sex ratio with variations in male density. Male behavior was also altered with increasing population density. As male density increased, males were less likely to be seen perching on their territories and more likely to be seen performing aggressive acts such as chasing nearby territorial males and chasing intruders. At high male density, the duration of territorial behaviors was shorter than at low male density. Thus, the percent of a time budget spent in any one activity did not change despite the change in number of males present. Male activity in L. luctuosa is not strictly determined by the opportunity for aggression. Costs of aggression associated with territoriality are minimized by maintaining flexible territorial behaviors.     

Social organization in the pheasant (Phasianus colchicus): harem formation, mate selection and the role of mate guarding

Harem formation and mate selection were studied in the pheasant in order to determine the advantages of territorial harem defence polygyny to the two sexes. We investigated the factors affecting harem size and the advantage to a female in remaining with one territorial male during breeding.
Female group size declined during late March and early April as females moved from large overlapping ranges into smaller, more widely dispersed breeding ranges. The proportion of female groups accompanied by males increased during this period.
Some males had a disproportionate share of females. Settled females were monogamous but, because a female's nest was generally outside the male's territory, her home range was larger than his territory.
Harem members were usually from the same winter group. Harem size was not related to territory quality in terms of food supply or nesting cover. Females were loyal to one male in more than one year even if his territory position changed. Older, territory-owning males had more females, both adult and immature, than males with newly-established territories. Harem size was not correlated with territory size.
We conclude that the mating system of the pheasant is based on mate guarding which protects females not only from the risk of predation or injury, but also from excessive energy expenditure incurred through being chased by other males. When escorted by a territorial male, females spent three times as much time feeding, one-fifth as much time running, and one-tenth as much time alert, as they did when not guarded.     

Territoriality and testosterone in an equatorial population of rufous-collared sparrows, Zonotrichia capensis

Territorial aggression, displayed by male vertebrates in a reproductive context, is generally thought to be mediated by testosterone. The challenge hypothesis predicts that in socially monogamous species, territorial challenges should induce an increase in plasma testosterone concentrations, which will enhance aggressive behaviour and territory defence. This hypothesis is based on northern latitude birds and needs to be tested in tropical birds before it can be universally accepted. We tested the challenge hypothesis in an equatorial population of rufous-collared sparrows in Papallacta, Ecuador. This population shows an extended breeding period during which males aggressively guard territories. During the early breeding season, males were challenged with conspecific or heterospecific simulated territorial intrusions (STIs) lasting 10 min. Conspecific-challenged males responded more aggressively than heterospecific-challenged males. However, there was no increase in plasma testosterone in response to the conspecific STI. During the breeding season, males were challenged with conspecific STIs lasting 0, 10 or 30 min. Males behaved aggressively regardless of STI duration, and did not differ in plasma testosterone or luteinizing hormone concentrations. During the breeding season, males were implanted with testosterone-filled or empty silastic tubes and subsequently challenged with a conspecific STI. Testosterone implants significantly raised plasma testosterone concentrations, but testosterone-implanted males were not more aggressive than blank-implanted controls. Combined, these findings suggest that testosterone concentrations above breeding baseline are not related to territorial aggression in this population and therefore do not support the challenge hypothesis.     

Seasonal and diurnal variation in vocal behaviour of the South Island robin

Abstract

The proportion of time spent by South Island robins (Petroica australis australis) of different sex, age, and status giving full song, subsong, and downscales, on a monthly and diurnal basis, is described. Females never gave full song. Males did so throughout the year, but least while moulting. Since bachelors sang significantly more than paired males, song probably functioned largely to attract females. Breeding males sang most during the pre-laying stage. From January to April adult males sang significantly more than immature males, but from May to July the reverse was true. Robins sang mainly in the early morning. Robins generally spent less than 0.5% of time during any stage of the breeding cycle giving sub-song. Outside the breeding season, males spent significantly more time giving sub-song than females, and adult males sang more than immature males. Robins in all categories gave more sub-song during the moult than afterwards. The diurnal pattern of sub-song production was bimodal. About half the downscales were followed by no obvious action from the caller or response from other robins, nor were the calls preceded by an obvious event. About 25% of the downscales were associated with interactions between members of a pair; the remainder were associated with territorial defence. Downscales probably served to maintain contact between members of a pair and to advertise possession of territory. These calls were heard rarely in the breeding season, and most frequently in April. Males gave downscales more than females, but use of downscales by both sexes was evenly distributed through the day.     

Late breeding season definitive prebasic molt in males,and late breeding season brood care by females,in central California Wilson’s warblers

I made observations of a central California population of Wilson''s Warbler, Cardellina pusilla, after July 1 over 10 breeding seasons. I sighted males in definitive prebasic molt from July 4 (in 2007) to September 1 (in 1999). Most territorial males molted on their breeding territories, and individual molt lasted up to 46 days. Following prebasic molt, territorial males engaged in subdued “post‐molt singing,” which lasted about 7 days in some males, and which I first heard on August 13 (in 2004) and last heard on September 6 (in 1999). I sighted no female in definitive prebasic molt, or in fresh basic plumage, during the study. Of 13 females sighted ≥ July 21, 11 were in late breeding season uniparental brood care, and I could not rule out late brood care for the other two. Most, and possibly all, females not engaged in late season uniparental brood care apparently vacated their breeding territories before July 21. This departure was much earlier than for resident males, the last of which I sighted on September 10 (in 1999). Early‐departing females presumably underwent prebasic molt after July 21 at locations not known. Remaining late‐nesting females must have molted much later than resident males and likely later than early‐departing females, and at locations unknown. I last sighted two uniparental brood‐tending females, still in worn plumage, on August 26 and 29, respectively. Two unique findings of this study are a male/female difference in location of prebasic molt, and a likely dichotomy of prebasic molt timing between females leaving their breeding territories early and those remaining in uniparental brood care. Another finding, post‐molt singing in most and possible all territorial males, is a largely unrecognized behavior, but one previously reported in several passerine species. Post‐molt singing may reliably indicate completion of prebasic molt.     

Pair territoriality in the longnose filefish,oxymonacanthus longirostris

The longnose filefish,Oxymonacanthus longirostris, usually lives in heterosexual pairs, the male and female swimming together and sharing the same territory. Pair territoriality in the species was examined in detail in relation to sexual differences in territorial defense activities. Rigorous pair territoriality was maintained only during the breeding season, although pairs used their home ranges exclusively to a certain extent, during the non-breeding season. The frequency of aggression against other conspecific pairs in the breeding season was higher than in the non-breeding season. Agonistic interactions appear to be over both mates and food resources, the strict pair territoriality in the breeding season possibly being due to mutual mate guarding. In intraspecific aggressive interactions, males usually led their partner females when attacking intruders. The feeding frequency of males was much lower than that of females in the breeding season. Mate removal experiments indicated that females could not defend their original territories solitarily and their feeding frequency decreased. Conversely, males could defend territories solitarily without a decrease in feeding frequency. These results suggest that males contribute most to the defense of the pair territory, with females benefiting from territorial pair-swimming with their partner males.