Rival Males Research Articles

Variation in the song of the great reed warbler Acrocephalus arundinaceus in relation to mate attraction and territorial defence

Variation in the song structure of the great reed warbler Acrocephalus arundinaceus was investigated using a variety of observational, analytical and experimental techniques. Males were found to have two types of song, called long and short songs. Short songs consisted of relatively few, stereo-typed, low-amplitude syllables, and were given by males during territorial encounters with rival males. Males were more reluctant to approach during playback of short songs, and when lured in by long songs retreated when playback was switched to short songs. Long songs consisted of a wide variety of high-amplitude elements added to the basic short song structure. Long songs were only given spontaneously by unpaired males, and ceased when a female had been attracted. In Acrocephalus warblers, monogamous species have evolved long, complex and variable songs for mate attraction largely through intersexual selection. Polygynous species have evolved short, simple and stereotyped songs for territorial defence through intrasexual selection. The great reed warbler is a partial polygynist, and through evolutionary compromise has evolved a variable song structure which can be shortened for territorial defence, and lengthened for mate attraction.

Vocal interactions, call matching and territoriality in a Sri Lankan treefrog, Philautus leucorhinus (Rhacophoridae)

The vocal repertoire of Philautus leucorhinus, a Rhacophorid frog, consists of several distinct call-types, each used in a different social context. Males defend space in choruses by calling, and ultimately by fighting off rival males. Vocal interactions between males begin with exchanges of territorial calls followed by multi-note calls. Males frequently ‘match’ their rival's preceding call by responding with a multi-note call containing a similar number of notes. Vocal interactions become more escalated as the distance between males decreases but the accuracy of matching is apparently unaffected by distance. Males respond to playbacks of advertisement calls or territorial calls by increasing the frequency of territorial calls and the number of notes in their calls. It is suggested that the level of escalation in vocal interactions is a graded threat, signalling the probability of attack. Two explanations of vocal matching are offered: matching may be an effective means of directing threat signals at a particular rival and/or it may be a consequence of vocal competition for females.

Flight Song and Song Flight in the Orange-Crowned Warbler

Birds of many species commonly sing while flying. The behavior is characteristic of many open-country species, such as larks, pipits, and Bobolinks (Dolichonyx oryzivorus) and also occurs among some woodland species, including several wood warblers (Parulidae; Ficken and Ficken 1962). In some of these warbler species, both the given during flight, and the itself, are distinctly different from perch and direct flight. Ficken and Ficken described such as a variable warbling [accompanied by a] rising on slowly flapping or quivering wings [and] typically a direct and silent descent. Workers have reported flight songs and song occurring in several species of Vermivora, including the Tennessee Warbler (V. peregrina; Bowdish and Philipp 1916), Nashville Warbler( (V ruficapilla; Bowles and Bowles 1906, and Thayer, reported in Chapman 1907), Bachman's Warbler (V. bachmanii; Howell 1924, reported in Bent 1953), and Blue-winged Warbler (V. pinus; Pitelka 1939). The and flights described for these species, however, appear to be less modified than those described by the Fickens for nonVermivora warblers. I observed and flights occurring in the Orange-crowned Warbler (V. celata) during behavioral studies of the species in its typical nesting habitat in Contra Costa County, central coastal California. I followed the behavior of unmated territorial males prior to 12:00, during March, April, and May of 1980, 1981, and 1982. Although I may have overlookQd the behaviors, I did not observe and flights in unmated birds during late February, June, and early July, nor among mated birds during any month. Populations of these warblers were relatively dense in my study areas, with all males having at least two territorial neighbors. Territorial disputes were common. Most I heard were begun in mid-flight, and completed on a perch. Occasionally the entire was rendered in the air. I could detect, by ear, no difference between sung during and those sung entirely while perched. When in flight, the wings of a warbler characteristically fluttered or quivered in a way I never saw in normal direct flight. I observed nothing resembling the rising and direct descent described by the Fickens. I noted nine instances of birds singing while in during 260 min of observation in which the individual Orange-crowned Warblers were in sight. Since these birds usually sang four to six per minute, it is apparent that occurred much less frequently than perch songs. Flight and flights apparently occurred at random, and I noticed no associated special circumstances, such as the presence of a female or a competing male. The and flights I observed in Orangecrowned Warblers differed from those described by the Fickens. They generally resembled those described for other species of Vermivora, although the fluttering in has hitherto been reported only for the Nashville Warbler (Bowles and Bowles 1906). I am aware of only two reports of and behavior resembling those I have reported here occurring in parulids other than species of Vermivora. The American Redstart (Setophaga ruticilla) apparently has an and often associated with encounters with females or rival males (Ficken 1962). The Kirtland's Warbler (Dendroica kirtlandii) also has such and flights, but they do not seem to be associated with any special environmental context (Mayfield 1960:133). Relatively unmodified and now are reported for the majority of North American Vermivora, suggesting that these forms of behavior are characteristic of the genus.

The Effects of Male Nuptial Coloration On Stickleback Aggression: a Reexamination

Abstract1. Territorial male threespine sticklebacks, Gasterosteus aculeatus, do not always attack an intruder (a dummy) with red undersides more than one lacking this feature even when it is presented within their own territory. Males in this study showed an overall tendency to bite a dummy without red undersides more than one with this feature during both simultaneous and serial presentations. 2. Considerable variation in attack rates exists between individual males, but whether or not a given male attacks the nonred dummy more appears to be unrelated to whether he exhibits high or low attack rates. 3. Males showed an increased attack rate after they acquired eggs in their nest, but the tendency for a male to attack the nonred dummy more than the red one appears to be unchanged after he acquires eggs. 4. It is suggested that the nuptial coloration of male threespine sticklebacks be interpreted more generally as an indicator of the male's social and physiological status, emphasizing its intimidating effects as well as its aggression eliciting effects for rival males. This is consistent with the observation that nuptial coloration is capable of increasing avoidance as well as attack in rival males and increasing sexual attractiveness to females.

The tusk of the narwhal (Monodon monoceros L.): interpretation of its function (Mammalia: Cetacea)

For over a century, scientists have speculated on the biological function of the tusk of the male narwhal. Proposed functions have included use of the tusk as a weapon, use for opening breathing holes in sea ice, use in feeding, use as an acoustic organ, and function as a secondary sex character. The weight of evidence in this literature review supports a theory that the narwhal tusk serves as a secondary sex character of males, for nonviolent assessment of hierarchical status on the basis of relative tusk size. Relative tusk size is evidently determined in frontal encounters by rival males.

Mating and Male Combat in Australian Blacksnakes, Pseudechis porphyriacus

We observed ritual combat and other agonistic behavior between male blacksnakes (Pseudechis porphyriacus) in a field population in central New South Wales. Combat bouts vary greatly in duration (2 to 30 minutes), and apparently function as male strategies to displace rival courting males. Direct attack and biting may serve to displace rival males in copulo. We briefly review published literature on male combat in snakes.

Adaptive significance of postcopulatory guarding of mates and nonmates by male Calopteryx maculata (Odonata)

1. The postcopulatory behavior of the damselfly Calopteryx maculata (De Beauvois) (Odonata: Calopterygidae) was studied in field populations to determine the adaptive significance of guarding of ovipositing females by males. Of particular interest was an explanation for the guarding of ovipositing nonmates by males. A promiscuous mating system and the large variation in mating success (Table 1) among territorial males indicated that sexual selection may have been a significant factor in the evolution of C. maculata postcopulatory behavior. 2. Territorial males defend ovipositing mates by chasing and displaying toward conspecific males attempting takeovers. Guarded mates averaged 12–15 min of undisturbed oviposition while unguarded females averaged only 1–2 min of oviposition prior to disturbance by males. Postcopulatory guarding is advantageous to both sexes because it allows undisturbed oviposition. 3. During mating, 88%–100% of the sperm stored by a female from a previous mating was removed by a male before he transferred his own sperm to her storage organs. Given this potential for sperm displacement, postcopulatory guarding is advantageous to the guarding male since it assures him of fertilizing a substantial number of eggs prior to a subsequent mating by his mate. 4. The duration of guarding (interval between matings) for males was 10–15 min. It did not differ significantly between two populations in on year. Guarding duration did not significantly change with (a) time of day, (b) time devoted to defensive behavior, (c) female arrival rate, and (d) presence of absence of an ovipositing female (Table 2). 5. Males frequently guarded females with which they did not mate. Nonmates were guarded only when the male was simultaneously guarding a mate or had recently mated. These nonmates deposited eggs fertilized by rival males. Their presence did not significantly increase the time and energy expended by guarding males but did attract additional females (Table 3). However, these additional females did not lead to an increase in mating frequency for the guarding male. 6. Three factors appeared to limit the ability of guarding males to exclude or attempt matings with arriving nonmates: (a) a lack of individual recognition, (b) a risk of losing a previous mate while failing to copulate with an arriving female, and (c) a probable physiologic limit to mating frequency. These limitations in male postcopulatory behavior were exploited by females. 7. Some males were not territorial. While appearing less effective at obtaining mates, they devoted no time and energy to defending territories or mates. Because of sperm displacement, their reproductive success depended upon the ability of their mates to exploit the limitations in guarding behavior of territorial males.

The Cost of Mating

The Cost of Mating

Theoretical aspects of sexual selection

Darwin (1859) gave a concise definition of sexual selection and its mechanism: “This depends, not on a struggle for existence, but on a struggle between the males for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring.” Darwin thought that the males’ chances of mating would depend not only on competition between rival males, but also on female choice. Sexual selection would thus promote the evolution of weapons for fighting other males and adornments for sexual display to females. In a polygynous species, the more highly endowed males may attract more females than their less fortunate rivals and therefore gain a considerable advantage. But, as Darwin (1871) noted, monogamous species are often sexually dimorphic: sexual selection must operate in monogamous as well as polygynous species. Darwin put forward a subtle theory to explain this. “Let us take any species, a bird for instance, and divide the females inhabiting a distinct into two equal bodies, the one consisting of the more vigorous and better-nourished individuals, and the other of the less vigorous and healthy. The former, there can be little doubt, would be ready to breed in the spring before the others... . There can also be no doubt that the most vigorous, best nourished and earliest breeders would on average succeed in rearing the largest number of fine offspring. The males, as we have seen, are generally ready to breed before the females; the strongest, and with some species the best armed of the males, drive away the weaker; and the former would then unite with the more vigorous and better-nourished females, because they are the first to breed. Such vigorous pairs would surely rear a larger number of offspring than the retarded females, which would be compelled to unite with the conquered and less powerful males, supposing the sexes to be numerically equal; and this is all that is wanted to add, in the course of successive generations, to the size, strength and courage of the males, or to improve their weapons.” Darwin further argued that the earlier and more vigorous females, by having a wider choice of mates than females coming into breeding condition at a later date, will exercise their choice in favor of the most attractive and highly adorned males, who will also gain a selective advantage.

A possible origin and adaptive significance of the mounting behaviour shown by some female mammals in oestrus

Summary It is suggested that female-female mounting, common in domestic cattle and various other mammals during oestrus, may have a function in attracting the male and ensuring a mating. As such it could serve as a potent alternative to more direct forms of solicitation. Especially where intra-male competition (sexual selection) is intense, behaviour characteristic of rival males (e.g. mounting, threat displays, etc.) should act as a powerful attractor of the dominant herd bull, thus having a dual advantage to the female, and explaining the origin of the behaviour. Anoestrus mounting of an oestrus mountee can be explained by kin selection and/or reciprocal altruism.

Copulatory plugs in snakes: enforced chastity.

The male of some snake species forms a copulatory plug which occludes the oviductal parts of the female's cloaca for a few days. The plug, apparently formed from secretions of the kidney immediately after insemination, probably prevents rival males from copulating with the same female.

Effects of marihuana (Δ9-THC) on behavior patterns and social roles in colonies of CBA Mice

The effects of marihuana (Δ9-THC) upon dominant and subordinate male behavior profiles were continuously observed in mice socially interacting in population cages. All males were magnetically tagged and triggered Hall Effect devices at each of the eight portals in the population cage. Ethologically oriented observations consisting of entry-exit rates, patterns of spontaneous behavior, and elapsed time in each functional area were made for each animal. The subordinates showed no significant change in their pattern of low locomotor activity after a single intravenous dose of 20 mg/kgΔ9-THC. By contrast, the high-activity dominants showed a significant reduction in entry-exit rates and in their patrol patterns. They fully recovered from their locomotor depression within 24–48 hr unless a rival male was present, in which case the dominant was severely attacked, lost his territory, and assumed subordinate behavior at both 2 and 20 mg/kg doses. A dose of 0.5 mg/kgΔ9-THC significantly decreased the dominant male's aggressive response to an intruder, but did not alter his social status. The behavioral effect of Δ9-THC in a freely interacting, mixed-sex group of rodents living in population cages is dependent upon social position in the hierarchy and upon the social composition of the group.

Sappho Fr. 31: Anxiety attack or Love Declaration?

In a recent article1 the psychiatrist George Devereux reached the following conclusion about fr. 31: Sappho as a ‘masculine lesbian’ experiences ‘a perfect, “text-book case”, anxiety attack’, elicited by ‘a love-crisis’, viz. by the presence of a male rival for the attention of Sappho's favourite girl. He then sums up: ‘In fact, even if there existed no explicit tradition concerning Sappho's lesbianism, her reaction to her male rival would represent for the psychiatrist prima facie evidence of her perversion’ (p. 21).

The Role of the Epaulets in the Red-Winged Blackbird, (Agelaius Phoeniceus) Social System

AbstractThe role of the epaulets of the male Red-winged blackbird, Agelaius phoeniceus, was examined. Territorial male Red-wings were captured and their epaulets blackened with Nyanzol D, a permanent black dye. The following results were obtained: 1) Sixty-four percent of the males with black epaulets lost their territories while only eight percent of the control males lost theirs. 2) Males with epaulets blackened prior to pair formation were still able to "attract" females and mate successfully. It was concluded that the epaulets communicate threat between rival males but that they have little if any role in intersexual encounters. The epaulets, therefore, have probably evolved in response to intrasexual (epigamic) selection pressure.

Effects of Conspecifics and Vegetation On Nest Site Selection in Gasterosteus Aculeatus L

AbstractVegetation and conspecific rivals both exert significant influences on the locations of territories as determined by the nest sites selected by naive male three-spined sticklebacks. The effect of a row of vegetation along one end of a tank depends on the size of the tank. In small tanks (up to I20 cm), a row of vegetation at one end repels males. In the 300 cm tank, a row of vegetation at one end did not appear to influence the overall distribution of nests, but those nesting in the end with the vegetation tended to nest in the vegetation. A row of vegetation at one end of the 600 cm ditch attracted some males who nested in the row. The remaining nests were located in the middle portion of the ditch,, and the end effect in the unplanted ditch disappeared. Thus the effect of a row of vegetation depends on the amount of open space available in front of it. In the 600 cm ditch, a row of vegetation standing away from the end attracted 65 per cent of the males who selected nest sites within and adjacent to the rows compared to 40 per cent when the row was at the end. The difference is not quite significant. With a rival behind a glass plate 30 cm from one end of the otherwise bare 600 cm tank, rival males selected nest sites at the opposite end of the tank. The repelling effect of a rival was effective over a relatively large distance in this bare environment. The repelling effect of the rival was exaggerated in some experiments in which a second glass plate was placed 30 cm from the opposite end. Separate experiments proved that a glass plate attracted males who tended to nest near it. The repelling effects of a rival was greatly reduced when a row of vegetation was placed at some distance from his territory boundary (glass plate).

Waning of the Aggressive Response in the Three-Spined Stickleback Upon Constant Exposure To a Conspecific. I, a Preliminary Analysis of the Phenomenon

AbstractStickleback males, which are held solitary under experimental conditions described above, give a more or less constant aggressive response toward a test-male (aggression test) when tested once or twice daily during a 4-day period following nest-construction. A distinct waning of this response is found in such males that have a continuous view of another male in a neighbouring territory behind a glass partition ('rival situation') : the frequency of biting decreases and becomes nil or fluctuates about a low level. Rival males and controls do not differ in the response toward a test-female (sex test). Therefore, rival males are said to have attained to a 'hypo-aggressive' condition. The stimulus situation that produces the waning of aggressiveness appears to have some specific properties, e.g. a goldfish neighbour does not lead to the same results. Waning of aggressiveness is also found toward the neighbour if it is used as a test-male. Waning is qualitatively independent of the presence of the glass partition, it occurs also in situations where neighbours can interact freely. Neighbours need not have a continuous view of one another to become hypo-aggressive, a (frequent) intermittent view leads to the same results. We conclude from our experiments that a recovery of aggressiveness, if present, takes place slowly (as a matter of days). A further analysis of the rival responses leads to the separation of three types: I, an unmodified response (similar to controls) ; II, a hypo-aggressive response without an increase of sexual activities toward the test-male; III, a hypo-aggressive response with an increase of sexual activities in addition. A large part of the type III males do not seem to discriminate a test-male and a test-female, the numbers of bites and zigzags in both test situations being nearly equal. Nest-building, or perhaps the presence of a complete nest, is a relevant factor for the occurrence of hypo-aggressiveness and the increase of sexual activities toward a test-male. The interaction of the aggressive and sexual tendencies is found to be entirely consistent with SEVENSTER'S (1961) results. In controls, biting and zigzagging result from the same aggressive and sexual tendencies irrespective of whether they are shown in aggression or in sex tests, and both tendencies are mutually inhibitive. The same conclusion is drawn for the interaction of aggressive and sexual tendencies in rivals. Though the interactions take place on quantitatively different levels, the relations of the tendencies remain qualitatively similar.

ON SOCIOLOGY AND BEHAVIOUR IN IMPALA (AEPYCEROS (MELAMPUS LICHTENSTEIN)

Summary1. The required habitat of impala, association with other herbivores and the relation to predators are outlined.2. The commonest types of group formation ‐ female herd with dominant male and bachelor herd ‐ and the factors determining the dynamic aspect of these formations are discussed.3. The daily activity rhythm is described, distinct activities are charac‐terlised as such and in relation to the social situation.4. The relationship between the dominant male and the female herd is analysed more closely. The herding activity of the male, the main forms of his courtship, and “roaring”, which occurs in the context of courting and as showing off and threat displays in male rivalry, are described.5. Social conflict amongst females and bachelors is of short duration and suggests the existence of a social hierarchy within the herds. Severe encounters and fighting occur between rival males exclusively over the possession of a female herd. The different forms of fightings and encounters are summarised and explained on the basis of the proportion of aggressiveness and inhibition of the rivals.6. Pre‐mating behaviour and copulation are described.7. The mother‐child bond is outlined in a preliminary form.8. The special features of impala sociology are discussed and compared with similar behaviour in other bovidae.