Satellite Males Research Articles

A simulation model of the effects of frequency dependence, density dependence and parasitoid flies on the fitness of male field crickets

There is substantial variation in the strategies animals use to obtain mates. In crickets, males may call to attract females or use a non-calling, or satellite, strategy and intercept females attracted to the calls of other males. Calling males are subject to attack by an acoustically orienting parasitoid fly and, after being parasitized, males die in 7–10 days. We used a simulation model to determine how frequency dependence, population density, and parasitoid flies affect the mating success of calling and non-calling males. The simulation demonstrated that calling males have higher mating success than satellite males under most conditions, and the fitness of both strategies increases with population density. Frequency-dependent selection did not have strong effects on calling or satellite male fitness. However, if parasitoid flies were present, satellite males had similar or higher mating success than calling males. These results demonstrate that the risk of parasitism strongly influences the fitness of calling and satellite males and likely contributes to the continued coexistence of alternative reproductive behavior in crickets.

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.

The Relationship Between the Presence of Satellite Males and Nest‐Holders' Mating Success in the Azorean Rock‐Pool BlennyParablennius sanguinolentus parvicornis

In the Azorean rock‐pool blenny, sexually active males may adopt alternative reproductive tactics. In the present paper the relationship between the presence of satellite males and the reproductive success of nest‐holders was investigated by comparing nests with and without an associated satellite male. Males with an associated satellite male suffered more conspecific intrusions but they did not display a higher frequency of attacks towards conspecifics. Nest‐holder males were more aggressive towards other conspecifics than towards satellites and the tolerance of nest‐holders towards satellites was inversely correlated with the time spent by the satellites in the breeding territory, which suggests control by the nest‐holder male of the satellite investment in shared territorial defence. Nest‐holders with an associated satellite male had higher condition factors and received more female visits and more spawnings. These results bear two possible interpretations. (1) Nest‐holders benefit from the presence of a satellite male by increased attractiveness of their nests to females; satellite males are mutualists helping to defend the nest‐owner's territory and to attract females, which is why they are tolerated. (2) Satellite males associate preferentially with more successful nest‐holder males which have higher condition factors, and by doing so have more opportunities to achieve parasitic fertilizations. Only experiments will allow these two hypotheses to be distinguished.

Skewed reproductive success among male white-spotted charr land-locked by an erosion control dam: Implications for effective population size

In 1996 and 1997, the spawning behavior of fluvial white-spotted charr Salvelinus leucomaenis, was observed in the upstream area of an erosion control dam. A small number of males with relatively large body size mated successfully with females as a pair, while almost all satellite males did not sneak successfully, resulting in a non-random mating system. The low sneaking success of subordinate males, in addition to the monopolization of spawning opportunities by a few dominant males, is one of the most important causes of skewed reproductive success among males. The total number of adult fishes in the study area (N: approximately half of the whole tributary above a dam) was estimated as 148 and 102 in 1996 and 1997, respectively. Based on these findings and some further assumptions, the estimated effective population size (Ne) was low in both years. The Ne/N ratio ranged from 0.33 to 0.36 in both years. In addition to reduced population size by construction of an impassable dam, the above-dam population suffered low Ne due to skewed reproductive success among males. The low Ne may be one cause of extinction in above-dam populations of fluvial charr, especially just after the construction of impassable barriers.

Skewed reproductive success among male white‐spotted charr land‐locked by an erosion control dam: Implications for effective population size

In 1996 and 1997, the spawning behavior of fluvial white‐spotted charr Salvelinus leucomaenis, was observed in the upstream area of an erosion control dam. A small number of males with relatively large body size mated successfully with females as a pair, while almost all satellite males did not sneak successfully, resulting in a non‐random mating system. The low sneaking success of subordinate males, in addition to the monopolization of spawning opportunities by a few dominant males, is one of the most important causes of skewed reproductive success among males. The total number of adult fishes in the study area (N: approximately half of the whole tributary above a dam) was estimated as 148 and 102 in 1996 and 1997, respectively. Based on these findings and some further assumptions, the estimated effective population size (Ne) was low in both years. The Ne/N ratio ranged from 0.33 to 0.36 in both years. In addition to reduced population size by construction of an impassable dam, the above‐dam population suffered low Ne due to skewed reproductive success among males. The low Ne may be one cause of extinction in above‐dam populations of fluvial charr, especially just after the construction of impassable barriers.

Male Sexual Polymorphism, Alternative Reproductive Tactics, and Androgens in Combtooth Blennies (Pisces: Blenniidae)

In species in which intense intermale competition for the access to females is present males of lower competitive ability may adopt alternative reproductive tactics (ART) to get access to mates. These ART translate in many cases into male sexual polymorphism, with individuals following distinctly different tactics. Usually two alternative male morphs can be recognized in species with ART: (1) bourgeois males that compete for access to mates invest in typically male behaviors, such as building elaborated nests or displaying ornaments; and (2) parasitic males that take advantage of the success of the bourgeois males in attracting females and attempt “sneaker” fertilizations (e.g., sneaker and satellite males). In combtooth blennies (Blenniidae) the co-occurrence of ART and male sexual polymorphism has been described for two temperate species: the peacock blenny, Salaria pavo, and the Azorean rock-pool blenny, Parablennius sanguinolentus parvicornis. Interestingly, while in the peacock blenny the alternative male morph adopts a sneaker tactic, in the rock-pool blenny parasitic males act as satellites to nest-holder males. Thus, this variation in the ART expressed in these two closely related species allows for a comparative study of the proximate and ultimate factors affecting the expression of the two ART. In this article we summarize the available information on androgen levels in bourgeois and parasitic males of natural populations of the two species and of recent studies on the effect of exogenous administration of androgens on tactic switching in parasitic males of the two species. The information is discussed within the frame of the relative plasticity hypothesis, which predicts that plastic alternative morphs should show differences in hormone levels and that the administration of sex steroids should be effective in promoting the switch from the parasitic to bourgeois tactic. The evidence is only partly consistent with this hypothesis. Alternatively, a social transduction hypothesis that better fits the available data on androgens and ART in teleost is proposed. It states that the observed differences in androgen levels between alternative morphs should not be interpreted as an organization vs activation effect of steroids, but rather as the limited vs lifelong responsiveness of the neuroendocrine axis to social regulation.

Courtship behaviour in a lekking species: individual variations and settlement tactics in male little bustard

We analysed the display behaviour of male little bustard Tetrax tetrax to identify displays that are used in the context of male–male competition and those that are used for attracting females. Courtship was the main activity of males during the breeding season. Calling activity occurred throughout the day, and leks were attended for more than 4 months. Male sexual displays included snort call, wing-flash, and jump display. Snort call was performed throughout the day and mainly involved male–male interactions. In contrast, the wing-flash display was given only at twilight, and was performed most commonly when a female was present, supporting an inter-sexual function for this display. The jump display was performed only in the presence of female at anytime of the day. Analysis of individual variations in display behaviour revealed that intra-individual variation was low compared to inter-individual variation, especially for the jump display. It is, therefore, possible that display rates provide information on male quality. Four male settlement patterns could be defined, singles, paired, lekking and satellite lekking, but only wing-flash display and stamped snort call differed among those categories. We suggest that satellite males are attempting to benefit from proximity to higher status males, in accordance with the hotshot hypothesis of lek evolution.

Male competition and breeding success in captively reared and wild coho salmon (Oncorhynchus kisutch)

In the Pacific Northwest, releasing captively reared adult salmon (Oncorhynchus spp.) for natural spawning is an evolving strategy for the recovery of imperiled populations. However, the ability of captively reared fish to spawn naturally may be compromised by their artificial rearing environments. In this study, wild coho salmon (O. kisutch) males outcompeted captively reared males and controlled access to spawning females in 11 of 14 paired trials in laboratory stream channels. In two cases where satellite males were observed participating in spawning, DNA genotyping results determined that they did not sire any of the progeny. When spawning occurred at night and was not observed, DNA results confirmed behavior-based determinations of dominance made before dark. Dominance was established soon after the males were introduced into a common arena containing a sexually active female. We hypothesize that decisions by subordinate males to avoid direct competition may have minimized conflict. The competitive inferiority of captively reared coho salmon in this and a previous study probably reflects deficiencies in rearing environments, which fail to produce appropriate body coloration and body shape and perhaps alter natural behavioral development.

Effects of Androgens on Social Behavior and Morphology of Alternative Reproductive Males of the Azorean Rock-Pool Blenny

In the Azorean rock-pool blenny Parablennius sanguinolentus parvicornis two sequential reproductive tactics occur. Larger and older males establish breeding territories, while some of the smaller males become attached to nest-holder territories, acting as satellites on these territories, which they help to defend while trying parasitic fertilizations when females go in the nests to spawn. In the present paper we tested the effects of the androgens 17α-methyltestosterone (MT) and 11-ketotestosterone (KT) in the expression of male secondary sex characters and bourgeois behavior in satellite males. One week after satellites were implanted with Silastic tubes containing MT, KT, or castor oil (control), androgen-treated satellites had developed male secondary sex traits such as longer and wider male-type genital papilla and anal glands that secrete a sex pheromone, both traits being less expressed or absent, respectively, in satellite males. Androgen treatment had no effect on the gonadosomatic index or on the development of the testicular gland. KT treatment had a positive effect on relative liver weight. In terms of behavior, androgen-implanted individuals were less aggressive both in a mirror test and toward females when these were introduced into their tanks. MT-treated individuals spend more time inside the provided nests. Only androgen-implanted satellites managed to have the females entering their nests. When given a chance in a group tank either to try to attract females to their own nest or to act as satellites of an already established nest-holder's nest, MT-implanted males spent significantly more time in their own nest than near the nest-holder nest. These data suggest that androgens, particularly testosterone, may be involved in mating tactic switching in this species.

Evidence for use of chemical cues by male horseshoe crabs when locating nesting females (Limulus polyphemus).

Horseshoe crabs come ashore in attached pairs during spring high tides to mate and nest on beaches of the Atlantic and Gulf coasts. Unattached males also come ashore and crowd around the nesting pairs as satellites and engage in sperm competition with the attached male. Females with no satellites and females with large numbers of satellites nest next to one another on the same tide. When females are removed and replaced by a cement model, satellite males continue to be attracted to the same location. Models over sites where females with many satellites had nested are more attractive to males than sites from which a female with no satellites had been removed or a site where no crab had been nesting recently. A second experiment demonstrated that males are responding to chemical cues. A sponge filled with seawater taken from below a female with many satellites and placed under a model female was more attractive to males than a sponge filled with seawater. This is the first demonstration that horseshoe crabs use chemical cues, in addition to visual cues, to locate mates.

Sperm characteristics associated with different male reproductive tactics in bluegills ( Lepomis macrochirus )

We examined the availability and motility of sperm from parental and sneaker male bluegills (Lepomis macrochirus), a colonially nesting sunfish (Family Centrarchidae) with male parental care and a high incidence of cuckoldry by both sneaker and satellite males. We found no differences between sneakers and parentals in length and swimming speed of sperm, or percent and duration of sperm activity. In sneaker milt, however, sperm was almost 50% more concentrated than in parental milt (16.5×106 vs 11.5×106 sperm/µl of milt, respectively). Despite this difference in sperm concentration, stripped ejaculates from sneakers contained almost 400 million fewer sperm (only 32% as many sperm) than those from parentals due to their much smaller stripped ejaculate volumes (only about 19% that of parentals). Thus unless sneakers can compensate by releasing more sperm or gaining closer proximity to eggs at the time of spawning, they may be at a disadvantage with respect to sperm competition. We discuss these results in relation to models for the evolution of alternative reproductive behaviours in this species and suggest that the cuckolders may be making the best of a bad situation.

Paternity in horseshoe crabs when spawning in multiple-male groups

Unpaired or satellite male horseshoe crabs, Limulus polyphemus, are attracted to and often form a group around a pair (a female with an attached male) that is nesting in the high intertidal zone. These males are engaged in sperm competition. We observed nesting pairs and their associated satellites in the wild, collected and reared their eggs and used genetic markers to examine paternity. We found that the unpaired, satellite males are highly successful at fertilizing eggs; two satellites can leave the attached male with few fertilizations. Two satellites together are each as successful as one spawning with a pair. A satellite's location around the female greatly affects his success, and males compete for access to a position over the dorsal canal between the prosoma and opisthosoma of the female and under the front margin of the paired male where they are most likely to fertilize eggs. Although eggs and sperm retain their viability for some time after spawning, nearly all eggs are fertilized by the satellites that are around the nesting pair at the time of egg laying and by the attached male. A number of factors including beach current, female size and male behaviour affect the outcome of sperm competition in this externally fertilizing species.

Acoustic satellite behaviour in the Australian bushcricket Elephantodeta nobilis (Phaneropterinae, Tettigoniidae, Orthoptera)

Male and female Elephantodeta nobilis duet with the female responding to the male's long and complex call. The duetting male's call consisted of four parts, described here as parts A, B, C and D. We found that the female replied 570ms after the male's D pulse, which followed the extended part B and short click of part C. Noncalling males were attracted to the duet and often used satellite tactics by inserting a volley of clicks 200ms before the alpha male's D pulse. Satellite males used part C of the alpha male song to cue their own call and this inserted call induced females to reply earlier compared with the alpha male call alone. Alpha males often extended their calls with additional D-type calls and so we examined the effectiveness of these calls as countermeasures to satellite calling. There was no influence of this alpha strategy on the satellite's propensity to call although more calls from the alpha male did cause the female to reply more frequently. We also examined the effect of relative intensity of alpha and satellite calls on the female's reply. Reduced satellite intensity increased the variance in the timing of the female response. Finally, we tested the effectiveness of the satellite's call on female phonotaxis within a two-speaker arena. Although females preferred the alpha male they were nevertheless attracted to the satellite calls regardless of the latter's relative intensity. We discuss the possible role of satellite calling as a novel conditional strategy.

Structure and Social Dynamics of Harem Groups in Artibeus jamaicensis (Chiroptera: Phyllostomidae)

The Jamaican fruit-eating bat ( Artibeus jamaicensis ) is one of the most common Neotropical chiropterans, but comparatively little is known about structure and dynamics of its social groups. In two caves of the Yucatan Peninsula, Mexico, we found Jamaican fruiteating bats forming harem groups, consisting of 4–18 females and 1–2 males, inside solution cavities that develop on the ceiling of caves. Other individuals roosted solitarily in the same caves, but outside solution cavities. We identified three types of males: dominants (one in each harem group), subordinates (present only in the largest harems), and satellites (not associated with a harem). Dominants were larger and heavier than males of the other two categories. During the 2-year study, harem groups always roosted in the same cavity and presented a high degree of stability, with few changes in composition. Satellite males and solitary females, in contrast, shifted roosting sites frequently and never formed cohesive groups. Adult females performed more movements from and to harem groups than males, and those movements were less frequent during the breeding season. Harems of the Jamaican fruit-eating bat presented subordinate males in large groups and differ from those of other phyllostomids in the lower degree of cohesiveness shown by females.

Forebrain Arginine Vasotocin Correlates of Alternative Mating Strategies in Cricket Frogs

In cricket frogs, Acris crepitans, sexually active males can switch between calling and noncalling (satellite) mating strategies and injections of the neuropeptide arginine vasotocin (AVT) stimulate calling behavior. We report here that this behavioral variation of animals under field conditions is associated with variations in AVT-immunoreactive (AVT-ir) staining in distinct brain nuclei. In both calling and satellite males, one AVT-ir brain region was found in a continuous string of cells between the medial amygdala and the nucleus accumbens (ACC). Satellite males possessed significantly more AVT-ir staining in the brain (cells and fibers) than calling males at the level of the ACC, although not in the medial amygdala. This difference in AVT-ir staining in the ACC can, in part, be explained by differences in the density of staining within the cells and in cell size. In addition, satellite males had significantly higher AVT-ir staining in the fibers medial to the ACC than calling males. Because other studies have demonstrated that AVT stimulates calling behavior, a plausible hypothesis is that calling males are releasing more AVT from neurons in the ACC, depleting reserves within the cells, and that the released AVT elicits calling behavior. AVT immunoreactivity levels are also higher in the ACC in both calling and satellite males than in female cricket frogs, which do not call. Satellite males may therefore have AVT reserves that might allow them to call depending on the social conditions.

Relationships between body composition, body size and alternative reproductive tactics in a lekking sandpiper, the Ruff (Philomachus pugnax)

1. The Ruff is a lekking sandpiper in which males have two genetically determined alternative mating strategies: ‘satellite’ or ‘independent’. Satellite males are non‐territorial, following groups of females on and off leks. Independent males attempt to establish territories on leks and can be either ‘resident’ territory holders, or non‐territorial ‘marginals’. The time budgets of the three behavioural tactics (resident, marginal and satellite) differ notably in time allocated to foraging, aggression and display activity. These differences have led to the suggestion that the benefits of size and energy stores may vary with mating tactic. 2. In this paper in vivo estimates of body composition (fat, fat‐free mass) for breeding male Ruffs using total body electrical conductivity (TOBEC) are presented. 3. Satellite males have significantly shorter tarsi and wings than independent males. 4. After correcting for size, independent males are significantly heavier and fatter than satellites, and marginals in particular are heavier and fatter than both residents and satellites. 5. Estimates of energy expenditure during flight suggest that satellites may maintain reduced energy reserves to minimize flight costs, while the larger fat stores of independent males are consistent with the benefits of endurance as a territory holder.

VARIATION IN PACIFIC SALMON REPRODUCTIVE BEHAVIOUR ASSOCIATED WITH SPECIES, SEX AND LEVELS OF COMPETITION

AbstractMale and female Pacific salmon compete for different resources; females for suitable spawning sites and males for access to ripe females. Aggression should thus be primarily intra-sexual rather than inter-sexual. When different species are sympatric, males should primarily attack conspecifics whereas females should attack all females, regardless of species because they all compete for the same resource-space. The level of aggression should be a function of density, being relatively low at low densities and peaking at either intermediate or high densities. These predictions were supported in most respects by data collected on the behaviour of adult sockeye (Oncorhynchus nerka), chum (O. keta) and pink (O. gorbuscha) salmon in a large, relatively homogeneous spawning channel. Males almost exclusively attacked other males, especially conspecifics. Females were more likely to attack female heterospecifics than males but still tended to attack conspecifics most often, and also directed many attacks at males. Male aggression and digging, apparently a form of intra-sexual display, were related to density of male conspecifics in the local area, and the intensity of competition from satellite males courting the female.

Alternative Tactics in the Breeding Behaviour of Male Coho Salmon

Abstract1. The movements and breeding behaviour of male coho salmon in Kanaka Creek, British Columbia, Canada, were studied by means of radio-telemetry and detailed observations of males in breeding groups. 2. Males were of three morphological types, large, three year old males (which we term alpha males), small, three year old males (which we term satellite males) and small, two year old 'jack' males (which we term sneak males). All three types of male were common in the population. 3. Males associated with females in breeding groups that included one alpha male and one or more of the two smaller male types. Alpha males dominated in breeding groups. Their movements tended to be restricted to a small section of the spawning stream where they had primary access to redd building females. 4. The majority of aggressive interactions were between resident alpha males and intruding large males, which the resident attempted to drive away. Alpha males would not tolerate another large male nearby and would attack until the intruder left the area. Aggressive interactions between alpha and satellite males or between alpha and sneak males were much less frequent. The alpha males moved from female to female within their section of stream, often returning several times to the same female over the space of a few days. 5. Satellite males adopted positions downstream from a breeding pair. Satellite males were highly mobile within the stream and were observed to join breeding groups at widely spaced locations without significant aggressive interaction with the alpha male. An established satellite male would oppose but not drive away other satellite males attempting to join the breeding group, allowing them to adopt subordinate positions further downstream. The first satellite male in a breeding group would also defend and court the female during periods when the alpha male was absent. 6. Sneak males were most often observed in the spawning redd with the alpha male and female. Sneak males were also found hiding outside the redd early in redd construction, when the cavity of the redd was still shallow, or if the sneak was larger than 30 cm. Sneak males were subject to little aggression from the alpha male or satellite males and displayed the lowest frequency of aggressive interactions of the three types of male. Sneak males would defend their position against other sneak males. Like alpha males, sneak males restricted their movements to a small section of the spawning stream. 7. Overall levels of aggression were lowest in breeding groups consisting of two or three males and much higher in groups consisting of just the alpha male or of four or more males. Intrusion by a large male that challenged the alpha increased the rate of aggressive interaction among all members of the group. 8. Our results suggest three unique breeding tactics among coho males, here termed alpha, satellite and sneak. On the basis of the information currently available, it cannot be determined whether the choice of tactic by a particular male is genetically determined, environmentally determined, or both.

Central Monoamines in Free-Ranging Lizards: Differences Associated with Social Roles and Territoriality

During the breeding season different social classes of field-active lizards, Sceloporus jarrovi, exhibit regionally specific changes in central monoaminergic activation. Changes in serotonergic content and turnover between lizards from different social classes are seen in forebrain structures (telencephalon and diencephalon) and reflect events associated with reproductive behaviors, stress and aggression. Males without territories (satellite males) exhibit higher forebrain serotonin (5-HT) system activation compared to territorial males and adult females. This serotonergic activation includes increased 5-hydroxyindoleacetic acid (5-HIAA) and 5-HIAA/5-HT ratio, suggesting increased release and catabolism. Satellite males also exhibit higher 5-HIAA/5-HT ratios (serotonergic turnover) compared to territorial males following agonistic interactions. Territorial males, immediately following aggressive defense of territories against intruder males, exhibit increased 5-hydroxytryptophan (5-HTP) levels, higher 5-HIAA levels and 5-HIAA/5-HT ratio, higher epinephrine levels, greater MHPG/NE, more DOPAC and larger DOPAC/DA ratio compared to territorial males that did not have an aggressive encounter. These differences suggest activation of 5-HT, norepinephrine (NE), and dopamine (DA) systems by the synthesis and release of more 5-HT and the release of more NE and DA during aggressive defense of territory. The highest activity of serotonergic systems is exhibited by satellite males compared to territorial males, perhaps reflecting stress in subordinate animals from social and ecological sources.

Alternative male mating tactics in a cichlid, Pelvicachromis pulcher : a comparison of reproductive effort and success

Pelvicachromis pulcher is a small African cichlid which breeds in holes. Males may either reproduce monogamously (pair males), polygynously (harem males), or be tolerated as helpers in a harem territory (satellite males). These helpers share in defence of the territory against conspecifics, heterospecific competitors and predators. There are two male colour morphs that are fixed for life and are apparently genetically deter- mined. These diAer in their potential mating strategy. Red morph males may become harem owners, while yellow morph males may become satellite males, and males of both morphs may alternatively pair up mo- nogamously. We compared the reproductive eAort and success of these three male reproductive strategies. Ef- fort was measured as attack rates, time expenditure and the risk of being injured or killed when attacking com- petitors or predators of three sympatric fish species. Reproductive success was measured by observing how many eggs were fertilized by each male when this was possible, and by using genetic markers. The number of fry surviving to independence of parental care was used as a criterion of success. The reproductive success of harem males was 3.3 times higher than that of pair males and 7 times higher than that of the average satellite male. Dominant satellite males, however, were as suc- cessful as monogamous pair males, using the measure of fertilized eggs. To our knowledge, this has not been found previously in any fish species. Both harem and pair males had lower parental defence costs per sired oAspring, however, than males using the alternative satellite tactic. Defence eAort was significantly related to the risk of injury.