Behavioral Ecology Vol. 13 No. 5: 676-681
© 2002 International Society for Behavioral Ecology
Resource attractiveness of the male beaugregory damselfish and his decision to court or defend
a Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA b Department of Psychology, Lehigh University, Bethlehem, PA 18015, USA c Discovery Bay Marine Laboratory, Discovery Bay, Jamaica
Address correspondence to N. Santangelo, Department of Biological Sciences, 31 Williams Hall, Lehigh University, Bethlehem, PA 18018, USA. E-mail: nis5{at}lehigh.edu.
Received 2 May 2001; revised 29 January 2002; accepted 20 January 2002.
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
We examined the decisions territorial male beaugregory damselfish (Stegastes leucostictus) make when presented with mating and aggressive situations simultaneously. Specifically, we tested how males responded to simultaneous and consecutive presentations of conspecific males and females in bottles. We hypothesized that (1) territorial males would show lower levels of courtship toward females when a competing male is also present compared to when only the female is present and (2) territorial males would show higher levels of aggression toward intruding males when a female is also present on their territories than when only the intruder is present. We predicted that males with high-quality breeding sites would court females and attack competitors more vigorously than males with low-quality breeding sites. Males on low-quality breeding sites exhibited fewer conspicuous courtship displays toward bottled females and a lower bite rate toward bottled males than did the males on high-quality breeding sites. We concluded that poor breeding-site quality was responsible for the decline in the most conspicuous aspects of both courtship and aggression. When presented simultaneously with a bottled male and a bottled female, defenders of both breeding-site types drastically reduced the number of courtship displays and the amount of time they spent near the female. Thus, all aspects of courtship were reduced in the presence of a male intruder. Time spent near the bottled male also decreased in these simultaneous presentations; however, this decrease was less dramatic than the reduction in time spent near bottled females. Habitat quality did not affect these trade-off decisions, but the bite rate exhibited toward the bottled male increased in the simultaneous presentations compared to the single presentations. Due to this increase in a territorial male's defensive behavior when a female is present, we conclude that the presence of a female temporarily increased the value of a territory. We suggest that the possible loss of a territory to an intruding male takes priority over the potential benefits of successfully courting a single female and that it is a male's future reproduction, as well as his current reproduction, by which he assesses his benefits.
Key words: aggression, beaugregory damselfish, Caribbean, coral reefs, courtship, mate choice, Stegastes leucostictus, territoriality.
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Discussions of both aggression and mate choice have focused on the trade-offs involved in making decisions. That is, aggression and mate choice are analyzed with respect to the costs and benefits individuals accrue from performing those behaviors. For example, during aggressive encounters, individuals selecting an appropriate aggressive response might base that decision on the quality of the resources at stake and on their own relative abilities (Enquist and Lemiar, 1987; Lemiar and Enquist, 1984
;
Parker, 1974). Benefits gained
from winning a fight must be at least equivalent to the costs of the fight
tactic used. Empirical studies on multiple species have supported this
cost—benefit relationship when animals engage in aggression, especially
when in defense of resources of different qualities (e.g., fish;
Itzkowitz, 1979;
Johnsson et al., 2000; Nijmon
and Heuts, 2000; birds; Ewald and Orians,
1983; spiders; Riechert,
1979; see also review by
Riechert, 1998). Similarly,
mate choice has been viewed as a process of assessing the relative qualities
among prospective mates (e.g., Halliday,
1983; Janetos,
1980; Johnstone et al.,
1996; Moore and Moore,
1988; Real, 1990;
Sullivan, 1994;
Wittenberger, 1983). Here
also, the cost of the behavioral tactic used to secure a mate is expected to
be balanced or exceeded by the benefits gained from that mating. Empirical
work has found that mate searching varies in response to certain risks, such
as predation (fish; Candolin and Voigt,
1998; Endler, 1987;
Forsgren, 1992;
Forsgren and Magnhagen, 1993;
water striders; Sih et al.,
1990; fiddler crabs; Koga et
al., 1998; see also review by
Magnhagen, 1991), revealing
that mate choice decisions also involve trade-offs.
Animals may often be faced with multiple trade-off decisions
simultaneously. For example, individuals may be confronted with both mates and
competitors, thereby forcing aggression and mate choice decisions to overlap.
In the variegated pupfish (Cyprinodon variegatus), the entrance of a
female into a male's territory will stimulate neighbors to intrude and disrupt
the courtship of the territorial male
(Itzkowitz, 1974).
Kodric-Brown and Brown (1984)
observed that territorial males of various species seem to court a female
while simultaneously defending against an intruder. Also, the mate-guarding
behavior of some birds might decrease their opportunity for extrapair
fertilizations (Westneat et al., 1990). Although territorial individuals have
been observed to deal with these competing options, few studies have
empirically determined the choices made when these competing options are
presented simultaneously. In a laboratory study, Candolin
(1997) showed that male
three-spined sticklebacks (Gasterosteus aculeatus) significantly
reduced their courtship and time spent with females when competitors were
present. However, her study did not include male—male interactions,
making it unclear what the decisions would be regarding a trade-off between
courtship and aggression.
When a territorial male is presented with a potential mate and a competing
male, the optimal behavior may depend on subtle fitness consequences
introduced by this situation. For example, if the cost of losing a mating is
higher than the cost of losing a territory, then courtship should take
precedence over aggression. Furthermore, if the competitor threatens to
attract the female away from the territorial male, the presence of the
competitor might cause the territorial male to increase his courtship relative
to a situation with no competitor. Alternatively, if the cost of losing a
territory is higher than the cost of losing a mating, than territorial defense
should take priority over that of courting a female. The cost of losing a
territory would depend on the reproductive benefit territorial owners have
over nonterritorial owners, the general availability of territories, and the
quality of an individual's territory (reviewed by
Maher and Lott, 2000).
Territory quality might, in fact, alter how males deal with these trade-off
decisions. For example, Real
(1991) and Reynolds
(1993) suggest that some males
might court less because they hold more attractive resources; therefore, it
might benefit males with high-quality territories to put more emphasis on
defense while males with low-quality resources emphasize courtship. The
presence of a female on a territory may in fact cause the territory to
momentarily become more valuable, and consequently, territory owners might
then be more aggressive toward competitors than when no female is present
(sensu Enquist and Lemiar, 1987; Lemiar
and Enquist, 1984; Parker,
1974). Related findings have been shown in brown-headed skinks
(Eumeces laiceps) where males incurred more risk when guarding a
female than isolated males (Cooper,
1999). Overall, if mating behavior and territorial defense are in
conflict, the time devoted to a male intruder or to a female should be less
when they are presented simultaneously than when they are presented
individually.
In the present study, we examined how the simultaneous presence of male
competitors and potential mates affects the fighting and mating decisions of
natural populations of the beaugregory damselfish (Stegastes
leucostictus). Males of this species defend small, permanent territories
where competing males often court the same females that pass near their
territories (Santangelo and Itzkowitz, personal observations). Natural
aggressive interactions between established territorial neighbors are uncommon
(Itzkowitz et al., 1995), but
intrusions with fights do occur when a receptive female is present (Itzkowitz,
personal observation). Therefore, S. leucostictus provides a good
social system in which to test the trade-off decisions territorial males make
when simultaneously presented with competitors and potential mates. We also
examined the effects of territory quality on the resident's choice of engaging
in courtship and/or defense. Previous studies have shown that our artificial
breeding sites (see Methods for description) quickly improve the reproductive
success of beaugregory damselfish males in comparison to their natural rubble
breeding sites (Itzkowitz,
1991; Itzkowitz and Makie,
1986; Itzkowitz et al.,
1995). Itzkowitz and Haley
(1999) showed that males on
artificial breeding sites increase their courtship intensity toward females
and suggested that courtship is an honest indicator of breeding-site quality.
This also suggests that males assess breeding-site quality, and therefore
breeding-site quality could influence how males deal with mating and
aggression decisions. An increase in territory quality has been shown to
increase the aggressive intensity of S. planifrons, a damselfish
closely related to the beaugregory damselfish
(Itzkowitz, 1979). We
therefore predicted that males with high-quality artificial breeding sites
would show higher levels of aggression to both the single and the simultaneous
male and female presentations compared to the males with lower quality
breeding sites. Although beaugregory damselfish males have been shown to court
more when they hold more attractive resources
(Itzkowitz and Haley, 1999),
the presence of an intruding male competitor could interact with territory
quality such that males defending high quality territories court less than
those defending lower quality territories.
A beaugregory damselfish male's decision to court or defend may depend on
his current reproduction (i.e., number of eggs within his breeding site) or
both his previous and current reproductive success (i.e., the number of eggs
he has secured overall in his territory). Because males will eat the eggs of
their neighbors (Itzkowitz, personal observation), we predicted that the more
eggs a territorial male guards, the more aggressive will be his defense. If
males base their assessment of breeding-site quality on the number of eggs
they obtained within that territory, then, regardless of their current
reproduction, territorial males may be more aggressive toward competitors if
their previous reproductive success is high. Although a previous study
(Itzkowitz and Haley, 1999)
found no relationship between a male's courtship and his current or previous
reproductive success, these factors may influence the courtship of territorial
males when they are presented with a female and a male competitor
together.
|
METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Locality and social system
This study was performed in the sand and rubble habitat found in the backreef environment in Discovery Bay, Jamaica. The study was carried out during July 1998.
Male beaugregory damselfish establish permanent, all-purpose territories in
quiet, shallow backreef habitats. Within their small territories (1-2 m
diameter), there is typically a breeding site consisting of a piece of rubble
that has a smoothed-walled crevice. When mating, a female enters the male's
territory and deposits her adhesive eggs on smooth walls within the crevice of
the breeding site and then leaves. The male provides no direct parental care
except to protect the eggs against diurnal fish predators
(Itzkowitz and Makie, 1986).
Within 6 days the eggs hatch, and the larvae float away as plankton.
Successful males often have multiple clutches from several females, and these
males will remain on the same territory for long periods of time, whereas
unsuccessful males move often until they find a territory of suitable quality
(Itzkowitz et al., 1995). The
relative size differences between males does not significantly correlate to
their differences in reproductive success
(Itzkowitz and Makie, 1986).
Nonterritorial males do not reproduce. We have never observed, nor has it ever
been reported, that males will sneak into another male's territory to spawn.
Therefore, the purpose of all intrusions appears to be the acquisition of the
territorial male's resources (i.e., food, breeding site, females, etc.).
Females have not been studied as thoroughly as males. They hold territories in
the vicinity of males but often travel considerable distances, bypassing
closer males, before choosing a mate and spawning
(Horne and Itzkowitz, 1995;
Renshaw, 1994).
Natural and artificial breeding sites
Natural breeding sites within the territories of reproductively successful
males are highly variable but typically have a piece of rubble that is usually
less than 0.5 m in height or diameter and contains a protected smooth-walled
crevice (see previous section). In an effort to compare males defending
similar breeding sites, artificial sites were devised (see
Itzkowitz, 1991;
Itzkowitz and Makie, 1986;
Itzkowitz and Haley, 1999).
These breeding sites were placed onto or next to males already defending
natural sites. Males began defending these artificial sites almost
immediately. The sites consist of four 15-cm length of 10-cm diam PVC pipe
bolted in an "+" pattern on a 30-cm square plastic base (see
photograph in Itzkowitz and Haley,
1999). Eggs were often deposited within the plastic tubes within
48 h. Eggs were too small to count in the field, and therefore estimates of
reproductive success were based on length x width (cm2)
measurements of the oval egg clusters. In this study we used only eggs that
were deposited within the past 24 h, as indicated by their bright yellow
color. After 24 h, the eggs darken and become black on the day of hatching
(approximately 6 days after being deposited).
Experimental design
We provided each of 28 males defending natural breeding sites with a new
artificial site. In a similar area, approximately 6 m away from the artificial
sites, we tagged the natural breeding sites of 28 other males. We separated
the artificial sites from the natural sites into two distinct areas because it
allowed us to shorten the time to both find and swim to specific males while
carrying a specific combination of stimulus bottles. Given our experience in
this backreef habitat (e.g., Itzkowitz,
1990,
1991;
Itzkowitz and Haley, 1999;
Itzkowitz and Mackie, 1986; Itzkowitz et al.,
1995,
2000), we were confident that
our selection of two separate localities for the different habitat qualities
would yield groups of males that were highly similar. The results presented
here are consistent with these past studies, indicating that the differences
between groups of males was based on the quality of their sites and not on
their general location.
Over a 21-day period, we monitored the reproductive success of males
defending only the artificial breeding sites. Accurate measurements of the
number of eggs found within natural sites are extremely difficult, and
previous studies have found that most males on natural sites rarely reproduce
(Itzkowitz, 1991).
On each of 7 consecutive days, we randomly selected 10 males using artificial breeding sites (out of 28) and another 10 using natural rubble (out of 28). Random selection was performed by picking numbers out of a hat that corresponded to particular males. The decision to use only 10 males a day from each breeding site quality type was based on time limitations, as the daily presentations took between 4 and 5 h. On each day of testing, each male tested was presented with (1) a bottled female and an empty bottle (the "single female" condition), (2) a bottled male and an empty bottle (the "single male" condition), and (3) a bottled male and a bottled female (the "paired male" and "paired female" conditions). The order of the presentations was alternated between days. At the end of the testing period, all males had been tested at least twice. Three males (one from the artificial sites and two from the natural sites) were dropped from the analysis due to missing data. The final sample sizes were 27 for the artificial sites and 26 for the natural sites.
The males and females were presented in 1-1 Nalgene bottles with holes
drilled into the covers to allow for the passage of any possible olfaction or
auditory stimuli between individuals. This is a common method of presenting
both heterospecifics and conspecifics to damselfish males
(Itzkowitz and Haley, 1999;
Itzkowitz and Mackie, 1986; Itzkowitz et
al., 1995; Myrberg and Thresher, 1974). Also, within our
experiment, test subjects appeared to behave normally toward bottled
individuals and recognized them as conspecifics (i.e., presented males were
attacked, whereas presented females were courted). Therefore, it is unlikely
that the results presented are an artifact of presenting the stimuli fish in
bottles.
To control for the effect of bottle numbers, an empty bottle accompanied the single presentations of the female and the male. In both the paired and single presentations, the two 1-1 Nalgene bottles were placed on opposite sides of the male's territory at about 30 cm from the breeding site (therefore the bottles were approximately 90 cm from each other). We observed the defender's behavior for 180 s. The bottled males and females were collected on each day of testing and thus there were daily changes in the males and females. On each day, the male and female used for the paired presentations were different from individuals used for the single male and single female presentations. Once a day's testing was completed, all four fish were released immediately.
After placing the two bottles near a male, we took the following records for 180 s: (1) the time the defender was within 10 cm of a bottle, (2) the number of times the defender made biting movements at the jar of the male, and (3) the number of courtship dips performed at any distance from the female's bottle. The dip display is a rapid downward movement of several centimeters and then a fast upward movement of about 10 cm. During a succession of dips, the dorsum of the male becomes bright yellow.
Analysis
During the course of the study, each of the 53 males received at least two
replicates of each stimulus (i.e., a single female presentation, a single male
presentation, and a paired presentation of a male and female). From these
replicates, means were generated for each behavior engaged in by the
territorial male for each type of presentation (i.e., time near male, time
near female, number of bites, bite rate, and number of dips). We analyzed
behavior toward the bottled male and toward the bottled female separately.
Each of the dependent measures was subjected to a 2 (single presentation vs.
paired presentation) x 2 (artificial breeding site vs. natural breeding
site) mixed within-subject factorial analysis of variance (ANOVA), with single
versus paired presentations a within subject (i.e., repeated-measures factor)
and artificial versus natural breeding sites a between subject (i.e.,
independent groups factor). To account for any heterogeneity of variances
between groups, we set our significance level at 0.025. Variance heterogeneity
causes an increase in the probability of making a Type I error, therefore
adopting a lower significance level is an appropriate correction
(Keppel, 1991). Furthermore,
nonparametric statistics yielded the same results reported below. However, we
used the ANOVA because of the ease it lends to testing, presenting, and
discussing data.
|
RESULTS |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Behavior toward the bottled male
Means (and standard errors) for time the defending fish spent near the bottled male are presented in Figure 1A. Less time was spent near the bottled male when the bottled female was also present compared to when she was not present (63% vs. 92% of session time; F1,51 = 106.79, p < .0001). There was no significant main effect of breeding-site quality (artificial vs. natural; F1,51 = 0.04, p > .80), nor was the interaction significant (F1,51 = 0.27, p > .60). In summary, breeding-site quality did not influence the amount of time a defender spent near a bottled male, and the presence of a female uniformly reduced the time near the bottled male.
|
To remove the confounding influence of the time spent near the bottled male, we calculated bite rate (i.e., number of bites per second of time near the bottled male) to measure the level of the territorial male's aggression. Both main effects were significant for bite rate (Figure 1B). Defenders of artificial breeding sites had a higher mean bite rate (0.51) than defenders of natural breeding sites (0.24) (F1,51 = 12.50, p = .0009). Also, the bite rate was higher for the paired condition (0.41) than for the single condition (0.33; F1,51 = 37.12, p < .0001). However, the interaction between the two breeding site types and the two types of presentation was not significant (F1,51 = 1.59, p = .21), indicating that the presence or absence of the bottled female had an additive effect on bite rate across breeding-site qualities.
In summary, a comparison of territorial males' bite rate revealed that males defending artificial breeding sites had a higher biting intensity toward the male intruder than those defending natural breeding sites and that the presence of a female uniformly increased biting intensity toward the male intruder across breeding-site qualities.
Behavior toward the bottled female
Defending males spent much more time near the bottled female in the single
condition (73% of session time) than in the paired condition (17% of session
time; Figure 2A;
F1,51 = 365.51, p < .0001). The main effect of
breeding-site quality (F1,51 = 0.50, p = .49) and
the interaction (F1,51 = 0.00, p = .99) were not
significant.
|
Males performed more dips in the single condition than in the paired
condition (Figure 2B;
F1,51 = 29.78, p < .0001) and performed more
dips on artificial breeding sites than on natural breeding sites
(F1,51 = 5.89, p = .0188). The interaction,
however, was not significant (F1,51 = 4.12, p =
0.05; 
= 0.025; see Methods), indicating that the effect of
breeding-site quality and the effect of the presence or absence of a bottled
male on the number of dips performed were additive.
In summary, although the time the defender spent near the bottled female was influenced only by the presence or absence of the male and not by breeding-site quality, the defender's courtship was influenced by both factors. That is, defenders of artificial breeding sites dipped more than defenders of natural breeding sites. Furthermore, the presence of a bottled male reduced the number of dips performed by territorial males, and the amount of this reduction was about equal for each breeding-site quality (i.e., there is no significant interaction between breeding-site type and presentation type).
Reproductive success, courtship, and aggression
Similar to previous studies that used these types of artificial sites,
reproductive success among males was highly variable (e.g.,
Itzkowitz, 1991;
Itzkowitz and Makie, 1986). To
assess the influence of daily reproductive success on the defender's courtship
and aggressiveness, we compared the number of eggs within a male's breeding
site with number of dips elicited toward the single bottled female and the
number of bites directed against the single bottled male on each day of
testing. We tested these relationships with the 10 males tested on each day of
the study. Neither the number of dips nor the number of bites was
significantly correlated with the number of eggs on any of the 7 test days
(Pearson correlation test; p > .05 for each day). (Note that for
N = 10, the power to detect a medium effect size of r = .30
is 0.13.)
To test if overall reproductive success influenced the aggression or courtship of a defender, we also compared the total number of eggs a male acquired during the study with his mean number of dips toward a single bottled female and his mean bite rate toward a single bottled male. As 10 males out of 28 were randomly selected on each day of testing, mean values were based on a variable number of tests. Neither the mean bite rate nor the mean dip number was significantly correlated with the total number of eggs a male received (bite rate vs. total eggs, N = 27, r = .23, p > .05; dips vs. total eggs, N = 27, r = -0.08, p > .05). (Note that for N = 27, the power to detect a medium effect size of r = .30 is 0.34.)
In the double bottle experiment, the paucity of courtship dips and the time spent near the bottled female precluded any analysis comparing reproduction to courtship behavior. However, similar to the single bottled male, there was no significant correlation between the bite rate directed at the male in the paired condition with the number of new eggs for any of the 7 test days (Pearson correlation test; p > .05 for each day).
In summary, the presence or absence of eggs, as well as the quantity of eggs, were not significantly correlated to aggression against bottled males nor to courtship directed at the bottled females. Furthermore, the mean bite rate and the mean dip number (for single presentations only) were not significantly correlated for males on artificial sites (N = 28, r = .19, p > .05) nor for males on natural sites (N = 28, r = .35, p > .05), indicating that there was no significant relation between aggression behavior and courtship behavior.
|
DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Territorial males on both habitat quality types spent less time with the bottled male and the bottled female when we presented them together compared to when we presented a male and a female singly. This indicates that mating behavior and territorial defense are in conflict in the beaugregory damselfish and that territorial males must engage in a trade-off when both situations occur. Although we predicted that defenders would reduce their courtship to a bottled female by spending time attacking the bottled male, we did not anticipate such a large decrease in courtship behavior. Clearly, our results support the hypothesis that the male values his territory, regardless of its quality, more than he does a potentially receptive female. For instance, defenders reduced their time near the female by about 75% when presented with an intruder and a female simultaneously compared to single-female presentations. Furthermore, defenders also substantially reduced their conspicuous courtship dips. Aggressive behavior toward the bottled male was less affected by the presence of the bottled female. That is, territorial males reduced their time near a bottled male by approximately 30% but exhibited a significantly higher bite rate when presented with a male competitor and a female simultaneously compared to single-male competitor presentations. This indicates that, aside from the territory itself, females also hold a value for the male and supports our contention that the presence of a female momentarily increases the value of a territory. This is similar to the findings of Cooper (1999
),
where the presence of a female skink increased the risk a male incurred
because of the potential reproduction she represented.
Within the present study, the overall emphasis on defense instead of
courtship by defenders on both high- and low-quality sites indicates that the
cost of losing a territory is greater than the cost of losing a mating. In a
previous study, Itzkowitz et al.
(1995) monitored the intense
competition that exists among males for breeding sites and observed that males
rarely defeat territory holders and that they acquire new territories only
when sites are created by storms that erratically rearrange the habitat. Thus,
the difficulty of replacing a breeding site (even of poor quality) lost to a
competitor may have longterm reproductive implications that overshadow the
loss of any single female. These results imply that the more males intrude on
a territory, the more females a territorial owner will ignore, and eventually
this strategy will have a negative effect on the male's reproductive success
(i.e., with many intrusions, defenders ignore all females). It is at this
point that the cost of being territorial will outweigh its benefit, and we can
predict that males would abandon territorial behavior.
As expected, males on low-quality sites showed lower aggression toward the
male intruder presentations than males on high-quality sites. Similarly, and
in support of previous results (Itzkowitz
and Haley, 1999), dip displays toward female presentations were
also significantly lower for males on low-quality sites than for males on
high-quality sites. The fewer number of dips and lower bite rate exhibited by
males on poor sites may reflect the costs associated with such behavior. For
example, we have observed males performing the gaudy dip display to be
especially vulnerable to predation by the common sand diver predator
(Synodus intermedius). Itzkowitz and Haley
(1999) suggested that males
are honest signalers of the quality of their breeding sites because females
eventually inspect, and perhaps reject, these breeding sites if the quality is
insufficient. This predation cost may be what causes males to be honest
signalers; otherwise, even males on low-quality breeding sites should court
females at high levels.
In the case of aggression, Itzkowitz
(1979) suggested that
damselfish appear to reduce the risks of aggression based on a decrease in the
potential reproductive payoffs of the territory. This indicates that males are
attempting to increase their survival and thus their chances of acquiring a
better quality habitat in the future. However, males on high-quality habitats
would not gain by restraining themselves and so exhibit elevated aggression to
protect their current territory. Alternatively, high-quality habitats may
provide males with more food and safety than low-quality habitats and thus
allow these males to exhibit more aggression and courtship. However, this
appears unlikely because food seems unlimited within the backreef habitat
(i.e., damselfish feed on algae), and the relatively open surroundings of the
artificial sites appear to provide these males with less safety than males
using natural sites crowded by rubble. In fact, all the predatory attempts we
observed against beaugregory damselfish were to males on high-quality
habitats.
The lack of a significant interaction between habitat quality and bottle presentation (i.e., single vs. simultaneous presentations) for aggression, courtship, and time spent at the bottles indicates that habitat quality had no effect on the male's trade-off decisions. This is surprising because, although territory quality influenced how territory owners treated intruding males and females, territory quality did not affect how males dealt with the decision to court or defend when they were presented simultaneously with an intruding male and a female.
The presence or absence of eggs did not change the defender's aggressive
behavior or courtship behavior in either the single or simultaneous bottle
tests. This confirms previous findings where the number of eggs present did
not affect the courtship intensity of territorial males
(Itzkowitz and Haley, 1999).
The fact that courtship and aggression were not related to individual
reproductive success but were affected by territory quality, as well as the
presence of a male and a female, suggests that territorial males assess the
quality of their breeding sites based on their future reproductive
potential.
Our inability to accurately predict the trade-off decisions when
territorial beaugregory males were confronted with both a female and a male
regardless of territory quality was unanticipated because the male's behavior
with either single stimulus (i.e., single bottled males or single bottled
females) was highly predictable for each of the territory types. Our results
clearly indicate that both the territory and the female are important to the
male. However, the precise benefit that accrues over time for securing either
a territory or a female is not known. We suspect that the complexity behind
these trade-off decisions was caused by having males decide between a stake
that has a long-term payoff (i.e., the territory) and a short-term payoff
(i.e., the female). This kind of mixed-stake cost—benefit model has been
effectively used to explain the schedules of reproduction individuals used
over their lifetime (Rogers and Sargent,
2001). To better understand the trade-off decisions depicted in
this study for the beaugregory damselfish, we believe a starting point is to
develop accurate measures for the lifetime reproductive success of identified
males defending specific territories (sensu
Clutton-Brock, 1988).
|
ACKNOWLEDGEMENTS |
|---|
We thank David Westneat for his invaluable insight and suggestions on previous drafts of the manuscript. We also thank John K. Leiser, Allison L. Cleveland, and two anonymous reviewers for their comments. This is publication no. 652 of the Discovery Bay Marine Laboratory.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONREFERENCES |
|---|
Candolin U, 1997. Predation risk affects courtship and attractiveness of competing threespine stickleback males. Behav Ecol Sociobiol 41: 81-87.
Candolin U, Voigt HR, 1998. Predator-induced nest site preference: safe nests allow courtship in sticklebacks. Anim Behav 56: 1205-1211.[Web of Science][Medline]
Clutton-Brock TH, 1988. Reproductive success: studies of individual variation in contrasting breeding systems. Chicago: University of Chicago Press.
Cooper WE, 1999. Tradeoffs between courtship, fighting, and anti-predatory behavior by a lizard, Eumeces laticeps. Behav Ecol Sociobiol 47: 54-59.[Web of Science]
Endler AJ, 1987. Predation, light intensity, and courtship behaviour in Poecilia reticulata (Pisces: Poeciliidae) Anim Behav 35: 1376-1385.
Enquist M, Leimar O, 1987. Evolution of fighting behavior: the effect of variation in resource value. J Theor Biol 127: 187-205.
Ewald PW, Orians GH, 1983. Effects of resource depression on use of inexpensive and escalated aggressive behavior: experimental tests using anna hummingbirds. Behav Ecol Sociobiol 12: 95-101.[Web of Science]
Forsgren E, 1992. Predation risk afffects mate choice in a gobiid fish. Am Nat 140: 1041-1049.[Web of Science]
Forsgren E, Magnhagen C, 1993. Conflicting demands in sand gobies: predators influence reproductive behaviour. Behaviour 126: 125-135.[Web of Science]
Halliday TR, 1983. The study of mate choice. In: Mate choice (Bateson P, ed). Cambridge: Cambridge University Press; 3-32.
Horne EA, Itzkowitz M, 1995. Behaviour of the female beaugregory damselfish (Stegastes leucostictus). J Fish Biol 46: 457-461.
Itzkowitz M, 1974. The effects of other fish on the reproductive behaviour of the male variegated pupfish, Cyprinodon variegatus (Pisces: Cyprinodontidae). Behaviour 48: 1-22.
Itzkowitz M, 1979. Territorial tactics and habitat quality. Am Nat 111: 585-590.
Itzkowitz M, 1990. Heterospecific intruders, territorial defense and reproductive success in the beaugregory damselfish. J Exp Mar Biol Ecol 140: 49-59.
Itzkowitz M, 1991. Habitat quality and reproductive success in the beaugregory damselfish. Environ Biol Fishes 30: 287-293.
Itzkowitz M, Haley M, 1999. Are males with more
attractive resources more selective in their mate preferences? A test in a
polygynous species. Behav Ecol 10:
366-371.
Itzkowitz M, Itzkowitz DE, Shelley D, 1995. Territory use and disuse in the beaugregory damselfish. Bull Mar Sci 57: 653-662.
Itzkowitz M, Ludlow A, Haley M, 2000. Territorial boundaries of the male beaugregory damselfish. J Fish Biol 56: 1138-1144.
Itzkowitz M, Makie D, 1986. Habitat structure and reproductive success in the beaugregory damselfish. J Exp Mar Biol Ecol 97: 305-312.
Janetos AC, 1980. Strategies of female mate choice: a theoretical analysis. Behav Ecol Sociobiol 7: 107-112.
Johnsson JI, Carlsson M, Sundstrom LF, 2000. Habitat preference increases territorial defence in brown trout (Salmo trutta). Behav Ecol Sociobiol 48: 373-377.[Web of Science]
Johnstone RA, Reynolds JD, Deutsch JC, 1996. Mutual mate choice and sex differences in choosiness. Evolution 50: 1382-1391.[Web of Science]
Keppel G, 1991. Design and analysis: a researcher's handbook, 3rd ed. Englewood Cliffs, New Jersey: Prentice Hall.
Kodric-Brown A, Brown JH, 1984. Truth in advertising: the kinds of traits favored by sexual selection. Am Nat 124: 309-323.[Web of Science]
Koga T, Backwell RY, Jennions MD, Christy JH, 1998.
Elevated predation risk changes mating behaviour and courtship in a fiddler
crab. Proc R Soc Lond B 265:
1385-1390.
Lemiar O, Enquist M, 1984. Effects of asymmetries in owner-intruder conflicts. J Theor Biol 111: 475-491.
Magnhagen C, 1991. Predation risk as a cost of reproduction. Trends Ecol Evol 6: 183-186.
Maher CR, Lott DF, 2000. A review of ecological determinants of territoriality within vertebrate species. Am Mid Nat 143: 1-29.
Moore AJ, Moore PJ, 1988. Female strategy during mate choice: threshold assessment. Evolution 42: 387-391.[Web of Science]
Myberg AA Jr, Thresher RE, 1974. Interspecific aggression and its relevance to the concept of territoriality in reef fishes. Am Zool 14: 81-96.
Nijman V, Heuts BA, 2000. Effect of environmental enrichment upon resource holding power in fish in prior residence situations. Behav Proc 49: 77-83.[Web of Science][Medline]
Parker GA, 1974. Assessment strategy and the evolution of fighting behaviour. J Theor Biol 47: 223-243.[Web of Science][Medline]
Real LA, 1990. Search theory and mate choice. I. Models of single-sex discrimination. Am Nat 136: 376-404.[Web of Science]
Real LA, 1991. Search theory and mate choice. II. Mutual interaction, assortative mating, and equilibrium variation in male and female fitness. Am Nat 138: 901-917.[Web of Science]
Renshaw AD, 1994. Behavior of the female beaugregory damselfish, Stegastes leucostictus (MS thesis). Bethlehem, Pennsylvania: Lehigh University.
Reynolds JD, 1993. Should attractive individuals court more? Theory and a test. Am Nat 141: 914-927.[Web of Science]
Riechert SE, 1979. Games spiders play. II. Resource assessment strategies. Behav Ecol Sociobiol 6: 121-128.[Web of Science]
Riechert SE, 1998. Game theory and animal contests. In: Game theory and animal behaviour (Dugatkin LA, Reeve HK, eds). Oxford: Oxford University Press; 64-93.
Rogers L, Sargent RC, 2001. A dynamic model of size-dependent reproductive effort in a sequential hermaphrodite: a counterexample to Williams's conjecture. Am Nat 158: 543-552.[Web of Science][Medline]
Sih A, Krupa J, Travers S, 1990. An experimental study on the effects of predation risk and feeding regime on the mating behavior of the water strider. Am Nat 135: 284-290.[Web of Science]
Sullivan MS, 1994. Mate choice as an information gathering process under time constraint: implications for behaviour and signal design. Anim Behav 47: 141-151.
Wittenberger JF, 1983. Tactics of mate choice. In: Mate choice (Bateson P, ed). Cambridge: Cambridge University Press; 435-447.
Zuk M, Caller GR, 1998. Exploitation of sexual signals by predators and parasitoids. Q Rev Biol 79: 415-438.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. M Leese, J. L Snekser, A. Ganim, and M. Itzkowitz Assessment and decision-making in a Caribbean damselfish: nest-site quality influences prioritization of courtship and brood defence Biol Lett, April 23, 2009; 5(2): 188 - 190. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. L. Snekser, J. Leese, A. Ganim, and M. Itzkowitz Caribbean damselfish with varying territory quality: correlated behaviors but not a syndrome Behav. Ecol., January 1, 2009; 20(1): 124 - 130. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. Santangelo and A. H Bass New insights into neuropeptide modulation of aggression: field studies of arginine vasotocin in a territorial tropical damselfish Proc R Soc B, December 22, 2006; 273(1605): 3085 - 3092. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||