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1.
Summary
Hyla ebraccata, H. microcephala and H. phlebodes commonly occur together in Panama. The three species have calls exhibiting broad frequency overlap and call during the same season and time of day from similar microhabitats, frequently in close proximity. The vocal repertoires of the three species are structurally and functionally similar. All employ multi-part advertisement and aggressive calls which consist of a primary note followed by a variable number of clicks. H. ebraccata males often responded to heterospecific calls with multi-note synchronized responses, and calls with primary notes greater than 150–200 ms were most effective in eliciting synchrony. Playback experiments with synthetic 1-note advertisement calls of different durations and both synthetic 1-note advertisement calls and 200 ms tones of different frequencies demonstrated that H. ebraccata males will synchronize with stimuli which are similar in frequency and duration to conspecific calls. Data from a two-choice experiment with female H. ebraccata demonstrate that calls of individual H. microcephala can reduce the attractiveness of a H. ebraccata male's calls if primary notes overlap. By synchronizing response calls to those of H. microcephala, a H. ebraccata may reduce the chances that his calls are rendered less attractive to potential mates.Aggressive calls of these species are graded and are characterized by higher pulse repetition rates and often longer durations than advertisement calls. H. ebraccata males respond to aggressive calls of H. microcephala and H. phlebodes as they do to their own calls. Heterospecific aggressive interactions probably occur because the species interfere acoustically. Our results demonstrate that H. ebraccata males behave in ways which enhance their ability to communicate in a noisy assemblage of conspecific and heterospecific males. 相似文献
2.
The evolution of male breeding aggregations is difficult to explain because males may reduce their reproductive success by
associating with their closest competitors. We examined aggregative behavior by male New Mexico spadefoot toads, Spea multiplicata, which form breeding choruses in rain-filled pools. We specifically asked whether males are attracted to conspecific calls
and, if so, whether they preferentially associate with those male calls that are also attractive to females. Field observations
revealed that males showed significant clustering with conspecifics within breeding ponds, whereas laboratory phonotaxis experiments
revealed that males preferentially associated with conspecific male calls. Moreover, when males were presented with conspecific
calls that differed in call rate, smaller males associated with the stimulus preferred by females (average call rate). Thus,
males appear to evaluate the attractiveness of competitors using the same trait employed by females to assess potential mates,
and males adjust their positions relative to competitors depending on their size. We discuss these results in the light of
several current hypotheses on the adaptive significance of male breeding aggregations.
Received: 20 December 1999 / Accepted: 18 March 2000 相似文献
3.
Summary The advertisement calls of Geocrinia laevis are diphasic, and consist of a single introductory note, followed by a series of repeated notes; diphasy is based on differentiation in the temporal structure of the two phases. In a series of field playback tests used to investigate the functional significance of diphasy, calling males were presented with one of three types of acoustic stimulus: complete calls (introductory and repeated notes), introductory notes only, or repeated notes only. There were no marked differences in the effects of these stimuli, and all resulted in a reduction in the rates of production of introductory notes and of repeated notes. Playback at levels of 110 dB PSPL and above caused virtual cessation of calling. The results suggest that one of the functions of the advertisement call, the communication of territoriality between males, does not reside in either the introductory note or the repeated notes, so that diphasy in the advertisement call has no apparent functional basis in this context. Whether the attraction of reproductively ripe females is a particular function of either phase remains untested. The advertisement calls of G. laevis are much less diphasic than those of a closely related species, G. victoriana, for which there is a clear partitioning of the functions of communication of territoriality and the attraction of conspecific mates between the introductory notes and the repeated notes, respectively. Furthermore, the acoustic repertoire of G. laevis is less complex than that of G. victoriana in lacking a vocalisation which functions specifically in close-range aggressive encounters between males. 相似文献
4.
Calling energetics of a neotropical treefrog,Hyla microcephala 总被引:1,自引:0,他引:1
Summary We investigated the calling energetics of Hyla microcephala, a neotropical treefrog with an unusually complex vocal repertoire. Males respond to the calls of other individuals by adding secondary click notes to their calls, thereby increasing the total number of notes given per minute. Rates of oxygen consumption of males calling in metabolic chambers were 0.41–2.80 ml O2/(g·h), corresponding to calling rates of 205–6330 notes/h. Note rate explained 95% of the variance in meta-bolic rate; the effect of variation in body size and temperature was small. Data from playback experiments with males in the field showed that note rate increased as as the number of notes in a stimulus call increased, and this resulted in substantial increases in the cost of calling. Average metabolic rates for males in the field were about 1.7 ml O2/(g·h), for a net cost of calling of about 20 J/h for an average-size male. However, estimated metabolic rates varied by more than 300% and were strongly influenced by the proximity and calling activity of other males in the chorus. Male H. microcephala appear to conserve energy by reducing calling rates when only a few males are active and increasing calling efforts only when vocal competition among males is intense. 相似文献
5.
In species where males use alternative reproductive tactics and male phenotypes are confronted with different risks of sperm
competition, theory predicts that between-male-type differences in sperm expenditure may evolve. In the frog Crinia georgiana big males can monopolize females, whereas small males often engage in polyandrous matings. Consequently, big males may experience
a lower risk of sperm competition than do small males. We tested if the predictions from theoretical models can be applied
to the mating system of C. georgiana. Our results showed that small males do not have larger testes relative to their body size compared to their larger counterparts
and that the efficiency with which sperm number, size, motility, and longevity are produced by the testes does not differ
between small and large males in the predicted way. These results are not in alignment with predictions from a loaded raffle
model of sperm competition on sperm expenditure in males with alternative phenotypes. The plasticity in mating tactics used
by C. georgiana males and a high intraseasonal variation in male densities may have prevented the evolution of enhanced sperm performance
in smaller males. A fair raffle in the sperm competition game played by C. georgiana males could also explain the observed patterns in sperm traits. Future investigations determining the parameters responsible
for the deviation from theoretical predictions in this system will test the degree to which current theoretical models can
indeed be applied to species with plastic reproductive tactics. 相似文献
6.
Summary The advertisement call of Geocrinia victoriana is markedly diphasic and consists of one introcuctory note (rarely two or three), followed by a series of repeated notes of similar carrier frequency, but much shorter duration and higher pulse rate. In two-choice field discrimination experiments with the two phases of the advertisement call presented as alternative stimuli, reproductively ripe females were attracted only to the repeated notes and contacted the source of these signals (a loudspeaker). Field playback experiments were carried out on residential males, with a complete call, an introductory note, or a series of repeated notes being used as the stimulus, and intensity varied upwards in 10 dB increments. With the complete call or the introductory note as the stimulus, calling behaviour of subjects altered significantly from the pre-stimulatory pattern, with a great reduction in output of repeated notes, and an increase in duration and decrease in pulse rate of introductory notes. The threshold intensity (lowest level for a significant change in calling behaviour) with the introductory note as the stimulus, 90–99.9 dB peak sound pressure level (PSPL), was at least 10 dB lower than that with the complete call as the stimulus (110–125 dB, PSPL). Playback of repeated notes had little effect on calling behaviour until the intensity exceeded 120 dB, PSPL. Playback of all three classes of stimulus at constant intensities below and above the threshold for the complete call (i.e. 99–99.9, and 110–125 dB, PSPL) indicated that changes in calling behaviour were due to the intensity of stimulus rather than to a cumulative effect based on the number of stimuli. Measurements of intensities of advertisement calls of nearest neighbours in natural breeding assemblages (modal class=104–106 dB, PSPL) were consistent with the experimental results. It was thus demonstrated that in G. victoriana the two functions of the advertisement call are partitioned: the repeated notes attract breeding females (hence are equivalent to the mating call), and the introductory notes are directed at other males in a territorial context. The increase in duration of the introductory note is graded rather than discrete, so that this phase of the advertisement call changes progressively from the equivalent of a long-range (first-order) to a short-range (second-order) territorial call, then to an encounter call. 相似文献
7.
Summary The vocal behavior of Hyla versicolor was studied in the field by means of behavioral observations and playback experiments, and these data were coupled with measurements of oxygen consumption in calling frogs to estimate the effect of social interactions on calling energetics. Male gray treefrogs have intense calls (median peak SPL=109 dB, fast RMS SPL=100 dB at 50 cm). At an air temperature of 23° C, males produced an average of 1,200–1,300 calls/h for 2–4 h per night. Calling rates and call durations differed among individuals, but were relatively constant for each male during periods of sustained calling. Males in dense choruses gave calls about twice as long as isolated males, but produced calls at about half the rate. Consequently, total calling effort and estimated aerobic costs were largely independent of chorus density. Playbacks of recorded calls to males in the field elicited increases in call duration and decreases in calling rate, regardless of the rate or duration of the stimulus. Males gave longer calls in response to long calls or to stimuli presented at high rates, but they did not precisely match either stimulus rate or duration. Calling effort and estimated oxygen consumption changed only slightly during stimulus playbacks. These results indicate that male-male competition elicits pro-found changes in the vocal behavior of calling males, but these changes have little effect on energy expenditure. We estimated that most calling males had metabolic rates of about 1.7–1.8 ml O2/(g\h), or about 280 J/h for an average size (8.6 g) male at 20° C. Although changes in call duration and calling rate did not affect aerobic costs of calling, males producing long calls at slow rates called for fewer hours per night than males producing shorter calls at higher rates. This suggests that calling time may be limited by the rate at which muscle glycogen reserves are depleted. 相似文献
8.
Size assessment in simulated territorial encounters between male green frogs (Rana clamitans) 总被引:2,自引:0,他引:2
Mark A. Bee Stephen A. Perrill Patrick C. Owen 《Behavioral ecology and sociobiology》1999,45(3-4):177-184
We examined the ability of male green frogs to assess the size of an opponent based on the dominant frequency of their advertisement
call, which is negatively correlated with size, using synthetic stimuli to simulate intruders of different sizes. In one field
playback experiment, we broadcast a pair of stimuli representing a small and a large male; in a second experiment, we broadcast
calls of a medium and a large male. In both experiments, males produced calls with significantly lower dominant frequencies
in response to each stimulus. Contrast analyses revealed that males lowered the dominant frequency of their calls more in
response to the large-male stimulus than in responses to the small- and medium-male stimuli. In the second experiment, males
also responded to the large-male stimulus by calling at higher rates. There were no differences in mean note duration or the
number of moves made toward or around the playback speaker in response to any stimulus. Thus, the frequency of an opponent's
calls elicits a differential modification of calling behavior, primarily in the form of differential dominant frequency alteration,
suggesting that males use dominant frequency to assess the size of opponents during aggressive encounters.
Received: 17 April 1998 / Accepted after revision: 7 October 1998 相似文献
9.
The function of call alternation in the African reed frog (Hyperolius marmoratus): precise call timing prevents auditory masking 总被引:3,自引:0,他引:3
T. Ulmar Grafe 《Behavioral ecology and sociobiology》1996,38(3):149-158
The function of call alternation in the African painted reed frog, Hyperolius marmoratus was studied. Males actively avoided call overlap with neighboring males in their natural habitat. Advertisement calls produced
by groups of two or three males showed less overlap than expected if they called at random. In addition, isolated males significantly
reduced their calling rate to match the periodicity of a playback of periodic tone pulses, with vocalizations given during
the silent intervals between tones. Gap-detection experiments showed that males suppressed vocalizations during playbacks
of constant-frequency tone bursts and gave more calls during silent periods than expected by chance. Females discriminated
against conspecific advertisement calls with many pulses in favor of calls with few or no pulses. This suggests that there
would be little selection pressure on males to alternate calls so that pulses are not obscured. To test if call alternation
functions to make calls more conspicuous, females were presented with identical conspecific advertisement calls from two speakers
in four different temporal patterns: simultaneous, overlapping, abutting, and alternating. Females did not discriminate when
calls were presented in a simultaneous, abutting, or alternating time pattern. When calls overlapped with the trailing call
delayed from 0.5 to 70 ms females discriminated in favor of the leading call. When the intensity of the leading call was reduced
by 6 dB the preference for the leading call was maintained when calls overlapped by 2 and 40 ms but was abolished or reversed
at 0.5 and 70 ms, respectively. These results support the notion that the second of two partially overlapping calls was acoustically
masked, rendering female painted reed frogs unwilling to approach or unable to locate such calls. It is suggested that either
simultaneous masking or the precedence effect are responsible for the observed behavior. Acoustic masking of the second call
by the first when calls overlapped was maintained even when the frequency of the first call was altered by 150 Hz above and
below the more preferred frequency of the second call.
Received: 13 April 1995/Accepted after revision: 5 November 1995 相似文献
10.
Advertisement call duration indicates good genes for offspring feeding rate in gray tree frogs (Hyla versicolor) 总被引:2,自引:0,他引:2
Indicator or ”good genes” models of sexual selection predict that mating preferences allow females to choose mates that are
genetically superior. Female gray tree frogs (Hyla versicolor) prefer male advertisement calls of long call duration, which can be indicators of enhanced offspring growth performance.
We tested the effects of father’s call duration and the presence of a caged predator (dragonfly naiad) on tadpole activity
and growth in a factorial experiment, controlling for maternal and environmental effects. The effect of food availability
(a repeated measure) on tadpole activity was also examined. Tadpoles responded to predator presence and to high food availability
by decreasing activity and feeding. Tadpoles exposed to a caged predator were smaller after 14 days than those exposed to
an empty cage, suggesting that spending less time feeding carries the cost of reduced growth. Offspring of males with long
versus short calls responded similarly to the presence of a predator. Nonetheless, offspring of long-calling males spent more
time feeding than did offspring of short-calling males, except when a predator was present but no food was available. Increased
time spent feeding may contribute to enhanced offspring growth and, therefore, to the indirect benefit that a female may realize
by selecting a mate with long calls. However, because the behavioral differences depended on the environment, and because
the fitness consequences of such behavioral differences should also vary with the environment, the benefit of mating with
a long-calling male may depend on the conditions encountered by the offspring.
Received: 15 February 2000 / Revised: 24 September 2000 / Accepted: 16 October 2000 相似文献
11.
William A. Searcy Susan Peters Silke Kipper Stephen Nowicki 《Behavioral ecology and sociobiology》2010,64(8):1343-1349
One explanation for why female songbirds attend to male song is that the quality of a male's song is associated with the quality
of his developmental history. We tested this hypothesis by playing back to female swamp sparrows (Melospiza georgiana) songs recorded from males of either inferior or superior developmental histories, as assessed by their rates of mass gain
during the first 18 days post-hatching. Females showed significantly higher levels of courtship display in response to songs
of males with superior growth than to songs of males with inferior growth. Out of nine song traits measured, only song duration
correlated with variation in female response; duration was also the only trait that differed significantly in univariate comparisons
between the superior growth songs and the inferior growth songs. In a multivariate analysis, however, inferior growth songs
were best discriminated from superior growth songs by combining three song traits: trill rate, stereotypy, and the number
of notes per syllable. We suggest that early developmental stress degrades song in many small ways, and that it is the cumulative
effect of the resulting deficits that explains lower female response. 相似文献
12.
Joshua J. Schwartz 《Behavioral ecology and sociobiology》1993,32(6):401-414
Summary Anuran choruses are acoustically complex assemblages of calling males. Little is known about the behavior of males or females in such natural sound environments. I studied calling behavior of males of Hyla microcephala in nature by using an interactive computer-based system that allowed me to simulate call interruptions by a number of males. I also monitored the calling behavior of groups of four to six males. When a male is interrupted by the call of another frog, he increases the spacing between the notes of his call. Responses of this kind are strongest to the loudest neighbor, and some males may ignore interruptions by all but a single close male. Interruptions using synthetic calls with silent gaps indicated that males respond vocally to reductions in sound intensity as brief as 20 ms. This ability helps to explain how males can rapidly alternate notes during pairwise interactions. Amounts of acoustic overlap between pairs of males in the choruses were usually below 10% of an individual's total calling time during bouts. The time a male spent calling that was free of acoustic interference by any other male ranged from 34–92% of his total calling time. When group size was decreased, this unobstructed calling time increased. Previous research showed that females of H. microcephala discriminate against calls that overlap so that the call pulse-train structure is degraded. Here I show that a 6 dB difference in intensity between the overlapped calls is sufficient to reduce the degradative effect of call interference. Females were also given a choice between interfering calls broadcast from two adjacent and two widely separated speakers. An angular separation between speakers of 120° was insufficient to elicit a preference for the separated sources. Together, data on behavior of males and females indicated that males actively reduce acoustic interference with those loud individuals most likely to degrade seriously the temporal structure of their calls. 相似文献
13.
Brood sex ratio is dependent on female mating status in polygynous great reed warblers 总被引:2,自引:0,他引:2
Isao Nishiumi 《Behavioral ecology and sociobiology》1998,44(1):9-14
Females capable of adjusting the sex ratio of their offspring should be more fit than females lacking such an ability. In
polygynous birds where breeding success in males is more strongly influenced by body size and/or attractiveness than in females,
females might produce more sons when predicting good conditions or when mating with attractive males. Polygynous great reed
warbler, Acrocephalusarundinaceus, males direct most of their feeding effort to the primary (first-hatching) nest and in these nests increase their feeding
effort in relation to the brood sex ratio (proportion of sons). Therefore, with the expectation of well-nourished sons, we
would predict that females which start breeding first within harems might produce more sons than those which start breeding
later, and in anticipation of sons with good genes, that females mated to polygynous males might produce more sons than females
mated to monogamous males. I took blood samples from hatchlings and determined the sex using DNA markers. The sex ratio of
primary (monogamous and polygynous primary) broods is more male-biased (mean 0.58 males, n = 50) than that of secondary (polygynous secondary and tertiary) broods (mean 0.46, n = 25). Moreover, in the secondary broods with the largest clutch (five eggs), in which offspring are most likely to suffer
food shortage, the sex ratio was distinctively female biased (mean 0.33, n = 10). In the primary broods, sex ratio was correlated to harem size. The results suggest that great reed warbler females
modify the brood sex ratio to produce both well-nourished sons and sons with good genes, but the former effect is probably
stronger than the latter factor.
Received: 11 March 1998 / Accepted after revision: 23 May 1998 相似文献
14.
Hamilton and Zuk proposed that bright plumage in birds indicates genetic resistance to parasites, and that by selecting brighter
males as mates, females can increase their offspring’s fitness due to this inherited resistance. The theory predicts a negative
relationship between parasite load and plumage brightness in males. We used Sindbis virus clearance rate after an experimental
infection to quantify parasite resistance in male greenfinches (Carduelis chloris) and related variation in clearance rate with variation in male plumage brightness. We found that certain aspects of brightness
of the male plumage (i.e. tail-patch area) could be used to predict the virus infection clearance rate. Wing brightness was
uninformative of virus clearance rate, but revealed age class. We found no clear relationship between antibody production
rate and virus clearance rate or total viraemia. However, males with large tail patches tended to have a higher antibody production
rate. The results suggest that the size of the male tail patch may function as an indicator of an individual male’s ability
to resist parasite infections, thus supporting the Hamilton-Zuk theory for a novel taxon of parasites, a virus.
Received: 11 November 1999 / Received in revised form: 13 March 2000 / Accepted: 1 April 2000 相似文献
15.
We examined variation in aggressive responses within and among individuals in the green frog, Rana clamitans. We tested the hypothesis that resident males respond in a graded fashion to changes in perceived intruder proximity (stimulus intensity). We also investigated how response level varied with responder body size. We found that green frogs differentially alter aggressive responses (increasing movement and calling rates while decreasing the duration and dominant frequency of their calls) with an increase in stimulus intensity. Body size did not appear to be a significant influence on most response levels. We suggest that aggressive responses are graded, and advertisement and aggressive calls represent opposite ends of a continuum. Green frogs do not exhibit clearly defined thresholds for responses like those reported for some other frogs. By using graded responses rather than discrete all-or-nothing responses, males may reduce the potential costs of aggressive encounters. 相似文献
16.
D. S. Pope 《Behavioral ecology and sociobiology》2000,47(6):432-437
Many territorial advertisement signals are thought to be dual-function signals, directed to both rival male and receptive
female conspecifics. However, few studies have tested this assumption by examining whether in fact both sexes are likely to
elicit signaling behavior from territorial males. In this study, I experimentally manipulated the social context of male sand
fiddler crabs (Uca pugilator) to investigate the effect of different audiences on the performance of the claw-waving display, a territorial signal that
is often presumed to be directed to both males and females. To test whether males perform this signal to both audiences, I
measured the frequency of waving behavior by focal males when housed in field enclosures alone, with only males, with only
females, or with both males and females. Focal males waved at a low frequency when alone, and the presence of males had no
effect on their level of waving. However, in the presence of females, focal males showed a significantly higher level of waving,
whether or not males were also present. In addition, there was no association between fighting and waving behavior. This experiment
provides evidence that from the perspective of the signaling male, the claw-waving display of U. pugilator is not a dual-function signal but rather is primarily directed to receptive females.
Received: 16 December 1999 / Received in revised form: 1 February 2000 / Accepted: 19 February 2000 相似文献
17.
We conducted playback experiments to examine how parent tree swallows (Tachycineta bicolor) use nestling begging calls to distribute feedings to individuals within broods. In a first study, we used a paired-choice
test to determine if parents discriminated between the taped begging calls of nestlings deprived of food and those of nestlings
that had been recently fed. Our results showed that parents directed their first feeding attempt towards model nestlings near
speakers playing deprived calls significantly more often than to models near speakers playing fed calls. They also made more
feeding attempts overall to models with deprived calls. In the second study, we varied call rate and amplitude to examine
which call features parents might use to discriminate begging calls. Parents directed significantly more first feeding attempts
and more feeding attempts overall towards non-begging nestlings near speakers playing high call rates than to nestlings near
speakers playing low call rates. They did not, however, discriminate between calls differing in amplitude. Previous studies
have shown that parent birds use begging calls to regulate overall feeding rates to the brood. Our results suggest that parent
tree swallows also use begging calls when feeding individual nestlings and, in particular, prefer calls associated with increased
levels of nestling hunger.
Received: 14 February 2000 / Revised: 6 October 2000 / Accepted: 16 October 2000 相似文献
18.
Bushcricket song structure and predation by the acoustically orienting parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) 总被引:2,自引:0,他引:2
Gerlind U. C. Lehmann Klaus-Gerhard Heller 《Behavioral ecology and sociobiology》1998,43(4-5):239-245
Males of most bushcricket species produce acoustic advertisement signals to attract females for mating. These signals can
also increase conspicuousness to predators. In the genus Poecilimon (Orthoptera: Phaneropterinae) males are attacked by the parasitoid fly Therobia leonidei (Diptera: Tachinidae: Ormiini) which locates males by their calls. In Greece T.leonidei parasitizes several Poecilimon species with different song structures: we examined whether host choice is related to song structure by comparing parasitism
rates in two closely related Poecilimon species. One of these species produces monosyllabic songs, the songs of the other species being polysyllabic. The tachinid
fly parasitized the polysyllabic species to a greater extent. We demonstrate in a field-experiment that this preference for
the polysyllabic species does not depend on local adaptations of the fly. The most probable explanation for the preference
of the fly for the polysyllabic singing species seems to be better detection of longer songs. This result is discussed in
the context of male song evolution.
Received: 4 November 1997 / Accepted after revision: 22 March 1998 相似文献
19.
Polyandry and enhanced reproductive success in the harlequin-beetle-riding pseudoscorpion 总被引:1,自引:0,他引:1
J. A. Zeh 《Behavioral ecology and sociobiology》1997,40(2):111-118
The growing molecular evidence that females of many species mate with several males calls for a critical reassessment of
the selective forces which act to shape female mating tactics. In natural populations of the harlequin-beetle-riding pseudoscorpion,
Cordylochernes scorpioides, females are polyandrous and typically produce mixed-paternity broods. Laboratory behavioral analyses and breeding experiments
indicate that polyandry in this pseudoscorpion is an active strategy which increases female reproductive success. Females
restricted to mating with a single male experienced a higher rate of embryo failure and produced significantly fewer offspring
than either females mated to more than one male in the laboratory or females naturally inseminated in the field. Forced copulation,
insufficient sperm from a single mating, male nutrient donations and variation in inherent male genetic quality cannot explain
the greater number of nymphs hatched by polyandrous females in this study. Evidence suggests that, by mating with several
males, C. scorpioides females may exploit postcopulatory mechanisms for reducing the risk and/or cost of embryo failure resulting from fertilization
by genetically incompatible sperm.
Received: 5 May 1996 / Accepted after revision: 16 October 1996 相似文献
20.
Birth sex ratios were examined for ringtailed lemurs (Lemur catta) at the Duke University Primate Center. This population provides a long-term database of births under a variety of demographic
and management conditions, including two semi-freeranging groups between which males transfer freely and females defend stable
territorial boundaries. We examined three hypotheses usually considered in studies of primate sex ratio bias. The Trivers-Willard
hypothesis predicts that dominant females produce males, local resource competition at the population level (LRC-population)
predicts that the dispersing sex (males) will be overproduced in dense populations, and local resource competition among individuals
(LRC-individual) predicts that dominant females overproduce the philopatric sex (females). We also examined a fourth hypothesis,
local resource enhancement (LRE), which is usually subsumed under LRC-individual in studies of primate sex ratio evolution.
LRE predicts that under certain conditions, females will produce the sex that provides later cooperative benefits, such as
alliance support for within- or between-group competition. Our data provide support for LRE: females overproduce daughters
given prospects of new group formation, either through group fission or threatened expulsion of young mothers. Behavioral
data from Duke and also wild populations show that daughters serve mothers as important allies in this context and LRE effects
also have been documented in other mammals that experience similar group histories. Nonsignificant trends in the data supported
the LRC-population hypothesis, and we suggest that LRC interacts with LRE to explain offspring sex ratios in ringtailed lemurs.
Received: 27 August 1999 / Received in revised form: 6 March 2000 / Accepted: 18 March 2000 相似文献