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Male courtship signal modality and female mate preference in the wolf spider Schizocosa ocreata: results of digital multimodal playback studies


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Females must be able to perceive and assess male signals, especially when they occur simultaneously with those of other males. Previous studies show female Schizocosa ocreata wolf spiders display receptivity to isolated visual or vibratory courtship signals, but increased receptivity to multimodal courtship. It is unknown whether this is true when females are presented with a choice between simultaneous multimodal vs. isolated unimodal male courtship. We used digital playback to present females with a choice simulating simultaneous male courtship in different sensory modes without variation in information content: 1) isolated unimodal visual vs. vibratory signals; 2) multimodal vs. vibratory signals, and 3) multimodal vs. visual signals. When choosing between isolated unimodal signals (visual or vibratory), there were no significant differences in orientation latency and number of orientations, approaches or receptive displays directed to either signal. When given a choice between multimodal vs. vibratory-only male courtship signals, females were more likely to orient to the multimodal stimulus, and directed significantly more orients, approaches and receptivity behaviors to the multimodal signal. When presented with a choice between multimodal and visual-only signals, there were significantly more orients and approaches to the multimodal signal, but no significant difference in female receptivity. Results suggest that signal modes are redundant and equivalent in terms of qualitative responses, but when combined, multimodal signals quantitatively enhance detection and/or reception. This study confirms the value of testing preference behavior using a choice paradigm, as female preferences may depend on the context (e.g. environmental context, social context) in which they are presented with male signals.
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Kozak & Uetz: Male courtship signal modality and female mate preference
Accepted Article
Male courtship signal modality and female mate preference in
the wolf spider Schizocosa ocreata: results of digital multimodal
playback studies
Elizabeth C. KOZAK and George W. UETZ*
Department of Biological Sciences, University of Cincinnati, P.O. Box 260006, Cincinnati, OH 45221-0006, USA
*Address correspondence to George W. Uetz. E-mail:
Handling editor: Zhi-Yun JIA
Received on 15 December 2018; accepted on 7 May 2019
Females must be able to perceive and assess male signals, especially when they occur simultaneously with those of other males. Previous
studies show female Schizocosa ocreata wolf spiders display receptivity to isolated visual or vibratory courtship signals, but increased
receptivity to multimodal courtship. It is unknown whether this is true when females are presented with a choice between simultaneous
multimodal vs. isolated unimodal male courtship. We used digital playback to present females with a choice simulating simultaneous
male courtship in different sensory modes without variation in information content: 1) isolated unimodal visual vs. vibratory signals; 2)
multimodal vs. vibratory signals, and 3) multimodal vs. visual signals. When choosing between isolated unimodal signals (visual or
vibratory), there were no significant differences in orientation latency and number of orientations, approaches or receptive displays
directed to either signal. When given a choice between multimodal vs. vibratory-only male courtship signals, females were more likely to
orient to the multimodal stimulus, and directed significantly more orients, approaches and receptivity behaviors to the multimodal signal.
When presented with a choice between multimodal and visual-only signals, there were significantly more orients and approaches to the
multimodal signal, but no significant difference in female receptivity. Results suggest that signal modes are redundant and equivalent in
terms of qualitative responses, but when combined, multimodal signals quantitatively enhance detection and/or reception. This study
confirms the value of testing preference behavior using a choice paradigm, as female preferences may depend on the context (e.g.
environmental context, social context) in which they are presented with male signals.
Key words: signaling, multimodal communication, wolf spider, Schizocosa, mate choice
Female mate preferences may differ or change depending on the social or environmental context in which females perceive
male courtship signals (Wagner 1998; Bateson and Healy 2005; Hebets et al. 2016; Uetz et al. 2017). In particular, there are
many species where females must respond to multiple males courting simultaneously (e.g., leks, choruses, skewed sex ratios,
high density populations). Animal communication, especially in the context of courtship displays, often utilizes multiple
sensory modalities (acoustic, visual, chemical, vibratory). In social contexts in which there might be multiple males
courting, a unimodal vs. multimodal signal may be more or less easily detected or interpreted within a complex environment
© The Author (2019). Published by Oxford University Press.
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Kozak & Uetz: Male courtship signal modality and female mate preference
(Taylor & Ryan 2013), and mating decisions become even more complex when there is microhabitat variation that might
affect the proper transmission of multimodal signals (Uetz et al. 2013). For example, a female might be able to perceive a
multimodal signal of one individual, yet receive a unimodal signal from another male due to the microhabitat blocking
transmission of the full multimodal signal (Uetz et al. 2013).
Studies in the past two decades have used experimental techniques, including digital visual and acoustic playback, to
examine the function and form of multimodal signals across animal taxa (anurans: Taylor et. al. 2007; lizards: Woo et al.
2017, Gunderson et al. 2018; bowerbirds: Doucet and Montgomerie 2003; fish: Hankison and Morris 2003, Hiermes et al
2016, Balzarini et al. 2017; spiders: Scheffer et al. 1996; Hebets and Uetz 1999, 2000; Elias et. al. 2005; Uetz et. al. 2009;
Wilgers and Hebets 2011; Hebets et al. 2013). Since its earliest uses (Clark & Uetz 1990, 1993; Evans & Marler 1991;
Evans et al. 1993), digital video playback has become a powerful and frequently used methodology in animal behavior
research, and a number of reviews have raised cautions and added refinements to these methods (D’Eath 1998; Fleishman et
al. 1998; Fleishman and Endler 2000; Oliviera et al. 2000; Uetz and Roberts 2002; McGregor 2013; Witte et al. 2017;
Chouinard-Thuly et al 2017). Previous experimental work with playback of multimodal male signals has either paired pre-
recorded male visual signals with vibratory signals from live males (Hebets 2008) or has paired video with (unsynchronized)
vibratory playback (Uetz and Roberts 2002). Some studies have presented females with male signals using a single
presentation paradigm, which, while effective, raises the question whether female preferences for male signals would
change in a different social or environmental context (Bro-Jorgenson 2010; Edward 2015; Dougherty and Shular 2015;
Hebets et al. 2016). In this case, two-choice studies that investigate preferences for unimodal vs multimodal signals or
unimodal signals of different modes might provide additional insight into the complex decision-making that females
occasionally use in specific social contexts with constraints from the physical environment.
The brush-legged wolf spider Schizocosa ocreata (Hentz) (Lycosidae) is a well-studied model for questions of
multimodal communication. Males court females using multimodal courtship displays, which consist of visual signals (tufts
of bristles on the forelegs; leg displays including tapping, double tapping and raising and extending the first pair of legs in a
“wave and arch”), accompanied by vibratory signals (substratum-borne vibration produced by pulses of stridulation and
percussion) (Stratton and Uetz 1981, 1983, 1986; McClintock and Uetz 1996; Uetz 2000). In single-presentation studies
with live spiders, females showed equal receptivity to isolated visual and vibratory signals, but greater responses to
multimodal courtship (Scheffer et al. 1996; Hebets and Uetz 1999; Uetz et al. 2009). In other studies, it was found that
females preferred males with larger tufts over smaller tufts in the isolated visual modality (McClintock and Uetz 1996; Uetz
and Norton 2007; Uetz et al. 2017), and preferred higher peak amplitudes and peak frequencies in the isolated vibratory
signal modality (Gibson and Uetz 2008). In recent studies using multimodal playback experiments (Stoffer & Uetz 2016a,b;
Uetz et al. 2017), female S. ocreata showed preferences for increased magnitude of male condition-indicating traits (larger
leg tufts, greater amplitude vibration signals) in both isolated sensory modes and multimodal signals. Choice tests showed
that with respect to information content of signals, females made expected choices between higher/lower quality multimodal
signals when male traits covaried positively, but preferred video/vibratory stimuli with larger tuft size when they covaried
negatively. These results suggest a previously unseen level of nuance acting on mate choice in this species, i.e. preference
for one signal mode over another when the information content of multiple sensory modes is different.
In this study, we use simultaneous digital multimodal playback in choice experiments to investigate further whether
female preferences for unimodal and multimodal courtship signals vary in this specific social context and the manner in
which signals are presented. In the set of experiments presented here, we provide signals with controlled information
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content (i.e., identical male quality in visual [tuft size, vigor] and vibratory [amplitude] components) but varied sensory
modality (multimodal or isolated vibratory or visual signals). In a two-choice design, we simulate a possible scenario likely
to occur in nature where females perceive two males courting simultaneously but for one male, one of the signal
components is absent (e.g., visual occlusion, discontinuous substrates, leaves not in contact). In this way, we attempt to
tease apart the different and possibly interacting aspects of multimodal signals in their social and environmental contexts.
Materials and Methods
Study species
The brush-legged wolf spider S. ocreata is a sexually dimorphic species found in deciduous leaf-litter habitat throughout the
eastern United States (Dondale and Redner 1978; Stratton 2005). Immature S. ocreata spiders were collected in the field
from the Cincinnati Nature Center Rowe Woods, Clermont County (39°7’31.15” N; 84°15’4.29” W) in the fall of 2011 and
reared in simulated springtime conditions until maturity. Laboratory conditions were maintained at 23-25°C and relative
humidity of 65–75%, and a 13:11 hour light:dark cycle to simulate late spring, when spiders mature. Spiders were
maintained in the laboratory in individual cylindrical plastic deli containers with lids (9 cm diam. × 5 cm ht.) that visually
isolated spiders. Spiders were fed twice each week with 3–5 small crickets Acheta domesticus, and water was provided ad
libitum. Female S. ocreata were tested approximately three weeks after reaching maturity, when they are at peak receptivity
(Norton and Uetz 2005; Uetz and Norton 2007).
Experimental apparatus
Video playback has been demonstrated as an effective method for presenting some spiders with visual stimuli, since wolf
spiders (Lycosidae) and jumping spiders (Salticidae) perceive and react to video images as though they are real (Clark and
Uetz 1990, 1993; McClintock and Uetz 1996; Uetz and Roberts 2002; Bednarski et al. 2012; Uetz and Clark 2013; Uetz et
al. 2016; Jakob et al. 2018). Several methods have been employed to present spiders with vibratory signals (live spiders:
Hebets and Uetz 1999; Gibson and Uetz 2008, Uetz et. al. 2009; playback methods: Uetz and Roberts 2002; Uetz et al
2016), with each method successfully meeting the needs for which it was designed. However, digital multimodal playback,
especially in a choice paradigm, requires a method for vibratory playback that is appropriately scalable to video playback,
small in size (i.e., two devices would need to fit in a 20 cm-diameter arena and provide a directional vibratory signal), and
able to reliably transmit the same vibratory signal for multiple trials.
Piezoelectric actuators, or disc benders, contain a piezoelectric crystal between a copper and a porcelain disc that
vibrates when voltage is applied across it—in this case, the voltage resulting from an audio signal being played through the
crystal—fit all three above criteria. Male vibratory signals were transmitted via piezoelectric disc benders (APC
International, Ltd. #20-1205) affixed flush with the poster board substrate of the trial arena using clear adhesive tape, and
placed in the center-front of each iPod Classic® (Figure 1.1). We used a 12mm diam. circular disc bender, as it was
0.23mm thick, and could therefore be placed in front of a video iPod®—to effectively pair its vibratory signal with the
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Kozak & Uetz: Male courtship signal modality and female mate preference
iPod’s® video signal—and easily laid beneath a piece of paper, through which vibratory signals could be transmitted. Copy
paper was placed over the entire area of the arena, on top of the disc benders but under the polycarbonate arena wall, such
that spiders could perceive vibration from disc benders via the copy paper throughout the arena. Vibration signals from pre-
recorded male S. ocreata courtship signals were delivered to the disc benders from an iPod® classic via an amplifier (Pyle
model PTA2). Disc bender output was calibrated using a Laser Doppler Vibrometer (LDV, Polytech model PDV-100) and
Raven (Cornell laboratory of Ornithology, version 1.3 Build 23) software to closely match the playback amplitude and
frequency to original recordings from live male S. ocreata courtship, and to ensure that vibratory signals from each disc
bender propagated throughout the area of the arena. Importantly, iPods® and disc benders were placed at a 90 degree angle
from each other, so that spiders would be able to perceive signals simultaneously coming from separate individuals (Kozak
and Uetz 2016). Otherwise, in an arena design with 180 degree separation, spiders might see only the screen they initially
face, which could create a preference bias based on first perceived movement (Clark et al. 1992; Scheffer et al. 1996;
Stoffer et al. 2016). In addition, disc bender output was also measured over distance across the parchment paper surface
with the LDV and matched to natural levels to allow spiders to determine direction from attenuation patterns. (Uetz et al.
2013; Kozak and Uetz 2016),
Trials were conducted in a 20 cm-diameter, clear plastic polycarbonate, circular arena placed upon a 0.092m2 (1ft2)
piece of poster board that rested on four 18 cm high granite “feet”, all of which was situated in an anechoic chamber,
effectively isolating the arena—and therefore female spiders--from extraneous environmental vibrations. Male visual
courtship signals were presented using two iPod Classics® inserted into slots cut into the poster board at 90° to each other
such that the bottom of screens were flush with the arena substrate, and male video exemplars would be within females’
line-of-sight. Video male exemplars represented the population mean for body size, leg tuft size, and courtship vigor as in
many previous studies (McClintock and Uetz 1996; Uetz and Roberts 2002; Uetz and Norton 2007; Roberts et al. 2007;
Roberts and Uetz 2008; Uetz et al. 2011; Clark et al. 2012), and their vibratory signals were synchronized when both signal
modalities were presented together. Vibratory signals accompanying each exemplar were previously recorded on the video
soundtrack (16bit; 48kHz) by a PCB Piezotronics ICP® accelerometer (PCB-352C23) via an amplifying signal conditioner
(PCB –480). To minimize background noise, recordings were made in a sound-attenuating room.
Experimental trials
Females (N = 81) were presented with one of three experimental treatments in which they had a choice between
isolated unimodal signals (visual alone vs. vibratory alone, N = 17), between a multimodal (visual + vibratory) and
visual-alone signal (N = 38), or between a multimodal and a vibratory-alone signal (N = 26). Signal origin (left or
right iPod®) was varied at random between females to control for any side biases. All trials were conducted with
females that were between 15–25 days mature, when females are at peak receptivity (Uetz and Norton 2007). Female
hunger was controlled by feeding all females one 10-day old cricket 12–24 hours before trials were conducted. Each
female was placed in the center of the experimental arena under a translucent plastic vial and allowed to acclimate for
1–2 minutes; during this time there was no playback of visual or vibratory signals. Trials commenced with the start of
playback and the careful removal of the vial so as not to disturb the female; trials lasted 10 minutes and were video
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recorded and later scored for female orientation and approach behaviors as well as receptivity displays (settle, tandem
leg extend, slow turn/pivot) to each screen. These behavioral displays were used as a proxy for actual mating in this
case, because copulation will usually not occur unless one or more of them is displayed (Montgomery 1903; Uetz &
Denterlein 1979; Stratton & Uetz 1981, 1983; Scheffer et al. 1996; Norton & Uetz 2005; Delaney et al. 2007; Johns et
al. 2009). In addition, the sum of receptivity displays was used as a comprehensive index of receptivity Uetz &
Roberts 2002; Uetz & Norton 2007; Rutledge & Uetz 2014).
Statistical analyses
All statistical analyses were performed using JMP ver. 10 (SAS Institute, Cary, NC, USA). Several response variables
(orientation (Y/N), latency to orient, number of orientations, number of approaches, comprehensive receptivity score)
representing spider behavior toward each iPod® screen in choice tests were analyzed using matched-pairs analysis. The
comprehensive receptivity score was computed as a sum of the total number of receptive behaviors (tandem leg extend,
slow turn/pivot, settle) the female exhibited toward each screen.
Ethical Note
Spiders are invertebrate animals, and there are no regulations and/or IACUC requirements of the University of Cincinnati,
the State of Ohio, and the United States of America regarding their care and maintenance. Our study species, Schizocosa
ocreata, is not an endangered or threatened species. We have made every effort to comply with the “Guidelines for the
treatment of animals in behavioural research and teaching”, published by the Animal Behavior Society (Animal Behaviour
85 (2013) 287–295). At the end of the study, spiders were humanely euthanized with CO2 anesthetization and freezing,
then placed in 70% ethanol.
Initial analyses of orientation to isolated visual vs. vibratory stimuli found equal probability of orientation to each (χ2 = 0.5;
df = 1; P = 0.479). There were no significant differences in latency to orient to either stimulus, and no significant
differences for any female behaviors directed to either unimodal signal (Table 1, Figure 2).
Orientation of females toward isolated vibratory vs. multimodal stimuli showed higher probability of orientation to the
multimodal stimulus (χ2 = 4.26; df = 1; P = 0.039), but no significant differences in latency to orient to either stimulus
(Table 1). Matched-pairs analyses yielded significant differences in mean number of orient, approach, and receptivity
behaviors for treatments presenting multimodal male courtship signals against unimodal vibratory male courtship signals
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(Table 1; Figure 3). Females that initially oriented to the multimodal stimulus were more likely to approach and show
receptivity to that stimulus (χ2 = 8.556; df = 1; P = 0.0034).
Female spiders responding to isolated visual vs. multimodal stimuli exhibited equal probability of orientation to each (χ2
= 0.00; df = 1; P = 0.100), and no significant difference in latency to orient to either stimulus (Table 1). Females oriented to
and approached multimodal male courtship signals significantly more often than they did unimodal visual male courtship
signals, although differences in receptivity to multimodal signals vs. isolated visual-only signals were not significant (Table
1; Figure 4). Females that initially oriented to the multimodal stimulus were more likely to approach and show receptivity to
that stimulus (χ2 = 7.879; df = 1; P = 0.005).
In social contexts where multiple males are courting at the same time, detection or interpretation of unimodal vs.
multimodal signals may vary (Taylor & Ryan 2013), and mating decisions become more complex, especially if there is
microhabitat variation that might affect the full transmission of signals (Uetz et al. 2013). This study investigated the effect
of unimodal vs. multimodal courtship signals of male S. ocreata wolf spiders in a choice paradigm used successfully in
other studies (Uetz et al. 2017; Stoffer and Uetz 2017). In particular, we used simultaneous presentation of synchronized
digital multimodal playback, while controlling for differences in male quality information. In this way, we tested the
relative importance of signal modes by simulating conditions a female might encounter in the field – e.g., a multimodal
signal from one individual vs. a unimodal signal from another constrained by microhabitat transmission properties (Uetz et
al. 2013). Results indicate that female S. ocreata preferences for male courtship signal modality may be dependent on the
context in which they are perceived. When presented with a choice between male courtship signals, females displayed no
preference for either individual signal mode in isolation, but significantly preferred multimodal courtship signals over
isolated vibratory male signals, and tended to prefer multimodal signals over isolated visual signals. In one experiment,
females displayed more orientation, approach and receptivity to multimodal signals over isolated vibratory signals.
However, when presented with a choice between multimodal signals and isolated visual signals, this strong preference
relaxed, perhaps because a visual signal was present in both choices. These results indicate the possibility of a hierarchy of
preference among sensory modes, with multimodal signals as most preferred, followed in order by visual signals and
vibratory signals (Uetz et al. 2017).
A number of studies have raised the question whether female preferences would change when presented with options to
choose from when selecting a mate (Wagner 1998; Bateson and Healy 2005; Hebets et al. 2016; Dougherty & Shukar 2015;
Uetz et al. 2017). Earlier work on this species and others has tested female preferences for multimodal vs. isolated modes
of male courtship signals without giving females a choice between those signals (Scheffer et al. 1996; McClintock & Uetz
1996; Uetz et al. 2009), although recent studies have used choice designs (Stoffer & Uetz 2015, 2016a,b; Uetz et al. 2017).
Because information content of paired signals (male quality-indicating traits) was held constant in this case, these results
support the hypothesis of redundancy of signal modes sensu Partan & Marler (2005), as females demonstrated the same
qualitative response (i.e. display receptivity) to both unimodal signals. Unimodal signals could be further classified as
“equivalent”, because responses (receptivity scores) were equal to both modes. However, while females’ preferences for
multimodal male signals varied depending on the signal modality it was paired with (visual or vibratory), receptivity
responses for multimodal signals tended to be stronger than either of the others, suggesting enhancement over equality of
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Kozak & Uetz: Male courtship signal modality and female mate preference
multimodal signals (Partan & Marler 2005). Although slightly different from results of earlier preference studies, which
found equivalence or redundancy of the visual and vibratory modes in multimodal signals when females make single-choice
mating decisions (Gibson and Uetz 2008; Uetz et. al. 2009; Gordon and Uetz 2011), current data more closely match recent
findings from direct tests of context-dependence (Uetz et al. 2017).
These results demonstrate the importance of testing for female preferences under different contexts, e.g, when females
are offered a choice vs. no-choice paradigm (Wagner 1998; Dougherty and Shukar 2015). It is possible that female
responses may be different in a choice paradigm that more closely mimics conditions in the field than when females are not
given a choice of stimuli to respond to. This is especially true for high density populations of with male scramble
competition, or lek mating systems, where multiple males court females simultaneously (Stoffer & Uetz 2015; Patricelli et
al. 2002; Coleman et. al. 2004; Patricelli et al. 2006; Patricelli et al. 2016). Ultimately, these results demonstrate the
importance of taking multiple approaches when investigating female preferences for male sexual characters, especially with
multiple signaling modes (Dougherty and Shukar 2015; Uetz et al. 2017).
This work represents a portion of a thesis submitted by ECK in partial fulfillment of the requirements for the M.S. degree from the
Department of Biological Sciences at the University of Cincinnati. This research was supported by grant IOS-1026995 from the National
Science Foundation (to GWU) and the UC Biological Sciences Wieman/Wendell/Benedict Student Research Fund (to ECK). We thank
the Cincinnati Nature Center for permitting us to collect spiders on their property, and Granite Concepts for providing the materials and
fabrication of the arena. Additional thanks to R Gilbert, A Sweger, B Stoffer, A Kluckman, R Wilson, M Williams and M. Lallo for
various assistance on this project. Thanks as well to E Maurer and J Layne for feedback on the research and especially to B. Stoffer and M.
Lallo for review of this manuscript.
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Kozak & Uetz: Male courtship signal modality and female mate preference
Table 1. Matched-pairs analysis of mean Orient, Approach, and Comprehensive Receptivity behaviors exhibited by females with a choice
between Multimodal and vibratory-only (Vis/Vib vs. Vib), Multimodal and visual-only (Vis/Vib vs. Vis), or vibratory-only and visual-
only (Vis vs. Vib) male courtship signals. Significant P-values in bold.
Treatment Response Paired t df P
Vib vs. Vis Orient Latency 0.509 16 0.673
No. Orient 0 16 1
No. Approach 0.33282 16 0.7436
Receptivity 0.43295 16 0.6708
Vis/Vib vs. Vib Orient Latency 0.939 22 0.362
No. Orient 3.21996 22 0.0039
No. Approach 1.89929 22 0.0354
Receptivity 2.62681 22 0.0154
Vis/Vib vs. Vis Orient Latency 0.987 34 0.343
No. Orient 3.36844 34 0.0019
No. Approach 3.2432 33 0.0027
Receptivity 1.103569 32 0.278
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Kozak & Uetz: Male courtship signal modality and female mate preference
Figure 1. Experimental arena for female choice trials. Black rectangles signify iPod Classics®, grey circles represent disc
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Kozak & Uetz: Male courtship signal modality and female mate preference
Figure 2. Mean number of female behavioral responses (± SE) directed to isolated visual and vibratory male courtship
signals: A) orientations; B) approaches; C) receptivity displays.
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Kozak & Uetz: Male courtship signal modality and female mate preference
Figure 3. Mean number of female behavioral responses (± SE) to multimodal and to vibratory male courtship signals: A) orientations; B)
approaches; c) receptivity displays.
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... Despite the lack of a well-supported phylogenetic hypothesis, Schizocosa has developed over the past decades as a model comparative system for studying spider communication and reproductive behavior (Herberstein and Hebets, 2013). Species exhibit extensive differences in morphological characters and behavioral signals used in courtship, making this group powerful for studying characters presumably experiencing strong sexual selection (Fowler-Finn et al., 2015;Hebets and Papaj, 2005;Kozak and Uetz, 2019;Rovner, 1975;Stratton, 2005;Stratron andUetz, 1981, 1986;Uetz and Denterlein, 1979;Uetz and Roberts, 2002;Uetz et al., 2016). Prior to the current study, males of fourteen described Schizocosa species were identified as having dark pigmentation on the first pair of legs, and seven species possess dense bristles on the tibia (Stratton, 2005). ...
... In the single study that examined mating success of S. ocreata in the light and in the dark, there was no difference in likelihood of mating across light environments, but latency to mating was longer in the dark (Taylor et al., 2006). Other studies on S. ocreata have found that female responses to vibratory displays increase when combined with visual displays (Kozak and Uetz, 2019;Stoffer and Uetz, 2017). Additional investigations with S. ocreata, mostly using video playback techniques, have found evidence for female responses increasing with increasing ornamentation (Persons and Uetz, 2005;Uetz et al., 2011;Uetz and Norton, 2007). ...
Members of the Nearctic spider genus Schizocosa Chamberlin, 1904 have garnered much attention in behavioral studies and over many decades, a number of species have developed as model systems for investigating patterns of sexual selection and multimodal communication. Many of these studies have employed a comparative approach using putative, but not rigorously tested, sister species pairs that have distinctive morphological traits and attendant behaviors. Despite past emphasis on the efficacy of these presumably comparative-based studies of closely related species, generating a robust phylogenetic hypothesis for Schizocosa has been an ongoing challenge. Here, we apply a phylogenomic approach using anchored hybrid enrichment to generate a data set comprising over 400 loci representing a comprehensive taxonomic sample of 23 Nearctic Schizocosa. Our sampling also includes numerous outgroup lycosid genera that allow for a robust evaluation of genus monophyly. Based on analyses using concatenation and coalescent-based methods, we recover a well-supported phylogeny that infers the following: 1) The New World Schizocosa do not form a monophyletic group; 2) Previous hypotheses of North American species require reconsideration along with the composition of species groups; 3) Multiple longstanding model species are not genealogically exclusive and thus are not “good” species; 4) This updated phylogenetic framework establishes a new working paradigm for studying the evolution of characters associated with reproductive communication and mating. Ancestral character state reconstructions show a complex pattern of homoplasy that has likely obfuscated previous attempts to reconstruct relationships and delimit species. Important characters presumably related to sexual selection, such as foreleg pigmentation and dense bristle formation, have undergone repeated gain and loss events, many of which have led to increased morphological divergence between sister-species. Evaluation of these traits in a comparative framework illuminates how sexual selection and natural selection influence character evolution and provides a model for future studies of multimodal communication evolution and function.
... The presence of more than one male phenotype, so-called "dimorphism", can be observed in many animal species, from fish to spiders [93]. In swordtail species, different categories of males are present. ...
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Southern swordtail fishes, which belong to the viviparous teleosts called Xiphophorus, are unique models for studies of evolution of sex chromosomes. Monofactorial sex-determining systems, with either the male or the female being the heterogametic sex, as well as sex determination involving more than two sex chromosomes, are found in swordtails and related species. Some swordtail species seem to have originated by crossing between two closely related species. Although the sword has disappeared in many Xiphophorus species during evolution, females of non-sworded species still prefer sworded males, demonstrating a discrepancy between natural and sexual selection. Natural sex change has not been documented sufficiently convincingly in swordtails, but, at least in some subspecies, two or more male phenotypes exist. In a laboratory experiment performed for over 30 years, it has been observed that sex-determining genes may be translocated from one chromosome to another in hybrids of these evolutionary young species. While the factors suggested to play central roles in sex determination and differentiation, e.g., Dmrt1 and AMH, are highly conserved during evolution, several master determining factors have been detected in teleosts. Endocrine-induced sex reversal has been demonstrated in the guppy Poecilia reticulata, another viviparous fish. In swordtails (X. helleri), endocrine disruptors such as nonylphenol and bisphenol A may cause testis cell degeneration and the inhibition of spermatogenesis. Furthermore, swordtails are very easy to breed in freshwater aquaria and, therefore, may be good models for studying the factors influencing sex determination and male differentiation.
... However, little is known on the perception of flat images in non-human animals 1 , although several zoos empirically began using images to study mate choice in captive animals with the goal of stimulating reproduction by mimicking situations of mate choice 2,3 . More generally, the use of artificial visual stimuli in a wide variety of behavioural experiments is becoming a powerful methodology across all taxa involving clay models, robots, pictures, video playbacks, computer animated stimuli or even the use of virtual reality techniques [3][4][5][6][7][8][9][10][11][12][13][14] . ...
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Although the environment is three-dimensional (3-D), humans are able to extract subtle information from two-dimensional (2-D) images, particularly in the domain of sex. However, whether animals with simpler nervous systems are capable of such information extraction remains to be demonstrated, as this ability would suggest a functional generalisation capacity. Here, we performed mate-copying experiments in Drosophila melanogaster using 2-D artificial stimuli. Mate copying occurs when naïve females observe the mating success of potential mates and use that social information to build their own mating preference. By replacing live demonstrations with (i) photos or (ii) simplified images of copulating pairs, we found that even crudely simplified images of sexual intercourse still elicit mate copying, suggesting that Drosophila is able to extract sex-related information even from a degraded image. This new method constitutes a powerful tool to further investigate mate copying in that species and sexual preferences in general.
... However, despite the great importance of vibrational signals for insect communication, their high information potential and flexibility (92,114), and their effectiveness at night and in dark habitats, their complementary role to other signaling modalities has been largely overlooked (143). The integration of vibrations into complex multimodal displays has been extensively studied in spiders (Lycosidae and Salticidae), where substrate-borne components are often an essential part of the signal, improving the reliability and the amount of transmitted information and, thus, the response of the receiver (73). Because vibrational signals are inherently associated with body movements, which are visually perceptible in diurnal species, and often simultaneously generate acoustic signals in the air (11), insects that rely solely on vibrational signals for communication (such as Auchenorrhyncha) may not be common. ...
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Communication by substrate-borne mechanical waves is widespread in insects. The specifics of vibrational communication are related to heterogeneous natural substrates that strongly influence signal transmission. Insects generate vibrational signals primarily by tremulation, drumming, stridulation, and tymbalation, most commonly during sexual behavior but also in agonistic, social, and mutualistic as well as defense interactions and as part of foraging strategies. Vibration signals are often part of multimodal communication. Sensilla and organs detecting substrate vibration show great diversity and primarily occur in insect legs to optimize sensitivity and directionality. In the natural environment, signals from heterospecifics, as well as social and enemy interactions within vibrational communication networks, influence signaling and behavioral strategies. The exploitation of substrate-borne vibrational signaling offers a promising application for behavioral manipulation in pest control. Expected final online publication date for the Annual Review of Entomology, Volume 68 is January 2023. Please see for revised estimates.
... a Estimated values for effects that contain a "song category" term are for songs without dance displays. & Uetz, 2019) and frogs (Preininger et al., 2013;Taylor et al., 2011). ...
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Multimodal signaling contributes to efficient communication by improving signal efficacy and increasing signal information. Songbirds often combine dance displays with songs according to the socio-sexual context; therefore, the song is assumed to function differently depending on dance displays. In this study, we tested how dance displays affect song patterns and the responses of paired partners using male and female blue-capped cordon-bleus (Uraeginthus cyanocephalus). Blue-capped cordon-bleus are a socially monogamous estrildid finch, and both males and females perform songs and distinct “tap dance”-like displays. Songs with dance displays were longer and more stereotyped than songs without dance displays in both males and females. Furthermore, both male and female paired partners showed more gestural responses to songs with dance displays than those without dance displays. Songs without dance displays were performed under both isolated and paired conditions, whereas songs with dance displays were only performed when the focal bird was housed with a paired partner. These results suggest that songs had different functions depending on dance displays and social contexts. The multimodal display of blue-capped cordon-bleus seems to draw the attention of paired partners to the physical abilities of the performer.
... are under sexual selection (Rovner 1975, Uetz and Denterlein 1979, Stratton and Uetz 1981, Uetz and Roberts 2002a, Stratton 2005, Hebets et al. 2013, Fowler-Finn et al. 2015, Uetz et al. 2016, Kozak and Uetz, 2019, Watts et al. 2019). Males of many species have dark pigmentation and/or tibial bristles on the first pair of legs, traits that are used in visual displays to females during courtship Uetz 1986, Hebets andUetz 2000). ...
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Animal body size has important evolutionary implications. The wolf spider genus Schizocosa Chamberlin, 1904 has developed as a model for studies on courtship, with visual and vibratory signals receiving attention; however, body size has never been carefully evaluated. Although species of Schizocosa can be distinguished from their close relatives by differences in genitalic structures, male ornamentation, and behavior, some species are morphologically similar, making diagnosis, and identification difficult. Evaluation of species boundaries using genetic data across Schizocosa is limited. The similar species S. maxima Dondale & Redner, 1978 and S. mccooki (Montgomery, 1904) are separated predominantly on the basis of size differences, with S. maxima being larger. We evaluate the evolution of size in these two Schizocosa species distributed in western North America, where gigantism of S. maxima is hypothesized to occur, particularly in California. We sampled subgenomic data (RADseq) and inferred the phylogeny of S. mccooki, S. maxima, and relatives. We apply a variational autoencoder machine learning approach to visualize population structuring within widespread S. mccooki and evaluate size within the context of a comparative phylogenetic framework to test the hypotheses related to genetic clustering of populations and gigantism. Our data show S. mccooki populations are not genealogically exclusive with respect to S. maxima. Likewise, S. maxima individuals are not recovered as a lineage and do not form an isolated genetic cluster, suggesting that the observed differences in size cannot be used to accurately delimit species. The cause of gigantism in S. maxima remains unexplained, but provides a framework for future studies of size variation and speciation.
1. Mate choice in females is influenced by intrinsic and extrinsic factors, including signal conspicuity, receiver body condition, and environmental properties. These factors interact in complex ways to modulate the choice of mates. Multimodal signals are more conspicuous than their unimodal components and therefore should elicit a stronger response. However, variations in female body condition and background noise can modify their responsiveness to signals of varying conspicuity. 2. Males of the diurnal stream-dwelling frog Crossodactylus schmidti emit unimodal e multimodal signals under variable noisy conditions, and the females vary greatly in body condition. We tested hypotheses on how signal type (unimodal or multimodal) interacts with female body condition and background noise to modify female responses. In a field experiment using a male mimicking robot frog, females were randomly exposed to acoustic-only (call, A), visual-only (toe flag, V), and multimodal (call + toe flag, M) stimuli, while female body condition was estimated and data on background noise was taken.3. Females exhibited three types of response: emission of acoustic signals, emission of visual signals, and movements toward the robot. All stimuli elicited responses, with a higher percentage of females responding to M, an intermediate percentage to A, and a lower percentage to V. Females in better physical condition exhibited a decreased probability of acoustic response, emitted signals at a lower rate, and took more time to emit signals or move towards the robot. With increasing noise, females exhibited decreased probability of responding with a visual signal to both the visual and multimodal stimuli, but when stimulated by the acoustic stimulus, females exhibited a higher probability of visual response as the noise increased. Finally, females at noisier sites also emitted signals at a higher rate but took more time to respond with visual signals and to move towards the robot.4. The results suggest that the multimodal signal had the highest female responsiveness. The negative effect of body condition and the positive effect of background noise on the response occurred because better-conditioned females were more selective in their choice, while noisy environments negatively interfered with mate assessment. Our study highlights the complex and context-dependent nature of female mate choice, influenced by signal conspicuity, female body condition, and noise levels.
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While members of the choosier sex often prefer courting mates with bright, large, or loud phenotypes, social experience can result in variation in mate preferences. Fewer studies, though, have investigated how multiple social parameters might interact to affect such preferences. In the brush-legged wolf spider, Schizocosa ocreata, asynchrony of maturation between sexes provides a time period in which females might be exposed to male courtship prior to making a mating decision. We tested whether adult females demonstrated plasticity in their preferences for vibratory signal amplitude after experience with vibratory playback during their penultimate stage. Penultimate instar females were presented unimodal vibratory courtship signals via piezoelectric disc benders, manipulating the perceived encounter rate (every other day or once per day), the number of males (one or two), and/or the vibratory amplitude (low or high). As adults, each female was presented vibratory playback of a low- or high-amplitude courtship signal in both no-choice and two-choice designs. In no-choice trials, previous experience with different amplitude signals significantly affected adult preferences, while other social parameters did not. Specifically, female S. ocreata preferred high-amplitude signals to low-amplitude signals if previously exposed to high-amplitude signals, while those previously exposed to low-amplitude signals preferred low-amplitude signals. In two-choice trials, however, females preferred high-amplitude signals regardless of their previous social experience, suggesting that innate preferences for high-amplitude signals might outweigh any learned preferences in some contexts. Results from this study complement previous social experience studies in S. ocreata, by clearly demonstrating a second sensory modality through which social learning can occur. Significance statement Social experience affects subsequent mate preferences in a variety of taxa, but in many instances, single parameters are examined at a time. Furthermore, in species that use multimodal communication, there remain questions about whether a single sensory modality is sufficient to elicit such plasticity. In this study, we manipulated multiple parameters using vibratory playback to examine whether social experience during the brush-legged wolf spider’s juvenile stage affected preferences for low- and high-amplitude signals as an adult. Ultimately, only the amplitude of the male’s signals that they were exposed to as a juvenile impacted adult mate preference—not the number of perceived males or how often they encountered the males. These results, along with previous studies, demonstrate that S. ocreata is capable of plasticity in response to social cues in multiple modalities.
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While most research on sexual signals as indicators of health status and infection has been focused on communication by visual (color), airborne acoustic (song structure, amplitude, frequency, and pattern), or chemical means, new evidence suggests that substrate‐borne vibratory signals can also be a reliable indicator of male quality and possibly infection history. In this study, we investigated the ability of the vibratory cues in multimodal sexual signals of Schizocosa ocreata wolf spiders to convey male health information to a female, and whether females adjust their mate choice decisions based on these cues. Individual components of the complete vibratory signal, including stridulatory pulse rate, mean amplitude, and peak amplitude, were all significant predictors of mating success in live trials. Males infected as a juvenile (during the penultimate molt) had significantly lower stridulatory rate and peak amplitude than control males. There were no significant differences in any of the vibratory signal components between control males and males infected as adults (1 h prior to mating trials). This suggests that the vibratory cues in this species may be altered when infection occurs during development, allowing females to avoid males that have been immunocompromised in the past. However, these cues are not reliable indicators of whether a male is actively infected, which means that the evaluation of these cues will not help a female avoid contact with infected individuals. Taken together, these results suggest that vibratory signals may convey honest information about male quality and past health, allowing females to choose mates that have not been compromised during development.
This study aims to create a mobile application for public interaction around the subject of wolf spiders, specifically the brush-legged wolf spider. The hope is that the public will have a reduced level of fear towards arachnids when given a chance to view arachnids in a digital setting. To assist this, the application employs augmented reality animation, which has been shown to have a positive impact on the viewer’s interest and learning. With the opportunity to view a digital spider interacting with surfaces in a repeatable and informative manner, viewers may find that their fears are more understood and can be controlled for both their benefit and that of the local arachnids. In order to accommodate multiple audiences, the application was set up to have a more cartoonish and simpler text as well as a realistic and advanced text. The area of information covered the brush-legged wolf spider’s anatomy, mating behaviour, and general safety practices for handling and avoiding wolf spiders. The modelling and animation were created using Zbrush and Blender, respectively. The programming and application creations used were Unity with Android and AR plugins.
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Colorful visual signals are important systems for investigating the effects of signaling environments and receiver physiology on signal evolution as predicted by the sensory drive hypothesis. Support for the sensory drive hypothesis on color signal evolution is mostly based on documenting correlations between the properties of signals and habitat conditions under which the signals are given (i.e., a correlational approach) and less commonly on the use of mathematical models that integrate representations of visual environments, signal properties and sensory systems (i.e., a functional approach). Here, we used an experimental approach in the field to evaluate signal efficacy of colorful lizard throat fans called dewlaps that show geographic variation in the lizard Anolis cristatellus. We used a remote controlled apparatus to display "fake dewlaps" to wild lizards to test for adaptive divergence in dewlap brightness (i.e., perceived intensity) among populations in situ. We found evidence of local adaptation in dewlap brightness consistent with the sensory drive hypothesis. Specifically, dewlaps that had the brightness characteristics of local lizards were more likely to be detected than those with the brightness characteristics of non-local lizards. Our findings indicate that simplified mathematical representations of visual environments may allow robust estimates of relative detectability or conspicuousness in natural habitats. We have shown the feasibility of evaluating color signal efficacy experimentally under natural conditions and demonstrate the potential advantages of presenting isolated components of signals to an intended receiver to measure their contribution to signal function.
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Complex signals of animals involve multiple sensory modes and contain multiple structural components, and teasing apart how these modes and components interact in receiver decision making is an experimental challenge. Females of many species have ordered preferences for increased size or expression of male indicator traits. However, studies also suggest other species may exhibit comparative evaluation of mates rather than absolute preference hierarchies. We examined mate assessment by female wolf spiders, Schizocosa ocreata, using digital playback of video and vibratory/seismic signals in preference and choice tests of male trait differences. In playback experiments, female wolf spiders showed ordered preferences for male condition indicating traits (leg tuft size, vibration signal amplitude) in both individual sensory modes and multimodal (combined) signals. Tests with single modes and multimodal signals showed that trait expression in either signal mode affects outcome of mate choice. Females exhibited transitive preferences, consistently choosing males with larger tuft size or higher amplitude vibration in no-choice and two-choice tests. Thus, female S. ocreata do not necessarily need to compare mates to exhibit preferences for particular traits. Choice tests with multimodal playback showed that females made predicted choices when male traits covaried positively, but in ‘cue-conflict’ (negative trait covariance) choice tests, females showed a bias for visual signal trait expression (tuft size), displaying priority for visual signals over vibratory signals when in conflict. These studies demonstrate that under controlled experimental conditions, differences in behavioural responses to manipulation of digital video and vibration playback can provide valuable insights about recognition and interpretation of complex signals and their components.
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The ideal animal stimulus is under total control of the experimenter, has visual traits, and behavior patterns that can be varied in any way, and it appears and behaves consistently between test trials that can be easily repeated many times and any time. Does this sound like wishful thinking of a biologist? Using and exploiting the potential of artificial stimuli in animal behavior research is actually not a new idea. Even in the time of Tinbergen, researchers used wood, clay, or other materials to build artificial dummy animals that would allow control over the presentation of the animal stimulus (Ter Pelkwijk and Tinbergen 1937). Since then, the idea of artificial model animals has evolved alongside technology. Even if still used today in its original form (Kim and Velando 2014), clay and wood models have inspired the use of robots, engineering objects that are specifically tuned for...
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Females often benefit from the ability to assess courting males using multiple signal modalities. Differences in the transmission properties of each signal modality, however, may hinder a female's ability to detect signals, and result in variation in individual sensory experience. Such variation in sensory experience would include, for example, variation in courtship modality experience. It is unknown, however, whether differences in courtship modality experience affect preferences for unimodal and multimodal signals. We tested the effects of juvenile courtship modality experience on adult mate preferences in the wolf spider, Schizocosa ocreata (Hentz). Male S. ocreata use a combination of visual and vibratory signals as a multimodal signal, and female S. ocreata (without previous experience) have been shown to weigh unimodal vibratory and unimodal visual signals equally. Whether individual variation in courtship modality experience affects the relative weight of unimodal signals is unknown not only in S. ocreata, but is poorly understood across animal taxa. We used playback techniques to manipulate the courtship modality experience (unimodal visual signals, unimodal vibratory signals, multimodal signals, or no signals) of penultimate females. Upon maturation, we counted the number of receptivity displays towards each unimodal signal and a multimodal signal on three consecutive days of single presentation studies. In no-choice adult trials, courtship modality experience affected unimodal, but not multimodal, preferences. Female S. ocreata preferred the familiar unimodal signal in no-choice presentations (e.g. females exposed to vibratory signals were more receptive toward those signals). However, females preferred multimodal signals over unimodal signals, regardless of their juvenile courtship modality experience. In two-choice trials, female S. ocreata significantly preferred visual signals, regardless of their experience. Taken together, an individual's courtship modality experience has the ability to affect unimodal courtship preferences, but may be limited based on whether adult females are presented unimodal signals in no-choice or two-choice trials.
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Rapid technical advances in the field of computer animation (CA) and virtual reality (VR) have opened new avenues in animal behavior research. Animated stimuli are powerful tools as they offer standardization, repeatability and complete control over the stimulus presented, thereby 'reducing' and 'replacing' the animals used, and 'refining' the experimental design in line with the 3Rs. However, appropriate use of these technologies raises conceptual and technical questions. In this review, we offer guidelines for common technical and conceptual considerations related to the use of animated CHOUINARD-THULY et al.: Using animated stimuli in studies of animal behavior 2 stimuli in animal behavior research. Following the steps required to create an animated stimulus, we discuss (I) the creation, (II) the presentation, and (III) the validation of CAs and VRs. Although our review is geared towards computer-graphically designed stimuli, considerations on presentation and validation also apply to video playbacks. Computer animation and virtual reality allow both new behavioral questions to be addressed and existing questions to be addressed in new ways, thus we expect a rich future for these methods in both ultimate and proximate studies of animal behavior.
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While females may benefit from being selective when choosing a mate, social experience can result in variation in mate preferences. Few studies, however, have investigated how multiple factors of the social environment (e.g., male phenotype and social demography) may interact to affect mating preferences. We used the brush-legged wolf spider, Schizocosa ocreata, to determine whether female visual preference for males with large tufts (foreleg bristles) varies based on adult social experience. Video playback was used to simulate social conditions during the early adult stage (1–6 days post-maturity) to test the effects on subsequent mating preferences (day 7 post-maturity) in a multifactorial design. Females were presented a variable number of males (one or three) that varied in their phenotype (small or large tufts) at a variable encounter rate (once every other day or twice per day). On day 7, females were presented a small-tufted and a large-tufted male in a two-choice design. The number of receptivity displays towards each male were counted, and statistical models were used to determine whether the encounter rate, the number of males, or male phenotype best predicted female selectivity. The male phenotype (small or large tufts) that females previously experienced best predicted subsequent female selectivity, such that female S. ocreata exhibited more receptivity displays towards “familiar” males. This study demonstrates the importance of the social environment in the mate preferences of an invertebrate and encourages future studies to use multi-factorial experimental designs to determine the relative importance of social parameters. Significance statement While our understanding of behavioral plasticity in mating behaviors of invertebrates has increased within the past decade, many researchers have used univariate approaches in such studies. This paper uses a multifactorial approach to investigate plasticity in female preferences of a wolf spider and is perhaps the first to manipulate three different parameters of the perceived social environment. In brief, we found that the “attractiveness” of the males that females previously saw affected subsequent mate preferences more than how often they saw males or how many males they saw per encounter. We also highlight a significant interaction between two variables that would not have been discovered using a univariate approach. Our paper should elicit interest from general behavioral ecologists, but perhaps more specifically those interested in the social environment, sexual selection, behavioral plasticity, video playback, and invertebrate biologists.
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Cross-modal integration, i.e., cognitive binding of information transmitted in more than one signal mode, is important in animal communication, especially in complex, noisy environments in which signals of many individuals may overlap. Males of the brush-legged wolf spider Schizocosa ocreata (Hentz) use multimodal communication (visual and vibratory signals) in courtship. Because females may be courted by multiple males at the same time, they must evaluate co-occurring male signals originating from separate locations. Moreover, due to environmental complexity, individual components of male signals may be occluded, altering detection of sensory modes by females. We used digital multimodal playback to investigate the effect of spatial and temporal disparity of visual and vibratory components of male courtship signals on female mate choice. Females were presented with male courtship signals with components that varied in spatial location or temporal synchrony. Females responded to spatially disparate signal components separated by ≥90° as though they were separate sources, but responded to disparate signals separated by ≤45° as though they originated from a single source. Responses were seen as evidence for cross-modal integration. Temporal disparity (asynchrony) in signal modes also affected female receptivity. Females responded more to male signals when visual and vibratory modes were in synchrony than either out-of-synch or interleaved/alternated. These findings are consistent with those seen in both humans and other vertebrates and provide insight into how animals overcome communication challenges inherent in a complex environment.
One way of circumventing the functional tradeoffs on eye design [1,2] is to have different eyes for different tasks. For example, jumping spiders (Salticidae), known for elaborate, visually guided courtship and predatory behavior [3], view the same object simultaneously with two of their four pairs of eyes: the antero-lateral eyes (ALEs) and the principal eyes (reviewed in [2]; Figure 1A). The ALEs, with immobile lenses and retinas, wide fields of view, and hyperacute sensitivity to moving stimuli [4], are structurally distinct from the principal eyes, which have the best spatial acuity known for terrestrial invertebrates and can discern fine details of stationary objects [5]. Behind the immobile corneal lenses of the principal eyes are miniature, boomerang-shaped retinas with correspondingly small fields of view (Figure 1B). The principal-eye visual fields are greatly expanded and overlap because of eye movements: these retinas are at the proximal ends of long, moveable tubes within the spider's cephalothorax [6]. By designing and using a specialized eyetracker, we tested whether principal-eye gaze direction is influenced by what the ALEs see. The principal eyes scanned stationary objects regardless of whether the ALEs were masked, but only when the ALEs were unmasked did the principal eyes smoothly track moving disks. The principal eyes, with high acuity but a narrow field of view, can thus precisely target moving stimuli, but only with the guidance of the secondary eyes.
Playback is the technique of rebroadcasting natural or synthetic signals to animals and observing their response. The ability to present a putative signal in isolation, without the potential confounding effects of other activities of the signaller, is the main reason for the depth and range of our knowledge of communication systems. To date, playback of sound signals has predominated, but playback of electric signals and even video playback of visual signals suggests that playback will become just as prevalent in studies of communication in other sensory modalities. This book is one of the outcomes of a workshop on playback held at Thombridge Hall in the Peak District National Park, England during August 1991. There were two reasons for organising the workshop. First, the considerable and lively debate in the literature about the design and analysis of playback experiments -the pseudoreplication debate -was in danger of generating more heat than light. A workshop forum seemed the obvious place to clarify and, if possible, resolve the debate. Second, with the number of new playback and analysis techniques increasing rapidly, it seemed an opportune moment to discuss these techniques and to review some rapidly developing areas of interest in sound communication.
The courtship behaviors of two morphologically similar spider species, Schizocosa ocreata and S. rovneri, are distinctive and prevent interbreeding. We used "forced" copulation between these species to investigate the mode of inheritance of the courtship behavior and to determine whether postmating isolating mechanisms exist. F1 hybrids proved to be behaviorally sterile, but they were capable of producing viable offspring when forced to interbreed. Analysis of the courtship behaviors of F1 , F2 , and backcross progeny showed that the inheritance of some aspects of these behaviors is consistent with models involving single autosomal loci. The inheritance of secondary sexual characteristics in the males is also investigated. The genes for courtship behavior and secondary sexual characteristics do not assort independently. The origin of the premating isolating mechanisms may be explained by either an initial habitat separation between the two groups, or by a founding event with each group subsequently diverging in slightly different habitats. It is suggested that the differences in the microhabitats may have a profound effect on what type of signal (visual or vibratory) would be effective.