Gone with the wind: Is signal timing in a neotropical katydid an adaptive response to variation in wind-induced vibratory noise?

Abstract

Wind, a major source of environmental noise, forces invertebrates that communicate with plant-borne vibrations to adjust their signaling when communicating in windy conditions. However, the strategies that animals use to reduce the impact of wind noise on communication are not well studied. We investigated the effects of wind on the production of tremulatory signals in the neotropical katydid Copiphora brevirostris. First, we recorded katydid signaling activity and natural wind variation in the field. Additionally, we exposed katydid couples during their most active signaling time period to artificial wind of different levels, and we recorded the number of tremulations produced by the males. We found that wind levels are at their lowest between 2:00 and 5:00 in the morning, which coincides with peak signaling period for male katydids. Furthermore, we found that males produce significantly fewer tremulations when exposed to wind rather than acoustic noise or silence. Wind velocity significantly affected the number of tremulations produced during the wind treatment, with fewer tremulations produced with higher wind velocities. Our results show that katydids can time their vibratory signaling both in the short- and long-term to favorable sensory conditions, either through behavioral flexibility in response to short-term fluctuations in wind or as a result of an evolutionary process in response to predictable periods of low-wind conditions. Significance statement Animal communication can be hampered by noise across all sensory modalities. Most research on the effects of noise and the strategies to cope with it has focused on animals that use airborne sounds to communicate. However, although hundreds of thousands of invertebrates communicate with vibrational signals, we know very little about how noise affects this form of communication. For animals that rely on substrate-borne vibrations, wind represents the major source of environmental noise. Wind velocity levels can be predictable at a long-term scale (hours) but rather unpredictable at a short time scale (seconds). Both scales of variation are important for communication. Using a combination of field observations and lab experiments, we investigated the strategies used by a neotropical katydid Copiphora brevirostris to cope with vibrational noise induced by wind. Our results demonstrate that C. brevirostris times its signals at the long- and short-term range. Katydids signaled more at the times at night when wind velocity was lowest. Moreover, when exposed to wind gusts during their peak time of activity, katydids signaled more during the wind-free gaps.

Hay meadow vibroscape and interactions within insect vibrational community

“…Such an activity pattern seems to be primarily regulated by temperature ( Figure 4 B), likely because in insects the processes associated with the production of mechanical signals are temperature dependent ( Sanborn, 2006 ). While some studies suggest that peak daily vibrational signaling activity coincides with low wind levels ( McNett et al., 2010 ; Velilla et al., 2020 ), at our field site, wind velocity generally followed the same pattern as signaling activity ( Figure 4 C).

Figure 4 Diel variation in vibrational signaling activity (A) Diel variation in temperature (orange dashed line) and VST abundance (green line) obtained during continuous 24-h recordings in the period July 6-8, 2017.

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Daily Signaling Rate and the Duration of Sound per Signal are Negatively Related in Neotropical Forest Katydids

“…This research has focused exclusively on acoustic signals, but similar tradeoffs may be seen in other modalities as well. Related katydid subfamilies use vibration signals and duets in addition to acoustic communication (Belwood 1990;Morris 1980;Rajaraman et al 2018;Velilla et al 2020). In species that use multiple modalities to establish duets and attract mates, comparative analyses may demonstrate similar tradeoffs between the daily repetition rate of signals and the duration of the signal emission, within or across modalities.…”

Using Virtual Reality to Assess Reading Fluency in Children

“…LMEs were used to analyze response time and fixation durations while Generalized (logistic) LMEs were used to analyze error and refixation rates. The models were fitted with the lmer (for LMEs) and glmer (for GLMEs) functions from the lme4 package (Bates et al, 2015) in R. We report regression coefficients (b), standard errors (SE) and |t-values| (for LMEs) or |z-values| (for GLMEs) for all factors. Fixed effects were deemed reliable if |t| or |z| > 1.96 (Baayen et al, 2008).…”