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Hall, A. S. (2016). Acute Artificial Light Diminishes Central Texas Anuran Calling Behavior. Amer. Midland Naturalist, 175(2), 183–193.
Abstract: Male anuran (frog and toad) advertisement calls associate with fitness and can respond to environmental cues such as rain and air temperature. Moonlight is thought to generally decrease call behaviors – perhaps as a response to increased perceived risk of predation – and this study sought to determine if artificial lighting produces a similar pattern. Using a handheld spotlight, light was experimentally introduced to natural anuran communities in ponds and streams. Custom call surveys where then used to measure anuran calls in paired unlit and lit conditions at six locations in central Texas. Among seven species heard, the number of frogs calling and call index declined in response to the acute light input. Local weather conditions could not explain differences between numbers of frogs calling between species, sites, survey order, or lighting order suggesting the main effect on number calling was light treatment. It appears acute artificial light alone can change calling behavior within several species in natural, mixed species assemblages.
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May, D., Shidemantle, G., Melnick-Kelley, Q., Crane, K., & Hua, J. (2019). The effect of intensified illuminance and artificial light at night on fitness and susceptibility to abiotic and biotic stressors. Environmental Pollution, 251, 600–608.
Abstract: Changing light conditions due to human activities represents an important emerging environmental concern. Although changes to natural light conditions can be independently detrimental, in nature, organisms commonly face multiple stressors. To understand the consequences of altered light conditions, we exposed a model amphibian (wood frog; Lithobates sylvaticus) to a control and two anthropogenic light conditions: intensified daytime illuminance and artificial light at night – ALAN (intensified daytime illuminance + extended photoperiod). We measured (1) metrics of fitness (hatching success as well as survival to, size at, and time to metamorphosis) (2) susceptibility (time to death) to a commonly co-occurring anthropogenic stressor, road salt (NaCl) and (3) susceptibility (infection load) to a common parasite (trematode). We also explored behavioral (swimming activity) and physiological (baseline corticosterone (CORT) release rates) changes induced by these light conditions, which may mediate changes in the other measured parameters. We found that both intensified daytime illuminance and ALAN reduced hatching success. In contrast, for amphibians that successfully hatched, neither treatment affected amphibian survival or time to metamorphosis but individuals exposed to ALAN were larger at metamorphosis. The light treatments also had marginal effects; individuals in ALAN treatments were more susceptible to NaCl and trematodes. Finally, tadpoles exposed to ALAN moved significantly less than tadpoles in the control and intensified daytime illuminance treatments, while light had no effect on CORT release rate. Overall, changes in light conditions, in particular ALAN, significantly impacted an amphibian model in laboratory conditions. This work underscores the importance of considering not only the direct effects of light on fitness metrics but also the indirect effects of light with other abiotic and biotic stressors. Anthropogenic-induced changes to light conditions are expected to continue increasing over time so understanding the diverse consequences of shifting light conditions will be paramount to protecting wildlife populations.
Keywords: Animals; frogs; amphibians; Lithobates sylvaticus
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Mège, P., Ödeen, A., Théry, M., Picard, D., & Secondi, J. (2015). Partial Opsin Sequences Suggest UV-Sensitive Vision is Widespread in Caudata. Evol. Biol., , 1–10.
Abstract: Ultraviolet (UV) vision exists in several animal groups. Intuitively, one would expect this trait to be favoured in species living in bright environments, where UV light is the most present. However, UV sensitivity, as deduced from sequences of UV photoreceptors and/or ocular media transmittance, is also present in nocturnal species, raising questions about the selective pressure maintaining this perceptual ability. Amphibians are among the most nocturnal vertebrates but their visual ecology remains poorly understood relative to other groups. Perhaps because many of these species breed in environments that filter out a large part of UV radiation, physiological and behavioural studies of UV sensitivity in this group are scarce. We investigated the extent of UV vision in Caudata, the order of amphibians with the most nocturnal habits. We could recover sequences of the UV sensitive SWS1 opsin in 40 out of 58 species, belonging to 6 families. In all of these species, the evidence suggests the presence of functional SWS1 opsins under purifying selection, potentially allowing UV vision. Interestingly, most species whose opsin genes failed to amplify exhibited particular ecological features that could drive the loss of UV vision. This likely wide distribution of functional UV photoreceptors in Caudata sheds a new light on the visual ecology of amphibians and questions the function of UV vision in nocturnal animal species.
Keywords: Animals; Caudata; amphibians; ultraviolet; ultraviolet vision; opsin; photobiology; SWS1; Paralog gene; Tuning site; Nocturnal species; Sliding window; Ka/Ks
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Vignoli, L., & Luiselli, L. (2013). Better in the dark: two Mediterranean amphibians synchronize reproduction with moonlit nights. Web Ecol., 13(1), 1–11.
Abstract: In Amphibians, both positive and negative correlations between activity and full moon phase have been observed. In this study, we present data for two anuran species (Hyla intermedia and Rana dalmatina) studied in a hilly Mediterranean area of central Italy. We analysed, in a two-year survey, the relationships between the number of egg clutches laid each night and the moon phases by means of circular statistics. Moreover, the studied species exhibited clear oviposition site selection behaviour influenced, at least in H. intermedia, by moon phases. We observed the occurrence of an avoidance effect by amphibians for oviposition and specific egg-laying behaviour during moon phases around the full moon. This apparent lunar phobia was evident in both species when yearly data were pooled. On the other hand, while this pattern continued to be also evident in H. intermedia when single years were considered, in R. dalmatina it stood just in one year of study. Nonetheless, during cloudy nights, when moonlight arriving on the ground was low, the frogs' behaviour was similar to that observed in new moon phases. We interpreted the observed pattern as an anti-predatory strategy. Overall, comparisons between our own study and previous research suggest that there was insufficient evidence to establish any unequivocal patterns and that further research in this regard is needed.
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