Calling behaviour under climate change: geographical and seasonal variation of calling temperatures in ectotherms

Abstract

Calling behaviour is strongly temperature-dependent and critical for sexual selection and reproduction in a variety of ectothermic taxa, including anuran amphibians, which are the most globally threatened vertebrates. However, few studies have explored how species respond to distinct thermal environments at time of displaying calling behaviour, and thus it is still unknown whether ongoing climate change might compromise the performance of calling activity in ectotherms. Here, we used new audio-trapping techniques (automated sound recording and detection systems) between 2006 and 2009 to examine annual calling temperatures of five temperate anurans and their patterns of geographical and seasonal variation at the thermal extremes of species ranges, providing insights into the thermal breadths of calling activity of species, and the mechanisms that enable ectotherms to adjust to changing thermal environments. All species showed wide thermal breadths during calling behaviour (above 15 °C) and increases in calling temperatures in extremely warm populations and seasons. Thereby, calling temperatures differed both geographically and seasonally, both in terrestrial and aquatic species, and were 8-22 °C below the specific upper critical thermal limits (CTmax ) and strongly associated with the potential temperatures of each thermal environment (operative temperatures during the potential period of breeding). This suggests that calling behaviour in ectotherms may take place at population-specific thermal ranges, diverging when species are subjected to distinct thermal environments, and might imply plasticity of thermal adjustment mechanisms (seasonal and developmental acclimation) that supply species with means of coping with climate change. Furthermore, the thermal thresholds of calling at the onset of the breeding season were dissimilar between conspecific populations, suggesting that other factors besides temperature are needed to trigger the onset of reproduction. Our findings imply that global warming would not directly inhibit calling behaviour in the study species, although might affect other temperature-dependent features of their acoustic communication system.

Climate change and frog calls: long-term correlations along a tropical altitudinal gradient

“…It is interesting that the frogs' advertisement calls are sensitive to the small long-term temperature increase despite relatively large daily temperature shifts (+5.18C) observed at the four low-altitude weather stations ( figure 3). The role of daily fluctuations in habitat temperature of a variety of species of ectotherms has recently come under scrutiny [24,25].…”

Evaluation of the Processing Times in Anuran Sound Classification

“…A proof of this fact can be seen in some studies [2,3] where the songs of some anuran species are proposed as an excellent indicator of climate change. However, these approaches are supported by a large number of audio recordings, which are usually collected in the field, and analyzed one by one later.…”

Calling phenology and detectability of a threatened amphibian (Litoria olongburensis) in ephemeral wetlands varies along a latitudinal cline: Implications for management

“…For example, Lemckert and Mahony (2008) document variation in calling season length between northern and southern populations of some Australian frog species. Llusia et al (2013) found both geographical and seasonal variation in calling at temperatures at the extreme ends of the distributions of some Europeans frog species. However, to date, no studies have quantified variation in amphibian breeding phenology along the entire latitudinal distribution gradient for a single species.…”

“…Generally, a combination of climatic variables serves as cues for reproductive activity, such as synergistic effects between environmental temperature and rainfall and the current state of pond inundation (Oseen & Wassersug 2002;Richter-Boix et al 2006;Steelman & Dorcas 2010). In some species, reproductive activity and life history traits can also vary along their latitudinal or altitudinal gradients (Beebee 1995;Morrison & Hero 2003;Llusia et al 2013).…”

“…Male calling varies temporally in many species, and interspecific and intraspecific variation can also occur among geographical localities at multiple scales (Oseen & Wassersug 2002;Morrison & Hero 2003;Wells 2007;Lemckert & Mahony 2008;Llusia et al 2013). Amphibians in different climatic zones can have different breeding strategies because of variation in predictability of environmental factors (e.g.…”