Abstract
Animal reproductive cycles are commonly triggered by environmental cues of favourable breeding conditions. In arid environments, rainfall may be the most conspicuous cue, but the effects on reproduction of the high inter- and intra-annual variation in temperature remain poorly understood, despite being relevant to the current context of global warming. Here, we conducted a multiyear examination of the relationships between a suite of measures of temperature and rainfall, and the onset and length of the breeding season, the probability of breeding and reproductive output in an arid-region passerine, the sociable weaver (Philetairus socius). As expected, reproductive output increased with rainfall, yet specific relationships were conditional on the timing of rainfall: clutch production was correlated with rainfall throughout the season, whereas fledgling production was correlated with early summer rainfall. Moreover, we reveal novel correlations between aspects of breeding and temperature, indicative of earlier laying dates after warmer springs, and longer breeding seasons during cooler summers. These results have implications for understanding population trends under current climate change scenarios and call for more studies on the role of temperature in reproduction beyond those conducted on temperate-region species.
Highlights
Reproduction involves high energetic and nutritional demands associated with the production of eggs and the development of embryos and, in many species, with subsequent care of offspring
The climate is characterized by low annual rainfall (432 ± 134 mm per year, range 187–789 mm, as recorded from 1990 to 2013; South African Weather Service), the majority of which falls between October and April, and by widely ranging temperatures: 2–19°C during the coldest months (June and July), and 17–32°C during the hottest months (December to February)
Our study focuses on six breeding seasons with complete data (1999, 2000 and 2010–2013) and includes three additional years (2002–2004) where data were only collected between August and December for the analysis of the onset of breeding
Summary
Reproduction involves high energetic and nutritional demands associated with the production of eggs and the development of embryos and, in many species, with subsequent care of offspring. The ability to time reproduction to match the peak of resource availability using predictive environmental cues is expected to be under strong selective pressure [1,2,3,4]. Temperature is an important determinant of reproductive success for these species due to its effects on food availability, energetic demands and physiological state [5,8,9]. In arid regions, rainfall can range widely within and between years and is expected to play a more important role in determining the incidence and timing of reproduction [10,11,12]. Few long-term studies, have investigated concurrently the influence of rainfall and temperature on breeding decisions and output in arid-region species [13,14]
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