Paper Reviewed
Prodon, R., Geniez, P., Cheylan, M., Devers, F., Chuine, I. and Besnard, A. 2017. A reversal of the shift towards earlier spring phenology in several Mediterranean reptiles and amphibians during the 1998-2013 warming slowdown. Global Change Biology 23: 5481-5491.

In a paper published in Global Change Biology by Prodon et al. examined an animal phenology database containing more than 50,000 observations to analyze trends in the date of first spring appearance (marking the end of hibernation) of 17 amphibian and reptile species over the period 1983-2013. The 17 species included Alytes obstetricans, Bufo bufo, Bufo calamita, Hierophis viridiflavus, Hyla meridionalis, Lacerta bilineata, Lissotriton helveticus, Malpolon monspessulanus, Natrix maura, Natrix natrix, Pelodytes punctatus, Podarcis liolepis, Podarcis muralis, Psammodromus algirus, Rhinechis scalaris, Timon lepidus, and Zamenis longissimus.

The spatial domain of the analysis included an area of about 44,500 km² in southern France between the Rhone River and Pyrenees mountain range. Trends in the data were derived using generalized additive models. Additionally, generalized linear models were utilized to explore the impact of temperature and/or precipitation on the appearance date of each species across time.

The results of the analysis revealed that reptiles and amphibians first appeared in the spring and average of 20 and 15 days earlier at the end of the record than they did in 1983. However, the trends in the words of the six French researchers were "far from linear." Six of the species, for example, showed no significant variation in first appearance over the three decade period. Furthermore, 11 species "showed a pause or a reverse temporal shift that, in certain cases, returned the first appearance date in 2013 to a date nor far from that of 1983." Additional analyses revealed this "reversal of the phenological shift from an earlier first appearance date to a later first appearance date that [was] observed from 1998 onwards ... mirrors the decreasing late-winter/early-spring temperature since that date."

Further exploration of the relationship between temperature and spring appearance date revealed a significant correlation between average daily maximum temperatures in February-March and animal first appearance date that was significant for all species at the p = 0.05 level. And, it demonstrated that "a species first appeared in spring on average 6.35 days earlier for every 1 °C increase in temperature with variation between species."

The importance of Prodon et al.'s work is summed up by their statement that "Mediterranean amphibians and reptiles respond without any time lag to variations in early-spring temperatures, with shifts of their appearance dates of up to 9 days earlier for every 1°C increase in temperature (average 6.35 days)." And this rapid phenological response of adjusting their date of first spring appearance in consequence of spring temperature fluctuation may well point to an inherent climatic resilience in coping with global warming projections.