Shells of the helicid Cepaea nemoralis were studied using taphonomic, isotopic and morphometric measurements to estimate late glacial–Holocene (~ 12.1–6.3 cal ka BP) environmental conditions in northern Spain. Higher taphonomic alteration among Holocene shells suggests lower sedimentation rates or higher shell-destruction rates than during glacial conditions. Shells preserved the aragonitic composition despite differing degree of skeleton damage. Shell δ13C values were − 10.3 ± 1.1‰, − 8.2 ± 2.3‰, and − 7.3 ± 1.6‰ for modern, Holocene and late-glacial individuals, respectively. Higher δ13C values during the late-glacial and some Holocene periods imply higher water stress of C3 plants and/or higher limestone contribution than today. Intrashell δ13C values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth. Shell δ18O values were − 1.1 ± 0.7‰, − 0.9 ± 0.8‰ and − 0.1 ± 0.7‰ for modern, Holocene and late-glacial specimens, respectively. A snail flux-balance model suggests that during ~ 12.1 − 10.9 cal ka BP conditions were drier and became wetter at ~ 8.4 − 6.3 cal ka BP and today. Intrashell δ18O profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells, despite possible larger hibernation periods. Shell size correlated positively with δ18O values, suggesting that growth rates and ultimate adult size of C. nemoralis may respond to climate fluctuation in northern Spain.

The annual cycle of adult butterflies was studied at seven rocky outcrops located along an altitudinal gradient in a northern Spanish mountain area (Picos de Europa) with a Eurosiberian climate in 1993 and 1995. Both total abundance and number of species of butterflies peaked in summer at all study sites. The cumulative species number uniformly increased over the season until late summer. These results imply that butterflies concentrated their activity when temperatures were higher in the year. Regardless of their diversity and total abundance, timing of the flight period was later for assemblages at high altitude than for assemblages at low altitude. A similar trend in increasing delay in flight period was found when data were analysed separately for each species. The duration of the flight period of assemblages was correlated with abundance in 1993, but it was correlated with altitude in 1995. Most species tended to show shorter flight periods at high altitudes in both study years. These altitudinal changes in timing of adult flight are likely to be linked with effects of temperature on developmental rates of early stages of the life cycle. Changes in duration of the flight period, however, might be partly related to variability in species abundance.