Seasonal and daily activity patterns of Vipera latastei in northern Portugal

The annual and daily activity cycles of Vipera latastei were investigated in northern Portugal from 1999 to 2001, based on field observations, radio-tracking data and road killed snakes. Annual activity was extended from early March to late October, although some snakes were active during winter. Two annual peaks of activity were observed, a minor one in March-May and a major one in September-October. The daily activity pattern of vipers in spring and autumn was unimodal, whereas in summer they expanded their activity from early morning to late afternoon, and were also active at night. Activity and body exposure of adult males were correlated with meteorological variables. Females had shedding periods in June and July, whereas males shed their skin more frequently in June and August. Sperm was detected in the vas deferens of males in October to December. Females ovulated in June and new-born vipers were found from early August. Mating season is apparently restricted to autumn, and spring mating is either absent or very reduced.