Measurements were made on 274 spawn clumps and 271 adult frogs in three consecutive years at breeding sites in the west of Ireland. Mean clutch size was 1008 ± 20 ova, mean egg diameter was 2·32 ± 0·01 mm, and mean clutch weight was 11·62 ± 0·37 g. At any particular body length, larger clutch sizes were associated with smaller egg sizes and vice versa. Clutch size, egg size and clutch weight all increased allometrically with body size. The bigger females produced more and smaller eggs and a heavier clutch, relative to their body size, than smaller ones. Egg size and clutch weight also increased allometrically with female age. Age‐specific clutch weight increased during the first two years of maturity and declined slightly thereafter. Age‐specific egg size increased with age throughout life. At any age, bigger females produced more but not larger ova, and at any length, older females contained larger but fewer eggs. Both bigger and/or older females exhibited greater variability in the reproductive parameters than smaller and/or younger ones. Laboratory mating experiments showed that egg fertility was positively correlated with absolute male length and with the relative male/female length in amplexus. The fertilizing ability of males, however, declined with mating frequency, irrespective of male length, clutch size or the time interval between successive matings. In the wild, egg fertility ranged from 24–100%, although over 90% fertility was common.

A total of 1560 breeding frogs were collected in three consecutive years at sites in the west of Ireland. Alt were weighed and measured and the ages of 702 individuals were determined by skeletochronology. The length‐weight relationship differed between gravid females, spent females and males, with the gravid females showing the largest weight gain for any increase in length. The majority of males bred for the first time at two years, but most females delayed maturity until they were a year older. While the two‐year olds were of similar size, the females subsequently grew at a faster rate and achieved larger maximal sizes than the males. However, both sexes exhibited a decelerating growth rate with age. There was no apparent difference between the sexes in post‐maturation survival, which was estimated to be about 50% annually. The oldest frogs were seven years old.

Age was determined in three anuran species inhabiting a temperate oceanic climate (Rana temporaria, Bufo calamita and Bufo bufo) by means of the histological structure of the phalanges. Narrow, haematoxylinophilic lines were visible in these, and evidence from the examination of subadults and frog (R. temporaria) recaptures showed the lines to be annual. The validity of using the lines as age indicators was tested most extensively on natural frog populations and the effects of endosteal resorption were not found to be significant. The evidence for this conclusion was provided directly by recapture data and indirectly by an analysis of histological measurements made on the phalanges.