Between September 1948 and December 1954, 2040 bats found in natural caves and disused mine tunnels in S. Devon, have been marked on the forearm withnumbered aluminium “rings”. These rings, which weigh 005 grams, are numbered consecutively and bear the identifying code initials ‘D.S.S.’ (Devon Spelaeological Society). Bats of seven species have been marked with such rings, as follows: Rhinolophus ferrumequinum, R. hipposideros, Myotis nattereri, M. daubentoni, M. mystacinus, Plecotus auritus, and Pipistrellus pipistrellus. The last-named species has not yet been found in a cave.

The great majority of the bats banded in Devon are of the family Rhinolo-phidae. 1364 bats of the species R. ferrumequinum have been banded, and of this number, 851 have been found again: this high order of recovery (62–3 per cent) has been maintained for several years. Many bats of this species have been recovered a number of times and one individual has been found again sixteen times since it was first banded. 597 bats of the species R. hipposideros have been banded during the period under review, but for this species the recovery is rather lower (approximately 28 per cent).

Rhinolophus ferrumequinum, although seen in numerous scattered haunts throughout S. Devon, is found chiefly in three main colonies, these being situated in groups of caves at Buckfastleigh and Chudleigh, and in a disused mine in the Tavy Valley. Although these colonies are many miles apart, some small interchange of population has been noted. Movements of the order of two to ten miles are common for this species, and 440 movements greater than one mile have been recorded. 143 of these movements have occurred during the months November to March (inclusive). This fact, coupled with general observations on the wakefulness and activity shown by such bats during the winter months, indicates that their hibernation is far from deep and is, at best, intermittent. Information concerning cross-country movements longer than fifteen miles is limited, but recently one individual, by making two flights between places forty miles apart, has provided some evidence that R. ferrumequinum ranges over a greater area than had hitherto been realized. For R. hipposideros, only thirty-two movements longer than one mile have been recorded in Devon. The longest of these, a journey of at least fourteen miles, took place during the winter months. During the winter season, R. hipposideros are found as solitary individuals, avoiding bodily contact, but R. ferrumequinum frequently cluster together in large, tightly packed groups. These groupings are temporary in nature and there is no segregation of the sexes.

Observations are included on general winter and summer behaviour, sex ratio, ectoparasites, and seasonal variations in weight. It has been shown for R. ferrumequinum that at the beginning of winter, the females weigh more than the males, that both sexes reach a maximum weight early in December, and that between December and the end of April a decrease in weight occurs which is equivalent to approximately 25 to 30 per cent of the peak value.