Hibernation Records on the Surface of Incisors in Radde's Hamster (Mesocricetus raddei, Rodentia, Cricetidae) from Dagestan

Abstract

The lower incisors of ten hamsters from the Khunzakh region of Dagestan were studied. One hamster implanted with a temperature data logger successfully survived one winter in natural conditions, and its body temperature curve revealed 25 episodes of hypothermia with the body temperature dropping to 1-9 degrees C, i.e., the period of hibernation. On the surface of the incisors, against a background of very indistinct increments, a zone with more distinct increments was observed. From the apical part of the zone to its basal part, the width of these increments decreased to very narrow, almost indistinguishable increments, and then increased. A comparison of the number of increments formed after this zone with the number of days the hamster survived after arousal from hibernation indicated that the zone was formed during hibernation. The pattern of variation in the increment width in the zone of hibernation corresponded to that observed in the episodes of normothermia during hibernation. A similar zone of hibernation was seen on the incisor surface in six of nine specimens caught in the field in June to early July. The date of their arousal was calculated from the number of increments corresponded to the date of arousal of the hamsters in this region, according to field observations. The pattern of the hibernation record on the incisors of these hamsters was mainly similar to that in the hamster with the temperature data logger and also demonstrated individual variations. Due to the poor contrast of increments on the incisor surface of these hamsters, it is difficult to use this record of hibernation for precise calculation of the data of arousal or for estimation of the duration of every episode of normothermia during hibernation. However, it is possible among the animals caught in spring to early summer to distinguish specimens aroused earlier or later using the position of the zone of hibernation on the incisor. It is also possible to estimate the relative duration of periods with short or long episodes of normothermia using the ratio of fragments with different widths of the increment in the zone of hibernation.