O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)

Brushko, Z. K. ; Kubykin, R. A.: Horsfield's tortoise (Agrionemys horsfieldi Gray, 1844) and the ways of its rational utilization in Kazakhstan 55-62. o.

Circadian activity rythra shows a two-peak character at 10-12 and again at 16-18 hours, but during bad weather these peaks are not so expressed, as activity is distributed over the whole day. With increase In temperature the length of activity period decreases from 5-6 to 2-3 hours. A maximum in activity is particular for the first part of the day. The time of feeding depends on the state of nourishment, the animals having been hungry for several days feed more intensively and longer. The digging activity is especially expressed in spring, though at this time as a rule the animals use simple shelters and do not dig deep holes. At night they usually dig into the ground little more than the height of the carapace, on the detritus-stone and small-hillock places, where digging is very difficult, they stay in one and the same shelters. Several days after appearing in spring, copulation begins and it reaches its maximum in April, but sometimes it may occur up to the beginning of May. It must be noted that the functional activity of male and female gonads does not coincide. The fertilization takes place at the expense of spermatozoa bearing appendages and at this thime testes are in the state of the relative rest. Females have the next portion of follicles maturing. The males being ready to mate, as well as the capacity of the spermatozoa to be stored in the epididymides the whole year round make it possible for them to copulate early and to fertilize maximal number of females. Tortoises mature late and in all parts of their range the ability of males to mate appears at much younger age than that of females. In South-Eastern Kazakhstan, while the former are able to mate when they are 11-12 years old with the carapaces 112-117 mm long (380-480 g), the latter mate at the age of 13-14 years with carapaces of 134-140 mm long (560-620 g). The copulating males are always smaller and younger than females, this reflects the general pattern of the age structure of the population (BRUSHKO 1977). Horsfleld's tortoises is remarkable for its relatively low reproductive rate. In SouthEastern Kazakhstan it lays eggs twice a year, a total of 5-6 eggs. As a result of asynchronous maturity of the gonads in specimens of different ages, females with mature eggs may be encountered from the middle of April to the first decade of June. Lot of females lay their first batch of eggs at the end of April or at the beginning of May and the second at the beginning of June (BRUSHKO 1978). Estimation of the number of unhatched eggs is rather difficult, as the hatched juveniles as a rule stay to winter underground till the spring of the next year. Various causes are responsible for their mortality. Thus, after the action of wind leaves the eggs uncovered they dry out in the sun or decay during cold and abundant precipitation. Eggs are taken by predators and shepherd dogs, they are trampled by numerous herds of sheep. Juveniles are eaten by birds and carnivores. In the breeding season under the nests of rookaries there are numerous carapaces of segolets and specimens of 1-4 years old, which form a considerable portion of the food of this birds. This is the reason for the juveniles being scarce in areas near rookaries. Segolets are frozen in severe and snowless winters. The low survival of juveniles is demonstrated by the extremely low number appearing after wintering. Thus in April and at the beginning of May 1976 on the transects only 17 juveniles (8%) among 211 adult animals were counted. The mean of data obtained on transects counts has shown that in the majority of cases the proportion of immature specimens reached 17-19%. In some untouched places their relative frequency was 30 - 50%. Perhaps this figure approximates the frequency distribution the age groups in nature. The reason for the juveniles being scarce in the exploited areas is that the juveniles are disproportionately harvested, because small and medium sized specimens are easier to catch and they are more suitable for transportation. Removing only a definite age group of animals leads to disruption of the population structure. It has been shown that the sex ratio of the animals changes under the influence of the peculiarities of their season activity. During the first part of April the males predominate over the females, and at the end of April and in May the ratio becomes 1:1, but at the first part of June the females become the dominant sex. On the whole, the specimens of different sexes are in even balance, or males may be somewhat preponderant. It is stated, that in exploited places during the second part of April and In May the disproportion of the sexes Is strongly expressed. As the collection of the tortoises takes place just after their hibernation, the predominant males are easily caught. They are also preferred because of their smaller size, composing 80% in the total catch of tortoises. Nowadays it is the practice of collectors to make total harvest of tortoises, thereby leading to complete removal from large areas. Because of the nature of tortoise movement the resettlement of these areas with reptiles from neighbouring areas may last for a long time or may not happen at all.