O. Gy. Dely szerk.: Vertebrata Hungarica 20. (Budapest, 1981)

Demeter, A.: Small mammals and the food of owls (Tyto and Bubo) in Northern Nigeria 127-136. o.

that individuals of M. pusillus were good at detecting and avoiding the mist nets placed near Wikki spring. Molossidae Tadarida (Mops) condylura (A. Smith, 1833)

X Material: Wikki, 10 and 13 August 1978, 46 specimens. A large colony of several hundred individuals roosted in the roof of the primary school at Wikki. Two samples of bats leaving the roost at dusk were mist-netted, on both occassions the first individuals emerged at 19 06 hours. In both samples sex ratio was 1.4 o": 1 o_, but the first sample contained a much lower proportion of pregnant females (57 %) and a much higher proportion of adult males (60 %) than the second one, collected two nights later (80 % and 28.6 %, respectively). The differences between the samples are perhaps related to the social behaviour of this species. On the first night the specimens came mainly from the vanguard leaving the the roost. This sample of 34 individuals probably did not have marked removal effect on the large colony. On the second night, however, the bats that first left the roost successfully avoided the mist net and it was rather the second group of individuals issuing forth from the roof which were captured. The above figures suggest that mature males and- non-reproductive females may be the first to leave the roost. Rodents Cricetidae Tatera kempi Wroughton, 1906 Material: 4 specimen, Wikki (3) and Yashi river (1). The low number captured, in contrast with the high proportion of this gerbil in the prey of owls (see later) may be due to trap selectivity, or Individuals of this species may have avoided the traps. The sex ratio was 1:1, males had scrotal testes and one pregnant female contained 3 embryos. This species occurs in savanna and riparian woodland. Taterillus gracilis Thomas, 1892 Material: 8 specimens, Wikki (7) and Yashi river (1). Seven of the eight specimens were captured in combretaceous scrub savanna practically devoid of grass cover. The sex ratio was 1,6 if: 1 o. Three of the males had scrotal testes and both females were lactating. One male seemed to be of subadult size and weight, the rest were all adult specimens. The mean total skull length of adults is 36.08 mm, range 43.2-38.1 mm. Muridae Mus musculoides Temminck, 1853 Material: Wikki, 6 specimens. The sex ratio was 1:1, two males had scrotal testes and two females were pregnant with 5 and 3 nearly full-term embryos, respectively. All specimens were adults. This species occurs in a variety of habitats (Table 2) and HAPPOLD (1970) also reported it from houses at Wikki. A corny s cahirinus Johannis Thomas, 1912 Material: 10 specimens, Wikki. The sex ratio was 1.5 <$ : 1 $. Two females were pregnant with 2 and 3 embryos,respectively. Five of the 10 specimens were subadults. This species Inhabits sandstone rocks around Wikki, but it also moves into adjacent flat areas in the savanna woodland. Myomys daltoni (Thomas, 1892) Material: 8 specimens, Wikki. The sex ratio was 1.7 ó" : 1 $>. In July, this species showed little sign of reproduction, as only two of the five males had scrotal testes. This species has the probably widest ecological tolerance of all Yankari rodents, as it occurs in a large number of habitats (Table 2). Its commensal nature has previously been noted (HAPPOLD, 1970; ROSEVEAR, 1969); however it was not