In actual fact, only about half the true bat population was accounted 
for by the old method. Furthermore, reference to Table II shows the 
consistency of the new method when observations over successive nights 
are compared in houses B and C, 
POPULATION IN INDIVIDUAL HOUSES 
From our population studies by the new method, it appeared evi- 
dent that individual houses maintained numerically similar bat popu- 
lations over the period of observation. A few examples are quoted 
(Table II) over specified periods of observation, 
TABLE II 
BAT POPULATIONS IN INDIVIDUAL HOUSES 


Actual Periods of 
Number counts Average observation 
B 198 ;203;184 195 Over 5 days 
C 14;10;10 11 Over 5 days 
C 12;17:17;16 15 Over 3 weeks 
E 36358344:53 48 Over 4 weeks at 
weekly intervals 
E 45 45 After 3 months 
(Control) 8 340;385;324 346 Over 6 months at 3 
monthly intervals 

These observations were all made from chemically untreated houses and 
show a wide range of bat population. 
In order to prove that these bat populations are in fact separate 
and stable for each individual house, a detailed study of the population 
dynamics and a bat-—banding or marking program would be necessary. 
