Iveson et ah Salmonella in an island marsupial 
caught and sampled a minimum of 6 times are presented 
in Table 5. Infections were predominantly transient, 
involving 10 different serotypes. Only 2 quokkas (male 
198) infected with S. chaster and (male 389) infected with 
S. oranienberg showed evidence of infections exceeding a 
period of 6 months. Conversely, 9 animals showed 
evidence of being free from infection for several months. 
It is possible, however, that when low numbers of 
organisms are present per gram of faeces, i.e. < 10, the 
standard swabbing procedure may fail to detect 
Salmonella (Hart etal. 1982). 
In the Thompson Bay settlement areas, including the 
camping area, Longreach Bay and Geordie Bay, 435 
individual quokkas were captured and 93 of these 
recaptured one or more times. Ninety five of these 
recaptures were within a 30-day period and could be 
subjected to analysis. Fifteen of these were positive 
initially and 14 on the second occasion. In the first group 
of 15, 8 were subsequently negative, 4 were positive with 
a different serotype and 3 (20%) were positive with the 
same serotype. Seven quokkas were negative at the first 
sampling but showed as positives during sampling in 
the following months. Of all the 93 animals recaptured in 
the settlement areas, only 4 were ever positive with the 
same serotype twice. 
In the Lighthouse Swamp population there were 100 
individual quokkas tagged and swabbed with a total of 
310 swabs from 75 recaptures. Of the 62 quokkas found 
to be positive at the first sampling time, 38 were 
subsequently negative, 7 were positive with a different 
serotype and 17 (27%) were positive with the same 
serotypes. 
In the Kingston Barracks/Bickley Swamp sample there 
was a total of 86 individuals tagged and 27 recaptures 
(second sampling) and 13 more recaptures at subsequent 
times. Of the 8 quokkas that were positive on the first 
sampling, one was negative subsequently, 4 were 
positive with a different serotype and 3 (38%) were 
positive with the same serotype. 
Movement of Animals 
There was movement of quokkas between Kingston 
Barracks, Bickley Swamp and the Settlement. These 
individuals, and any others moving more than 500 m, 
were scored as 'mobiles' on reaching the settlement. 
There were frequent movements by quokkas of over 50 
m between sampling sites within the settlement but the 
majority of animals was captured only on few occasions 
in the camping area, as well as in the main settlement 
area. Within the settlement and Kingston Barrack/Bickley 
Swamp sites, 114 individuals were recaptured only at the 
same site as their initial capture, showing evidence of 
high philopatry, whilst 48 individuals were recaptured 
in at least one other site. There was great variation in the 
length and frequency of movements recorded in the 
mobile groups with some individuals being recaptured 
in other sites and then reappearing at the initial site of 
capture. Only a few quokkas, however, were captured at 
more than two sites, even when adjacent or nearby. 
The frequency of movements and approximate 
distances travelled by quokkas are presented in Table 6 
with 50% of these under 100 m, highlighting the basically 
sedentary nature of the quokka. Only 14% of the records 
Table 6 
Frequency of movement and distances travelled by tagged 
quokkas, Setonix brachyurus, on Rottnest Island. 
Distance Travelled 
Number 
Frequency (%) 
<100 m 
29 
50 
100-200 m 
12 
20.5 
200-500 m 
9 
15.5 
>500 m 'Mobiles' 
8 
14 
Totals 
58 
100% 
Table 7 
Estimates of population 
size at various capture sites for the 
quokka, Setonix brachyurus, on Rottnest Island. For the location 
of sites, refer to the text. 
Capture Site 
Population Estimate 
Camping Ground and Lodge 
360 
Garden Lake 
175 
Police Station 
64 
South Settlement 
75 
Lighthouse Swamp 
98 
Kingston Barracks and Bickley Swamp 
101 
Total 
873 
were in excess of 500 m, five being recorded at 2100 m 
between Kingston Barracks and the camping area. 
Population Estimates 
Very approximate estimates of population size for the 
various capture sites, based on mark-and-recapture 
efforts, are summarised in Table 7. The main settlement 
area at Thompson Bay, comprising Bathurst Point, the 
camping ground. Lodge, Garden Lake, Police Station and 
South Settlement supports an estimated population of 674 
quokkas which translates to an extraordinarily high 
density of approximately 21 animal.ha ’. The Lighthouse 
Swamp site suggests that a discrete population of 
approximately 100 individuals is receiving 
supplementary feeding from tourists. The Kingston 
Barracks/Bickley Swamp population is roughly of the 
same size but quokkas are not fed by tourists. 
Human Transmission and Public Health Issues 
During the study period, patients exhibiting 
symptoms of gastro-enteritis rarely submitted faecal 
samples and S. typbimuriiim PT 202 was isolated from 
one patient. Monitoring of the sewage system revealed 
26 serotypes and S. Adelaide, S. chaster, S. javiana, S. 
muenchen and S. typhimurium PT 202 were detected in 
coastal waters, catchment sumps and water storage 
tanks. One hundred and twenty samples of seagull 
droppings collected from al fresco dining areas popular 
with the public were tested and resulted in the isolation 
of 11 serotypes including S. adelaide, S. javiana and S. 
typhimurium PT 202. 
Discussion 
Salmonella in wildlife 
Tliere is an increasing appreciation of the widespread 
occurrence of Salmonella serovars in wildlife species, and 
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