2.3 Fence Survey
In February 2018, a pilot fence survey was conducted to identify
portions of the fence with holes used by wild suids. We term these holes
as sites. The fence was divided into four main sections to relate fence
crossings by pigs to the localities of farms. Thirty-two sites were
identified on the western part of the reserve, 57 on the South-western
side, 46 on the south-eastern and 6 on the eastern side. Two bouts of
fence surveys were conducted to identify wild suid activities at the
respective sites: the wet season survey was conducted on 27 consecutive
days of February 2018 and the dry season survey was conducted in August
2018 for 30 consecutive days. The number and location of all the sites
were the same for both surveys. On each day, each site was inspected for
the presence of bushpig and/or warthog tracks. Once tracks were
observed, the researcher, with the help of experienced tracker game
scouts, took note of the species responsible, identity of the site, and
the number of tracks counted. For each observed set of tracks, the
species was identified, based on the footprints (on a few occasions
droppings). Three items were recorded for each site: a) whether tracks
indicated wild suids crossing the fence (= a crossing event); b) the
species of suid; c) an estimate of the number of wild suids that had
crossed at that point, based on the tracks leading to and from the site.
A crossing event refers to an occasion when one or more
warthogs/bushpigs crossed the fence at a specific site. The mean number
of crossing events/site/day during a survey (fc) is the
mean daily number of crossing events/site for a specific section of the
fence during the survey (Table 5). Similarly, the mean number of wild
suids/site/day during a survey (fp) represents the mean
daily number of wild suids/site for a specific section of the fence
during the survey (Table 5). Since the statistical distribution of the
number of crossings was similar to that described by a negative
exponential function, we performed analyses on the natural
log-transformed values of fc and fp. For
detecting differences among the four sections of the fence, a 1-way
ANOVA was separately performed on fc as well as on
fp classified by fence section. For detecting
differences between the dry and wet seasons, a repeated-measures ANOVA
was separately performed on fc as well as on
fp categorised by season. Standard errors of the
estimates (S.E.M.) for the number of wild suids crossing the whole fence
each day were generated by performing 1000 bootstrap samples of the
observations at each fence site and finding the S.E.M. of the 1000
estimates of the wild suid crossing rate. R V3.4.4 (R Core Team, 2018)
was used for all statistical analysis and statistical significance was
set for P-value lower or equal to 0.05.