|
- Improving Buffalo Estimates - Monitoring
law enforcement and illegal activity
The difficulty with buffalo surveys
Aerial surveys are not ideal for estimating buffalo populations.
The errors which may arise from estimating numbers are potentially
large. Present air survey techniques are not suited to detect
a yearly increase of 5% in a buffalo population which was
nominally 3,000 animals.There are no guarantees for air surveys
that, even if they are carried out at exactly the same time
of year, other variables (e.g. rainfall) may not affect the
numbers of buffalo actually present in the Caprivi at the
time The typical semi-random distribution of most large mammal
species can be well captured by transects flown about 1km
apart with a strip width of about 150m each side of the aircraft.
The estimate which results from sightings which fall within
the stripwidth is usually fairly precise with statistical
confidence limits which can be better than + 20% of the value
of the estimate.
Because buffalo occur in large herds which may exceed 500
animals and may cover a physical area which spans more than
one adjacent transect line, the errors which may arise from
estimating numbers are potentially large. For example, if
the entire buffalo population in a particular survey stratum
exists as one large herd of several hundred animals and that
herd happens to fall outside the survey strip width, the estimate
for the population is zero. If the herd fall entirely within
the strip width, the estimate is high when the sample area
is extrapolated to the total stratum area and there are no
confidence intervals because of the single data point. A range
of intermediate situations can arise, all of which give rise
to the very large confidence intervals which are associated
with buffalo estimates. A second problem is the inability
of observers to make accurate estimates of numbers when confronted
with very large groups - the general tendency is to underestimate
(Sinclair 1973). The problem is exacerbated when a herd is
partly in and partly out of the transect strip width and when
the observer is called upon to make an estimate when moving
at a forward speed of 100km/hour. At present there is no acceptable
alternative to the standard transect survey method or the
random block count method. Systems which rely on "total counts"
or "actual observations" are statistically inferior because
no accuracy or precision can be attached to the estimate.
Improving Buffalo Estimates
Gibson (pers.comm.) has proposed a method by which better
estimates might be obtained for buffalo. On any survey buffalo
will be encountered both in large herds and in small groups
(usually 'bachelor' herds) and the standard air survey method
is adequate to capture the smaller groups. To estimate the
numbers in large groups a second aeroplane should fly above
and behind the first at height such that it is surveying a
strip width of about 1km either side of the transect line.
The observers in the second aircraft are solely concerned
with detecting large buffalo herds which, when encountered,
are photographed and counted from the photograph after the
survey. By the application of the same statistical methods,
the large herds can be incorporated accurately within the
census. Such a survey would be expensive but it need not be
repeated very often.
Back to top
Monitoring law enforcement and illegal activity
Bell (1986) and Jachmann (1998) give excellent systems for
monitoring law enforcement and illegal activity. The rationale
underpinning the systems 
is that when no effort is applied to anti-poaching no illegal
activity is detected and, as effort is increased in the early
stages, an increasing amount of illegal activity is detected.
At some point as effort continues to be increased, the amount
of illegal activity actually decreases and, with further effort,
it can be reduced to a level which is acceptable to wildlife
managers and sustainable by wildlife populations (Figure
20).
It should be noted that illegal activity can seldom, if ever,
be eliminated completely and increasing expenditure on this
aspect of park management produces diminishing returns.
The objective of this monitoring is to detect whether the
situation is deteriorating or improving over time and whether
additional funds and effort have to be allocated to anti-poaching.
However, there are other secondary spin-offs from such a system:
it provides a comparative analysis amongst scouts of performance
on patrols (which can be valuable for promotion purposes or
for dismissal of malingerers), it can provide the basis for
an incentive system and it can be combined with a basic field
system for monitoring wildlife population numbers.
Law enforcement effort can be measured in several ways. The
number of times a particular grid square (e.g. 5 x 5 km )
is visited provides one type of index and measuring the total
distances walked in the course of patrols provides another.
These are fairly crude measures which can be considerably
improved by using a GPS to record actual distances travelled
and locations visited.
Illegal activity requires to be quantified by developing
an index which is appropriate for the park concerned and which
weights various activities according to the severity with
which they are viewed. Bell (1986, pages 326-329) gives a
points system by which illegal activity can be scored and
this could very easily be adapted to the needs of the different
parks in the Caprivi. Reports of arrests, weapon confiscations
and snares recovered are valueless unless organised into an
index which can be plotted against patrol effort.
Both Bell and Jachmann emphasize the importance of sound
patrol reporting systems and the time which must be spent
on debriefing after patrols have been completed if the data
collected are to have any validity. Jachmann also details
the important rôle which carriers (labourers) play in improving
the law enforcement performance and, in an analysis of illegal
hunting in the Luangwa Valley, Zambia, it was found that the
employment of carriers significantly reduced the illegal offtake
of elephants
Back to top
|
