Dissertation (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The use of helicopters has become almost universally accepted as the method of
choice in the enumeration of large ungulates in Southern Africa. In most cases
decisions affecting management of these populations are made based on a
single count result. In all these instances the within technique variance is
ignored, often leading to decisions based on type I or type II statistical errors
where the within technique variance is misconstrued as the population change.
Many studies have investigated the issue of accuracy of counting methods and a
few have quoted precision values for various methods. Very few have, however,
investigated power and those extant have approached the problem from a
prospective point of view and predicted power values. This study has made use
of replicated counts from 12 sites of the original 23 in four vegetation types of the
then Transvaal Province. The study sites vary in terms of size and all counts
were undertaken with an experienced, trained team in which only four observers
were used. A comprehensive post hoc analysis of the results of the field surveys
shows precision and power to vary widely according to species and vegetation
type and concludes that gamecounting results are largely site specific. A decline
in observations during the course of four hours of survey is demonstrated and
although the exact cause cannot be determined, correction factors have been
constructed for two vegetation types. Observers are shown to differ from one
another in observation profile during the course of surveys. This study
demonstrates, describes and quantifies the existence of several phenomena
suspected to exist by experienced game counters, biologists and wildlife
managers and makes proposals in terms of improving the data returned from
expensive aerial surveys. / AFRIKAANSE OPSOMMING: In Suider-Afrika word die gebruik van 'n helikopter vir die tel van hoefdiere byna
algemeen aanvaar as die metode wat voorkeur geniet. In meeste gevalle word
besluitnemings rakende die bestuur van hierdie populasies gebaseer op die
resultate van 'n enkele telling. In al die gevalle word tegniekverwante afwykings
buite rekening gelaat en dit het die gevolg dat bestuursbesluite gebaseer word
op tipe I en tipe II statistiese foute, en dit lei weer op hulle beurt dat tegniekverwante
afwykings verkeerdelik geïnterpreteer word as die rede vir
veranderings in die bevolkings. Verskeie studies het al die feitegeskil omtrent die
akkuraatheid van telmetodes ondersoek en sommige het herhaalbaarheidswaardes
vir die verskillende metodes aangehaal. Baie min het egter statistiese
mag ondersoek en die wat dit wel gedoen het, het prospektiewe magsanalise as
uitgangspunt gebruik en statistiese magwaardes voorspelom die probleem aan
te spreek. Hierdie studie het gebruik gemaak van herhaalde tellings van 12
gebiede uit die oorspronklike 23 in vier veldtipes geleë in die ou Transvaal
Provinsie. Die studiegebiede verskil in groottes. Alle tellings is deur 'n
bekwaamde opgeleide span gedoen wat slegs vier waarnemers ingesluit het. 'n
Omvattende post hoc analise van die resultate van die veldopnames dui aan dat
herhaalbaarheid en statistiese mag baie varieer met betrekking tot spesies en veldtipes en word die gevolgtrekking gemaak dat wildtellingsresultate grootliks
gebiedsgebonde is. In Afname in waarnemings gedurende die verloop van In
vier uuropname, is waargeneem en alhoewel die ware oorsaak nie vasgestel kan
word nie, is korreksiefaktore bereken vir twee veldtipes. Dit blyk dat waarnemers
van mekaar verskil het met betrekking tot hul waarnemingsprofiele gedurende
die verloop van die opnames. Hierdie studie dui aan, beskryf en kwantifiseer die
bestaan van verskeie verskynsels wat vermoedelik bestaan het by ervare
wildtelIers, bioloë en wildlewebestuurders en maak voorstelle met betrekking tot
die verbetering van data wat tydens duur lugopnames ingesamel word.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52027 |
| Date | 12 1900 |
| Creators | Reilly, Brian Kevin |
| Contributors | Van Hensbergen, H.J., Stellenbosch University. Faculty of AgriSciences. Dept. of Forest and Wood Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 363 p. : ill. |
| Rights | Stellenbosch University |
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