Myanmar - Global Tiger Initiative

Part 6: Historical Data, Field Survey Methods and Data AnalysisFrom the training a group of six talented young forestry professionals were selected to formthe first roving tiger field survey team to participate in field assessments for tigers at selectedforest sites across Myanmar.6.7 Methodology. The surveys were intended to determine presence-absence for tigers, andrelative abundance for prey species, so as to permit the evaluation of study areas for theirpotential for tigers. The surveys were not intended to determine numbers of tigers in the reserves.Tigers, like other tropical mammals, are generally difficult to observe directly due to theirrarity, cryptic behaviour, partial nocturnality and avoidance of humans (Griffiths & vanSchaik 1993; Schaller 1967). A combination of indirect and direct survey methods was usedto detect tigers and other large mammals; potential prey species.Field observations of tigers can be categorized so as to facilitate interpretation of theirecological status. Four types of observations are given in Table 6. Tigers may be detected ornot detected by a given survey technique. The detection of tigers confirms presence but mayor may not indicate a reproductive population. Where tigers are not recorded, this couldindicate problems with sampling, for example where tigers are missed due to extreme rarity,or true absence.Where tigers occur at densities under 0.38 tigers/100 square kilometre, very large amountsof sampling with camera-traps (>1,000 trap nights) needs to be done in order to detect them(Carbone et al. 2001). In this study sampling of >1,000 trap nights were not feasible so thattigers might not be recorded at some low-density sites even though they were present.Table 6. Interpretation of Tiger Population Status from Field Observations.Observation Population Status Interpretation1a Tigers recorded Reproductive population Indicated by observations ofpregnant females, juvenilesand/or cubs1b Tigers recorded Present but not necessarily Indicated by observations ofreproductive adult male or non-pregnant adultfemale individuals2a Tigers not recorded Low density, ecological Tigers may be present at loweffective absence density but are not recorded dueto sampling errors e.g. tigers notpresent in survey area. A tigerpopulation may be disrupted, sexratios skewed, or individuals havedifficulty finding mates so thatreproduction is not possible(Allee effect)2b Tigers not recorded True absence Tigers are not recorded over aperiod of monitoring at a site27.