Ecological and anthropogenic covariates ... - GANGAPEDIA

Marked animals were accorded no exclusive treatment, since captures and subsequent
recaptures through photo-identification is a non-invasive technique.
5) Geographic and demographic closure:
Since the timing of this study preceded the gharial hatching season, the likelihood of
the demographic closure assumption being violated was low. Similarly, since the
study coincided with the dry-season (low-water level), the likelihood of animals
moving in and out of the study area was low, supporting the assumption of geographic
closure.
Identification Methods
Individual identification of gharial were made, primarily, by comparing natural
blotches and markings on the lateral scutes on the tail, and by using additional cues
like size classes, injuries and scars. Each of these encounters was photographed, given
a unique identity number and geo-tagged using a Global Positioning System (Garmin
GPS 72). Group composition data (number of animals in aggregations and size-class)
were collected. Gharial size-classes were determined by calibrating natural objects or
landscape features beforehand and by setting up measured reference markers at
basking sites and then estimating gharial lengths from photographs using the software
'ImageJ' (Wayne Rasband, National Institute of Health). Alternately, gharial body
lengths were also estimated from tail scute spoor (Bustard & Singh, 1977).
Individuals < 90 cm long were considered to be yearlings, those 90–180 cm as
juveniles, those 180–300 cm as sub-adults, and those > 300 cm as adults.
The tail of the gharial is laterally compressed, and on its sides, it has black markings
on a base of light to dark brown. Proximally, the tail has a double crest of projecting
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