size: 5036KB - Crocodile Specialist Group

101
necessary as the endurance of the foot tags was unknown. An aluminium tag which carries
an unique combination of rcflective colours was also applied to both sides ofthe head of each
animal by suture with surgical wire. This technique is essential in matk_relocauon procedure
as-the head is the only part of the body that is consistently visible. Tagging had no apparent
effect on the performance or survival of the anjmal. Head tags ci- bJ apptieO without
causing trauma or bleeding. No moiality occured as a direct risult of tagging.
Animals_were then held in damp jute sacks, transported by boat and released in balches at
pieviously s€lected sites throughout the estuary. The rcleases were made in mid-February
and early April 1992. The second batch was delayed for the ar:rival of the radios, transpon
across 70 km of lake and to allow initial monitoring of the first batch to proc€ed.
"Recapture"- is in
th9 form of resighting. The sarnpling procedure involves searching
s€ctions of the shoreline of the estuary at night with a ipo;-light and all crocodiles seen are
classified by size. Tags become identihable at approximately l0 m ahd the identity and
location of tagged individuals is specifically recorded.
Physical recapture of tagged animals js attempted at intewals of > 60 days to reweigh and
remeasure individuals for growth i.crements and to repair damaged or losi tags. Capiure of
wild crocodiles of similar size is attempted whenever possible diring night sampling. Such
animals are prccessed, tagged and rcleased at the site of capture.
The data takes the form of a series of ,,capture,, histories which are used to calculate survival
estimales bas€d on Jolly's closed model (Arnason and Baniuk lg7g).
Radio tansmitters were attached to 25 selected individuals before release. The transmitte$
(Model FRT-S; I-otek Engineering, Aurora, Canada) are small (160 g), sealed units designed
for aquatic strrcies. They are mounted dorsally on a neck collar witl- i t -s cm wHp antenna
directed backwards. Problems have been encountercd with rotation of the colhrJ although
acc€ptable range is obtained even when this has occurred and with prematurc rotting oia
degradable insert.
Each transmitter is located xt approximately 3 day intervals. The date, location and activity
of each fix is recorded, providing a similar series of capture histories. The data are often
retrospe.ctive as animals are seldom seen and are inferrej to be alive when subsequently
found at another location, The data are analysed following a restricted version of the iaplan
pl""dg."
:.lr:r:t
9lrlribed by pollock, Winrerstein, Bunck & Curtis (1989) and pollock,
Nichols, Brownie & Hines 0990).
CURRENT STATUS AND PRELMINARY RESULTS
149 l;€Eed animals were rcleased in two batches - g2 in Feb 'g2 and 67 in ADnl. 124
animals werc tagged only with visible head-tags and the rcst (25), aI had ndio tiansmitrers
attacted (/ l5 with h/rags and l0 without). Monitodng started in late March and has
continued more or less continually ever srnce.
l) Survival
A total of 374 locations have since been made on 89 individuals, The difference in technioue
is immediately apparent, for example only 2 animals have been located on 5 or more
ocesions while 17 radio-tagged animals have been located on more than 5 occasions, up to