size: 5036KB - Crocodile Specialist Group

79
Values of the life lable parameters (lr and m^ in Equation 1) and the assumed confidence mnges were
denved from the lilemture on the Nile crocodile (6rdarn,l968, Hutton,l988) and otier crocodiliars
(Nichols q 4!, 196, Smilh and Webb, 1985, webb 9l!4!., 1989). These are summarised in Table l.
Some imprcvement to existing information on tho gmwth curve for the Nile crocodile was considered
essential and this was derived afresh using previously unpublished daia on size-relai€d growth increments
from scute sections t.ken ftom Cahon Bassa crocodiles. Grcwlh in crocodiles was assumed to lake the
fom:
length(netres\ = 13,2 + 0,004C) . (1, - O,ge-ctl -.. -). .
This (Craig g!d., 1992) is most sensitive to lhe value of g, which was the subject of the renewed
estimate.
Table 1. Values used to estimate life-table Dammeters
PARAMETER VALUE RANCE % IMPORTANCE
I Cbs$ .ne qihr
s 0,093 0.073 - 0,126
2 ACe ar n$rnnry (flm ll l6 1.2 - 20
45-65 0,1
0.1 0,025 0,175 41.5
22,1
0,99 0.s8 - 1.0 0,8
7 Ess los 0,t 7 0.1l - 0,23 02
0,7 06 - 0,8 1,0
0,53 o.2
10 Esg inwiability 0,1I 0,09,0.r3 0,t
-128 -136 - -120 0,3
Equation 1 was solved for e' to oblain fi estimate of potenrial rate of increaie for the Nile crccodile. This
was repeated for upper and lower mnge values for all panmetets in which uncertainty was assum€d.
Regression coeffiicients of estimated e' against the confidence interval of each uncertain pammeter were
used to give overall approximale confidence limits to lhis estimate, and to estimate the relative
contributions to this uncerlainiy of the uncertainty of individual p:uamerers (Craie glel,1992).