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132 Table 4. Details of night counts in the Kilombero river, Tanzania' 1990 (CV = l97o\. Section Length (km) Nos. Cr0(5 Cro(s/km d' Camp-Jtlnction 2 36 18 324 Junctiun-Tree 36 5't6 Tree-Single Channel 2 2'l 18.2.25 '7.5 Channel-Game camp 2 l5 56.25 Came camp-end 1.5 l8 12 144 Total 9 Table 5. Detdls of night count - Lake T{galallt (CV = 2.197o). Section Length (km) Nos. Crocs Cr(,Ls/km dr Camp-Entrance 7 435 62.12 386t.734 Entiance-Camp 6 381 63.5 4032.250 Total 816 r25.62 7893.984 Table 6. Details of ni,rht counts on the Rufiji river Section Leng(h (km) Nos. Croqs Crocs/km Kidai-Tagallala 9 304 Nzerakera-Rufij i 12 168 16.6 The channelengths and lake-shores suNeyed during the aerial count in the lower Rul'rji total 105 km. It is estimated that 30 - 50 % were not coveted, especially where the river has fbrged a new cou6e. The lower e,stimate would put the shoreline and channels at 135 km. Speculation on the total amount of crocodiles in the lower Ruflii al.rne is as follows: Total number of crocodileseen tiom the air 804 Channel correction (1.3) 1 045 Night count correction (4.2) 4 390
133 The numbers of crccodiles during a night count can be as little as l0 % ofthe total population but is usually between 30 and 60 % (Hutton and Woolhouse, 1989). This woutd give upper and lower estimates of 7 024 and 5 707 respectively. GENERAL There were a numbe. ofproblems associated with this survey. All ol these tend to indicate that the count were underestimates and they are detailed below. Observers, although proficient and experienced on large mammal counts, were new and inexperienced counting crocodiles. The correction factor for the one observer tested dudnp a tandem count was 4.1. Many ofthe rivers were surveyeduring the middle of the day. This was because of the long distances involved, both transit and survey. It is known that many crocodiles will return to tbe water during the middle ofthe day (e.g. Cott, 1961) where they are more difficult to spot from an aeroplane. The tightly meandering nature of many of the rivers surveyed meant that the percenrage covered was less than ideal. This possibly leads to under-estimation which I have attempted to correct (albeit subjectively) by estimating a percent covemge for each river. Densely wooded or reeded banks with overhanging trees als,, ob\cure(l the view (rf some of the riverl. Owing to several delays this suNey continued into the first of the ,'short rains'.. This meanthat sone surveys were carried out either while it was raining or under very overcast conditions. Although there is no data it is considerecl that crocodiles are more dillicult to sllot under these conditions. If any survey of crocodile densities is to be used lor monitoring trends in a population then it should have some measure of precision. The co-efficient oi variation (CV). which is the standard eror expressed as a percentage ot the counr. is a commun method (Graham. lggg). In crocodile counts estimation ofthe CV can be achieved in two ways but it should be stresse{.I that these CVs are not corrparable betwee nethods_ l). The double counting or tandem method is the simplest and reqlires that one observet record three categories of sightings crocodile seen by himself,uld not the other observer, crocodileseen by the other observer but not by himself and crocodilqseen by both observers (Magnusson. Caughley and Grigg, 1978; craham, 1988). In pracrice this means that one observer must point out every crocodile seen to tle obseNer/aecotder or both observers independentjy record sightings on maps. 2). The second method is to divide the river iDao sub,sections and use these as samDle counts to estimate the CV (Graham, lg88) Sample counting is problematic as some dvers are lacking noticeable t'eatures to form the saople boundaries and it would be very difficult to replicate these in subsequent surveys. The CV's obtained by this metbod become very large if there is uneven (listr;bution of crocodiles along the river. Tandem counting has the advantage that observer errors can be estimated and a correction factor calculated. It allows some estimation of variance between ohservers and the CVs are used to decide if counts are precise enough to indicate trends.
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CROCODILES Proc€€dings of the l
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FOREWORD The two volumes of this PR
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Elsey, R M, McNease, L & Joanen, T:
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CFAZ CIIAIRMAN'S OPENING COMMENTS F
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PRESENTATION FROM THE MINISTER OF E
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Fitting Curves to crocodilian Aqe-s
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7 a.set of uniforrn random nunbers.
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2. VON BERTAI"ANFFY MODEL FOR GROWT
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11 The -following four tables give
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UNIFoRU sarnpling MEDfUM sahpl ing
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15 Sectior IV: Actual Croc Data, l,
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1'l (ii) Linear regressron. same ra
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1,9 rejecting nufl hypotheses that
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21 Brisbin, I.L., Jr., c.c. White,
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Iength lthich corresponds to the ni
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25 Because of lack of funds Eo carr
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27 Despite the fact that during a p
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29 FIGURE N9 2 BLACK CAIIIAN POPULA
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I'Effect of diets conplenented vith
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3i Two of the 6 x 2 m. tanks four e
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: .i ; -3, E .-1 t FFdF !_9 + + + +
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10 Table IV : fl aernathological Re
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4l 4.- CONCLUSIoNS 1) The most favo
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43 THE INVOLVEMENT OF RURAL COMMUNI
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45 the rainy season and, in conhast
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47 difficulties and the isolation o
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49 Eacb time that one of the villag
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51 CONCLUSION Naturally, these rcsu
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53 LONG-TERM POPUT-A.TION S'ruDIES
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55 'Ile study reporled here was des
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5'7 made of transmilteFequjpped ndm
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59 wilhin the reservoir was lypific
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6l However the use of such winter d
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6.1 surface to breathe (Kellogg 192
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65 ACKNOWLEDGMENTS This work was su
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Murphy, T. M., P. M. Wilkinson, J-
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69 t 3 ^ 3 :9s 3P o ;x !B 'rr.l9 3e
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7l FoDd B + i Poud C I Pltllr. l. U
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73 9 October 1991 L t' I L t' 26 Ma
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75 80 -r- 1987-88 + 1991-92 t -40 .
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77 GROWTH RAIE OF CAIMAN (Caiman cr
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79 Values of the life lable paramet
Page 87 and 88: 81 REFERENCES Craig. G.C., D. Si.C.
Page 89 and 90: 83 CUMATIC F{w L Stirldi .6.aiDS EF
Page 91 and 92: 85 2. Behavioral facilitation of re
Page 93 and 94: 87 TeEperature, hy&ic coaditionq aa
Page 95 and 96: 89 The sexual behaviors of irdividu
Page 97 and 98: 9l 2o I E F conuor o.r r.0 r0.0 a0.
Page 99 and 100: 93 Referetrces Ber!, H.A. (1990). T
Page 101 and 102: 95 GROWTH RATES AND BODY CONDITION
Page 103 and 104: 97 LIPID AND FATTY ACID COMPOSMONAL
Page 105 and 106: 99 be removed sustalnably, provided
Page 107 and 108: 101 necessary as the endurance of t
Page 109 and 110: 103 Table 2. The ratio of first sig
Page 111 and 112: 105 3) Movement and dispersal The r
Page 113 and 114: 107 Disease Trend$ on Crocodite Far
Page 115 and 116: 109 Fuigol and other dermar,?ir - d
Page 117 and 118: 111 THE FEEDINC ECOLOGY OF TWO NILE
Page 119 and 120: 113 areas outside the National park
Page 121 and 122: 115 been done for a tlpical populat
Page 123 and 124: 117 ACKNOWLU)GEMENTS This study was
Page 125 and 126: 119 THE STATUS AN'D DISTRIBUTION OF
Page 127 and 128: Figure l: Crocodile Survey - Tanzan
Page 129 and 130: 123 :rD ES e € a 69 PE e 3 Er t !
Page 131 and 132: 125 Ruaha River (Figure 2) The Ruah
Page 133 and 134: 127 lake Mtera (Figure 4) This is a
Page 135 and 136: t29 with 6shermenand subsistence f'
Page 137: lil Kilimmjaro/Tanga Region Pa gani
Page 141 and 142: 135 REFERENCES Chabreck, R.H. 1966.
Page 143 and 144: l -37' 3.1.4 lagal Trad.e Local tra
Page 145 and 146: l.l9 In order to gecure credibility
Page 147 and 148: l4l 'rould apply to 6kins of good h
Page 149 and 150: 143 This infdrrDation cduld be supp
Page 151 and 152: l.l-s ].nternational reEplfnstbitit
Page 153 and 154: t4'/ illegal sttjns in their pr,r,d
Page 155 and 156: 149 CROCODILE SKIN INDUSTRY IN ETII
Page 157 and 158: l5l Table 2. Ouotas for Ethiopian c
Page 159 and 160: 153 depriving EWCO of incentive for
Page 161 and 162: 155 A PRELII{] NARY ASStsSS!.IENT O
Page 163 and 164: 15',7 Origin l Payert lltosk Breedi
Page 165 and 166: 159 dropped, producing 23 and l9 eg
Page 167 and 168: l6l This figure ts even lorrer than
Page 169 and 170: 163 =z 3F \riciNoraj {
Page 171 and 172: 165 References EArr,ER, R.D. ( 1976
Page 173 and 174: t6'1 IPPIIDIX tt BtoBtE cI0@(DILX n
Page 175 and 176: l()t/ Backqround l,lelano5uchus nio
Page 177: t7l The numbers of black cainan c'b
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