Proceedings of the 18th Working Meeting of the Crocodile Specialist ...

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Figure 3. Potential distribution of Morelet’s Crocodile in Mexico 6. Potential distribution: available habitat As 49% of the GARP area was found to be currently altered (see Figure 4), it was discarded, thus leaving a 51% in comparatively good condition for C. moreletii. Assuming an analogous proportion of shoreline length still in good shape, the cut yielded a more realistic, precautionary 25,227 Km of available habitat length, and this figure was then used for subsequent estimates. Nevertheless, it is important to mention that COPAN informed having recorded Morelet's crocodiles also in altered areas; thus, habitat might be somewhat underestimated by our calculations. Figure 4. Potential distribution of Morelet’s Crocodile in Mexico, minus areas with agricultural and urban disturbance. 259
7. Population estimates for each country in the species' range Based on the previous calculations, the value of 3.16 ind./Km, was considered as an overall index for Mexico (very close to the Mode and much lower than the average). It was used to estimate total population size in Mexico as shown below: 7.1. Mexico Abundance index used = 3.16 ind./Km (near Mode, from field data by COPAN). Suitable habitat length, precautionary estimation by GARP-GIS = 25,227 Km. Total animals estimated in the wild: 79,718 individuals. Total of adults estimated in the wild (19% of total, proportion from COPAN Project): 15,146 individuals. Similarly, with available published data, calculations were done for Guatemala and Belize, as follows: 7.2. Guatemala Abundance index used = 2.078 ind./Km (average of values cited by Lara, 1990). Suitable habitat length inferred from literature data = 6,994.5 Km (from data on extension and degradation of the Peten; Castañeda-Moya, 1998). Total animals estimated in the wild: 13,911 individuals. Total of adults estimated in the wild (19% of total, using proportion from Mexico as a surrogate): 2,643 individuals. 7.3. Belize Abundance index used = 2.63 ind./Km (from Platt, 1998). Suitable habitat length inferred from geography = 3,347 Km. Total animals estimated in the wild: 8,803 individuals. Total of adults estimated in the wild (19% of total, proportion in Mexico as a surrogate: 1,673 individuals. 8. A total wild population estimate From data and calculations explained above, a tentative global figure of 102,432 (for a downward rounding of ca. 100,000) individuals of all ages in the wild was estimated for the whole range of the species. From this value, an estimated total of 19,462 (downward rounding of ca. 19,000) adult individuals were calculated. The latter figure lends support to earlier considerations by experts made in the 1995 workshop and to subsequent work summarized by Ross (1998) departing from consultations with experts, both indicating that in excess of 10,000 free adults were thought to exist within the species’ range (see IUCN Red List, 2005, online). 9. Prospective dynamic modelling of potential population trajectory Current data on natural history and fresh field information from COPAN on wild populations, and from literature in the case of Guatemala and Belize, were input into the Vortex 9.42 program (Lacy et al., 2003) to generate and initial exploratory population trajectory model for C. moreletii. 260
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