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

These levels of exploitation seriously imperilled wild populations along its whole
range. Consequently, Mexico imposed a ban to commercial hunting of wild
individuals in 1970, which is in place up to date. Also in response to that situation,
the species was included in the ESA as Endangered in 1970. At that time, this
measure reinforced Mexico’s policy for the recovery of the species. In order to
complement these actions, the Mexican government, in conjunction with NGOs and
national institutions, promoted the installation of captive rearing programs, meant to
serve as reservoirs for potential reintroduction or restocking programs. In addition,
many Natural Protected Areas have been decreed in Mexico in the last two decades,
and this has significantly increased the species area and habitat under protection.
These continuing actions sowed the seed for the recovery of this crocodile that recent
field evidence is demonstrating.
3. Field study results
Field surveys included ten States of Mexico, summing up 63 localities. So far, 40 new
localities have been recorded, for a total of 105 (IUCN had cited only 40 of those
previously reported). From the total known (historic) localities, the COPAN Project
visited a sample of 21.9% of these, and persistence of the species in all of them was
recorded. In addition, 24 localities were surveyed for habitat quality for the species,
and from these 57% were evaluated by the COPAN field team as with habitat apt for
C. moreletii. According to reports of these surveys, self-consumption fishing and
cattle raising appear to mildly affect the species, while urban development and
industry are the least compatible activities. Agricultural areas have historically altered
crocodile habitat in Mexico, and this factor was taken into account as will be
explained later.
4. Abundance and population structure
Abundance indices obtained by COPAN were moderate in most areas, with a single
surprising case of 38 ind./Km, which was not taken into account for further analyses
as it represents an obviously outlying value (see Figure 2). Averaging of abundance
indices reported resulted in 5.76 ind./Km and a wide interval of confidence (0.31 to
10.16 ind./Km). But as data did not show a statistically normal distribution, the
average and SD were discarded for further work. Besides, as arithmetical averaging
does not reflect actual frequencies of values, from the same database the Mode was
then calculated, and resulted in 3 ind./Km. Also, a general index of abundance could
be calculated as total individuals seen / total Km surveyed in the more than 60
localities in Mexico. This exercise gave a figure of 3.16 ind./Km. As this overall
index for Mexico was very close to the Mode, and much lower than the average, it
was used for further calculations, in order to keep a precautionary approach. Based on
COPAN results, a working estimation of wild population size for C. moreletii in
Mexico was conducted, though it is recognized that periodic updating may improve
the analyses we report here.
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