Human–crocodilian interactions 793
LED white light to search for the brightness of crocodilian eyes by projecting the light beam between the boat and the mangroves (Chabreck, 1966). When we located eye-shinewe decreased speed and slowly headed towards the individual, to identify it (differentiation of the species was by the pres- ence of bony crests and ossified inter-orbital bridge in the case of C. crocodilus, and the absence of these characteristics in C. acutus). The 28 kmof the ElHueyate estuarymonitored were the same stretch of the estuary surveyed in earlier stud- ies (Martínez-Ibarra et al., 1997; Sigler & Martínez-Ibarra, 1998; Peña, 2011).
Results
FIG. 1 La Encrucijada Biosphere Reserve, with the locations of the six negative interactions (cases) between people and crocodilians recorded during 2005–2018 (Table 2), five with American crocodiles Crocodylus acutus and one (Case 5) with a spectacled caiman Caiman crocodilus chiapasius, and nests recorded in 2014. For details of the six cases, see Table 2.
species has been recorded (Sigler & Martínez-Ibarra, 1998; González-Desales et al., 2016a,b), and therefore we examined human–crocodilian interactions and abundance of crocodi- lians only in the core zone. During October 2013–September 2014 we conducted
unstructured interviews in the principal settlements on the margin of the El Hueyate estuary (Aztlán, Brisas del Hueyate and La Ceiba) with 22 people (five women and 17 men; 22–51 years old), who were either involved in incidents, or relatives of those involved. As the total population in these settle- ments is 543, (CONABIO, 2014), we interviewed 4% of the total population. We focused on obtaining information about the date and location of any interactions, any actions taken against the crocodilians, activities that people were performing at the time of the incidents, and information from people that witnessed the events. From 2014 onwards we have made 2–3 visits per year to monitor reports of any additional negative interactions. We have knowledge of an incident that occurred in March 2017 but we have not yet been able to interview the family members of the affected person. The abundance of C. acutus and C. crocodilus chiapasius
was analysed using the Relative Abundance Index Rsp/ travelled distance, where Rsp is the number of records of each species and travelled distance is the total number of km travelled during monitoring (Sigler et al., 2011). We obtained relative abundance data of both crocodilians from literature (Martínez-Ibarra et al., 1997; Sigler & Martínez-Ibarra, 1998; Peña, 2011) and our fieldwork in 2014. In ElHueyate estuary we conducted 24 surveys during March–October 2014 during the nesting season of C. acutus and C. crocodilus chiapasius. The surveys were performed from a 6 m boat with a 15 HP outboard motor, using a 19
Negative interactions with C. acutus in Mexico CrocBITE (2018) contains 121 records of negative interac- tions between people and C. acutus in Mexico during 15 August 1993–8 June 2018, and no reports of interactions with C. crocodilus chiapasius. Of the 121 records only 117 in- cluded geographical location. There was a significant nega- tive relationship between the frequency of interactions and distance to the nearest nesting site (r = –0.76;P,0.05); i.e. there were more interactions closer to nesting sites. There was also a significant relationship between the number of negative interactions and presence records of C. acutus (r = 0.92;P,0.05). There was no significant relationship between the frequency of negative interactions and the relative abundance of C. acutus (r = –0.49,P.0.05). With respect to the date of incidents, there were significantly more negative interactions during the nesting season than at other times (χ2 = 22.87,df = 1,P,0.001; Fig. 2). Regard- ing the socio-economic characteristics of the 70 municipal- ities where there were negative interactions or presence records, the economic activity ‘services’ was the most com- mon in municipalities where interactions (24 munici- palities) and sightings occurred (34 municipalities), human population density was lower in municipalities with nega- tive interactions (mean 0.9 ± SD 1.1 inhabitants/km2), and in municipalities with negative interactions 57.1% of the adult male population (15–64 years old) had a mean of 7.4 ± SD 1.2 years of education.
Human–crocodilian interactions in El Hueyate estuary
We obtained data on the relative abundance of C. acutus in El Hueyate estuary for 1997, 1998, 2002 and 2008–2010, with 1.14–7.11 individuals per km, and for C. crocodilus chiapasius for 2002 and 2008–2010, with 0–2.42 individuals per km (Fig. 3a). The relative abundance index calculated for our fieldwork in 2014 was 1.5 C. acutus per km and 2.71 C. crocodilus chiapasius per km. We obtained information on six negative interactions between people and crocodilians in El Hueyate estuary
Oryx, 2021, 55(5), 791–799 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319000668
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