NEW RECORDS OF HUMAN-CROCODILE INTERACTIONS IN MEXICO FROM 2018 THROUGH THE FIRST HALF OF 2021

.— The growing human population and its associated economic activities have increased human-wildlife interactions. Herein, we provide new records of human-crocodile (HC) interactions in Mexico from 2018 through the first half of 2021. Fifty-one cases were recorded in this study; 2018 had the highest number of cases (n = 19), and 2021 (the first half) had the lowest number of cases. The states of Tamaulipas and Quintana Roo on the Gulf of Mexico represented 40% of the cases, while Oaxaca and Nayarit on the Mexican Pacific coast represented 22% of the cases. Male victims (n = 32) were more commonly associated with human-crocodile interactions than females (n = 10). Forty-four cases were non-fatal and only seven were fatal. As far as we know, our records of HC interactions increase the number of conflicts in Mexico to 250 cases.

The growing human population and its associated economic activities have increased human-wildlife interactions (Weladji & Tchamba, 2003). Wildlife conflicts likely increase when an ever-increasing number of human populations gather in a limited area close to natural habitats (Inskip & Zimmermann, 2009), especially with large predators (Lamarque et al., 2009). From a human perspective, some interactions are positive, and others are negative (Flores-Armilla et al., 2020). The interactions that are perceived negatively are referred to as human-wildlife conflicts (Inskyp & Zimmerman, 2009), when these interactions have negative effects -either real or perceived-trigger human reaction that can result in harmful impacts on wildlife individuals and populations (García-Grajales, 2013;Morzillo et al., 2014).
Some of the causes that contribute to the increase in this type of conflict are human population growth (Fukuda et al., 2014); the transformation of undeveloped lands, coastal rivers, swamps and shorelines for urbanization (Pooley, 2015;Redpath et al., 2015); and human encroachment into crocodile habitats for tourism, recreation, agriculture, fishing or other purposes (Wallace et al., 2011;Fukuda et al., 2014). Unfortunately, human expansion has put pressure on crocodilian habitats, reducing the natural physical space available. Despite this pressure, crocodile populations have recovered during the last two decades thanks to law enforcement and conservation efforts, such as permanently banning crocodile hunting in the 1970s.
As a result of this recovery of crocodilian populations, along with a growing human population and its associated economic activities, negative interactions between people and crocodiles have escalated (González-Desales et al., 2021). These conflicts should receive attention from the federal government to improve public safety and prevent the extermination of crocodiles by local communities (García-Grajales, 2013), who often react emotionally to the incidents (Lamarque et al., 2019).
It is not possible to track the number or severity of interactions between crocodiles and humans if there is no concerted effort to monitor new reports and log the data (Porras-Murillo and Mata, 2020). Countries such as Australia, as well as several nations in Asia, Africa and Latin America are also facing crocodile species attacks, but incidence rates are unknown due to a lack of reporting (Caldicott et al., 2015;Porras-Murillo and Mata, 2020). In Mexico, between 2000 and 2018, 149 unprovoked crocodile attacks on humans were registered, with 102 cases corresponding to the Pacific coast and 47 to the Gulf of Mexico coast (García-Grajales and Buenrostro-Silva, 2019). Although Pooley et al. (2020) provide an update of human-crocodilian interaction in Latin America, their records for Mexico are questionable, mostly because of their numerical inconsistencies. Therefore, we provide new records of human-crocodile (HC) interactions in Mexico from 2018 through the first half of 2021 and an update on incidents for the country.
We compiled the publicly available data on incidents of HC interactions from 2018 through the first half of 2021 (Table 1). Our data compilation was obtained through various methods: 1) interviewing victims, witnesses, police officers or rangers involved in the incidents by telephone or email; 2) searching media sources, such as newspapers, magazines and websites (Croc-Bite database, CrocBite 2021); 3) communicating in person with some researchers; and 4) personally experiencing attacks in our respective states (Jalisco, Guerrero and Oaxaca). All incidents were grouped and classified by date; location; sex, age, activity and origin of the affected person; time (daylight or nocturnal); presence of witnesses; type of crocodile habitat; region; political unit (municipality); and type of attack (fatal or non-fatal). We grouped the victims into six age categories (1-10, 11-17, 18-40, 41-60, >60), based on the economically active ages in Mexico. Furthermore, when it was possible with nonfatal attacks, we classified the type of outcome as disabling (the extent of the loss of tissue continuity resulted in amputation or the impairment of motor functionality, limiting or impeding daily physical activities) or non-disabling (no amputation or lack of motor function, which allowed the victims to continue with daily physical activities). In all cases it was possible to determine the species and total length of crocodile involved.
Fifty-one HC interactions were recorded from 2018 through the first half 2021; 2018 had the highest number of cases (n = 19) and 2021 (in its first semester) had the lowest number of cases (n= 7). The Gulf of Mexico had the highest number of cases (n = 29), and the Mexican Pacific coast had the lowest number (n = 20), highlighting two additional cases that occurred inside the continent (Coahuila and San Luis Potosí). Tamaulipas and Quintana Roo on the Gulf of Mexico represented 40% of the cases, while Oaxaca and Nayarit on the Mexican Pacific coast represented 22% of the cases. Regarding the municipalities, Tampico had the greatest number of cases (n = 7).
Male victims (n = 32) were more commonly involved in incidents of HC interactions than females (9), however, a small percentage (18%), it was not possible to identify the human sex involved because of the features of the report. Forty-four cases were non-fatal, and only seven were fatal (5 males and 2 females). The most common activities at the time of non-fatal incidents were fishing (22%), swimming (14%) and walking near the water's edge (10%). The ages of the victims involved in the majority of the attacks ranged from 18 to 40 years old (32%), followed by those from 41 to 60 years old (20%). With a significant percentage of victims, it was not possible to determine their age (32%).
With respect to the injuries caused by non-fatal attacks, the highest proportion of victims (80%) showed non-disabling injuries, with only two cases resulting in the amputation of a limb (disabling sequelae). Regarding the months in which the attacks occurred, June and July presented the highest number of crocodile attacks (11 cases, respectively), and in February, no attacks occurred over the years evaluated. Both, fatal and nonfatal attacks took place more commonly in the daytime (88%). Of the crocodile species involved, Crocodylus acutus and C. moreletii had the same number of cases (n = 25), respectively. Only, in one case, it was not possible to identify the species involved in the incident. In recent years, the number of HC incidents have been increasing in many parts of the world (Langley, 2005;Pooley, 2015;Das & Jana, 2018); however, the statistics are skewed because numerous episodes involving crocodilians go unreported or     are poorly documented (Fukuda et al., 2015). Also, widespread access to social media makes interactions more visible, leading to unresearched reports in real time (Porras-Murillo & Mata, 2020).
The pattern of HC interactions described here is like the trend shown by Garcia-Grajales & Buenrostro-Silva (2019) in Mexico, as well as other countries, such as Costa Rica (Porras-Murillo & Mata, 2020). Data for the American alligator (Alligator mississippiensis) in the United States show that most of the people attacked were in the water or at the water's edge (Conover & Dubow, 1997). Caldicott et al. (2005) found that in Australia, most attacks occurred when people were in bodies of water or on the shore, especially during fatal attacks. Similar data have been found for HC incidents in Mexico (García-Grajales & Buenrostro-Silva, 2019).
Most of the attacks described here involved men, which is similar to the data gathered by Fukuda et al. (2014), García-Grajales & Buenrostro-Silva (2019) and Porras-Murillo & Mata (2020). Additionally, as reported by Fergusson (2004), Caldicott et al. (2005), García-Grajales & Buenrostro-Silva (2019) and Porras-Murillo & Mata (2020), most of the attacks took place during the day. In Mexico the prevalence of specified economic gender roles in rural areas such as agriculture and fishing, favor males; more specifically, men 18-40 years old who are more likely to be engaged in high-risk jobs because they are the most economically active group (García & Buenrostro-Silva 2019). For these reasons, we found this group to be the most vulnerable to HC incidents. Moreover, fatal and non-fatal attacks happened more frequently in the daytime, presumably because some activities such as fishing and swimming were more commonly conducted during daylight hours (Fukuda et al., 2014).
The peak periods for HC incidents (March to September) coincide with the species' nesting season and with the beginning and end of the wet season on both coasts in Mexico. These connections can be explained by three hypotheses: first, during the rainy season, crocodiles are widely dispersed because of a rise in water levels, and the possibility of negative HC interactions increases because of this. Second, crocodiles are ectothermic and are more active (and consequently, hungrier) during the hotter months of the year; therefore, the possibility of negative interactions increases during this period. Third, although there is little evidence, crocodiles are more dangerous during the breeding season because the large adult females guard their nests and fast until their hatchlings are ready to emerge (Pooley, 2015); therefore, they are intolerant to humans approaching their nesting areas, and as a result, are more aggressive towards people (Lang, 1992). According to Caldicott et al. (2005), it is uncommon for crocodiles to attack and eat humans, and data reported here showed that most incidents are due to a person's intrusion into a crocodile habitat.
Most coastal states in Mexico where there is a natural distribution of crocodiles has presented at least one case of HC interaction, but there was one curious case in Piedras Negras, Coahuila, in a state that is not included in a geographical distribution area for any of the crocodile species. Our hypothesis, however, is that a crocodile had been released into the Río Bravo generating conditions for possible negative interaction, due to the passage of immigrants into the United States.
During the time in which this work was revised (August-October 2021), other three incidents took place in Puerto Vallarta, Jalisco (n= 1), Nuevo Vallarta, Nayarit (n=1), and Villahermosa, Tabasco (n= 1); therefore, the number of cases increases to 250 cases. It should be noted that in these cases there were people in drunk, foreigners and homeless involved.
Understanding the underlying causes behind the increase in HC interactions will require careful logging of the events leading up to each incident, which is why a national, standardized database is so important (Porras-Murillo & Mata, 2020). An updated dataset would also help authorities identify priority areas, to facilitate targeted mitigation. From our new records, we believe that the environmental and tourism authorities have enough information to develop solutions for prevention and coexistence rather than focusing solely on controlling crocodile populations.
Similar to the proposal of Fukuda et al. (2014), public education through a variety of media outlets (e.g. loca television, radio, newspaper, and websites) will be the most effective means of informing the public about the potential danger of waterrelated activities in crocodile habitats.
Finally, we must use the information already available to transform negative interactions and conflicts into coexistence between crocodiles and humans (Porras-Murillo & Mata 2020). As far as we know, our records of HC interactions increase the number of conflicts in Mexico to 250 cases from 2000 to the first half 2021.