Negative interactions between people and crocodilians have increased worldwide, but in Mexico there have been few systematic reports and no rigorous evaluation of this problem. We compiled information on negative interactions between people and the spectacled caiman Caiman crocodilus and American crocodile Crocodylus acutus from the Worldwide Crocodilian Attack Database for 1993–2018, and we investigated interactions in greater depth, through interviews with people in La Encrucijada Biosphere Reserve. We examined the relationship between the occurrence of negative interactions between people and C. acutus and the species' nesting season and abundance, and presence records. In Mexico, the frequency of negative interactions increases when anthropogenic activities occur close to nesting sites (< 30 km) and during the nesting season (February–September). In La Encrucijada, following negative interactions with crocodiles, the local inhabitants killed 30 crocodiles measuring > 2.5 m long in 2011–2012. The frequency of negative human–crocodilian interactions was not correlated with the abundance of crocodilians but was correlated with the number of presence records of crocodiles. Strategies to minimize these interactions include warnings at nesting sites, increased monitoring of anthropogenic activities during the nesting season, and management of nests to prevent them being destroyed by people.

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Nesting of the American crocodile (Crocodylus acutus) is affected by natural and anthropogenic processes. In Mexico, few studies exist on reproductive traits of wild populations. We assessed the key reproductive characteristics ofC. acutusin the La Encrucijada biosphere reserve and the environmental and anthropogenic factors that influence them. From February to June 2014, we searched for nests in the reserve. Clutch incubation temperature was recorded by data loggers and climatic variables were obtained from La Encrucijada meteorological station. Additionally, outside the study area, net primary productivity was obtained for different sites in Mexico to relate it to clutch characteristics. We found 34 nests in nine nesting areas. Egg laying occurred in March, and hatching took place from mid-May to early June. Mean clutch and eggs characteristics are among the higher reported forC. acutus. Some egg attributes had a relationship with the net primary productivity. There was no relation between hatching success and external and internal characteristics of the nest. A high percentage of nests was poached (50%) mainly for egg consumption and fear of crocodiles, and the nests closer to the river, trees or human settlements are more likely to be poached.

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Ticks are common ectoparasites of amphibians and reptiles but very few reports of such parasites on crocodylians exist worldwide. Herein, we report the first detailed observations of Amblyomma dissimile Koch, 1844 on the 3 crocodylian species present in Mexico, with the first report of tick parasitism on Crocodylus acutus and the second on Caiman crocodilus chiapasius. This is also the first report of A. dissimile in the state of Quintana Roo. Proportions of infested individuals found in this study ranged from 0.51 to 1.96%, suggesting that tick parasitism in crocodylians is likely opportunistic and occurs when individuals leave the water for terrestrial activities. Tick parasitism does not represent a major threat to crocodylians. The increasing habitat destruction/fragmentation and cattle expansion in southeastern Mexico, however, could increase tick populations and trigger tick parasitism and tick-borne diseases in herpetofauna and other vertebrates, including humans. Thus, studies are needed to better understand these relationships.

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