Science and conservation of Amazonian crocodilians: a historical review

Abstract

Crocodilians represent one of the oldest extant vertebrate lineages. They have co‐existed with humans throughout the Amazon basin for thousands of years, often having a strong cultural and economic influence on people's lives. Shifts in the socio‐economic and political reality of the Amazon basin during the last century have led crocodilian populations to face large variations in their numbers according to different levels of exploitation and strategies for their conservation. This article reviews the scientific knowledge obtained between 1945 and 2019 on the biology, conservation and management for the four Amazonian crocodilian (caiman) species (Caiman crocodilus, Melanosuchus niger, Paleosuchus palpebrosus and Paleosuchus trigonatus). It provides a general overview on past and current population status and research efforts involving caimans in the Amazon basin and discusses perspectives for the future. The most significant studies on the ecology, genetics and management strategies are examined in more detail and this information is contextualized to provide an overview of the most relevant findings that might explain caiman population trends over the last 75 years. Systems for sustainable management in the Amazon basin have been discussed for the past 20 years, but remain rarely applicable. It is necessary to develop new ways to maintain healthy caiman populations through innovative management programmes. Sustainable harvesting of wildlife has been shown to promote conservation targets, especially those initiatives based on community co‐management. In this article, we propose some general guidelines for future management schemes, in the expectation that the information provided by the scientific community will be considered fully without political agendas determining the priorities.

Physiological stress response in free‐living Amazonian caimans following experimental capture

“…If high levels of corticosterone are associated with high phenotypic plasticity of C. crocodilus , this is an issue to be examined. This species has the largest distribution among caiman species, and is widespread in the American continent (Marioni et al, 2021), including in highly anthropized environments, such as several small polluted streams that flow through urban areas of Manaus (Oliveira et al, 2021).…”

“…In Amazon, these caiman species have a historically negative relationship with human populations, especially those found along the tributaries (riverine communities) that have imposed a remarkable threat to these natural populations, such as intense hunting for meat consumption and habitat destruction, especially for M. niger , one of the largest Amazonian predators of the Neotropical region (Mendonça et al, 2016). Despite the anthropic interferences, caiman populations are recovering, and in Brazil, they are now classified as a Least Concern species based on International Union for Conservation of Nature (IUCN) guidelines (Marioni et al, 2021).…”

Hidden in plain sight: Integrated population models to resolve partially observable latent population structure

“…We believe the additive structure used in the model is appropriate because when given the opportunity, alligator hunters generally select for relatively larger size classes that have the highest survival rates, based on the few existing crocodilian demographic studies (Briggs‐Gonzalez et al, 2017). Moreover, multiple historical examples demonstrate that crocodilian populations are relatively sensitive to overharvest consistent with additive mortality, particularly with a fixed‐quota harvest strategy as used in South Carolina (Bradshaw et al, 2006; Marioni et al, 2021; SCDNR, 2017; U.S. Fish and Wildlife Service, 1967; Webb et al, 1984).…”

Molecular Characterization of Salmonella spp. Isolates from Wild Colombian Babilla (Caiman crocodilus fuscus) Isolated In Situ

“…in reptiles, such as Caiman crocodilus , is due to the fact that bacteria colonize them systemically via water, soil, contaminated food, and/or through vertical transmission as its entry route [ 20 ]. The Caiman crocodilus is a reptile that is found in the wild and was domesticated for production due to its economic value for its meat and skin [ 21 ]. Some Salmonella serotypes frequently associated with reptiles and isolated in humans are S. Poona, S. Weltevreden, S. Enteritidis, S. Java, S. Stanley, and subspecies S. enterica diarizonae , all known to have caused infection in humans and produced diarrhea in most cases [ 19 , 22 ].…”