On 2 April 2023, the Roberto Franco Tropical Biology Research Station of the National University of Colombia and the Colombian National Natural Parks Agency led the reintroduction of 14 Critically Endangered Orinoco crocodiles Crocodylus intermedius (12 females and two males) into their natural habitat in the Tomo River in El Tuparro National Park, in the Colombian Orinoco region. This is the first reintroduction of a large group of adults of one of the largest Neotropical freshwater predators. The midterm goal is to restore this species by increasing its abundance in areas where it was historically present, following the objective of the Orinoco Crocodile Action Plan to establish three wild populations in protected areas in the species' historical distribution, with at least five breeding females each, within 15 years.

The 14 individuals, each > 3 m long and > 100 kg, were selected based on appropriate genetic and phenotypic profiles, preconditioned for 2 years in semi-captive conditions away from permanent human presence and fed with live prey. Satellite transmitters were installed on 12 of the crocodiles (10 females and 2 males), to gather information such as survivorship, nesting times and sites, home ranges and movement patterns. Reintroducing adult crocodiles saves time, as they are reproductively active, and helps restore populations by reducing the risk of predation, which limits recruitment rates.

Previous social research along the Tomo River has shown that local people recognize the Orinoco crocodile as important in the ecosystem and value it highly, believing that where there is a crocodile, deep water bodies remain and there is plenty of fish. The local communities do not consider the crocodile a threat, which is a significant advantage for the conservation of the species. As it is critical to understand the social implications of the crocodile's presence in areas where it has been absent for decades, we continue to work with local communities along the Tomo River where the reintroduction took place, promoting coexistence with the species.

This project had the technical and financial support of the Wildlife Conservation Society Colombia, University of Florida, CrocFest, Colombian Air Force, Colombian National Police, Colombian Civil Defense, Merecure Park, and Cormacarena Environmental Agency. This newly formed institutional alliance is also a relevant outcome of this project and facilitates restoration of the Orinoco crocodile. Conditions are now favourable for the reintroduction of additional crocodiles in the Tomo River, increasing the possibility of forming the first known natural population originating from captive individuals.