The species is listed as Critically Endangered by the IUCN after disappearing from 99% of its original habitat.

At Terra Natura Benidorm, a comprehensive veterinary and genetic study has been made on a pair of Siamese crocodiles (Crocodylus siamensis) with the aim of advancing knowledge of their health and reproductive status as part of international conservation strategies for the species. The study included a medical examination and the collection of genetic samples that will help determine the animals’ suitability for future coordinated breeding programmes.

The Siamese crocodile is classified as Critically Endangered (CR) on the Red List of the International Union for Conservation of Nature (IUCN). In the wild, the species has disappeared from around 99% of its historical range, mainly due to habitat loss, poaching for the skin trade and the collection of eggs for crocodile farms. As a result, every conservation-focused action plays a crucial role in ensuring the species’ long-term survival.

The intervention required meticulous planning and precise coordination between the different teams involved. Prior to the procedure, the facilities, the characteristics of the species and the individual animals, as well as the human and technical resources required, were carefully assessed in order to guarantee the safety of both the animals and the staff.

Three working teams were organised for the operation. Two main teams — made up of the veterinary staff, the conservation biologist, the area manager and specialised keepers — were responsible for sedation, moving the animals to the veterinary clinic, collecting samples, carrying out the clinical examination, monitoring vital signs and supervising their recovery. At the same time, a third team of keepers managed the temporary capture and relocation of the crocodile while the pond was drained, a task carried out with the support of the park’s maintenance staff.

Coordination was essential throughout the process, as some tasks had to be performed simultaneously while others required a carefully planned sequence. This synchronised work made it possible to anticipate potential reactions from the animals and keep full control of the intervention at all times.

Throughout the procedure, the animals’ vital signs were monitored regularly, including respiration through the nostrils, thoracic expansion and heart rate — slow but steady — which was checked using a stethoscope despite the characteristic thickness of the reptiles’ skin. At the end of the procedure, both crocodiles remained in a dark and quiet space with controlled temperature for recovery.

Data find from the study

During the check-up, the animals were weighed and measured. The female measures 2.50 metres in length and weighs 80 kilograms, while the male measures 2.65 metres and weighs 95 kilograms. Although the male is larger, he shows a more timid temperament, while the female displays a more restless and defensive character.

The pair coexist well and courtship behaviour has been observed on several occasions. However, despite several egg-laying events, the eggs were not fertile, reason to carry out this reproductive assessment.

In addition to the clinical examination, the team made several tests aimed at gaining a deeper understanding of the pair’s genetic and reproductive status. These included the collection of tissue samples for genetic analysis in order to determine whether the animals are genetically pure or hybrids. Fertility tests were also carried out on both individuals, as establishing a reliable genetic profile is essential when assessing their potential inclusion in international breeding programmes.

This work is part of the European Endangered Species Programme (EEP) coordinated by the European Association of Zoos and Aquaria, which manages the genetic and demographic sustainability of threatened species in European zoological institutions. Its main objectives include rigorous genetic management to prevent inbreeding and hybridisation, the development of reservoir populations that may support future reintroductions into the wild, and collaboration with conservation projects in protected areas.

Following their recovery, both crocodiles have returned to their usual habitat at Terra Natura Benidorm. The team will continue to monitor them regularly to ensure that their behaviour, feeding habits and general condition remain normal. Interventions such as this highlight the role of modern zoological institutions as parks for conservation, research and international cooperation.