The Science of Reintroduction and how Zoos are Saving the Siamese Crocodile

All Photos by Lonnie McCaskill are used with permission.

The Siamese crocodile is a medium-sized species that is found in the wetlands and waterways of
Southeast Asia. As a shy species, it is believed that wild populations are dwindling to a mere 250 animals.
A degradation of the habitat by humans is only partially to blame. Poaching is an epidemic, where nests
are raided for eggs and crocodiles are frequently stolen. Many victims end up in farms across Cambodia, Thailand, and Vietnam. At these facilities, large captive stocks of the species are being held and bred for leather and meat. This practice is especially troublesome for preserving the purity of the species. Many of these farms are encouraging hybrid breeding practices. Blending the Siamese genetics with that of a Cuban crocodile results in larger clutches of animals that are praised for faster growth and a higher quality of skin.


The collaborative efforts of multiple facilities in the United image004States are setting the stage to change the fate of the Siamese crocodile in Cambodia. Years of behavioral studies, genetic testing, and a successfulcaptive breeding project are paving the way for the careful introduction of juvenile animals back into the wild in a race to cease extinction. The Detroit Zoo possesses a captive breeding program that serves as the cornerstone for Association of Zoos and Aquariums’ (AZA) Species Survival Plan (SSP) regarding the Siamese crocodile.  The goal is to generate genetically diverse, healthy, and self-sustaining populations.


This past summer the Detroit Zoos’ Holden Reptile Conservation Center transferred ten of their Siamese hatchlings over to the St. Augustine Alligator Farm in St. Augustine, Florida. This facility is world-renowned for its expertise in crocodilian care and conservation. The St. Augustine Alligator Farm welcomed the hatchlings and selected an adult pair of their Siamese crocs to serve as foster parents for the new arrivals.  Jen Brueggen (a crocodile biologist in St. Augustine) explains that parental care is a vital component in successfully rearing crocodilians. In the wild, crocs spend the first two or three years of their life living under parental supervision. A strong social group is forged. Crocodilians are far more intelligent than scientist once believed. If an animal is lacking in socialization, reintroduction into the wild can be fatal. This is especially true during the breeding season. Thus, every precaution was taken to ensure that these babies are raised with surrogate parents in an environment that stimulates a highly naturalistic scenario. The hope is that these animals will develop into well-adjusted adults with appropriate social skills that can be generalized in a wild context.


image001During our discussion, Jen Brueggen detailed how much care is going into taking DNA samples to ensure that there is a variety of bloodlines among the hatchlings. Their hope is to raise these animals over the next two to three years while working with government officials in Cambodia on a plan to have the animals shipped into remote regions. With hybridization being an ever growing concern in Southeast Asia, researchers are striving to offer diversity and purity in captive animals. The ultimate goal is to offset the polluted bloodlines and limited stock remaining in the wild. The St. Augustine Alligator Farm proudly features a donate a dollar program from ticket sales each month. The target species rotates but naturally, the Siamese crocodile was selected. Additionally, Jen Brueggen orchestrated a CrocFest fundraiser in October of 2015 to increase the revenue that could be allocated to the Siamese project. Over $4,000 was raised for this Cambodian endeavor thanks to her efforts and that of the St. Augustine Alligator Farm.  The zoo is hopeful that these ten babies, along with some future animals will one day roam free in Cambodia.


image002Even with pristine captive care, and raising with the intent of release, the road to reintroduction is paved with many obstacles. Lonnie McCaskill (the Co-Chair for the IUCN Crocodile Specialist Group of Southeast East Asia) met with me to discuss the process. Fauna and Flora International was the first international conservation group to travel over to Cambodia. When working on a tiger census, they unexpectedly caught a glimpse of the first wild Siamese crocodile in Cambodia on one of their photo traps.  Very quickly, the conservation group moved from a place of discovery to protection.  Wild populations were identified, and then measures for protection were designed. Despite the plethora of croc farms in the region, and near levels of extinction in the wild, Cambodia possesses an enormous amount of national pride in the Siamese croc. The species is not only pertinent to the ecosystem, but also to the culture. One can find the species sprinkled throughout myths and local carvings.


The rich cultural heritage of crocodiles in Cambodia is perhaps best embodied by the stone carvings of Siamese crocs that adorn the walls of ancient Angkorian Temples. Additionally, there has never been a reported unprovoked human attack by a Siamese crocodile in Cambodia. Thus, Fauna and Flora International have found success working local communities and assigning socioeconomic positives to the species. This helps build cooperative politics for programs like that of the St. Augustine Alligator Farm. CITES permits and permission from the Cambodian government must all be obtained prior to their fostered animals being granted permission for reintroduction.


image006Reintroduction is much more complicated than one might imagine. Lonnie McCaskill has had success in releasing an initial round of Siamese crocodiles into the wild and described the intricate process. The Phnom Tamao Wildlife Rescue Center provided eighteen Siamese crocs to be outfitted with radio transmitters for tracking. Lonnie McCaskill and his team constructed crates of bamboo and loaded the animals for transport to the base of the Cardamom Mountains. The following morning, the team met up with sixteen bikes carrying supplies as they journeyed to the release site.

The team selected a remote area far from human populations and constructed a bamboo pen in the river. It was essential to allow time for the young crocs to acclimate from their voyage. Release into the wild is not an immediate action. A ten day adaption period was formulated to ensure the safety of the animals upon their release. The river presented many inherent challenges for the young Siamese crocs. Large tanks and captive enclosures image010do not prepare the animals for negotiating swift rapids, deep waters, nor does it teach predator avoidance. These are all skills that are essential for survival outside of captivity. Appropriate social skills are also paramount to this process working.



The bamboo pen was connected to the river and assembled during the dry season. This allows for shallower waters with a slower moving current for safer assimilation. The animals were carefully monitored for the ten days to ensure that they were learning how to coexist within the novel surroundings. The team trained the crocs to avoid contact with humans (and other predators). By day two, when the researchers looked through the bamboo pen, the animals would bolt into the water in search of hiding places.


image011By day five, the animals became so aware of their new habitat that they earned to listen for footsteps.
The team discovered that the crocs were already taking cover in the water before the team could reach the pen to conduct observations.  This is another testament to the immense intelligence that crocodilians possess. Ultimately, this groundbreaking project was a success! It also teaches the general public that releasing captive animals into the wild can be dangerous, and should only be done so after very careful consideration.


The ambition of the St. Augustine Alligator Farm’s endeavor is that their foster Siamese crocs will be given a similar fate. They are hopeful that the Cambodian government will open the doors for more genetically diverse Siamese crocs to be introduced into the region in a highly calculated manner. Through the combined efforts of these two nations and multiple zoological facilities, the critically endangered Siamese crocodile has a realistic opportunity to rebound in the wild. These zoological efforts are invaluable tools for combating extinction. As the project moves forward, the hatchlings being reared in St. Augustine will also encounter a careful reintroduction process to ensure optimal odds at survival. All of that begins by carefully constructing social groups and utilizing foster parents from the very beginning!


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