At first glance, the reintroduction of wildlife to its natural habitat appears to be a relatively straightforward process. A sufficient number of individuals of a species is simply released into a suitable area with the expectation that the natural biodiversity will then be restored.
But these reintroduced populations are often quite vulnerable, and their typically small size means that they can be at risk to unexpected changes in their environment. Even apparently healthy populations may not be able to persist in the long-term. The Arabian oryx, once considered to be successfully re-established in Oman after two decades, was subsequently heavily targeted by poachers over a three-year period to the extent that the wild population could no longer sustain itself.
Nonetheless, attempts to reintroduce endangered species are becoming increasingly common. One recent effort concerns the red-billed curassow (Crax blumenbachii), which is native to the Atlantic rainforest in south-eastern Brazil. Fewer than 200 individuals of this largely terrestrial bird remain, having suffered from severe hunting and habitat loss over the years. A captive breeding programme was established in Crax Brazil breeding centre. From this, a total of 53 young birds were released into the Guapiaçu Ecological Reserve (REGUA) between 2006 and 2008.
All of the birds were fitted with a backpack radio transmitter which allowed researchers to closely follow their movements and activities for up to two years. However, once the battery pack died, the programme had to rely on the assistance of volunteers to monitor the fate of the surviving birds. Local inhabitants, including park rangers, were taught to record ring numbers, locations, and how to distinguish sexes.
This additional monitoring was essential as it allowed the team to gather information on the breeding behaviour of the birds, which were only just reaching sexual maturity. Indeed, one of the main aims of reintroduction programmes is that the release generation and their offspring should be able to reproduce. And thanks to the efforts of the volunteers, a number of observations of breeding behaviour were recorded. Wonderfully, this included the sighting of young birds without any rings, indicating that they had been born in the wild.
It is hoped that these wild-born birds will now go on to breed themselves. Ultimately, the main goal is that the reintroduced population will be able to persist continuously without any human assistance. But as this programme highlights, such objectives can only be assessed through long-term monitoring of the re-established population.
Bernardo C. S. S., & Locke N. (2014). Reintroduction of red-billed curassow Crax blumenbachii to Guapiaçu Ecological Reserve, Brazil Conservation Evidence, 11, 7-7
Seddon PJ (1999). Persistence without intervention: assessing success in wildlife reintroductions. Trends in Ecology & Evolution, 14 (12) PMID: 10542463
Image: Joao Quental