Eagles To Pupfish: Wildlife Reintroductions In The USA
Written by Wildlife & Welfare Researcher Adam Martin.
As part of our April edition of the Wildlife Calendar, we have been focussing on endangered species in the USA. This blog post investigates the reintroduction of wildlife in America and some of the results to date.
Introducing species as food and pest control has been a practice of humans for thousands of years, but it wasn’t until the 20th century that wildlife was reintroduced for conservation. Reintroduction is the deliberate release of species into the wild from captivity or other wild populations. The goal is to establish a healthy, self-sustaining population in an area where it has been wiped out, or to boost an existing population. Many species are reintroduced as they are threatened or endangered in the wild. A wide variety of species have been reintroduced throughout the history of conservation, around the world, and as we will find out, in the USA.
Did you know that some of the USA’s most iconic species have been the subject of reintroductions?
This includes the bald eagle (Haliaeetus leucocephalus) - national symbol of the USA. Historically abundant across North America, the species became victim to human persecution and pesticide-caused losses in the mid-1900s causing populations to plummet. Happily, since 1980 various strategies have led to populations recovering, including a reintroduction programme in California’s northern channel islands. Sixty one juvenile bald eagles were released on the islands between 2002 and 2006 and since then the population has once again become an important part of the local ecosystem, including being critical to the recovery of the endangered island fox (Urocyon littoralis) by reducing golden eagle predation.
But reintroduced species come in all shapes and sizes. The desert pupfish (Cyprinodon macularius) is a shiny minnow-like fish which may look like a typical aquatic species but is one of the most extreme survivors on the planet. Capable of tolerating temperatures from 4°C to 45°C as well as salinities and low-oxygen conditions more extreme than virtually all other freshwater fish. Despite this, the species has been on the endangered species list since 1986 due to competition from non-native species like tilapia and habitat loss and fragmentation from groundwater pumping. Organ Pipe National Monument in Arizona has a spring and pond that provide the perfect habitat for these small, spectacular fish, but invasive species outcompeted and took over. In response, park staff drained the pond, removed the invasives, and reintroduced pupfish. As of today, an estimated 4,000 to 5,000 desert pupfish thrive in the park's Quitobaquito Springs.
Many other species have been reintroduced throughout American history including wolves such as the red wolf (Canis rufus) which you can read about in our Wildlife Calendar entry for April! Links to information and projects on some other species reintroductions in the USA can be found in the table below, though there are many others!
Wildlife reintroductions are not always successful, as shown by attempts to reintroduce the Canadian lynx (Lynx canadensis) in the Adirondacks in New York state. Eighty three lynx were released from 1889 to 1991 but unable to maintain a viable population due to highway mortality and long-distance dispersal. Reintroduction biology is still a work in progress and finding the required conditions for success remains a major question for conservationists.
In 2021 scientists published a paper recommending Jaguars (Panthera onca) be reintroduced across Arizona and New Mexico in the future. They once roamed here before populations were decimated by hunters in the mid-twentieth century leaving no breeding pairs in the area. So keep an eye out for this and other exciting future reintroduction projects too!
