What happens to a tiny salamander once it is released into the wild?

Corrie Navis
PhD Student at the University of Georgia
November 2022
A captive-reared larval Striped Newt explores the boundaries of its new environment, just after release into a screened wetland enclosure. – Corrie Navis

This is one of the questions I have been exploring through my doctoral research on Striped Newts (Notophthalmus perstriatus), a rare species of salamander found only in south Georgia and northern/central portions of Florida. These salamanders may be quite small—approximately the size of a standard crayon—but play an important role in the semi-permanent wetlands they occupy. For millions of years, the species has inhabited such fish-free small wetlands in the southeastern U.S. coastal plain, acting as one of the top predators in these ecosystems. Much of their original habitat has been lost or fragmented, however, and they are now known to remain in only a few dozen locations in Florida and just five across south Georgia (Farmer et al. 2017).

Over the past few years, I’ve had the great fortune of studying Striped Newt population dynamics in the most abundant known population that remains in Georgia, gathering data that will help fill gaps in knowledge about the complex life history of this poorly-known species and allow conservation entities to make more informed decisions about efforts to conserve Striped Newts. Not all Striped Newt populations are doing so well, however. Even over the past few decades, the species has disappeared from numerous locations where it had previously persisted (Farmer et al. 2017).

A paedotypic adult Striped Newt. Paedotypic newts retain some characteristics of their larval stage (such as their bushy external gills) while quickly reaching maturity, able to reproduce within their first year of life. Many Striped Newt breeding wetlands are dominated by this adult form, yet common captive rearing techniques seem to inhibit this developmental pathway. – Corrie Navis

Where suitable Striped Newt habitat remains (or has been actively restored), many conservation organizations are pursuing releases of captive-reared individuals as a way of returning the species to southeastern wetlands. Captive breeding programs are a valuable tool of amphibian conservation efforts, but it can be challenging to assess how much they benefit wild populations. Tiny, secretive Striped Newts are difficult to recapture in wetlands, meaning that little is known about the outcomes for captive-reared animals after their release. How long do they survive? Do they go on to successfully reproduce? Are they well suited to the ecosystem, or does their early time in captivity have lasting impacts on their development and fitness?

A young Striped Newt is released into the wetland after being collected from a screened enclosure due to declining water levels. Though this individual retained its aquatic lifestyle, it lost its external gills and is not yet reproductively mature. That developmental pathway is not documented in wild Striped Newt populations but is a common outcome for captive-reared individuals. – Corrie Navis

Over the past two years I have sought the answers to these questions by monitoring released captive-reared Striped Newts in their natural environment. To mitigate the challenges of recapturing released newts, I constructed screened enclosures and installed them within a Striped Newt breeding wetland, allowing the newts to live in their native habitat while allowing me to more easily monitor their survival and development. Survival of larval amphibians in the wild tends to be quite low, so in 2021 I released cohorts of larval newts at a range of sizes to assess how increasing size may improve their odds of survival after being released. In 2022, I again released cohorts of larval Striped Newts into the enclosures, this time attempting to hone in on the “sweet spot” of newt size at the time of release: maximizing their survival while minimizing the developmental impacts of spending their early life in the unnatural conditions of captivity. With financial support of the Orianne Society Grant Program for Reptile and Amphibian Conservation in the Southeast, I was able to travel at least monthly to my study site to recapture newts from the release enclosures, estimating the number surviving and documenting their growth and development.

Release enclosures installed in the study wetland. While screen surrounds the sides and bottom, the tops of the enclosures are left open to allow entry of invertebrates, some of which serve as food and some of which are potential predators of young Striped Newts. This design is meant to approximate the conditions newts would face after being directly released into a wetland, allowing for more accurate assessment of their survival rates. – Corrie Navis

An ever-present challenge in field-based ecological research is dealing with the unexpected and uncontrollable. I had planned to also release Striped Newts into enclosures at a second site this year, but the wetland dried early in the summer before the newt larvae had reached their target release size. The large wetland typically holds water year-round, last drying briefly in fall 2019. As this hot south Georgia summer softened into fall, however, it became clear during my monitoring visits that water levels were steadily on the decline. I crossed my fingers for rain and kept a close eye on the weather, but it was soon apparent that the wetland wouldn’t be getting the rainfall boost needed to keep it ponded throughout the fall. Colleagues assisted me in collecting all remaining newts from the enclosures and recording final data on them before releasing them into the small area of water still present.

Grant recipient, Corrie Navis, dipnetting within release enclosures to recapture Striped Newts to track their survival, growth, and development. – Vanessa Terrell

While I wasn’t able to track this year’s batch of newts for as long as I would have liked, what I learned about their outcomes through the first months after their “release” is still a valuable addition to my data set. These data will be incorporated with the information I collected during the first year of this study, totaling nearly 250 Striped Newts for whom I now have post-release data. This new information on what happens to captive-reared young newts after release will inform recommendations for those captive rearing and release strategies most likely to contribute to self-sustaining wild Striped Newt populations.

Literature Cited

Farmer, A. L., K. M. Enge, J. B. Jensen, D. J. Stevenson, and L. L. Smith. 2017. A range-wide assessment of the status and distribution of the Striped Newt (Notophthalmus perstriatus). Herpetological Conservation and Biology 12:585–598.