programs Natural Resources

Black-spotted Newt

(Notophthalmus meridionalis)

Background

The black-spotted newt lives along the coastal plain of Texas from the San Antonio River to the Rio Grande. The historical range of the species extends for several hundred more miles along the Gulf Coast into Mexico.

In the mid-1980s, the U.S. Fish and Wildlife Service (FWS) surveyed 221 historic populations and found that five remained: two in Texas and three in Mexico. Biologists believe resorts and intensive agricultural development have wiped out the historic populations in Mexico since the completion of those surveys. The black-spotted newt has been on various FWS watch lists since then but has never been listed under the ESA.

The newt relies on both land (for foraging) and water habitats (for reproduction) during its life cycle. Adult newts lay eggs in ephemeral wetlands. After hatching, gilled larvae will spend up to a couple of months in the water until they metamorphose into terrestrial adults. Scientists hypothesize that the newt can endure prolonged droughts by burrowing into the earth, where it waits for the rains to return. This trait allows the newt to survive the flood/drought cycles of the Texas coast. Because it depends on both terrestrial and aquatic habitats, the black-spotted newt may be exposed to a broad range of potential threats.

In 2009, the FWS found that listing the newt may be warranted due to threats from pesticide use in both its aquatic and terrestrial habitats. As of May 2019, the agency has taken no further action.

Meanwhile, Texas Parks and Wildlife Department (TPWD) listed the species as threatened and funded research through the University of Texas-Rio Grande Valley (UTRGV) to better understand the status of the species and the threats it faces. The researchers at UTRGV experimented with using cameras on the ends of flexible tubes to peer into potential burrows and extracted environmental DNA (eDNA) from water samples to detect newts in potential breeding ponds. As those survey methodologies proved to be successful, TPWD reached out to the Texas Comptroller of Public Accounts (CPA) to discuss funding a broader survey effort. The UTRGV team was finding newts in unexpected places such as irrigation pipes. It was clear the initial assumptions about the species’ range, habitat and status needed to be re-assessed on a broad scale.

Research Description

In 2018, the CPA contracted with UTRGV to conduct a two-step study based on surveys for black-spotted newt individuals. First, the university biologists conducted preliminary surveys at known sites to prove and improve their survey methodology and to see if the newt had any clear habitat requirements. If successful, the biologists will then identify likely habitats across the species’ entire historic range in Texas. The second step will include testing as many of these sites as possible to establish a new range map, estimate densities and propose methodologies for evaluating potential threats the surveys may identify.

A tropical depression in June 2018 caused widespread flooding across the Rio Grande Valley and set the stage for what are assumed to be ideal survey conditions for the rest of the year.

So far, five sites have tested positive for newt eDNA, including an unexpected site in Starr County. The researchers have until December 2021 to determine all they can about when, where and why the black-spotted newts live where they do.

Deliverables Due at Contract End, Nov. 30, 2021

  • All occurrence records
  • Updated map comparing historic range to current known range including habitat characteristics, presence/absence and densities, if possible
  • Recommendations for assessing the magnitude of threats and the species’ response to those threats, as well as other conservation measures to potentially mitigate and assess threats
  • Identification of remaining knowledge gaps and long-term viability of species

Why This Research Matters

The black-spotted newt is a poorly understood species with a historic range that spans two fast-growing port cities: Brownsville and Corpus Christi. Based on current published data, the species has experienced a massive loss of habitat and reductions in population density and is likely facing extinction. Unfortunately, our lack of understanding of this species makes conservation efforts challenging.

By filling in these knowledge gaps before the FWS begins the species status assessment process for the species, we can be proactive and ensure the listing decision is based on sound science.