10/16/2026
By 2021, the population of Relict Leopard Frogs inhabiting the North Fork Refugium Ponds at the Springs Preserve was thriving. In fact, our rewilding efforts had been so successful that the number of tadpoles seen each year began to greatly exceed the ponds’ carrying capacity. As a result, we decided to see if they could survive at a nearby location, the Preserve’s recreated Cienega wetland (also known as the Meadows Detention Basin).
Unlike the refugium ponds, the Cienega was not designed or managed as habitat for the Relict Leopard Frogs or Pahrump Poolfish. While large in area, the Cienega experiences fluctuating water levels, has variable water chemistry and is often a dead end for trash from connected flood control channels. Nevertheless, we moved 192 Relict Leopard Frog tadpoles from the refugium ponds to the Cienega in July 2021. This marked the first time an urban flood control basin was used as part of an attempt to establish a population of an imperiled species. That fall, a survey documented a single frog. To give the population a boost, we moved another 212 tadpoles in July 2022. To our dismay, the fall survey did not detect any living frogs.
We reasoned that the sunken detention basin might cool more quickly in the fall than the refugium ponds. Instead of moving more tadpoles in 2023, we surveyed the Cienega in August when frogs would still be active, if present. To our delight, we observed 23 Relict Leopard Frogs that year, including 17 adults and 6 juveniles. From that point on, we scheduled Cienega surveys for August.
A key question still remained: Were the frogs in the Cienega breeding, or were they simply dispersing from the Refugium Ponds during rain events? Our spring surveys had not revealed any evidence of breeding, such as egg masses or tadpoles. That changed in 2025, when a Southern Nevada Health District employee who was trapping mosquitofish in the Cienega caught a tadpole in a minnow trap. A subsequent staff survey rustled up two more large tadpoles. In both 2024 and 2025, the August surveys documented 48 Relict Leopard Frogs in the Cienega.
Everything changed in 2026 when wildlife cameras recorded American Coots catching and feeding a concerning number of large tadpoles to their young. That same year, while surveying for Woodhouse's Toads, biologists observed more than 100 Relict Leopard Frog tadpoles in the Cienega shallows. With the addition of several trail cameras, we have since been able to photograph large numbers of frogs in the Cienega.
The trail cameras also documented a host of avian predators attracted to the thriving urban frog population, including several species of herons, hawks, egrets and grackles. It appeared to be a buffet down there! As scientists, it is important for us to document predatory activity, but it was also difficult to watch a Black-crowned Night Heron consume a very large female frog, one of many frogs that have croaked. The population continues to thrive, though.
Due to the 24/7 avian onslaught, the surviving frogs are no longer catchable by us mere mortals. They have become extremely skittish and often dive into the water or shoreline vegetation before they are even seen. Frogs that hesitate, let predators approach too closely, or have slow response times may not stick around for long. Survival of the fittest appears to be alive and well.
In addition to the 110 frogs observed in 2026, we heard 33 more jumping into the water or bulrushes. It's safe to say that the Cienega has a minimum of 150 frogs, but there could be a lot more. Despite the avian onslaught, we are astounded by the growth of the Cienega frog population, which is now at least 2.3 times larger than in 2025. The lesson here is that abundant predators don't automatically result in declining prey populations. The predation pressure from the birds has produced “super frogs.”
Combined with the Springs Preserve’s original North Fork Refugium Ponds established in 2018, the frog population at the Springs Preserve has increased from 169 frogs in 2025 to 320 frogs in 2026, almost doubling the number of frogs that call the Springs Preserve home! The Springs Preserve Relict Leopard Frogs now make up 23% of the frogs of this species in existence.
