2022 Start-Up Grant: Ex situ rescue of the Rancho Grande Harlequin Frog (Atelopus cruciger) in Venezuela

The Rancho Grande harlequin frog (Atelopus cruciger) is the only harlequin toad with known viable populations in Venezuela. Although it disappeared in the late 1980s, presumably due to chytridiomycosis, this species was rediscovered in 2003. Only two nearby subpopulations have been detected, despite continuing efforts to find these toads in their former habitats.

Grantee: Margarita Lampo

A. cruciger is currently listed as Critically Endangered (CE) in the IUCN Redlist and recommended for ex situ rescue. Relict populations have maintained few hundred mature individuals for almost one decade, despite the presence of chytrid fungus. Chytrid transmission is low and juvenile recruitment is sufficiently high to compensate for losses due to Bd-induced mortality. This means that scenarios that increase Bd transmission rates could rapidly push these populations to a collapse, and possibly the species to extinction, if backup captive colonies are not available.

Our goal is to establish an ex situ facility for A. cruciger at the Leslie Pantin Paya Zoo, as a stopgap measure for an integrated long-term conservation plan that includes its reintroduction into former habitats in lowland habitats (i.e. thermal refuges). During a pilot study—with very limited resources—we were able to obtain one egg batch, but low tadpole survival and high incidence of spindly leg syndrome (due to calcium deficiency) resulted in a low success in metamorphosis. Nonetheless, we have demonstrated that A. cruciger can breed in captivity.

With the start-up grant, we expect to obtain F1 juveniles. Funds will be applied to the acquisition of equipment for establishing one large reproduction unit and twenty small maintenance tanks. Required permits have already been obtained and proposals to obtain further funds for scaling up have been submitted to the UK Embassy in Caracas and the Price Bernard Nature Fund.

The Rancho Grande harlequin toad (Atelopus cruciger) continues to be the only harlequin toad with two known large subpopulations in Venezuela. Explorations during the last three years have failed to detect new populations.

During 2022–2023, we established the Centro para la Reproducción e Investigación de Arlequines (CRIA) with two units, one at the Foundation for the Development of Physical, Mathematical, and Natural Sciences (FUDECI) in Caracas, and another at the Leslie Pantin Zoo in Turmero, where an ex situ program for the Rancho Grande harlequin toad was initiated. The program currently supports 22 founders from one subpopulation in Cuyagua and a cohort of 35 F1 tadpoles in stages 34–38. At the Leslie Pantin Zoo, an exhibit on the Rancho Grande harlequin toad was set up as part of an educational program aimed at raising public awareness about the threats that this species currently faces. 

Our program was able to secure funds for CRIA’s operation—thanks in part to Amphibian Ark—during its first 18 months as well as for exploring potential sites for future releases. With Amphibian Ark’s Extension Grant, we expect to obtain F1 individuals from various parents to increase the size and genetic diversity of the captive population for future release. Funds will be applied to increase husbandry capacity, to replenish consumables and spare parts to secure CRIA ́s operation for 2023-2024.

Year 3: securing the first reintroduction of juveniles. 

After securing an ex situ facility capable of producing up to 150 juveniles per year, building local capacity, and updating breeding and husbandry protocols for A. cruciger, challenges remain in breeding a genetically diverse ex situ colony. 

With the goals of securing a genetically diverse backup colony and do the first reintroductions of post-metamorphic individuals in 2025, this extension grant will support the ex situ facility to continue to produce captive-bred juveniles and secure juveniles and adults for the first reintroduction trials.

Read the Species Action Plan for A. cruciger here.