Pond Construction

There are currently three reintroduction sites with man-made release and breeding ponds constructed by recovery group partners. The first ponds were constructed in Manglillo, Guánica Forest in 1992. Two large naturalistic breeding ponds were installed in Manglillo in 2000, but salt water infiltrated the pond liners and made them too saline for the development of eggs and tadpoles. A new concrete breeding pond was built to replace the unsuitable ponds in 2011.


Manglillo release pond


Manglillo breeding pond















The second series of release ponds were built in 2005 at El Tallonal, Arecibo and the ponds in Coamo, Gabia were built in 2006 and 2010. The design of the ponds have metamorphosed over the years through a learning process that has allowed partners to continue to improve upon previous construction methods and move from purely functional systems to ponds that are more naturalistic.


Gabia reintroduction pond
Gabia breeding pond












Numerous factors are considered by partners when choosing pond sites including access, appropriate karst habitat and refugium sites, food base, presence of potential predators and introduced species, amount of sunlight, vegetation abundance and type, moisture content of soils, water drainage/runoff, size of habitat and adjacent properties, protection of habitat and future development plans for the region, pesticide or agricultural usage in the area or adjacent areas, recreational use of the area if applicable, etc. Every pond is unique and designed to fit within natural depressions that allow them to fill naturally during rain events and evaporate within 30 to 45 days. Keeping the ponds ephemeral allows the crested toads enough time to breed and for larvae to metamorphose, but keeps other invasive species such as marine toads and bull frogs, from breeding in the ponds year-round and establishing large populations.


After initial area surveys are conducted by relevant partners at new sites, a hydrological assessment is made of the area by the Center for Applied Tropical Ecology and Conservation to aid in the pond’s design. Each reintroduction site includes a small release pond and a larger breeding pond. Both types of ponds are made using concrete or pond liners and include drains and overflows. The reintroduction ponds are used to release captive-bred tadpoles into a semi-protected area that has been cleaned and allowed to fill with algae two weeks prior to a release. The older release ponds are made of concrete and designed after the cattle troughs in the north that crested toads commonly used as reproduction sites. Some of the reintroduction ponds are covered with mesh to keep out dragon flies whose larvae feed voraciously on small tadpoles. The breeding ponds are bigger and are designed to attract and support a large number of breeding adults, but are still shallow enough to evaporate during dry parts of the year. The ponds are designed to be low maintenance and durable. Minor alterations have been made at some sites to prevent major predation events and provide as much “head-start” assistance as possible for the released tadpoles and newly metamorphosed toadlets. However, it is theorized that some level of predation is healthy in order for the development and/or retention of predator avoidance tactics of captive born progeny.


Release pond at El Tallonal
Release pond with protective screening