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1.  What you can do
2.  Water
3.  Ecology
4.  Amphibians
5.  Environmental Issues
6.  Keystone species
7.  Get Wet!-
     Field Study Ideas

8.  The Zoo Experience
9.  Frogs & Friends
10. Case Studies
11. Resources
12. Glossary

Case Studies

1. Global Amphibian Decline
2: The Decline of the Leopard Frog
3: The Introduction of the Cane Toad to Australia
4: The Puerto Rican Crested Toad - A Species Survival Plan
5: The Bullfrog - A Species in Decline
6: Blanchard's Cricket Frog

(Level: 7 : 10 acad : 10 appl : 11 acad : 11 appl : 12 acad )

The current biodiversity of the planet is expected to decline by at least twenty percent in the upcoming decades. The evolutionary death of a species is a natural process which has been dramatically accelerated by the invasion of human beings. When a population disappears, it is lost forever. Although the future of every animal cannot be secured, Species Survival Plans offer hope for many. The Puerto Rican Crested Toad was the first amphibian to be included in the American Association of Zoological Parks and Aquariums' (AAZPA) Species Survival Plan (SSP). The toad was believed to be extinct at one time, until the discovery of a few isolated populations. Through captive breeding and habitat creation, the future of the Puerto Rican Crested Toad may be secured.

Two Crested Toad populations have been studied since the rediscovery in 1967. The North-east coastal plane near Quebradillas contains 25 individuals, and the southern Guanica Forest population, discovered in 1984, is home to approximately 3,000 toads. The rugged and harsh terrain of the Guanica Forest site is composed of jagged limestone where temperatures reach over 40 C during the day. Once a year, the Crested Toad is observed in the shallow breeding ponds created by heavy rains.

Despite the larger size of the southern population, the toads are at the mercy of the climate. The breeding pond, which is located 100 metres from the sea, could be destroyed by the inundation of salt water in a tropical storm. In addition, the contaminates produced by the busy beach side parking lot threaten the water quality of the breeding pond.

The Species Survival Plan could aid in the re-establishment of the Crested Toad in Puerto Rico by the year 2000. The plan involves the captive breeding of the toad at various centres, including the Toronto Zoo. In 1983, the Metro Zoo received 10 Crested Toads from the Buffalo Zoo. Reproduction, without the aid of hormone injections, was accomplished in 1985. The Crested Toads were released later that year in a human-made pond in Cambalache Forest reserve. Although the site did not have a existing population of toads, it was within the historical range.

In June, 1990 a research team from the Toronto Zoo visited the Guanica Forest to determine the range of the Crested Toad. Twelve toads were captured at the site and radio transmitters were used to monitor their movements. Each transmitter was about the size of a pencil eraser, and was attached to the toad via a tiny harness. The harness was designed by Comrags, an international fashion designer. The harness was constructed of a non-irritating, permeable material. In the event that the toad was not recovered at the end of the survey, the catgut thread in the "backpack" would decay to release the toad.

The toads were tracked for sixteen days during their migration from the pond. The toads travelled north, covering the greatest distance during the first four days. The inquiry provided critical information on the total distance travelled by the toads, and the daytime shelter locations.

The long term survival of the Puerto Rican Crested Toad is dependant upon the protection of existing breeding sites, education of the local community, and the establishment of satellite populations. The breeding site in the Guanica Forest has been protected with the aid of the Puerto Rican Department of Natural Resources, and the Guanica State Forest Manager, Miguel Canal. The drainage of the beach parking lot into the breeding pond was eliminated, and the area is now closed to the public during a three week breeding period. Signs explaining the road closure were posted at the beach to encourage tolerance for the endangered species. The Toronto Zoo has initiated the design of a poster to encourage the local community to conserve and protect the toad.

In 1990, data was collected by the Metro Toronto research team on the pH, salinity, calcium, and temperature of the Guanica site. This information is vital to locate or create additional breeding sites. An artificial pond was created in 1993 by the Puerto Rican government to encourage the breeding of the Crested Toad.

The Species Survival Plan has been an integral part of the conservation of the Puerto Rican Crested Toad. Captive breeding, combined with habitat creation and protection will contribute to the survival of the toad. The most important aspect of this conservation project is the education and involvement of the Puerto Rican people. Ultimately, it will be the actions of the community members which will determine the future of the Crested Toad.


  1. Is it likely that the Puerto Rican Crested Toads had a wider historical range? Discuss the reasons for your conclusions.
  2. What are the threats to the future survival of the Puerto Rican Crested Toad, and how might these be addressed?
  3. Why are small populations vulnerable to normal environmental fluctuations?
  4. Although the numbers of this population are low, this may have always been the case. Discuss the specialization that allows plants and animals to survive with such low numbers.


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