Fowler’s Toad Experimental Breeding Ponds
In recent decades, phragmites reeds have swept through North American wetlands, including Long Point’s marshes. These invasive plants convert the shallow, open water that Fowler’s toads need for breeding into impenetrable thickets of reeds. Long-term research has shown a direct correlation between the advance of the reeds and the decline of the toads.
Current methods to control and eliminate phragmites have a limited impact. Some of these methods, such as applying herbicides, can have negative effects on wildlife, especially amphibians. That’s why Wildlife Preservation Canada supported McGill University research into a novel solution: constructed breeding ponds.
Between 2013 and 2014, 11 ponds were excavated at Long Point. Each breeding pond is fenced off to protect it from predators.
The McGill project aims to determine whether the toads can find these ponds and breed in them and how to optimize conditions for growth and survival. The project team has also used the ponds to save egg masses laid in small, temporary pools that naturally form on Long Point beaches, but which dry out before the tadpoles can metamorphose.
Once the tadpoles in the ponds metamorphose into toadlets, the juveniles are photographed and catalogued using image-recognition software that identifies individuals based on their unique spot patterns. The fencing is then removed and the toadlets head back to the wild. Individuals are tracked in future surveys, revealing their survival and dispersal rates.
Rescuing unviable egg masses from beach pools and moving them to the breeding ponds has proved very successful: approximately 30 per cent of tadpoles survive to metamorphosis, compared to a typical rate of just eight per cent in the wild and zero survival in temporary beach pools.
In 2014, every Fowler’s toad born in the study area came from one of the three clutches of eggs rescued and reared in the ponds. Intensive monitoring failed to locate any other breeding sites or egg masses. In 2015, wild Fowler’s toads were observed breeding in the ponds for the first time. As of 2016, the population stabilized, though at a low level of abundance, and is no longer declining.
By increasing the number of toadlets entering the environment at Long Point, the project is improving this endangered population’s chances of survival. In addition, the techniques being developed here can be used elsewhere to save local amphibian populations facing phragmites invasions.
David M. Green. 2016. Amphibian breeding phenology trends under climate change: predicting the past to forecast the future. Global Change Biology, 2016; DOI: 10.1111/gcb.13390
Middleton, J., and D.M. Green. 2015. Adult Age-Structure Variability in an Amphibian in Relation to Population Decline. Herpetologica September 2015, Vol. 71, No. 3: pp. 190-195. DOI: http://dx.doi.org/10.1655/HERPETOLOGICA-D-14-00074
The principal researcher is David Green, a professor at McGill University and the director of the Redpath Museum. He is internationally recognized for his expertise in amphibian biology and the conservation of endangered species in Canada.
For 14 years, David co-chaired the Amphibians and Reptiles Subcommittee of the Committee on the Status of Endangered Wildlife in Canada (COSEWIC), helping to develop Canadian federal endangered species protection and policy. He was also the first chair of the Declining Amphibian Populations Task Force in Canada (DAPCAN) and edited its comprehensive report Amphibians in Decline. In addition, he has authored over 130 refereed publications and book chapters.
It was during his Ph.D. work that he first began to study Fowler’s toads. Today, his long term-study of the population at Long Point spans more than 25 years.