Habitat loss due to development often results in mitigation actions and for protected amphibians this typically means creation of new habitats such as ponds and species translocations. However, the value of such work has been repeatedly questioned in recent years, especially in relation to the long-term effects of translocation of animals into new environments. Also, there is research showing that mitigation action designed to replace wetland habitats such as ponds is misleadingly easy and that in effect the ponds are not replaced by similar structures as new ponds can be extremely different communities from well-established good quality ponds. Creating ponds of similar size and aspect does not appropriately include various other elements such as microbial and invertebrate communities but also complex aquatic macrophyte structure. Equally, newly created ponds, due to the open niches, could be more susceptible to colonisations from invasive plants and animals as well as potentially diseases.
In this context, a new study from Australia has investigated which factors contribute to breeding failure within newly created wetland habitats for a released population of endangered green and golden bell frogs (Litoria aurea) and compared them to populations from natural breeding ponds as well as natural ponds where breeding did not occur.
The study revealed that the created habitat had lower diversity in vegetation and invertebrate species than the natural ponds, which could have resulted in fewer nutritional resources available to the frogs for breeding. Also, a greater proportion of frogs in the created habitat were carrying the chytrid fungus, compared to the populations in the natural ponds. There is data linking the chytrid fungus with a reduction in the reproductive functioning in males L. aurea. The newly created ponds also had an invasive fish present although that was deemed unlikely to have prevented the frogs from breeding.
This is an important piece of evidence to add to the body of data that suggests that habitat replacement can be a highly complex and long-term process and simply creating new pond habitats will not compensate for the potential loss of well-established habitat. Ponds are best created in networks that support species colonisation, both terrestrial (for species such as amphibians) and wind-blown (for plant seeds) and undertaken in addition to existing pond habitats rather than to replace them. Where endangered species are translocated to new habitats adequate monitoring should be implemented to verify the success rate of the translocation and to be able to intervene if problems become apparent, such as the introduction of invasive species or the lack of breeding.
If you see any dead or diseased amphibians or reptiles please report this to Froglife using the firstname.lastname@example.org email or directly to the Garden Wildlife Health project where Froglife are partners http://www.gardenwildlifehealth.org/.
Kaya Klop-Toker, Jose Valdez, Michelle Stockwell, Loren Fardell, Simon Clulow, John Clulow, Michael Mahony. We Made Your Bed, Why Won’t You Lie in It? Food Availability and Disease May Affect Reproductive Output of Reintroduced Frogs. PLOS ONE, 2016; 11 (7): e0159143 DOI: 10.1371/journal.pone.0159143