Investigating the presence of the amphibian chytrid fungus in a non-native species

Methods

Summary

The use of call playbacks will be used to help locate toads as well as active searches within the gardens where the toads are know to inhabit. All potential refugia and previously known areas where the toads have been found will be searched to ensure that as many are swabbed as possible. When midwife toads are located, they will be placed in separate zip-lock bags for a short duration until the search has been completed; this will be no longer than twenty and thirty minutes. Each bag will have sufficient moisture and air in for the toads, this method is designed to prevent cross contamination.  

Before the toads are swabbed, data such as their sex, weight and snout to vent length will be taken. A set of digital scales and plastic Vernier callipers will be used to collect this data. As part of the swabbing process, each individual is sprayed with a small amount of water in order to free their ventral surface of any dirt or detritus which may interfere with the later analysis process. Sterile cotton tipped swabs (Medical Wire & Equipment, MW-100) are the preferred swab to use, swabbing the abdomen, thighs, groin and feet of each individual between 10 and 15 times. After being swabbed, each of the midwife toads will be photographed for future reference before being released at the point of capture.

All appropriate biosecurity measures will be taken when handling the toads including the use of nitrile gloves, the changing of gloves between each site and the use of Virkon S when disinfecting field equipment after use.

Challenges

Females and juvenile toads don't call or respond to the playbacks and so active searching is the only method that we can use to locate them. This can be costly in terms of time and energy especially when moving heavy objects. To overcome this, we may seek the assistance of additional field assistants in order to minimise the risk of injury to ourselves as well as the toads. As the toads are very cryptic and nocturnal, the use of strong torches will be used to be able to search for them within the appropriate search area.

Pre Analysis Plan

As our analysis is testing for the presence of the amphibian chytrid fungus, our data output is going to be binary (present or absent). From this we will be able to confirm or reject our hypothesis that the toads are currently infected with the amphibian chytrid fungus.