Frog fungi gone feral

(Image: Taryn Crispin, 2013)

Batrachochytrium dendrobatidis (Bd), or "Chytrid", is the fungi responsible for one of the most dramatic examples of vertebrate species decline present-day. 

The target class of vertebrates, amphibians, are typically bound to moist habitats in order to survive and successfully breed, and their skin is permeable to water, air and electrolytes. The physiological importance of the skin in amphibians makes them particularly vulnerable to skin infections, and their tight association with moist habitats makes them susceptible to Bd skin infection, as this fungi is believed to transfer and duplicate in water. 

The specific mechanism by which Bd causes fatality in amphibians is unclear, but it is generally agreed upon in the scientific community that it impairs the regulatory functioning of frog skin. 

Bd infection is spreading world-wide at an alarming rate, and it is believed that the global trading of frogs (as food for human consumption, and previously for pregnancy testing in humans) is responsible for this spread.

Countries where amphibian skin samples have tested positive for Bd, number of incidences of Bd per country shown as colour shematic. (Image: Global Bd-Mapping Project)

Nightwatch: a guide to finding animals after dark

I get great pleasure from seeing animals in the wild. Not only is it a great experience to be standing close to something untamed, but it is also a great opportunity to observe interesting quirks in an animals’ behaviour. But let’s face it: in Australia, most of our animals are active at night. I’m sure you’ll all agree with me that running around in the dark to find these nocturnal natives is not very appealing (or safe). But for those of you who, like me, have the desire to look for Australia’s charismatic wildlife in-action, here are a few pieces of information you may find useful in having a successful (and safe!) night-search.

The gear
First of all, you need the right equipment:

•  a buddy to accompany you
•  a decent spotlight or head-torch (preferably 75 lumens)
•  water
•  appropriate footwear (closed-in shoes)
•  a map of the area you are going to
•  a compression bandage (in the very unlikely event of snake-bite)
•  a mobile phone (make sure you have reception in the area you are going to

 With this equipment, you are now ready to hit the trail and look for night-life!
 

What can you see at night?

Depending on what animals you want to see, bushwalks are typically the best for mammals and owls. After recent rains, you are likely to encounter some very colourful frogs in the bush as well. I recommend you pick an area you are familiar with after a day-walk, and stick to the trail. Make sure that when you go out at night you scan the trees – that’s where the possums, gliders, and birds are!

The skills required

Spotting animals is actually quite easy once you learn this one trick: hold the spotlight at eye-level, beside your face.

What you are looking for is not so much the movement or silhouette of an animal, but what is called “eye-shine”. This is the same as the reflection of light, or “glowing”, in the eyes of dogs or cats when a light is shone near their eyes at night. 

The theory behind holding the spotlight at eye-level

Because wild animals are excellent at camouflage, and typically freeze when they hear a person approach, the best way to spot them is to catch a glimpse of eye-shine, then you can head over and get a closer look! The reason your spotlight or torch has to be held at eye-level is because the light in the animals’ eyes are reflected back at the same level as your torch or spotlight, so you can only see eye-shine if your eyes are level with the light source.

An example of what eye-shine looks like. Bilbies only emerge from their burrows at night, so here’s a reason to go spotlighting in the Scotia National Park, NSW, Australia (Jeremy Ringma, 2012. Photo with permission)

Final words

Spotlighting for animals can be a real fun (and cheap) activity for amateurs and professional naturalists alike. When I was young, my father would take me to the beach to go spotlighting for ghost crabs! I was always amazed at how many animals scuttle across the beach at night when the area was such a popular attraction for swimmers during the day. What experiences have you had with spotlighting for wildlife?