Observing Nocturnal Animals
Night observation is very different from observation during daylight. At night we rely on our sense of hearing combined with sight and artificial light to locate animals. Nocturnal birds and mammals have very acute senses compared to ours and they are usually aware of us long before we see them. Often I find an animal by its call or the noise it makes as it moves, then I locate it using eye-shine.
Many animals can be attracted by replaying the calls they make and sometimes by the calls made by other species. Recorded calls are often used during owl surveys and by photographers and occasionally I use them when I look for owls at a new location. Call playback can be highly disruptive and stressful to the animal if not used judiciously and I do not encourage its general use. Playback should be avoided near nest sites during the breeding season. Owls are strongly territorial so you should resist the temptation to divulge their locations to other photographers and twitchers, as word will quickly spread and the owls are sure to be harassed ("loose lips sink ships").
Eyes contain two fundamental types of light receptors called cones and rods. Day active animals (diurnal) have an abundance of cones which require relatively bright light to function and enable them to see well during the day. Diurnal animals have several cone types, each type having a peak sensitivity to a different wavelength (spectral colour). The brain 'sees' colour not the eyes and it does so by combining the signals from the different cone types, analagous to mixing the primary paint colours to achieve all the colours of the rainbow. The more cone types a species has the better is its colour vision. The diagram below shows the colour sensitivity of the three types of cone cells in the human eye.
Rod cells only work in very low light levels and enable nocturnal animals to see well in the dark. Unlike cone cells, eyes only have a single type of rod which is sensitive to light centering on a wavelength of approximately 500nm (cyan). In darkness, the brain receives information from the rod cells only, which enables excellent monochromatic vision with no perception of colour. The graph below shows the sensitivity of rods in the human eye and reveals why they have no response to red light.
Rods don't see red! For observing animals at night I use home-made LED headlamps that use red LED's. As well as not disturbing the animal, red light does not spoil your own night vision. My favourite headlamp shown below uses a 3 watt red LED and a rechargeable battery. It can be attached to a tripod and the beam can be focused tightly or spread to control the width and brightness. Nocturnal animals have poor sensitivity to red because their eyes have relatively few cones, however they can see it. The main disadvantage of using red light is that it is monochromatic and everything appears in shades of red.
With red light, you are able to watch and photograph nocturnal animals behaving naturally. The photo below of a nesting Powerful owl was a 1/3 second exposure at f6.3 and ISO 6400 illuminated with the headlamp shown above. I observed this nest for many years with the aid of red lights and the owls were always aware of my presence but were unconcerned. I watched this adult leave the hollow on dark and return a short time later with a Ringtail possum to feed its young. If I had used white light it probably would not have returned whilst I was watching or it may have abandoned the nest altogether.
White light is the second best option for viewing animals at night but should not be used for watching owl nests. White light has the advantage that you can see the true colour of an animal's eye-shine, which can be a useful for identification at distance. During a holiday in Sabah (Malaysian Borneo). I heard this animal in the forest just outside my hotel and with the aid of a LED torch held close to my own eyes, I located it by its beautiful blue eye-shine. It was a Mouse deer, not much larger than a rabbit.
Clothing and gear
Long-sleeved shirts, long pants and sturdy boots are essential in the bush at night to protect from cuts, scratches and bites. Depending on the weather and where I am walking, I may also take warm clothing, rain jacket, snacks, water, insect repellent, first aid kit and something to sit on.
For a casual walk or scouting a new location, I may take only a headlamp. On other occasions I may take additional equipment, for example navigation aids, camera, binoculars, tripod, sound recorder etc. With extra gear a casual walk can become a hard slog so I usually try to carry only the essentials for the occasion.
Safety at night
Being in the bush can be very rewarding and you usually locate more animals if you are alone because your senses are heightened. When alone you need to be better prepared and more careful. Your vision and sense of travel direction is poor compared to during the day and it is easy to become disoriented or fall on something you didn't see. Each of these experiences has happened to me and now when I venture out alone I always:
· Tell someone where I am going and when I expect to return
· Know my exact location at all times and if unsure, stop until I have worked out where I am
· Stay on the intended route unless I have navigation equipment or am familiar with the area
· When I venture off-track I always watch where I place each footstep to avoid a fall.