The Dark: Nature's Nighttime World

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Human senses are not well adapted for life in the dark so it's not surprising that we are not familiar with what goes on when the sun goes down.

The opportunity to be a presenter on a TV expedition to South America is one that few biologists would pass up. But The Dark: Nature's Nighttime World would be even more challenging, as most of the filming would be done at night.

Recent advances in thermal and infrared imaging make it possible to get a real idea of what nocturnal creatures are doing without altering their behaviour.

Headlamp beetles: Scientists think they use their lights to attract a mate

The most taxing aspect for the team was that we had to work all night on location and try to sleep during the day.

The heat and humidity made sleeping difficult and sometimes impossible.

As darkness falls, the danger of working in wild places such as jungles increases considerably. Without daylight it it's much easier to get lost as you tend to focus your attention in a much narrower field of view.

Venomous species such as snakes become very hard to spot.

During the filming I encountered a fer-de-lance on a path in the Peruvian Amazon.

This extremely dangerous snake is responsible for more human fatalities in South America than any other species.

It was curled up under dry palm frond just by the side of a track and as I tried to get a better look I realised that the snake was well over more a metre long - much longer than the stick I used to lift the frond up.

These snakes are very aggressive and do not react well to bright lights. There have been very few times in my life when I have been in mortal danger - this was one of them.

I backed away very slowly and lowered the frond. I still consider myself very lucky not to have been bitten.

My real passion is insects and spiders, and for me one of the highlights was finding and filming headlamp beetles.

After dark but only for about an hour or so, these strange click beetles with two luminous green spots on their thorax fly through the forest.

Collect enough in a jar and you read a book by their eerie glow. Stranger still is the orange light on the underside of the abdomen that illuminates briefly at they take to the air.

Another highlight were trapdoor spiders.

Trapdoor spiders only risk coming out for a fraction of a second after dark

Normally they are very hard to spot as the silk-hinged lids to their burrows are so neat and tight fitting but when they are hungry they raise the lid just a fraction.

These ambush hunters seize passing insects and drag them below.

To shoot footage for episode two, we visited a Venezuelan tepui, or table top mountain.

Living for several days deep inside a cave in the heart of the tepui was quite testing.

I was alone in the dark for several hours as the rest of the team went off to rig some climbing kit and I turned off my headtorch to conserve the battery.

The interior of the three-mile cave has never seen the sun in all the millions of years it has existed and the darkness is absolute.

The stream that flows through the passages makes splashing and gurgling sounds as it goes and these are amplified and distorted as they echo through the cave system.

It was not long before my brain, struggling to make order out of the acoustic chaos, began to play tricks on me.

I was sure I could hear voices calling - and laughter, changing imperceptibly into gentle sobbing. If you got lost down here for any length of time you could go mad.

Dr George McGavin is a biologist with a particular expertise in insects.

The Dark: Nature's Nighttime World begins on Sunday, 29 July at 9pm on BBC Two. For further programme times, please see the episode guide.

Comments made by writers on the BBC TV blog are their own opinions and not necessarily those of the BBC.

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