0:00:03 > 0:00:08On Deadly 60, I've had loads of incredible animal encounters.
0:00:09 > 0:00:11Here's just one of my many favourites.
0:00:12 > 0:00:17This is Deadly 60 Bites.
0:00:17 > 0:00:20Today, we're in the Sonoran Desert in Arizona.
0:00:20 > 0:00:25Despite what many people think about deserts being alive with snakes,
0:00:25 > 0:00:31they can be quite shy of people and often very hard to find.
0:00:31 > 0:00:35Luckily, though, we've got some Deadly 60 technology on our side.
0:00:37 > 0:00:39Matt, talk us through how this works.
0:00:39 > 0:00:41This antenna's directional,
0:00:41 > 0:00:45so it'll tell you the strongest signals where the snake is.
0:00:45 > 0:00:48- So if you listen, you can... - BLEEPS
0:00:55 > 0:00:58- It's a little louder that way. - It does seem stronger in that direction.
0:00:58 > 0:01:01Perfect. I'm following you.
0:01:01 > 0:01:06I should point out that this isn't just a magic snake-finding device.
0:01:06 > 0:01:09All the animals we'll be looking for have been caught
0:01:09 > 0:01:11and implanted with a radio transmitter
0:01:11 > 0:01:14about the size of my little finger.
0:01:14 > 0:01:16That's the signal we're trying to pick up now.
0:01:17 > 0:01:20'So this is what we're looking for.
0:01:20 > 0:01:23'Rattlesnakes are the classic desert predator,
0:01:23 > 0:01:27'arguably the most sophisticated snake on the planet,
0:01:27 > 0:01:31'with hinged fangs, a superfast strike
0:01:31 > 0:01:34'and an amazing sense of smell.
0:01:35 > 0:01:39'This is the animal most people try and avoid.
0:01:43 > 0:01:47'Even with this technology, it won't be easy finding a rattler,
0:01:47 > 0:01:51'and with the temperature soaring to over 35 degrees,
0:01:51 > 0:01:54'the crew are really having to work hard.
0:01:58 > 0:02:01'While we sweat it out on the search,
0:02:01 > 0:02:03'take a look at the demo me and the crew did
0:02:03 > 0:02:08'to show you how the rattlesnake is such an effective killer.
0:02:08 > 0:02:12'But to do this, we need to turn the lights out.'
0:02:13 > 0:02:16This is a thermal imaging camera.
0:02:16 > 0:02:21It actually picks up the heat generated by objects around you.
0:02:21 > 0:02:24So things like...
0:02:24 > 0:02:26this cactus here.
0:02:26 > 0:02:29Obviously cactus have an awful lot of water in them,
0:02:29 > 0:02:31and all that water is still quite warm,
0:02:31 > 0:02:34so the cactus stands out beautifully
0:02:34 > 0:02:36against the black of the sky.
0:02:36 > 0:02:40And if I turn this onto the camera crew...
0:02:40 > 0:02:42And Johnny, the cameraman,
0:02:42 > 0:02:44the camera's dark,
0:02:44 > 0:02:47and his head is almost white.
0:02:47 > 0:02:50So, got a foxy bit of kit. Let's go see what we can find.
0:02:55 > 0:02:58'This detection of heat is exactly how a rattlesnake
0:02:58 > 0:03:01'is able to see its prey in the dark.
0:03:01 > 0:03:03'It has supersensitive heat sensors
0:03:03 > 0:03:08'on its face that pick up the heat given off from its prey's body,
0:03:08 > 0:03:10'allowing the snake to catch its supper
0:03:10 > 0:03:12'in the pitch black of night.'
0:03:14 > 0:03:19A good-sized rat is eyeing me up from the rocks in front of me.
0:03:19 > 0:03:22You can see the warmth generated by his body heat.
0:03:22 > 0:03:26His eyes, particularly, seem to be very hot.
0:03:34 > 0:03:38I'm being watched very intently
0:03:38 > 0:03:41from no more than about ten feet away,
0:03:41 > 0:03:44by a very bright pair of yellow eyes.
0:03:46 > 0:03:48This is an Elf Owl.
0:03:48 > 0:03:50He's probably...
0:03:50 > 0:03:55no more than about that high, I'm guessing.
0:03:55 > 0:03:57He is beautiful.
0:03:57 > 0:04:00'This is exactly what a rattlesnake would see
0:04:00 > 0:04:02'if it was looking at this owl.
0:04:06 > 0:04:11'Now let's turn the lights back on and see if we can find one.'
0:04:17 > 0:04:18Ow!
0:04:23 > 0:04:27Some of these cactus could be well over 100 years old.
0:04:27 > 0:04:30Even older than Nick, our sound man.
0:04:32 > 0:04:34STEVE LAUGHS
0:04:37 > 0:04:42There's a lot of reasons why reptiles do so well in dry desert environments like this.
0:04:42 > 0:04:45Firstly, being so-called cold-blooded,
0:04:45 > 0:04:49they get their energy from the sun, and there's plenty of that here.
0:04:49 > 0:04:51Also, they have remarkable watertight skin,
0:04:51 > 0:04:55so they don't sweat or lose any water to the outside environment.
0:04:55 > 0:04:58They have the ability, in times when there's not much food around,
0:04:58 > 0:05:00to just lie around and do nothing,
0:05:00 > 0:05:04and, in extreme cases, even hibernate.
0:05:15 > 0:05:18That one is a snake.
0:05:18 > 0:05:20'Matt's locked on to a signal from a rattlesnake.
0:05:20 > 0:05:25'We're getting close and we need to be really careful where we tread.'
0:05:30 > 0:05:31- Where?- You see him?
0:05:31 > 0:05:34OK, he's right there? Good.
0:05:39 > 0:05:41Perfect.
0:05:42 > 0:05:46If you can get him on the first shot, that's good.
0:05:46 > 0:05:47One fell swoop.
0:05:50 > 0:05:52Come around the other side now.
0:05:53 > 0:05:55RATTLING
0:05:55 > 0:05:57Listen to that!
0:05:57 > 0:06:03That is THE sound of the Sonoran Desert.
0:06:04 > 0:06:06RATTLING
0:06:11 > 0:06:15Let's get him out in the open where we can look at him.
0:06:16 > 0:06:18RATTLING
0:06:20 > 0:06:22Listen to that rattle!
0:06:24 > 0:06:27LOUD RATTLING
0:06:27 > 0:06:31That wonderful sound is really the signature sound of the desert.
0:06:31 > 0:06:33You hear it in all the Western movies.
0:06:35 > 0:06:38Interlocking segments of keratin,
0:06:38 > 0:06:41the same substance that's in our fingernails,
0:06:41 > 0:06:45rattle together and create that incredible buzzing sound.
0:06:47 > 0:06:50'Matt's marked the wild snakes he's studying with some paint
0:06:50 > 0:06:53'so he can identify them.'
0:06:54 > 0:06:57This is a tiger rattlesnake.
0:06:57 > 0:07:01The dark and light bands running across the body
0:07:01 > 0:07:04are for camouflage and are what give it its name.
0:07:04 > 0:07:09These tongs look like they're squashing the snake, but it's a resilient creature.
0:07:09 > 0:07:12They're not doing it any harm at all.
0:07:12 > 0:07:17It's not a particularly big snake, but it does have very potent venom.
0:07:17 > 0:07:20Certainly enough to mean I have to be very wary of it.
0:07:20 > 0:07:23What a beauty!
0:07:23 > 0:07:26Actually, what this is is an incredible predator.
0:07:26 > 0:07:29The reason for that is a supersense.
0:07:29 > 0:07:31Looking at the front of the head,
0:07:31 > 0:07:35the snake almost appears to have two sets of nostrils.
0:07:35 > 0:07:38The lower ones are what's called a loreal pit,
0:07:38 > 0:07:42which picks up the warmth generated by the moving muscles of its prey.
0:07:42 > 0:07:46It can literally see animals moving in the dark.
0:07:47 > 0:07:51'Exactly as we saw earlier with our thermal camera.'
0:07:53 > 0:07:56So all it has to do is to sit and wait
0:07:56 > 0:08:00for a small mouse or other warm-blooded mammal to walk too close by,
0:08:00 > 0:08:03and then it'll strike with its potent venom.
0:08:03 > 0:08:08First of all, it instantly starts to slow the prey down.
0:08:11 > 0:08:14But the prey also starts to bleed internally
0:08:14 > 0:08:17and to urinate as it runs away,
0:08:17 > 0:08:20leaving a scent trail which the rattlesnake can follow.
0:08:21 > 0:08:24'So, dangerous to us they may be,
0:08:24 > 0:08:26'but the rattlesnake is going on the Deadly 60
0:08:26 > 0:08:32'because of its ability to track, ambush and immobilise its prey.
0:08:36 > 0:08:40'Venom, speed, supersenses, camouflage,
0:08:40 > 0:08:42'and... did I mention venom?
0:08:42 > 0:08:46'Well, there you go. The rattlesnake.'
0:09:00 > 0:09:02Subtitles by Red Bee Media Ltd
0:09:02 > 0:09:05E-mail subtitling@bbc.co.uk