00:00 the archerfish.
00:01 Omnivorous, opportunistic, and an expert marksman.
00:09 It will consume anything floating in the water,
00:14 but has developed an extraordinary skill
00:18 for hunting prey far beyond their aquatic domain.
00:22 (dramatic music)
00:28 (arrow whooshing)
00:30 A master of physics, the archerfish
00:33 can make lightning quick calculations
00:35 to perfect its aim and dislodge prey.
00:39 (arrow whooshing)
00:44 A garden orb weaver spider has selected a branch
00:53 to form the foundation of its web.
00:55 (dramatic music)
00:57 Little does it know, the new property
01:00 is well within the fish's accurate six foot range.
01:04 When eyeing its quarry,
01:09 the archer must compensate for refraction,
01:12 the bending of light as it passes from air to water.
01:17 Viewed from below, the target isn't exactly where it seems.
01:24 (dramatic music)
01:27 Despite the accurate shot,
01:30 the spider manages to maintain its grip on the branch.
01:33 Compressing its tongue against a groove in its mouth,
01:39 the fish creates a tube to funnel the water.
01:42 A special cover over the gills rapidly snaps shut,
01:47 forcing the water through the tube.
01:53 Once again, the spider clings on.
01:56 This archer must also account
01:59 for the curved trajectory of the water jet,
02:02 letting gravity bend the shot toward the target.
02:09 Success.
02:21 Beneath the tar on the valley floor,
02:24 rare pools of water team with life.
02:26 Freshwater fish.
02:29 Only three species survive in the Al Hajar mountains,
02:33 and this one is the Oman gara.
02:35 They endure only in isolated permanent pools of the wadi.
02:40 These tiny fish get by scraping algae
02:45 and any other detritus from the rock walls
02:47 of their watery prison.
02:49 (dramatic music)
02:51 Their survival depends on much needed rainfall
02:54 to replenish their shrinking refuge.
02:56 But rain is unpredictable in Arabia.
03:02 Some years it does not rain at all.
03:08 Then some pools will dry up,
03:12 and the fish in those will die.
03:16 80% of the water that falls in the mountains will evaporate.
03:20 The rest quickly runs off the hard ground
03:23 and into cracks in the rocks.
03:25 Rain here in the Al Hajar mountains
03:30 is erratic and unreliable.
03:32 A mere six inches falls each year,
03:37 and it comes in only a few short, heavy bursts.
03:45 The rain runs off the mountains,
03:47 building momentum as it descends to the valley floor.
03:50 Light rain can quickly turn tranquil pools into rapids.
03:58 While toads stay clear,
04:07 the rushing water has the opposite effect on the garra fish.
04:14 This is the opportunity they've been waiting for.
04:17 They have a mysterious, instinctive drive
04:23 to always explore upstream,
04:25 driven by the need to expand their territory.
04:28 They take whatever opportunity they can
04:35 to forge into the current.
04:37 This is how the species can recolonize areas
04:42 where the previous inhabitants have perished.
04:44 But this is not just fish swimming up river.
04:50 These fish undertake an epic climb.
04:54 Their sucker mouths,
04:59 which usually scrape algae from the rocks,
05:02 become anchors,
05:03 securing them against the fast-flowing water.
05:06 (water splashing)
05:09 A group inches its way up the rocks.
05:14 The fish must stay within the splash zone
05:22 in order to breathe,
05:24 but stay out of the main flow
05:26 to avoid being washed back downstream.
05:36 The fish can travel up to nine feet up sheer rock faces.
05:40 For those that make it into new pools,
05:47 there are fresh possibilities,
05:49 food, and a new territory to colonize.
05:53 The stress of the journey is also thought
06:00 to trigger their spawning behavior
06:03 to make sure every new pool is quickly populated
06:06 by the pioneers.
06:07 Their sticky eggs will settle in the gravel
06:13 to stop them washing back downstream.
06:15 (upbeat music)
06:18 (water splashing)
06:21 (upbeat music)
06:23 (upbeat music)
06:26 [MUSIC]
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