The Remarkable Senses Of Animals | Nature's Great Migrations | BBC Earth

Elephants can respond to rain falling as far as 280 km away. It's not yet certain how they do this, but it's thought they might be able to detect the low-frequency sounds of the distant storms. Although zebra can't hear at such low frequencies as elephants, perhaps they've evolved their own way of detecting distant storms, timing their migration to coincide with rains that fall 250 km away in Naipan. But for now, the Chobe zebra are still staying put. There have been a few local showers, but something is stopping them from continuing their journey. The data from their collards show that they feed on the nutrient-rich grass in the burnt, wooded area during the day, and then travel back to the safety of the open plains at night. So why has Socks not done the same? Has she misread the cues? Or did another as-yet-undiscovered factor spur her on? It's becoming clear that the zebra's decision-making process is far more complex than first thought. A chance to check on Socks comes at one of the fire breaks, swathes cut in the forest to stop fires spreading over large areas. The collar data shows that Socks is due to cross one at any moment. It should give the team a chance to assess her condition and, crucially, to see whether she's had her foal. The team only get a glimpse of Socks, but it's enough. 90 km from her destination, they can confirm that she's alive and well and yet to give birth, information the satellite data alone could never provide. But it's also clear that there are only three zebra. Where is the rest of the family and, in particular, the stallion? Without his protection, these three are in even more danger of predation. Soon, after losing sight of Socks in the dense forest, her collar suddenly stops sending GPS location updates. Without this essential data, there is little chance of finding Socks in this vast wilderness. Her last known position is 40 km from Nykamp.