Earthing an electric fence

I've never really thought about electric fences before and hadn't realised that they needed an Earth connection until I saw this  on St Agnes. The battery has two terminals, + and -. The + terminal is connected to the wire giving it a potential. When the animal touches the wire, it's feet are at 0 Volts so current will flow through it from the high potential to the 0 Volt potential. But for a suitable current to flow from the battery there needs to be a complete circuit. Current needs to flow back from the Earth to the battery, hence the Earth lead is connected to the - terminal on the battery. It turns out that the wetter the ground the better because the wet ground conducts, having a lower resistivity. https://www.rappa.co.uk/advice-centre/28-earthing-guide-for-electric-fencing     https://kencove.com/fence/97_How+an+Electric+Fence+Works_resource.php