Nature's Calling Cat Litter. Nature’s Calling is an all-natural annually renewable resource making it one of the most environmentally friendly cat litters available. This super absorbent Nature's Calling Cat Litter is not only incredibly effective at absorbing ammonia and neutralising odour, but also clumps quickly on contact - making the removal of those unwanted lumps a breeze. All of which means there is less waste, so even the smallest pack of Nature’s Calling could last up to 30 days before the whole litter tray needs changing. Let your cat try this Natures Calling Cat litter made from the reclaimed lining of walnut shells making it completely 100% natural, biodegradable and flushable! The cat litter has proven odour control, fast clumping action and low dust which means less mess for both you and your cat!