Wooden products ccn split, crack and rot; think of a treetrunk as a bundle of straws filling up with water when it rains and drying out when it’s sunny, constantly expanding and contracting.
Here is a basic overview of how to prolong the life of the wood:
Keep it raised off the ground, an inch or two, either with screws in the underside or on pebbles or pot feet, this will allow air to circulate underneath and stop the carving from soaking up excess water.
Do not place your carving in direct sunlight; keeping it in a shady spot will stop it from heating up and cooling down too often and help to manage the moisture levels and any splits.
If it is already oiled then continue to oil it once a year. The oil will stop it from taking on water. Any external oil will do, but some will change the colour of the carving, always read the label. If the carving is not oiled then many apply generous coats in the first few months.
The carving may split or crack at some stage, depending on how wet the wood is. This is a natural process and can't be avoided. Splits tend to open up when it gets hot and close up when it's damp or cold. Keeping your carving out of strong sunlight and off the ground will help to reduce the the severity of cracks.
During the winter, large cracks can be made worse by water freezing inside them, protect the carving by covering it or placing it out of the way of frost and snow, perhaps under a tree.
Finally, don't forget to enjoy your carving; perhaps move it around now and then, hide it to confuse other members of the household, place comical things on it, take photos of it doing silly stuff, paint it or buy it another carving to keep it company!