A pet trust can be established thorough a testamentary trust or with an inter vivos trust.
An inter vivos trust is one that takes place immediately upon the completion and execution of the document. We generally think of this type of trust as a living trust and it is usually revocable by the trust grantor, creator or settlor (all of these terms are used interchangeably).
The living trust can be used to plan for unforeseen circumstances such as incapacity, disability and eventually the death of the grantor.
The grantor also usually serves as the original trustee or co-trustee. In the case where two or more co-trustees serve, the trust instrument can provide that either trustee may act alone on behalf of the trust or require both co-trustees to actor sign.
The trust may never actually be needed or used until the death of the grantor, but it is always available if necessary. It can be changed or altered or even revoked by the grantor at any time.
In a pet trust, this provides that there will be no lapse of care or treatment for your pet and no delay because of any probate process.
On the other hand, a testamentary trust is one that is created in a will.
Since a will is an ambulatory instrument, in that it never is effective until the testator (the one who writes the will) actually dies, this trust will not spring to use until the pet owner is no longer around.
Additionally, a will must go through the probate process, see here, and there may well be some time delays.
This delay may cause issues for the ability of your pet caretaker to secure the means and authority to take care of your pet.
One advantage of this type of trust is that is may be less expensive than the living trust. The trust clauses can be incorporated into the will of the pet owner and thus, become an integral part of the overall estate planning process.