Yaakov placed twelve stones around his head to protect him from animals. Why was he not scared that animals would attack the rest of his body and how would those small stones, which were small enough to collectively fit under his head when he slept, protect his head at all? Also, if he placed them there for protection wouldn't the miracle of them merging into one to all be his pillow defeat his intention of using them as defense?
Rashi quotes from the Midrash that the purpose of these stones was to protect him from the wild animals roaming free in the area. It seems strange that Jacob should think that a single row of stones could provide him with any real protection against the attack of wild animals. The truth is however that Jacob here teaches us a most important lesson: A person should in any given situation do whatever he can to protect himself and to provide for him and his family by any honest means available. At the same time, he must be aware that his personal effort will not protect him or provide for him; rather, G'd's constant watching over him is what takes care of his every need.
The Chassidic Masters explained this event as follows: Jacob knew that he was leaving the comfortable, holy presence of his father and mother in Israel, to wander into the unknown, corrupt territory of his uncle Lavan in a foreign land. There he would work day and night, trying to survive and still keep his moral character together, his trust and devotion to G-d intact. That’s why he prepared himself with an additional time secluded in learning about G-d and instilling these values internally. But even so, once he would enter the world of the conniving Lavan, how could he possibly keep his moral character strong? This is why Jacob surrounded only his head. Jacob was saying: “I’m not scared of the physical wild animals, but the spiritual ones! My spiritual integrity and beliefs will be attacked at every moment, and therefore I must always keep what’s in my head - what I have learned and what I believe now – intact.