The three wires at the top of the pole carry 7200V three phase. One of those phases is tapped and provides power to the transformer. If the animal takes out that line, all power to the transformer and all power to the street is lost.

Once the transformer has power (7200V) it reduces the 7200V to the split single phase common to most residences (240V). This setup is three wires, two with voltage and a common neutral. The two with voltage are 120V, 180 degree out of phase to produce 240V when measured against each other. Any one of the two 120V lines will read 120V when measured against the common neutral.

If one of those 120V legs is lost at the transformer, the residences will lose about one-half of the circuits in the house (as one leg is now zero). Also, none of the 240V appliances will function as they can only receive 120V from the single working leg (and might receive nothing if the failed leg is floating without a ground).