Recent research shows that animals can be guided remotely by stimulating regions of the brain. Therefore, it is possible to set up an animal wireless sensor network for search and rescue operations, which is of great importance to society with a broad spectrum of applications, including natural disaster recovery, homeland security, and military operations. In a wireless biosensor network, each animal carries a backpack for data capture, processing, and network communications, and collaborates in routing and forwarding packets for each other. In this article the system architecture and operation of the biosensor network are introduced. A simple but efficient routing scheme tailored for this special sensor network is presented, as well as our implementation of a backpack prototype used to capture and transfer video data. Other major technical challenges and interrelated issues for this biosensor network are also addressed.