| Wireless sensor nodes deployed in hostile network conditions are required to report events such as enemy movements quickly and reliably. Unfortunately, current CSMA-based MAC protocols for wireless sensor networks suffer from varying degrees of starvation. Such starvation could lead to significant portions of the sensed area being {\it invisible} to the sink. It has been shown by prior research that such starvation is caused due to spatial bias and CSMA-based channel access. In this experimental work, we study how the use of B-MAC, the default CSMA-based MAC protocol can be the cause of starvation in a 35 node multihop wireless sensor testbed. We then show that the use of Z-MAC,
a hybrid MAC, can alleviate such starvation, while at the same time giving high channel utilization.
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