Since 1994, we have used Trailmaster TM Model TM1500 camera systems to monitor mule deer (Odocoileus hemionus) populations and habitat use in the central Sierra Nevada. Factory-provided mounts, 1-m tall wooden stakes, and an infrared pulse length of 0.25 sec (5 pulses) were used with the systems during the winters of 1994-95 and 1995-96. We used three plywood boxes, 1.5-m tall steel t-posts, and an infrared pulse length of 0.75 sec (15 pulses) during the winters of 1996-97 and 1997-98. Different mounts and pulse settings were used from 1996-1998 to minimize problems we encountered with factory mounts, stakes, and shorter pulse from 1994-1996. The number of pictures with deer increased (P < 0.001), while the number of pictures without deer decreased (P < 0.001) with the boxes, t-posts, and longer pulse used in 1996-98. The boxes and t-posts protected the units from inclement weather, and provided a stable platform for the transmitter and receiver. Lengthening the pulse made the units less sensitive to rain, snow, and fog and leaves, twigs, and vegetation blowing in the wind that might break the infrared beam and trigger the camera to take photographs of non animal events.
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