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Desert Bighorn Sheep: Monitoring Survival

Group of bighorn sheep In Fall 2001, we worked with the Nevada Division of Wildlife (NDOW) to collar five desert bighorn sheep (Ovis canadensis nelsoni) with satellite-received Platform Transmitter Terminals (PTTs) and relocate them to the Delamar Mountains in southern Nevada. Our objectives were to monitor the movements and survival of these relocated sheep with daily interpretation of collar sensor data received and to quickly advise NDOW when a mortality or dropped collar was indicated. Timely notification allowed state biologists to find a carcass within 72 hours while it was still possible to determine the cause of death. We provided biologists with the coordinates of satellite telemetry location estimates and they further homed to a VHF transmitter that was attached to each collar.

Daily, we evaluated the data and used information from changes in an animal’s locations and the activity and temperature sensors in the PTT to decide if there was potential for a mortality or dropped collar.

Below is a sensor data summary from a PTT collar on a live desert bighorn sheep. The count of changes in the activity sensor is incrementing regularly and the range of temperatures inside the PTT is normal. Thus we conclude for this period that the collar is on a live desert bighorn sheep.

We successfully detected all four mortalities that occurred and and NDOW personnel were able to find and study the carcasses, usually within 72 hours.

Table of Monitoring Data

date time (UTC) activity temp (C )
7/4/02 21:26:30 235
7/5/0200:07:37 2
7/5/0211:27:0926
7/6/02 01:04:4820
7/6/0201:46:5035
7/6/02 02:46:532031
7/6/0213:38:2326
7/6/0214:07:2526
7/7/0201:33:572832
7/7/0202:25:59 3029
7/7/0214:05:3238
7/7/0216:20:3931
7/7/0217:51:4336
7/8/02 05:17:155428