干旱区生态环境知识资源中心

We studied mule deer (Odocoileus hemionus) presence associated with the All-American Canal (AAC) before, during, and after the U.S. Bureau of Reclamation and Imperial Irrigation District replaced a 36.8-km section of the earthen canal in Imperial County, California with a concrete-lined canal. The concrete-lined canal had steeper sides and higher water velocities than the unlined canal, increasing the risk of mule deer drowning in the canal. Our objective was to determine if the concrete-lined canal had an effect on the occurrence of mule deer along the AAC based on observations, aerial surveys, track plots, and camera traps. We examined deer presence at the AAC prior to lining (2004-2006), during lining (2007-2009), and post-lining (2010-2014). We monitored 1-m(2) track plots north and south of the AAC from 2004 to 2010. We did not find deer south of the canal and deer were rarely found north of the canal from December to April; thus, during 2011-2014, we monitored areas north of the canal from May to November. We also monitored deer at two mitigation catchments (established based on the first years of the study), one previously established catchment, and a sheet pile seam (i.e., 6-m wide gap or seam where the canal has a piece of sheet metal covered with rip-rap rock and dirt instead of cement) that deer used to access the canal. During the pre-lining phase, only one deer was reported near the canal. During the lining-phase we detected deer in a small area north of and adjacent to the canal. There were occasional observations of deer: three that drowned and two that were rescued from the canal. During the post-lining phase we documented continued deer presence at the canal and mitigation catchments. One deer drowned in the canal and one was rescued. The number of deer tracks at the canal remained consistent from 2008 to 2010 and from 2011 to 2014 as did the number of photos; thus, the mitigation catchments did not reduce deer use of the canal. We recommend that the sheet pile seam deer use to access the canal be maintained and kept free of vegetation. Further, we conclude the development of water catchments for this small population of deer crossing sand dunes to acquire water was not necessary. Deer use of the sheet pile seam was unanticipated and fortuitous for deer attempting to acquire water from the AAC.