Movement patterns and survivorship of black-tailed deer migrating across Trinity Reservoir, California

We assessed seasonal movement patterns and survivorship of black-tailed dee r, Odocoileus hemionus columbianus, crossing Trinity Reservoir (Clair Engle Lake) in northern California by monitoring 2 fall and 2 spring migrations, beginning in fail 1993. Black-tailed deer traversed the reservoir using 43 routes located predominately in the narrowest sections of the reservoir. A group of 2-3 black-tailed deer typically swam together. Adult males and fe males were segregated by sex, but not by date. We estimated that as many as 389 black-tailed deer swam across the reservoir during daylight in a singl e migration. Two hundred and ninety-two of 302 black-tailed deer observed s wimming crossed successfully, The fate of the remaining 10 was not determin ed. Trinity Reservoir does not appear to be a major mortality source for mi grating black-tailed deer when it is ice free.