Using Vaginal Implant Transmitters to Aid in Capture of Mule Deer Neonates

Abstract

Estimating survival of the offspring of marked female ungulates has proven difficult in free-ranging populations yet could improve our understanding of factors that limit populations. We evaluated the feasibility and efficiency of capturing large samples (i.e., .80/yr) of neonate mule deer (Odocoileus hemionus) exclusively from free-ranging, marked adult females using vaginal implant transmitters (VITs, n ¼ 154) and repeated locations of radiocollared females without VITs. We also evaluated the effectiveness of VITs, when used in conjunction with in utero fetal counts, for obtaining direct estimates of fetal survival. During 2003 and 2004, after we placed VIT batteries on a 12-hour duty cycle to lower electronic failure rates, the proportion that shed 3 days prepartum or during parturition was 0.623 (SE ¼ 0.0456), and the proportion of VITs shed only during parturition was 0.447 (SE ¼ 0.0468). Our neonate capture success rate was 0.880 (SE ¼ 0.0359) from females with VITs shed 3 days prepartum or during parturition and 0.307 (SE ¼ 0.0235) from radiocollared females without VITs or whose implant failed to function properly. Using a combination of techniques, we captured 275 neonates and found 21 stillborns during 2002À2004. We accounted for all fetuses at birth (i.e., live or stillborn) from 78 of the 147 females (0.531, SE ¼ 0.0413) having winter fetal counts, and this rate was heavily dependent on VIT retention success. Deer that shed VITs prepartum were larger than deer that retained VITs to parturition, indicating a need to develop variable-sized VITs that may be fitted individually to deer in the field. We demonstrated that direct estimates of fetal and neonatal survival may be obtained from previously marked female mule deer in free-ranging populations, thus expanding opportunities for conducting field experiments. Survival estimates using VITs lacked bias that is typically associated with other neonate capture techniques. However, current vaginal implant failure rates and overall expense limit broad applicability of the technique. (JOURNAL OF WILDLIFE MANAGEMENT 71(3): 945-954; 2007)

Growth and mortality of sympatric white‐tailed and mule deer fawns

“…We conducted fawn searches from late May through late August in 2004–2006 because white‐tailed deer birthing peaked near 20 June and mule deer birthing peaked 1 month later (Haskell et al ). We used vaginal implant transmitters (VIT) to help locate birth sites and capture true neonates <24 hours postpartum (Carstensen et al , Bishop et al , Haskell et al , Tatman et al ). We monitored very high frequency (VHF) signals of VITs daily from the ground between 0001–0700 hours to preclude false‐negative signals caused by direct sunlight on heat switches of expelled VITs (S. P. Haskell, personal observation).…”

Comparison of pregnancy detection methods in live white‐tailed deer

“…We used trans‐abdominal ultrasonography (SonoSite 180™; L38/10–5 MHz transducer; SonoSite, Inc., Bothell, WA) to determine pregnancy (Bishop et al 2007) and estimate maximum rump fat depth (MXF; Cook et al 2001) to the nearest 0.1 mm, as described by Stephenson et al (1998). Generally, our ultrasound pregnancy observation time was ≤5 minutes.…”

Vaginal Implant Transmitters as a Tool for Pronghorn Fawn Capture

“…Vaginal implant transmitters (VITs) are radio transmitters inserted into the vaginal canal of a female ungulate and held in place by flexible silicone wings to be expelled at parturition. Use of VITs can improve precision and accuracy in determining parturition timing and location, resulting in better estimates of juvenile survival (Carstensen et al , Bishop et al , Haskell et al , Tatman et al ). Vaginal implant transmitters have been used for a variety of ungulates including mule deer ( Odocoileus hemionus ; Johnstone‐Yellin et al , Bishop et al , Haskell et al ); Columbian black‐tail deer ( O. h. columbianus ; Pamplin ); white‐tailed deer ( O. virginianus ; Haskell et al ); elk ( Cervus elaphus ; Vore and Schmidt , Johnson et al ); and bighorn sheep ( Ovis canadensis ; Smith et al ; Table ).…”

“…These first‐generation VITs were surgically sutured into mule deer, which frequently caused localized trauma and increased infection risk (Garrott and Bartmann , Barbknecht et al ). Eventually, VITs were equipped with flexible wings to secure them in place, eliminating the need for suturing, and greater wing width improved retention of VITs (Bishop et al , Haskell et al ). Antenna clipping (i.e., shortening) became standard practice to prevent ungulates (primarily white‐tailed and mule deer) from removing transmitters with their teeth (Seward et al , Haskell et al , Barbknecht et al , Tatman et al ); although this behavior has only been documented once, by Carstensen et al () who found bite marks on one VIT antenna post‐expulsion.…”

“…Previous studies used VITs that were equipped exclusively with a temperature sensor designed to change the pulse rate of the VIT to indicate expulsion (Carstensen et al , Johnstone‐Yellin et al , Bishop et al , Barbknecht et al , Tatman et al ). Temperature sensors activated precise event transmitter (PET) codes when the VIT temperature dropped below 34° C (Tatman et al ).…”