https://cpw.cvlcollections.org/files/original/5d353c06a1c72cc517d19a53d7f1d133.pdf 4dd720af10a75f376c0b84a9cb753bf4 PDF Text Text The research in this publication was partially or fully funded by Colorado Parks and Wildlife. Dan Prenzlow, Director, Colorado Parks and Wildlife • Parks and Wildlife Commission: Marvin McDaniel, Chair • Carrie Besnette Hauser, Vice-Chair Marie Haskett, Secretary • Taishya Adams • Betsy Blecha • Charles Garcia • Dallas May • Duke Phillips, IV • Luke B. Schafer • James Jay Tutchton • Eden Vardy �The Journal of Wildlife Management 75(8):1797–1806; 2011; DOI: 10.1002/jwmg.229 Research Article Effectiveness of a Redesigned Vaginal Implant Transmitter in Mule Deer CHAD J. BISHOP,1 Colorado Division of Wildlife, 317 W. Prospect Road, Fort Collins, CO 80526, USA CHARLES R. ANDERSON Jr., Colorado Division of Wildlife, 711 Independent Avenue, Grand Junction, CO 81503, USA DANIEL P. WALSH, Colorado Division of Wildlife, 317 W. Prospect Road, Fort Collins, CO 80526, USA ERIC J. BERGMAN, Colorado Division of Wildlife, 317 W. Prospect Road, Fort Collins, CO 80526, USA PETER KUECHLE, Advanced Telemetry Systems, 470 First Avenue N., Isanti, MN 55040, USA JOHN ROTH, Advanced Telemetry Systems, 470 First Avenue N., Isanti, MN 55040, USA ABSTRACT Our understanding of factors that limit mule deer (Odocoileus hemionus) populations may be improved by evaluating neonatal survival as a function of dam characteristics under free-ranging conditions, which generally requires that both neonates and dams are radiocollared. The most viable technique facilitating capture of neonates from radiocollared adult females is use of vaginal implant transmitters (VITs). To date, VITs have allowed research opportunities that were not previously possible; however, VITs are often expelled from adult females prepartum, which limits their effectiveness. We redesigned an existing VIT manufactured by Advanced Telemetry Systems (ATS; Isanti, MN) by lengthening and widening wings used to retain the VIT in an adult female. Our objective was to increase VIT retention rates and thereby increase the likelihood of locating birth sites and newborn fawns. We placed the newly designed VITs in 59 adult female mule deer and evaluated the probability of retention to parturition and the probability of detecting newborn fawns. We also developed an equation for determining VIT sample size necessary to achieve a speciﬁed sample size of neonates. The probability of a VIT being retained until parturition was 0.766 (SE ¼ 0.0605) and the probability of a VIT being retained to within 3 days of parturition was 0.894 (SE ¼ 0.0441). In a similar study using the original VIT wings (Bishop et al. 2007), the probability of a VIT being retained until parturition was 0.447 (SE ¼ 0.0468) and the probability of retention to within 3 days of parturition was 0.623 (SE ¼ 0.0456). Thus, our design modiﬁcation increased VIT retention to parturition by 0.319 (SE ¼ 0.0765) and VIT retention to within 3 days of parturition by 0.271 (SE ¼ 0.0634). Considering dams that retained VITs to within 3 days of parturition, the probability of detecting at least 1 neonate was 0.952 (SE ¼ 0.0334) and the probability of detecting both fawns from twin litters was 0.588 (SE ¼ 0.0827). We expended approximately 12 person-hours per detected neonate. As a guide for researchers planning future studies, we found that VIT sample size should approximately equal the targeted neonate sample size. Our study expands opportunities for conducting research that links adult female attributes to productivity and offspring survival in mule deer. ß 2011 The Wildlife Society. KEY WORDS birth site, capture, Colorado, fawn, fetus, mule deer, neonate, Odocoileus hemionus, parturition, vaginal implant transmitter (VIT). Mule deer (Odocoileus hemionus) fawn production and neonatal survival is inﬂuenced by dam characteristics (e.g., body condition, disease status, habitat use). To understand fawndam relationships, manipulative ﬁeld studies are needed that allow fawn production and survival to be estimated as a function of treatments applied to adult females. For example, a study evaluating the effectiveness of winter range habitat treatments on subsequent neonatal survival would require the capture of fawns from marked adult females that veriﬁably used, or did not use, the habitat treatments the previous Received: 27 June 2010; Accepted: 23 March 2011; Published: 16 September 2011 1 E-mail: chad.bishop@state.co.us Bishop et al. � Vaginal Implant Transmitters in Deer Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife winter(s). Such studies depend on a technique that enables newborn fawns to be captured from marked adult females. The most promising technique employed to capture neonates from marked adult females is use of vaginal implant transmitters (VITs), which are placed in the vagina of adult females during early to mid gestation. In theory, adult females retain VITs until parturition, at which point VITs are expelled at birth sites along with newborn fawns. Assuming VITs are routinely monitored, researchers can promptly radio-locate shed VITs and capture the newborn fawns. Recent applications of VITs in white-tailed deer (O. virginianus; Carstensen et al. 2003, Haskell et al. 2007, Saalfeld and Ditchkoff 2007), black-tailed deer (O. hemionus columbianus; Pamplin 2003), mule deer (Bishop et al. 2007, Haskell et al. 2007), and elk (Cervus 1797 �elaphus; Johnson et al. 2006, Barbknecht et al. 2009) have been moderately successful. Vaginal implant transmitters also permit measurement of fetal survival in free-ranging populations, which has important implications in populations where stillborn mortality occurs (Bishop et al. 2007, 2008, 2009). An additional advantage of using VITs to capture neonates may be a reduction in sampling bias when compared to capture techniques that rely on opportunistic fawn capture (White et al. 1972, Ballard et al. 1998, Pojar and Bowden 2004). Opportunistic techniques are susceptible to bias because of unequal capture success among vegetation types, distances to roads, fawn ages, and stages of fawning. For example, if roads are used to conduct opportunistic searches, fawn capture probability will decline with increasing distance from a road and neonates will be disproportionately sampled in areas with high road densities. When using VITs, the distribution of radio-marked adult females carrying VITs determines where neonates are sampled. Inferences will be less biased with VITs than with opportunistic capture techniques if all VITs are monitored with equal intensity during fawning and the sample of radio-marked adult females was captured with minimal bias. Thus, VITs could have broad applicability regardless of whether study objectives require that fawns be captured from previously marked adult females. The most signiﬁcant problem associated with VITs has been premature expulsion and subsequent failure to locate birth sites or newborn fawns, especially in mule deer (Johnstone-Yellin et al. 2006, Bishop et al. 2007, Haskell et al. 2007). The VIT has ﬂexible, plastic wings coated with a soft silicone that induce pressure against the vaginal wall to retain the transmitter. The VIT design facilitates a quick, non-surgical insertion process and is safe for the animal (Johnson et al. 2006), but the current wing design is inadequate with respect to retention. Bishop et al. (2007) found that 43% (SE ¼ 4.7) of VITs in mule deer shed prepartum, although the probability of capturing �1 fawn was relatively high (0.792, SE ¼ 0.0847) when VITs shed only 1–3 days prepartum. They noted that 25% (SE ¼ 4.1) of VITs shed >3 days prepartum and that retention probability declined as deer body size increased, indicating the retention wings were too small to be effective in larger deer. Several other VITs in their study went missing during spring migration and may have been shed prematurely as well. Based on these results, considerable oversampling of adult females would be required in the design of future projects to achieve a target sample size of fawns. That is, extra adult females would need to be sampled to offset those adult females that shed VITs prematurely. Oversampling, in this instance, is undesirable from an animal care and use perspective and unnecessarily expensive. Thus, our objective was to redesign the plastic– silicone retention wings of VITs to allow maximum retention in larger deer species. To date, the wings used to retain VITs have been purchased from a company in New Zealand (Carter Holt Harvey Plastic Products, Hamilton, New Zealand) that originally produced them for an application in the livestock industry (Bowman and Jacobson 1998). The company manufactured 1 large 1798 Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife wing and 1 small wing; the former has been used in production of VITs for bison (Bison bison) and elk (Cervus elaphus) whereas the latter has been used in production of VITs for deer (Advanced Telemetry Systems, Isanti, MN). Advanced Telemetry Systems (ATS), in cooperation with wildlife researchers, made an initial effort in 2004 to lengthen the retention wings by adding resin to the wing tips. Using these VITs with antennas cut to the appropriate length, Haskell et al. (2007) reported that 81% of VITs (n ¼ 21) in deer were retained until parturition. Retention improved but the aftermarket wing-modiﬁcation was problematic because the wing tips were hard and thus not ideal for placement in the vaginal canal. The Haskell et al. (2007) study provided justiﬁcation to pursue further wing development. We therefore redesigned retention wings of VITs used in deer and similarsized ungulates, fabricated a new production mold, and evaluated retention rates of VITs in free-ranging mule deer. STUDY AREA We conducted our research in Piceance Basin and on the Roan Plateau in northwest Colorado (Fig. 1). Our winter range study area comprised 4 study units distributed across much of the Piceance Basin. The 4 units ranged in size from 70 km2 to 130 km2 and were referenced as South Magnolia, Story-Sprague, Ryan Gulch, and Yellow Creek (Fig. 1). These study units are part of a larger research study evaluating effects of natural gas development and mitigation on mule deer (Anderson and Freddy 2008). Winter range habitat was comprised predominantly of pinyon pine (Pinus edulis) and Utah juniper (Juniperus osteosperma) and secondarily of big sagebrush (Artemisia tridentata), serviceberry (Amelanchier spp.), mountain mahogany (Cercocarpus montanus), bitterbrush (Purshia tridentata), and rabbitbrush (Chrysothamnus spp.). Drainage bottoms were characterized by stands of big sagebrush, saltbush (Atriplex spp.), and black greasewood (Sarcobatus vermiculatus), with the majority of the primary drainage bottoms having been converted to irrigated, grass hay ﬁelds. Elevations ranged from 1,860 m at Piceance Creek in Ryan Gulch to 2,280 m in Yellow Creek and Story-Sprague study units. Our summer range study area comprised roughly 1,700 km2 across the Roan Plateau and Piceance Basin (Fig. 1). Principal summer range habitat types included aspen (Populus tremuloides), mountain shrub, oakbrush (Quercus gambelii), big sagebrush, and pinyon-juniper. Serviceberry, snowberry (Symphoricarpos spp.), and chokecherry (Prunus virginiana) were common species in mountain shrub communities. Elevation ranged from 2,000 m in Piceance Creek at the mouth of Story Gulch to 2,600 m on Roan Plateau. METHODS We worked with ATS personnel to redesign the M3930 VIT presently manufactured by ATS. The existing M3930 has been described in detail elsewhere (Bowman and Jacobson 1998, Carstensen et al. 2003, Johnstone-Yellin et al. 2006, Bishop et al. 2007). Our redesign included changes to the retention wings and the means by which they are attached to the transmitter body (Fig. 2). Speciﬁcally, we modiﬁed The Journal of Wildlife Management � 75(8) �Figure 1. Location of winter and summer range study areas in Piceance Basin and Roan Plateau, northwest Colorado, 2009. Winter range study units where we captured and radio-marked mule deer are noted as: YC (Yellow Creek), RG (Ryan Gulch), SM (South Magnolia), and SS (Story-Sprague). dimensions of the retention wings by lengthening them from 57 mm to 68 mm and widening them from 9 mm to 13 mm. We also added ridges to the wing surface as means to increase probability of retention to parturition. The wings were made of ﬂexible plastic encased in silicone. We initially produced a small number of the newly designed wings using a relatively inexpensive prototype mold, which met our target speciﬁcations and therefore was deemed acceptable. We then manufactured a production mold, necessary to produce a large number of the wings. We incorporated ejector pins into the VIT design that allow wings to be attached to the VIT transmitter body in the ﬁeld. In the original design, ATS permanently afﬁxed wings to the transmitter body during the VIT assembly process. Although we only used 1 wing size in this study, ﬁeld-attachment will allow researchers to use �1 wing size or style, without purchasing extra transmitters, if additional production molds are manufactured over time. For each wing design (i.e., production mold), extra wings could be inexpensively purchased and available in the ﬁeld to Bishop et al. � Vaginal Implant Transmitters in Deer Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife afﬁx to the ﬁxed number of transmitter bodies. Researchers could then individually ﬁt VITs to animals in the ﬁeld much in the same way radiocollars are individually ﬁtted. During late February and early March 2009, we captured 60 adult female deer using helicopter net guns (Barrett et al. 1982, Krausman et al. 1985, White and Bartmann 1994) in conjunction with ongoing research addressing other objectives (Anderson and Freddy 2008). We captured 20 deer each in Ryan Gulch and Yellow Creek, and 10 deer each in South Magnolia and Story-Sprague study units (Fig. 1). We hobbled, blind-folded, and ferried captured deer �5 km by helicopter to a central handling location. For each captured deer, we used transabdominal ultrasonography (SonoVet 2000; Universal Medical Systems, Bedford Hills, NY) to determine pregnancy status and number of fetuses (Stephenson et al. 1995, Bishop et al. 2007, Bishop et al. 2009). We also measured rump fat depth of each deer using ultrasonography and estimated a body condition score using palpation to estimate percent body fat (Stephenson et al. 1799 �Figure 2. Three-dimensional view (A) and dimensions (B) of a modified retention wing used to retain vaginal implant transmitters in adult female mule deer. The displayed dimensions at bottom include a nylon core with an elastomeric overmold that protects deer from any sharp or rigid edges. 2002, Cook et al. 2007). We measured mass by placing each deer on a stretcher and attaching the stretcher to a scale supported by a steel frame. We measured chest girth by placing a cloth tape around the chest immediately posterior to the front shoulders and recording measurement when deer exhaled. Last, we measured hind foot length of each deer and estimated age by evaluating tooth replacement and wear (Severinghaus 1949, Robinette et al. 1957). This aging technique is susceptible to measurement error (Hamlin et al. 2000). However, 2 trained observers, each with experience aging >1,000 deer in the ﬁeld, estimated age of all deer to minimize error and to insure that relative age differences across all deer in our sample were correctly recorded. We performed handling procedures in a wall-frame tent to create a dim environment for viewing ultrasound imagery. We ﬁtted each pregnant deer with a radiocollar and VIT. We programmed collar transmitters to turn off on Saturdays 1800 Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife and Mondays to extend battery life for meeting other research objectives (Anderson and Freddy 2008). Each collar was equipped with a mortality sensor and store-on-board Global Positioning System (GPS). We programmed mortality sensors to switch signal transmission from 60 pulses to 120 pulses per minute after remaining motionless for 8 hr. Each VIT had a temperature-sensitive switch and a precut antenna (6 cm in length) with the antenna tip encapsulated in a resin bead to eliminate sharp edges. The temperature-sensitive switch caused the VIT to increase pulse rates from 40 pulses to 80 pulses per minute when the temperature dropped below 328 C, which was indicative of VIT expulsion. We sterilized VITs in a chlorhexidine solution prior to insertion in the ﬁeld. We inserted VITs using a clear, plastic swine vaginoscope (Jorgensen Laboratories, Inc., Loveland, CO) and alligator forceps. The vaginoscope was 15.2 cm long with a 1.59 cm internal The Journal of Wildlife Management � 75(8) �diameter and had a smoothed end to minimize vaginal trauma. We placed vaginoscopes and alligator forceps in cold sterilization containers with chlorhexidine solution between each use, used a new pair of surgical gloves to handle the vaginoscope and VIT for each deer, and applied lidocaine topically to the deer’s vagina to minimize irritation during VIT insertion. To insert a VIT, we folded the wings together and placed the VIT into the end of the vaginoscope. We liberally applied sterile KY Jelly1 (Johnson and Johnson, New Brunswick, NJ) to the scope and inserted it into the vaginal canal until the tip of the VIT antenna was approximately ﬂush with the vulva. We used previous ﬁeld experience to guide insertion distance and antenna length (Bishop et al. 2007). We extended alligator forceps through the vaginoscope to ﬁrmly hold the VIT in place while the scope was pulled out from the vagina. During winter and spring, we monitored live-dead status and general location of radiocollared adult females daily from the ground, except when collars were inactive, and biweekly from the air via ﬁxed-wing aircraft. During June, we checked VIT signal status each morning of the week that radiocollars were active by aerially locating each radiocollared doe carrying a VIT. We began ﬂights at approximately 0630 hours and completed them by 0900–1100 hours. Early ﬂights were necessary to detect fast signals because temperature sensors of VITs expelled in open habitats and subject to sunlight often exceeded 328 C by mid-day, which caused VITs to switch back to a slow (i.e., prepartum) pulse (Newbolt and Ditchkoff 2009). When we detected a fast (i.e., postpartum) pulse rate, we ground-located the VIT and radiocollared doe within �3 hr using very high frequency (VHF) receivers and directional antennae. We attempted to observe behavior of the collared adult female, established whether the VIT was shed at a birth site, and searched for fawns in the vicinity of the adult female and expelled VIT. In cases where the dam moved away from the VIT (i.e., >200 m), we located the VIT to determine whether shedding occurred at a birth site and whether any stillborn fawns were present and subsequently located the collared dam to search for fawns at her location. We attempted to account for each dam’s fetus(es) as live or stillborn. We typically worked in pairs, which allowed us to effectively partition effort across the study area while maintaining efﬁciency when searching for neonates (i.e., 2 people were more effective locating a hidden neonate than 1 person). We described effort associated with locating fawns by calculating the number of person-hours per fawn. We also quantiﬁed cost per fawn by considering all operating and personnel expenses, including capture and VIT costs for adult females. All deer capture and handling procedures and use of VITs were approved by Colorado Division of Wildlife’s (CDOW) Institutional Animal Care and Use Committee (Project # 17-2008). We assigned the fate of each VIT to 1 of 4 categories: 1) retained (i.e., VIT expelled during parturition), 2) nearly retained (i.e., VIT expelled �3 days prepartum), 3) not retained (i.e., VIT expelled >3 days prepartum), or 4) censored. We determined a VIT was retained if we located the VIT at a birth site and located neonate(s) near the VIT or in Bishop et al. � Vaginal Implant Transmitters in Deer Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife close proximity to the dam. In some cases, the VIT was not at a birth site but we readily found the dam and her newborn fawn(s) nearby, sometimes at a birth site 10–100 m from the VIT. In these situations, we considered a VIT retained if we documented <1-day-old fawn(s) <24 hr after the VIT was expelled. We also considered a VIT retained if it was located at an evident birth site irrespective of whether we subsequently located fawn(s). Birth sites appeared as atypically large deer beds with soil appearing damp and with forbs and grasses ﬂattened and radiating outward, consistent with a deer licking the site clean. On some occasions, fawns and/or placental remains were still present at birth sites when we arrived, providing positive conﬁrmation of birth site characteristics. We distinguished VITs expelled �3 days prepartum as nearly retained because they provided useful information for locating fawns, consistent with Bishop et al. (2007). We documented such cases by locating a dam’s neonate(s) �1 days after the VIT was expelled and comparing neonate age to VIT expulsion date. We estimated neonate age using hoof characteristics, condition of the umbilical cord, pelage, and behavior (Haugen and Speake 1958, Robinette et al. 1973, Sams et al. 1996, Pojar and Bowden 2004). We assumed a VIT was shed >3 days prepartum if the VIT was not at an evident birth site and we documented �2 of the following characteristics: 1) the adult female was located with other deer during repeated relocations for >3 days after the VIT was shed, 2) the adult female exhibited no behavioral cues indicating she had a fawn, 3) the adult female was noticeably still pregnant, and 4) we failed to locate a neonate following repeated searches for �1 week after the VIT was shed. We censored VITs from our retention analysis when adult females died prior to parturition or when adult females were located on private land that we did not have permission to access. In either case, we were unable to evaluate VIT retention to parturition. All females dying prior to parturition were still carrying the VITs upon death. We modeled VIT retention probability using a generalized logits model (i.e., multinomial logistic regression) in PROC LOGISTIC in SAS (SAS Institute, Cary, NC). We evaluated goodness-of-ﬁt of the global model (i.e., model containing each predictor variable) by dividing model deviance by its degrees of freedom. We considered 3 levels of retention consistent with our description above (i.e., retained, nearly retained, not retained) and we removed all censors from the dataset prior to analysis. Our primary purpose for this analysis was to evaluate whether our VIT design modiﬁcations increased VIT retention probability in larger deer. We based our design modiﬁcations on the observation by Bishop et al. (2007) that VIT retention probability declined as deer body size increased. We modeled VIT retention as a function of mass (kg), hind foot length (cm), chest girth (cm), adult female age (yr), and body fat (%). We considered only linear models because we lacked a rationale for evaluating higherorder polynomial functions. Several of the variables we considered in our analysis were likely correlated because they represented different ways of expressing deer body size. We did not expect models comprising each of these variables to 1801 �receive more support than simpler models. Thus, we focused our candidate model set on models with 1 or 2 variables. We evaluated all single-variable models plus we evaluated 2variable models that included age with each other variable. Body size partially related to age. However, the number of times a female had previously given birth also related to age, as might individual behavior, either of which could inﬂuence retention probability. Thus, age tested hypotheses about retention probability that were not just related to body size or condition. We also considered several biologically plausible models with �3 variables. We evaluated 13 models in total and selected among models using Akaike’s Information Criterion adjusted for sample size (AICc; Burnham and Anderson 2002). To facilitate model comparisons, we reported the difference in AICc values between a speciﬁed model and the model with the minimum AICc (DAICc). We selected among models using model weights (wi; Burnham and Anderson 2002), which sum to 1 and can be interpreted as probabilities. Models with the lowest AICc and highest wi values were best supported by the ^ data. We model-averaged beta parameter estimates ( b; Burnham and Anderson 2002) to incorporate model selection uncertainty when evaluating whether VIT retention probability varied as a function of the variables in our analysis. We did not model-average real parameter estimates because each of our predictor variables was continuous. We modeled fawn detection probability based on adult females that retained or nearly retained VITs. We planned to conduct separate analyses for singleton and twin litters, but we achieved perfect detection with singleton litters. We therefore modeled fawn detection probability considering only females with twin fetuses using a generalized logits model in SAS, and we evaluated goodness-of-ﬁt by dividing model deviance by its degrees of freedom. We used 3 detection levels (0, 1, 2 fawns) and we modeled detection as a function of VIT retention status (retained vs. nearly retained), VIT shed-day, adult female age, and vegetative cover at VIT expulsion site. Shed-day distinguished between VITs detected on fast pulse on Sundays and Tuesdays (dummy code ¼ 1) and VITs detected on fast pulse during Wednesday–Friday (dummy code ¼ 0). We used the shed-day variable to evaluate whether delayed response time, caused by our inability to monitor deer on Saturdays and Mondays, inﬂuenced our ability to detect fawns. We included adult female age in our analysis to evaluate if older females may have been more experienced at hiding fawns. Last, we used vegetative cover to evaluate if fawns were more difﬁcult to detect in heavier cover. We expressed vegetative cover categorically as low, medium, or high based on a visual assessment at the site. We characterized the low cover class as having limited understory and overstory vegetation with minimal visual obstruction at ground level (e.g., sparsely vegetated grass, sagebrush, or mountain shrub slopes). The medium cover class had moderate to heavy vegetative cover within 1 m of the ground but limited cover above 1 m (e.g., typical sagebrush, mountain shrub sites). High cover class comprised moderate to heavy vegetative cover from ground level up to >1 m with nearly complete visual 1802 Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife obstruction (e.g., oakbrush, aspen-mountain shrub, dense serviceberry). We evaluated all single-variable models in addition to 4 models with �2 variables to determine whether there was any support for models with higher numbers of parameters. We evaluated 9 models in total and we selected among models using AICc, AICc, and wi (Burnham and Anderson 2002). We did not model-average parameter estimates because it would have resulted in 10 different estimates of each level of fawn detection probability for a total of 30 probability estimates. These differences were not supported by the model selection results. We used our VIT retention and fawn detection probabilities to guide calculation of VIT sample sizes for planning future neonatal studies. We expressed the expected number of neonates to be encountered from a sample of VITs as E½nNeo � ¼ nVITs SAdF RVIT ½TAdF ðp1jTwins þ 2p2jTwins Þ þ ð1�TAdF Þp1jSingle � where nNeo is the neonate sample size, nVITs is the sample size of adult females with VITs, SAdF is the probability an adult female survives to parturition and is accessible, RVIT is the probability an adult female retains her VIT to within 3 days of parturition given she survives to parturition and is accessible (i.e., VIT is retained or nearly retained), TAdF is the probability adult female has twin fetuses, p1jTwins is the probability 1 fawn is detected given an adult female retains her VIT and has twin fetuses, p2jTwins is the probability 2 fawns are detected given an adult female retains her VIT and has twin fetuses, and p1jSingle is the probability 1 fawn is detected given an adult female retains her VIT and has 1 fetus. Since we had perfect detection with singleton litters and observed a high probability of detecting at least 1 fawn from twin litters, we simpliﬁed the above equation to E½nNeo � ¼ nVITs SAdF RVIT ðpFawn þ TAdF p2jTwins Þ where pFawn is the probability of detecting at least 1 fawn, irrespective of litter size. Thus, given a targeted sample size of neonates, the estimated number of VITs required can be calculated as nVITs ¼ E½nNeo � SAdF RVIT ðpFawn þ TAdF p2jTwins Þ We incorporated our estimates into the above equation to provide guidance for planning future studies. RESULTS A retention wing of 1 VIT snapped at its base when the wings were squeezed together for placement into a vaginoscope, prior to insertion into a deer. No other retention wings exhibited any cracking or weakness when squeezed together, even after VITs were recovered from animals during spring and summer. Thus, we found this to be an isolated incident, and our resulting sample size was 59 deer with VITs. The probability that an adult female receiving a VIT in winter survived to parturition and was accessible (SAdF) was 0.797 (SE ¼ 0.0529). We observed 9 adult female mortalities during winter and spring, and there was no evidence to The Journal of Wildlife Management � 75(8) �suggest VITs were related to the mortality events. Four of the mortalities occurred within 1 week of capture and were likely capture related. We were unable to ground-monitor 2 other adult females during the fawning period because they were located on private land that we did not have permission to access. One other adult female was inadvertently deleted from the aerial monitoring list due to miscommunication. We censored these 12 deer from our analysis of VIT retention because they did not permit evaluation of VIT retention to parturition, resulting in a sample size of 47 deer. Our global model of VIT retention probability (no. of parameters (K) ¼ 12) adequately ﬁt the data (deviance/ df ¼ 0.670, P ¼ 0.991). The model of VIT retention probability with the lowest AICc included only the intercept (K ¼ 2, DAICc ¼ 0.00, wi ¼ 0.331), although the model with deer age received some support (K ¼ 4, DAICc ¼ 1.42, wi ¼ 0.163; Table 1). Examining the model-averaged estimates, there was some evidence that retention probability ^ age;not retained ¼ 0.169, SE ¼ 0.256; was lower in older deer (b Fig. 3). Also, there was some evidence that retention prob^ hind foot; not retained ¼ 0.086, ability was lower in larger deer (b SE ¼ 0.171; Table 1). Based on the intercept-only model, the probability of a VIT being expelled during parturition (i.e., retained) was 0.766 (SE ¼ 0.0605) and the probability of a VIT being expelled �3 days prepartum (i.e., nearly retained) was 0.128 (SE ¼ 0.0477). Thus, the probability of a VIT being retained to within 3 days of parturition (RVIT) was 0.894 (SE ¼ 0.0441). Our global model of fawn detection probability (K ¼ 12) adequately ﬁt the data (deviance/df ¼ 0.846, P ¼ 0.730). The model of fawn detection probability with the lowest AICc included only the intercept (K ¼ 2, DAICc ¼ 0.00, wi ¼ 0.600), whereas the model with the next lowest AICc included the VIT shed-day variable (K ¼ 4, DAICc ¼ 1.80, wi ¼ 0.244; Table 2). Thus, we observed some evidence that fawn detection probability was inﬂuenced by our inability to ^ shed-day; singleton ¼ 0.537, monitor deer 2 days of the week (b SE ¼ 0.738). The probability of detecting twins was 0.688 (SE ¼ 0.114) when we located adult females <24 hr after their VITs switched to fast pulse, whereas twin detection probability was 0.500 (SE ¼ 0.115) when our response time was delayed due to irregular monitoring. There was no Figure 3. Estimated probability and 95% confidence interval of adult female mule deer retaining vaginal implant transmitters (VITs) to within 3 days of parturition as a function of deer age in northwest Colorado, 2009. evidence that probability of fawn detection was inﬂuenced by dam age or vegetative cover class. Also, fawn detection probability did not meaningfully differ between females with retained and nearly retained VITs. We detected 58 neonates and 2 stillborns from 42 adult females (1.4 neonates/female) that retained or nearly retained VITs. We detected a neonate from each adult female that had 1 fetus (p1jSingle ¼ 1.0, n ¼ 8). For adult females with twin fetuses (n ¼ 34), based on the intercept-only model, the probability of detecting 1 neonate (p1jTwins) was 0.353 (SE ¼ 0.0803) and the probability of detecting twins (p2jTwins) was 0.588 (SE ¼ 0.0827). Combining litter sizes, the probability of detecting at least 1 neonate (pFawn) was 0.952 (SE ¼ 0.0334). The probability of an adult female having twin fetuses (TAdF) was 0.810 (SE ¼ 0.0613). On average, we located 1 neonate or stillborn per VIT in our initial sample (nNeo ¼ 60, nVITs ¼ 59). Thus, inputting our estimates into our sample size equation, we found that VIT sample size should roughly equal the targeted neonate sample size nVITs ¼ E½nNeo � E½nNeo � ¼ ð0:80Þð0:89Þ½0:95 þ ð0:81Þð0:59Þ� 1:02 Table 1. Model selection results from an analysis of vaginal implant transmitter (VIT) retention in adult female mule deer as a function of adult female age (yr), mass (kg), hind foot length (cm), chest girth (cm), and body fat (%) in northwest Colorado, USA, 2009. Results are based on number of model parameters (K), Akaike’s Information Criterion with small sample size correction (AICc), difference in AICc values between the specified model and the model with the minimum AICc (DAICc), and model weights (wi; Burnham and Anderson 2002). Model K AICc DAICc wi Intercept only Age Foot length Age, fat Mass Fat Chest girth Age, chest girth Age, foot length Age, mass Age, foot length, chest girth 2 4 4 6 4 4 4 6 6 6 8 70.58 72.00 72.88 72.96 73.57 73.66 73.79 75.10 75.45 76.32 78.53 0.00 1.42 2.30 2.39 2.99 3.08 3.21 4.52 4.88 5.74 7.95 0.331 0.163 0.105 0.100 0.074 0.071 0.066 0.035 0.029 0.019 0.006 Bishop et al. � Vaginal Implant Transmitters in Deer Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife 1803 �Table 2. Model selection results from an analysis of fawn detection probability associated with adult females that retained or nearly retained vaginal implant transmitters (VITs) in northwest Colorado, 2009. We modeled detection probability as a function of VIT retention status (retained vs. nearly retained), adult female age (yr), the day of the week VITs were shed (i.e., shed-day), and amount of vegetative cover at VIT shed sites. We evaluated detection probability relative to shed-day because we were unable to monitor radio signals on Saturdays and Mondays. Results are based on number of model parameters (K), Akaike’s Information Criterion with small sample size correction (AICc), difference in AICc values between the specified model and the model with the minimum AICc (DAICc), and model weights (wi; Burnham and Anderson 2002). Model k AICc DAICc wi Intercept only Shed-day Retention status Age Cover Shed-day, cover Shed-day, cover, retention status Age, shed-day, cover 2 4 4 4 6 8 10 10 61.94 63.74 66.07 66.26 70.46 73.22 79.53 80.24 0.00 1.80 4.13 4.32 8.52 11.28 17.59 18.30 0.600 0.244 0.076 0.069 0.008 0.002 0.000 0.000 We expended approximately 700 person-hours during the fawning period to locate 58 neonates and 2 stillborns, or approximately 12 person-hours per fawn located. This estimate includes hours spent searching for fawns from adult females that expelled VITs >3 days prepartum, although we were never successful in these attempts. We expended $31,000 to net-gun our sample of adult females, $15,000 on VITs, $10,000 on ﬁxed wing monitoring, and $20,000 on personnel. Thus, we expended approximately $1,267 per neonate located. We did not include adult female radio collars in this cost estimate because we used GPS collars to meet other research objectives, yet VHF collars would have sufﬁced for locating neonates. Assuming VHF collars were used on adult females at a rate of $250 per collar, our cost estimate is approximately $1,520 per fawn. DISCUSSION Our wing modiﬁcation increased VIT retention in adult female mule deer. Our results are consistent with Haskell et al. (2007), who observed 81% retention (17/21) in the ﬁnal year of their study after lengthening VIT wings and preventing antennas from protruding >1 cm past the vulva. Our study expanded on Haskell et al. (2007) by incorporating VIT wing modiﬁcations into the manufacturing process and conducting a focused ﬁeld evaluation of those modiﬁcations. Investigators using the original VIT wing design in mule deer observed much lower rates of retention than we observed (Johnstone-Yellin et al. 2006, Bishop et al. 2007, Haskell et al. 2007). Using the original design, Bishop et al. (2007) found that the probability of VIT expulsion during parturition was 0.447 (SE ¼ 0.0468), and the probability of VIT expulsion during parturition or �3 days prepartum was 0.623 (SE ¼ 0.0456). We employed the same methodology as Bishop et al. (2007), except for the wing modiﬁcation. Our study area was 100 km north of where Bishop et al. (2007) conducted their study. Assuming the 2 studies are comparable, our wing modiﬁcation increased VIT retention to parturition by 0.319 (SE ¼ 0.0765) and VIT retention to within 3 days of parturition by 0.271 (SE ¼ 0.0634). The intercept-only model of VIT retention probability received the most Akaike weight, which is partly a reﬂection of our limited sample size. However, overall high rates of 1804 Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife retention likely explain why we did not observe any strong relationships between VIT retention and deer body size. Bishop et al. (2007) found that larger deer were more likely to expel VITs prematurely, which was our basis for modifying VIT wings and conducting this study. Our results suggest the wing modiﬁcations effectively reduced premature expulsion (Fig. 4). We documented a high probability of detecting at least 1 fawn from adult females that retained or nearly retained VITs, regardless of litter size. When a VIT was shed and evidence suggested the adult female was near parturition or had already given birth, we conducted intense searches up to 1 hr in length for successive days until a fawn was found. Thus, irrespective of vegetative cover or other covariates we assessed, we usually found a fawn when a VIT was adequately retained because it focused our search effort. Our likelihood of detecting twins was somewhat lower, in part because of our irregular monitoring schedule. However, other factors explain why twin detection probability was lower. First, our search intensity decreased when searching for a second fawn. For example, if we had searched most of an hour before detecting the ﬁrst fawn, we typically limited our search time for a second fawn to minimize our disturbance to the adult Figure 4. Estimated probabilities and 95% confidence intervals of adult female mule deer retaining vaginal implant transmitters (VITs) to within 3 days of parturition as a function of deer body mass in Colorado using original (solid line, Bishop et al. 2007) and modified (dashed line, this study, 2009) VIT retention wings. The Journal of Wildlife Management � 75(8) �female. Second, we did not place radio collars on fawns, and therefore, we could not relocate radiocollared fawns to search for their siblings. The technique of relocating a radiocollared fawn to locate its sibling was found to be successful in a previous Colorado study (Bishop et al. 2009). During this earlier study, when a dam was known to have twin fetuses yet only 1 fawn was located and radiocollared during the initial capture attempt, the sibling fawn was found 45% of the time (10/22) by relocating the initial radiocollared fawn 1–2 days post-capture (C.J. Bishop, CDOW, unpublished data). Based on this rate, we would expect our probability of detecting both fawns from twin litters to be roughly 0.77 had we radiocollared fawns during our study. We found that our sample size of detected neonates roughly equaled our sample size of VITs, which provides a useful guide for planning future research using our modiﬁed wing design. However, this recommendation may overestimate VIT sample size because of our lower rate of twin detection and because adult female survival was lower than we anticipated. Fortunately, accessibility of adult females was higher than expected considering we lacked permission to access a large tract of land in the middle of summer range. Bishop et al. (2007) observed 0.97 survival of adult females to parturition and 0.99 were accessible during fawning (SAdF ¼ 0.95). Adult female survival and accessibility is speciﬁc to study area. Twinning probability may also vary regionally. We therefore recommend use of the following equation for planning VIT sample size that incorporates information speciﬁc to the study area or region of interest nVITs ¼ E½nNeo � SAdF ½ð0:85Þ þ TAdF ð0:53Þ� Bishop et al. (2007) expended 7 person-hours per captured fawn from adult females with successful VITs, 16 personhours per fawn from females with partially successful VITs, and 42 person-hours per fawn from females with failed VITs and females not receiving VITs. Given their observed VIT success rates, Bishop et al. (2007) would have required approximately 1,315 person-hours to locate 60 neonates, or 22 person-hours per fawn. Assuming these studies are comparable, increased VIT success associated with our modiﬁed wing design resulted in a 45% reduction in labor required to locate a fawn from a radiocollared adult female. The VIT technique is effective but expensive to employ. Actual cost of the technique, however, depends on what costs are already incurred to meet other research objectives. For example, in Colorado and elsewhere, researchers have begun estimating late-winter deer body condition as a response variable to accompany survival estimates. In these cases, adult female capture and radio collar costs are already accounted for in the base study, and thus, incorporation of VITs to facilitate neonate capture becomes much more costeffective. In our study, where adult female capture and collar costs were covered by ongoing research efforts, the added cost of incorporating VITs and neonate capture was $750 per fawn. Bishop et al. � Vaginal Implant Transmitters in Deer Downloaded From: https://bioone.org/journals/Journal-of-Wildlife-Management on 06 Jul 2021 Terms of Use: https://bioone.org/terms-of-use Access provided by Colorado Parks and Wildlife MANAGEMENT IMPLICATIONS Use of VITs in well-designed ﬁeld studies should increase our understanding of factors limiting deer populations by allowing investigators to link fawn production and survival to dam characteristics under free-ranging conditions. A primary drawback of VITs in deer has been the failure of many adult females to retain VITs to parturition. We increased VIT retention in mule deer by lengthening and widening wings used to retain a VIT in the vaginal canal. Researchers employing VITs with our modiﬁed wing design should require minimal oversampling to offset failures caused by early expulsion, thereby rendering the technique more costeffective and reliable. Our ﬁndings provide explicit guidance for planning a fetal-neonatal deer study involving VITs. The question remains as to whether premature expulsion of VITs can be eliminated in mule deer. We observed modest evidence that deer expelling VITs >3 days prepartum were older and larger than deer that retained or nearly retained VITs. We therefore recommend manufacturing slightly larger wings for large, older mule deer (e.g., >65 kg and >5 yr old) as a possible strategy to further investigate VIT retention. ACKNOWLEDGMENTS Project funding was provided by Colorado State Severance Tax Fund, Williams Production RMT, Shell Petroleum, EnCana Corporation, Federal Aid in Wildlife Restoration–Project W-185-R, Colorado Oil and Gas Conservation Commission, Colorado Mule Deer Association, and Mule Deer Foundation. We thank helicopter pilots R. Swisher and M. Shelton and their crews for capturing deer. L. Coulter and L. Gepfert provided many hours of ﬁxed wing radio monitoring. We thank D. Finley, C. M. Flickinger, T. Knowles, P. Lendrum, B. J. Marsh, A. R. Murkowski, M. M. Reitz, J. C. Rivale, A. Romero, T. P. Segal, K. R. Taylor, T. S. Weisgerber, B. R. Wilson, and other Colorado Division of Wildlife personnel for assistance handling deer and conducting ﬁeld work. L. L. Wolfe assisted with ultrasound and insertion of VITs. J. Broderick, W. J. deVergie, D. J. Freddy, K. Kaal, R. H. Kahn, D. Riggs, J. T. Romatzke, and R. Velarde helped coordinate with energy development companies and make the project possible. We thank D. J. Freddy for helping develop and support the project from inception and P. M. Lukacs for advice on statistical analysis. D. J. Martin and J. P. Runge improved the manuscript through constructive reviews. LITERATURE CITED Anderson, C. R., and D. J. Freddy. 2008. Population performance of Piceance Basin mule deer in response to natural gas resource extraction and mitigation efforts to address human activity and habitat degradation. Study Plan, Colorado Division of Wildlife, Fort Collins, USA. Ballard, W. B., H. A. Whitlaw, D. L. Sabine, R. A. Jenkins, S. J. Young, and G. J. Forbes. 1998. White-tailed deer, Odocoileus virginianus, capture techniques in yarding and non-yarding populations in New Brunswick. Canadian Field-Naturalist 112:254–261. Barbknecht, A. E., W. S. Fairbanks, J. D. Rogerson, E. J. Maichak, and L. L. Meadows. 2009. 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Associate Editor: David Forsyth. The Journal of Wildlife Management � 75(8) � Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Journal Articles Description An account of the resource CPW peer-reviewed journal publications Text A resource consisting primarily of words for reading. Examples include books, letters, dissertations, poems, newspapers, articles, archives of mailing lists. Note that facsimiles or images of texts are still of the genre Text. Dublin Core The Dublin Core metadata element set is common to all Omeka records, including items, files, and collections. For more information see, http://dublincore.org/documents/dces/. Title A name given to the resource Effectiveness of a redesigned vaginal implant transmitter in mule deer Rights Information about rights held in and over the resource <a href="http://rightsstatements.org/vocab/InC-NC/1.0/" target="_blank" rel="noreferrer noopener">In Copyright - Non-Commercial Use Permitted</a> Date Created Date of creation of the resource. 2011-09-16 Subject The topic of the resource Birth site Capture Colorado Fawn Fetus Mule deer Neonate Odocoileus hemionus Parturition Vaginal implant transmitter (VIT) Description An account of the resource Our understanding of factors that limit mule deer (Odocoileus hemionus) populations may be improved by evaluating neonatal survival as a function of dam characteristics under free-ranging conditions, which generally requires that both neonates and dams are radiocollared. The most viable technique facilitating capture of neonates from radiocollared adult females is use of vaginal implant transmitters (VITs). To date, VITs have allowed research opportunities that were not previously possible; however, VITs are often expelled from adult females prepartum, which limits their effectiveness. We redesigned an existing VIT manufactured by Advanced Telemetry Systems (ATS; Isanti, MN) by lengthening and widening wings used to retain the VIT in an adult female. Our objective was to increase VIT retention rates and thereby increase the likelihood of locating birth sites and newborn fawns. We placed the newly designed VITs in 59 adult female mule deer and evaluated the probability of retention to parturition and the probability of detecting newborn fawns. We also developed an equation for determining VIT sample size necessary to achieve a specified sample size of neonates. The probability of a VIT being retained until parturition was 0.766 (SE = 0.0605) and the probability of a VIT being retained to within 3 days of parturition was 0.894 (SE = 0.0441). In a similar study using the original VIT wings (Bishop et al. <a href="https://wildlife.onlinelibrary.wiley.com/doi/abs/10.1002/jwmg.229#bib5" class="bibLink tab-link">2007</a>), the probability of a VIT being retained until parturition was 0.447 (SE = 0.0468) and the probability of retention to within 3 days of parturition was 0.623 (SE = 0.0456). Thus, our design modification increased VIT retention to parturition by 0.319 (SE = 0.0765) and VIT retention to within 3 days of parturition by 0.271 (SE = 0.0634). Considering dams that retained VITs to within 3 days of parturition, the probability of detecting at least 1 neonate was 0.952 (SE = 0.0334) and the probability of detecting both fawns from twin litters was 0.588 (SE = 0.0827). We expended approximately 12 person-hours per detected neonate. As a guide for researchers planning future studies, we found that VIT sample size should approximately equal the targeted neonate sample size. Our study expands opportunities for conducting research that links adult female attributes to productivity and offspring survival in mule deer. Creator An entity primarily responsible for making the resource Bishop, Chad J. Anderson Jr, Charles R. Walsh, Daniel P. Bergman, Eric J. Kuechle, Peter Roth, John Language A language of the resource English Is Part Of A related resource in which the described resource is physically or logically included. The Journal of Wildlife Management Format The file format, physical medium, or dimensions of the resource application/pdf Extent The size or duration of the resource. 10 pages Bibliographic Citation A bibliographic reference for the resource. Recommended practice is to include sufficient bibliographic detail to identify the resource as unambiguously as possible. Bishop, C. J, C. R. Anderson, Jr., D. P. Walsh, E. J. Bergman, P. Kuechle, and J. Roth. 2011. Effectiveness of a redesigned vaginal implant transmitter in mule deer. The Journal of Wildlife Management 75:1797-1806. <a href="https://doi.org/10.1002/jwmg.229" target="_blank" rel="noreferrer noopener">https://doi.org/10.1002/jwmg.229</a> Source A related resource from which the described resource is derived Bishop, C. J, C. R. Anderson, Jr., D. P. Walsh, E. J. Bergman, P. Kuechle, and J. Roth. 2011. Effectiveness of a redesigned vaginal implant transmitter in mule deer. The Journal of Wildlife Management 75:1797-1806. <a href="https://doi.org/10.1002/jwmg.229" target="_blank" rel="noreferrer noopener">https://doi.org/10.1002/jwmg.229</a> Type The nature or genre of the resource Article