T R A N S - P E C O S P RO N G H O R NR E S T O R AT I O N A N D R E S E A R C H R E P O RT , 2 0 1 2 By Louis A. Harveson, Shawn Gray, Billy Tarrant, James Weaver, and Justin Hoffman
THE PRONGHORN DECLINEP ronghorn populations in Texas have seen better days. Their distribution once ranged as far east as Interstate 35but are now restricted to the Trans-Pecos,Panhandle, western Edwards Plateau, andsouthern Rolling Plains regions. The Trans-Pecos region alone supported 60-70% of thestate’s pronghorn, with numbers reaching ahigh of 17,000 animals during the mid-1980s.With few exceptions, the pronghornpopulation in the Trans-Pecos has been in asteady decline since the 1980s and experienced Trends in pronghorn numbers in the Trans-a 30-year low of 3,745 animals in 2011. Pecos region of west Texas.Although pronghorn herds have been affectedby drought, precipitation alone can not explain Current projects and initiatives summarized inthe continued decline. Following the drought this report include:of the 1990s, pronghorn populations showedinitial recovery, but their populations Evaluating the role of barriers on thecontinued to decline despite average to above- genetic diversity of Trans-Pecos pronghornaverage rainfall and habitat conditions. herds,Realizing the urgency of the pronghorn Identifying diseases in pronghorn anddecline, the Trans-Pecos Pronghorn Working determining their effects,Group was formed comprised of arearanchers, biologists, hunting guides, Assessing the effects of predation onveterinarians, and scientists. The Working pronghorn fawns,Group has helped direct restoration and Documenting the success of pronghornresearch priorities for pronghorn in the Trans- restoration efforts, andPecos. The Trans-Pecos Pronghorn WorkingGroup has been an effective organization for Monitoring the movements of pronghornleveraging money for conservation and following translocation.research, communicating with landowners, andfor devising and implementing strategies for SPONSORSthe recovery of pronghorn. Funding for these projects comes from TexasThis research report is being provided to our Parks and Wildlife Department, Dixon Waterpartners, donors, and supporters across the Foundation, Horizon Foundation, Borderlandsstate to better inform them of our current Research Institute, Safari Club Internationalresearch investigations. Chapters (West Texas, Lubbock, El Paso, Southern New Mexico, Pittsburgh), and from the Pronghorn Benefit Dinner and Dance.
Habitat fragmentation and geneticsH abitat fragmentation is a growing concern across Texas. Habitats become fragmented when obstaclesor barriers inhibit free movement of wildlifefrom one habitat patch to another. Strugglingpronghorn populations in the Trans-Pecosmay be susceptible to the effects of habitatfragmentation. Barriers can potentially inhibitpronghorn from finding adequate food andwater, reduce gene flow which can causeinbreeding, and reduce genetic diversity andhealth of populations. Pronghorn are reluctant to jump over or maneu-In other western states, natural (e.g., ver through fences, making them susceptible to habitat fragmentation and genetic isolation.mountains and canyons) and manmadeobstacles (e.g., fences, railroads, and roads) seasons, we obtained 344 tissue samples fromhave been shown to reduce pronghorn across the Trans-Pecos, Panhandle, andmovements and isolate populations. western Edwards Plateau. We then extracted DNA from the tissue and analyzed it forWe evaluated the effects of fences, highways, genetic variation and compared our geneticand other barriers on pronghorn movements data across management units and delineatedand genetic variability. Using hunter-harvested barriers.pronghorn during the 2007 and 2008 hunting Our data suggests that few barriers currently exist in the Trans-Pecos to curtail genetic flow of pronghorn. Additionally, our findings revealed moderate levels of genetic diversity for Trans-Pecos and Panhandle pronghorn herds. However, the northwestern portion of the Trans-Pecos (Culberson and Hudspeth counties) did show genetic differences. These herd units are separated from most of the Trans-Pecos pronghorn herds by several mountain ranges and Interstate 10. We also discovered that Trans-Pecos and Panhandle had similar genetic diversity. The levels of genetic diversity may be a result of adequate movements of pronghorn across herd units in the Trans-Pecos or from previousBarriers such as roads, railroads, and fences may translocation efforts.reduce genetic flow for pronghorn in the Trans-Pecos.
Diseases and parasitesO ne of our leading hypotheses regard- parasite loads in the Trans-Pecos; they also had ing the decline of pronghorn popula- the lowest fawn production during this time. tions includes the presence of dis- Comparing all pronghorn, average parasiteeases or parasites. During a pronghorn die-off loads were highest in 2009 (552 worms/in the summer of 2009, we identified unprece- abomasum) compared to 2010 (268) and 2011dented parasite loads from several pronghorn (461).that we were able to necropsy. Barber poleworms (Haemonchus spp.) are parasitic round-worms that attach to the inner lining of thedigestive system and an average adult worm isable to draw off 0.1 cc of blood/day. Addi-tionally, where the worms attach in the stom-ach becomes scarified inhibiting the ability ofthe stomach to absorb nutrients. Parasiteloads of 2,000 for an individual sheep or goatwould jeopardize their survival. To better un-derstand the role diseases and parasites have inpronghorn survival, we initiated a thorough Average loads of Haemonchus for pronghorn ininvestigation. the Trans-Pecos across sampling units and years. During our study we were also able to establish a noninvasive technique for evaluating parasite loads—fecal egg counts. From our data, fecal egg counts are highly correlated to abomasum parasite load (92%) thus allowing us to moni- tor parasite loads without sacrificing prong- horn. This technique is especially important asThe barber pole worm (Haemonchus spp.) is we begin evaluating parasite loads of prong-a parasitic round worm frequently found in horn herds for potential restoration efforts.domestic ruminants and some wildlife. Although Haemonchus have been documentedIn the fall of 2009, 2010, and 2011 we col- in pronghorn prior to our findings, infestationslected samples of hunter-harvested pronghorn of this magnitude have not been reported pre-to evaluate parasite loads, as well as the occur- viously. The high levels of parasites can haverence of blue tongue, epizootic hemorrhagic detrimental impacts on pronghorn survival.disease, and copper and selenium levels. We Infested pronghorn can become anemic andobtained 102, 95, and 41 pronghorn samples in weak making them more susceptible to preda-2009, 2010, and 2011, respectively. Over 95% tion and other mortality factors. Most re-of the pronghorn evaluated in our study had cently, our collaborators suggest that the strainHaemonchus in their abomasum. Some parasite of Haemonchus does not appear to be from live-loads exceeded 4,000 individual worms. The stock and that it may be a new strain specificherd units in the Marfa Plateau had the highest to pronghorn, desert environments, or both.
Fawn SurvivalF or wildlife populations to sustain or capture fawns were weighed, aged, ear-tagged, grow, gains (births and immigration) and a light-weight, expandable radiocollar was must exceed population losses (deaths affixed. Fawns were monitored from afar toand emigration). For pronghorn populations document their behaviors and fate.in the Trans-Pecos, immigration and emigra-tion can be considered negligible. Thus, forpronghorn populations suffering from a re-gion-wide decline, pronghorn recruitment isparamount to population recovery. Fortu-nately, pronghorn have the reproductive po-tential to recover from catastrophes given thatadult does have high incidence for twinning(~98%) including yearling does on a high nu-tritional plane.Since 2008, annual pronghorn surveys have Causes of mortality for pronghorn fawns monitored in the Trans-Pecos, 2011.revealed exceptionally low fawn recruitment.In fact most of the Trans-Pecos experiencedfawn recruitment of less than 10% for two In 2011, we captured and radioed 26 neonateconsecutive years in 2010 and 2011. These low fawns over 4 study sites throughout the Trans-fawn crops are a major contributing factor to Pecos region. We documented high predationthe overall pronghorn decline in the Trans- rates of fawns in our study where only 2 of thePecos. Several hypotheses emerged regarding 26 fawns survived to 6 months old. Mortalitiespronghorn recruitment including fertilization were attributed to bobcats (29%), coyotesrates, conception rates, fawning rates, inci- (25%), and unknown predators (42%). Onedence of twinning, and fawn survival. fawn was inadvertently trampled by cattle. One of the more alarming statistics we docu- mented in our study was the extremely low body weights of fawns. The abnormally low body weights suggest that the nutrition of fawns was compromised. We speculate that the drought conditions experienced in 2011 depleted the nutritional reserves of pregnant does during their last trimester of pregnancy and during lactation following parturition. TheNeonate pronghorn fawns were captured and nutritional condition of pronghorn were fur-outfitted with radiocollars to monitor survival. ther jeopardized by high concentrations of Haemonchus. Fawn production across theTo address fawn recruitment in the Trans- Trans-Pecos was consistent with our malnutri-Pecos, we initiated a fawn survival study. tion hypothesis in that many pregnant doesFawns were capture prior to 2 weeks of age were documented, but few fawns survived to 6using hoop-nets and spotlights at night. Upon months of age.
Restoration efforts and survivalT ranslocating pronghorn has been a During the first common management technique to 8 weeks follow- improve and sustain pronghorn popu- ing release, welations in Texas and North America. In fact, documented 26since the 1930s almost 6,000 pronghorn have mortalities pri-been translocated across Texas. Because of marily from cap-the severity of the declining pronghorn popu- ture myopathylation, we initiated efforts to supplement exist- and predation.ing pronghorn herds in the Trans-Pecos. A Food resourcessurplus of pronghorn was identified in the started to be-northwest Panhandle of Texas, where prong- come morehorn were depredating agricultural crops. scarce as tem-Working with landowners in the Panhandle peratures beganand Trans-Pecos, we coordinated one of the to climb and thelargest translocations in the state. body condition of the translo- Using helicopters and netguns,In February 2011, we captured 200 and re- cated pronghorn 200 pronghorn were translo-leased 194 pronghorn (176 F, 18 M) to 5 re- started showing cated to the Trans-Pecos.lease sites in the Marfa Plateau. Because previ- signs of malnu-ous studies had not documented translocation trition. We documented an additional 38 mor-success and we anticipated subsequent translo- talities from April-July that were a combinationcations, we took the opportunity to monitor of predation, Haemonchosis, vehicle collisions,site-fidelity, movements, survival, and fawn and unknown causes. In late July, the rainsproduction of the translocated pronghorn. To returned to portions of the Trans-Pecos stimu-monitor mortality and investigate limiting fac- lating forb growth. Mortalities waned, but thetors affecting their survivability, 80 (40%) fawn production was nonexistent.pronghorn were equipped with radiocollars (62F, 18 M). To date, we recorded 63 mortalities of the 80 radio-collared pronghorn (82%). Unknow- ingly, several natural and climatic events had dramatic impacts on our efforts to restore pronghorn including record setting freezes, drought, heat, and wildfires. It appears that younger pronghorn were more adaptable to the harsh conditions that pre- vailed following the release. Despite the out- comes of the translocated pronghorn, translo- cations will continue to serve as a vital tool inCauses of mortality for translocated pronghornin Trans-Pecos, Texas. The extended drought sustaining and recovering pronghorn popula-wreaked havoc on pronghorn survival. tions in the future. Results from this effort will be used to further our ability to recover prong- horn populations in the Trans-Pecos.
Movements following translocationW hen evaluating the success of any Fixed Kernal Density Estimator (KDE) at wildlife restoration effort, surviv- both 95% and 50%. Overall range use areas for ability is typically top priority during 100% MCP was a 9,521 acres with KDE 95%assessment. However, understanding the and 50% being 14,085 and 2,718 acres, respec-movements and post-release behavior of trans- tively. Range use areas generally decreasedlocated animals and how they change over time from month-to-month. Translocated prong-are important aspects for assessing the success horn selected areas of disturbance or low-lyingof translocations and improving future efforts. areas (e.g., swales and draws) that contained-We assessed the behaviors and movements of deeper, moister soils with higher forb availabil-translocated pronghorn by equipping 28 (15 F, ity.13 M) pronghorn with GPS radiocollars. GPSradiocollars were designed to obtain 1 loca-tion/hr with a 300-day battery life. Net-wire fencing impaired the movements of translocated pronghorn.A herd of translocated and resident pronghornmeander through the Marfa Plateau. Scatter plots of radioed pronghorn also re-Mean distances of locations in relation to the vealed some interesting data. Movement pat-initial release site were measured for dispersal. terns were much larger than anticipated andWithin 24 hours of release, pronghorn dis- many pronghorn were not able to navigate thepersed from 3.6-10 mi. As time progressed, existing fences. We speculate that the exten-mean distances gradually increased, but indi- sive fencing system may have contributed toviduals responded differently. The differences the death of several pronghorn. In fact, duringin these values suggest habitat and resource a severe drought in the 1960s net-wire fencesavailability, fences, resident pronghorn, and in the Trans-Pecos prevented a pronghornother factors influenced the degree of site fi- herd from moving into areas with availabledelity exhibited. Pronghorn moved an average forage. That population subsequently experi-of 814 ft/hr. Diurnal movement rates (1,345 enced a 60% die off due to malnutrition.ft/hr) were greater than nocturnal movement This information will allow wildlife managersrates (791 ft/hr). in the future to understand how pronghornRange use areas were measured by utilizing initially adapt to a new environment and assist100% Minimum Convex Polygon (MCP) and in improving monitoring and site preparation efforts.
The future of pronghornThe Borderlands Research Institute, Texas Parks and Wildlife Department, and Trans-PecosPronghorn Working Group are dedicated to restoring pronghorn to their former habitats.However, we will need your help in our efforts.We are currently planning several projects to better understand the pronghorn decline: Continued efforts to restore pronghorn to historic habitats, including the “super-stocking” technique. Assessment of the nutrition quality of forage. Evaluating the role of fire and other disturbances on habitat quality. Monitoring the movement of resident pronghorn on the Marfa Plateau. To find out how you can help with future restoration and research efforts please contact: Dr. Louis A. Harveson, Borderlands Research Institute P.O. Box C-16, SRSU, Alpine, Texas 79832 Phone: 432.837.8488; Fax: 432.837.8822 Email: firstname.lastname@example.org Website: http://www.sulross.edu/brinrm Trans-Pecos Working Group MembersJon Means, Bobby McKnight, Albert and Bill Miller, Dr. Dan McBride, Dr. Ken Waldrup, Robert Potts, Jim White, Billy Tarrant, Ernie Davis, Shawn Gray, and Louis A. Harveson.