Conservation and Ecology of Mammals I

Contributed Paper
ROOM: Rooms 27 – Picuris, 29 – Sandia and 31 – Santa Ana Combined

1:10PM Behavioral Responses in the Endangered Sonoran Pronghorn to Variation in Short- and Long-Term Risk Arising from Border-Related Human Activity
Stephanie E. Doerries; David A. Christianson
The U.S. population of endangered Sonoran pronghorn (Antilocapra americana sonoriensis) has fluctuated near extirpation in recent decades, and increases in human activity along the U.S.-Mexico border are thought to be involved. Ungulates often perceive human activity as predation risk and mount behavioral responses to minimize these risks. Such responses can alter energy budgets and nutrient intake, influencing reproduction and long-term survival. The effects of human activity on the behavior of Sonoran pronghorn are poorly understood. To address this, we conducted behavioral observations on 533 pronghorn groups over three years. Each observation consisted of 13 herd scans conducted at 3- or 5-minute intervals. We quantified proportion of time spent vigilant, foraging, moving, bedded, and standing while risk from human activity varied at two scales: 1) short-term risk associated with immediate presence of humans (vehicles or on foot) near the observed group, and 2) long-term risk associated with background levels of human use varying by land management practice. Adult female pronghorn were moving 31.2% of the time, foraging 23.3% of the time, and vigilant 12.1% of the time. Pronghorn nearly tripled time spent vigilant (6% vs. 17%) in response to immediate risk arising from natural predators (coyotes), while responses to short-term risk from humans was less pronounced (8% for vehicles, 12% for humans on foot). In contrast, pronghorn foraging time declined by one-third (21% vs. 14%) in response to vehicles, with smaller responses to the immediate presence of humans on foot or coyotes. Encounters between pronghorn and humans on foot were rare, occurring during only 3% of behavioral observations, while encounters with vehicles occurred seven times more frequently. Vigilance generally increased and foraging time decreased with long-term risk. These patterns suggest that pronghorn responses to humans are different from responses seen to natural predators but may still have demographic consequences.
1:30PM Mitochondrial, Microsatellite, and Genomic Single Nucleotide Polymorphisms Markers for Assessing Landscape-Scale Population Structure and Diversity in Bighorn Sheep Across Wyoming, United States
Sierra M. Love Stowell; Roderick B. Gagne; Holly B. Ernest
Bighorn sheep (Ovis canadensis) are a charismatic component of the biodiversity of Wyoming and the North American west. Bighorn populations declined steeply in the 20th century mainly due to unregulated hunting and disease. With translocations and other management efforts, many populations have stabilized or increased, while others have declined and continue to require management. To promote population health and support effective management, we conducted a state-wide population genetic analysis with the objectives of 1) identifying genetic structure; 2) describing effective population size and genetic diversity within each genetic group; and 3) quantifying gene flow among herds, by dispersal or translocation. We used blood or tissue samples from 275 individual bighorn sheep collected across the state of Wyoming, aiming for a minimum of 20 individuals from each of 20 hunting license areas and 10 major mountain ranges, reflecting the natural density of wild sheep. Individuals were genotyped using three complementary marker types: 40 nuclear microsatellites and 524 bp of mitochondrial D-loop sequence that have been used to assess bighorn sheep in other regions, and genome-wide nuclear SNPs generated using restriction site-associated DNA (RAD) sequencing (1,949,088 loci) and the Ovine HD Illumina BeadChip for a subset of individuals (600,000 loci). We compared the power of these markers for resolving population structure and assigning individuals. We found at least four genetic clusters in Wyoming, reflecting the core native herds and the history of extensive translocations within the state. Genetic diversity likely reflects the history of disease extirpations and founding events following translocations. These data form a foundation for monitoring the genetic health Wyoming’s herds in the future, represent additional genetic markers for forensic analysis, and provide an opportunity to better understand disease threat and response.
1:50PM Disentangling the Gordian Knot of Mountain Lion Predation on Bighorn Sheep
Eric M. Rominger
ABSTRACT Although, many predators kill bighorn sheep (Ovis canadensis), only mountain lions (Puma concolor) are considered to have negative population-level consequences under current ecological and sociological conditions. The proximate and ultimate factors influencing high levels of mountain lion predation on bighorn sheep are complex and theoretical. Three primary factors are: 1) Increased presence of mountain lions in habitats where they were historically absent or rare because of the expansion of mule deer (Odocoileus hemionus) following the extensive conversion of native-American fire maintained grasslands to shrublands in the late-1800s, 2) the extirpation of the two often sympatric and dominant apex carnivores, wolves (Canis lupus) and grizzly bears (Ursus arctos), during this same time period and a hypothesized numerical response of mountain lions to those extirpations, and 3) the end of more than 70-years of intensive predator control has often produced mathematically unsustainable mountain lion-bighorn sheep ratios, especially for desert bighorn sheep. Additionally, the effect of mountain lion predation is exacerbated by 1) declines in bighorn sheep that are not associated with declines in mountain lions because of the ability to prey-switch to mule deer, elk (Cervus elaphus), or domestic cattle, 2) kleptoparasitism of mountain lions kills, by Ursids and Canids, resulting in higher kill-rates for mountain lions, and, 3) a possible evolutionary trap where adaptations derived over evolutionary time are no longer adaptive because of human induced changes in the sympatric apex predator guild. Control of mountain lions, when mountain lion-ungulate ratios are high, may be required to protect small and/or endangered bighorn sheep populations, and to produce surplus bighorn sheep for restoration and/or hunting.
2:30PM Evaluation of Aerial Population Estimation Techniques for Pronghorn in Texas
Caroline L. Ward; Randy W. DeYoung; Timothy E. Fulbright; David G. Hewitt; Shawn S. Gray
Aerial surveys, although efficient, often result in underestimates of population size because investigators do not see some of the animals. Failure to observe animals, termed visibility bias, can be corrected for, but corrections must be validated for the geographic regions and survey protocols to which they will be applied. In Texas, aerial surveys for pronghorn (Antilocapra americana) are conducted on strip transects using a fixed-wing aircraft flown at low altitude (30.5 m) to obtain abundance and herd composition estimates. We evaluated the performance of distance sampling and sightability modeling for aerial surveys of pronghorn in the Panhandle and Trans-Pecos regions of Texas. Pronghorn were captured and fitted with GPS collars at 2 sites in each region during March 2014 and February 2015. We surveyed herd units that contained collared pronghorn during June 2014 and 2015, and recorded activity, group size, vegetation type, percent cover, terrain, color, and distance from the survey line. We compared estimates derived via distance sampling and sightability modeling to an independent estimate based on mark-resight. The uncorrected counts underestimated population size by 23.1% compared to mark-resight estimates, 44.6% vs. distance sampling estimates, and 68.9% vs. sightability modeling estimates. Pronghorn detection probabilities were similar to past studies (sightability modeling: 73.1%; distance sampling: 65.2-66.5%). Significant variables in the sightability model were animal activity, distance, cover, terrain, and light. However, population estimates from sightability modeling were often high and variable compared to mark-resight estimates. Distance sampling with animal activity as a covariate generated estimates similar to mark-resight. We concluded that distance sampling with animal activity as a covariate was the best approach for low-level population surveys. Our results emphasize the importance of tailoring survey methodologies to the conditions and data requirements specific to a given geographic region and management needs.
2:50PM Refreshment Break
3:20PM Resource Selection in Desert Bighorn Sheep: Trade-Offs Associated with Recruitment
Marcus Blum; Kelley Stewart; Mike Cox; Brian Wakeling; Brian Wakeling
Selection of resources that effect the development of a fetus and increase probability of survival for neonates is essential for maintaining viable populations in large ungulates. Therefore, it is crucial that biologists understand how species select resources across gestation to increase their ability to manage recruitment. Desert bighorn sheep (Ovis canadensis nelsoni) populations have dwindled across their range over the last several decades and translocations have been a key management strategy for recolonizing areas. When selecting translocation sites, it is essential that biologists select areas with habitat types that positively influence recruitment. To increase understanding of sheep resource selection during gestation and following parturition, we captured and collared 30 adult, female sheep on Lone Mountain (west of Tonopah, NV), of which 15 were translocated to the Garfield Hills (west of Mina, NV) range. In addition to receiving collars, all individuals were given vaginal implant transmitters to provide parturition timing information. Following captures, we monitored parturition events, adult resource selection, and neonate survival. We used mixed effects logistic regression to identify habitat selection during gestation, following parturition events, and following the mortality of neonates. In addition, we used program MARK to model neonate survival and identify the primary factors influencing survival through weaning and recruitment. Our results indicated that adults shifted resource selection from areas with higher nutritional availability to more precipitous terrain immediately following parturition events. In addition, our results indicated that females shifted resource selection to areas with higher quality vegetation and reduced terrain ruggedness following the mortality of a neonate. These results support the hypothesis that females trade-off areas with high quality nutrition to increase probability of neonate survival. However, following the death of a neonate, females adjust resource selection to increase nutrient intake. This behavior may allow individuals to invest more nutrients into future reproduction and survival.
3:40PM Desert Bighorn Sheep Behavioral Responses to Recreation and Urban Visitor Use of the Pusch Ridge Wilderness Area, Arizona
Brett C. Blum
From 2013-2016 the Arizona Game and Fish Department released a total of 110 desert bighorn sheep (Ovis canadensis mexicana) in the Pusch Ridge Wilderness area (PRW), Arizona. Bighorn were released in an effort to re-establish a former endemic population that was extirpated in the mid to late 1990’s after experiencing rapid population decline. Reasons for the decline are likely multifactorial, however, urbanization and an increase in backcountry recreation are often cited as likely contributing factors. Many prey species exhibit antipredator responses in the presence of humans. These responses may lead in turn to behavioral modification and spatiotemporal avoidance strategies that can be energetically expensive, reduce foraging time or limit recruitment. Our research was developed to better understand the effects of backcountry recreation on the behavior and distribution of desert bighorn sheep. The study site was dissected by six primary US Forest Service (USFS) and multiple non-designated trails. Human use of the PRW was quantified across the study site using real time observer field counts and modeled use metrics derived from motion activated trail cameras located at the bottom, midpoint and terminus of each USFS trail (n=15). We conducted 125 behavioral observations at multiple spatial scales from January of 2015 through May of 2016 to quantify bighorn activity budgets and responses to human interaction. Bighorn behavior was characterized in a generalized linear model (GLM) to examine how human use and spatial covariates affect time spent grazing, browsing, vigilant, moving or bedded. Our models indicate an increase in human activity in the PRW is inversely correlated with time spent grazing. As a potential trade off bighorn significantly increased time spent bedded. These results suggest that bighorn behavioral responses to repetitive human activity are likely scalable and may manifest in a way that is most energetically conservative when the perceived risk is predictable.
4:00PM Role of Harvest and Environmental Factors on Horn Size of Mountain Sheep
Tayler N. LaSharr; Ryan A. Long; James R. Heffelfinger; R. Terry Bowyer; Vernon C. Bleich; Paul R. Krausman; Justin M. Shannon; Kevin L. Monteith
Harvest-induced evolution can have important implications for the sustainable management of populations world-wide; yet, the true effects of harvest remain highly debated. Even at limited temporal and spatial scales, population-level responses to harvest can occur across taxa, and include reduced size of weapons and growth rate, and early sexual maturation. Nevertheless, in most populations, the threshold of selection intensity that prompts evolutionary change is unclear. Harvest can affect patterns of weapon size in two distinct ways. First, intensive harvest can result in demographic changes, where declines in mean weapon size result from an increasing proportion of young animals harvested through time. Alternatively, selection for males with fast-growing weaponry may favor the persistence of males with slow-growing weaponry through time and result in declines in the average size of weapons in a population despite no change in age structure. Mountain sheep (Ovis canadensis and Ovis dalli) represent an ideal system to test the effects of harvest on weapon size because harvest of mountain sheep is highly regulated throughout their range and a wealth of phenotypic data exists. Additionally, reliable age data, which is critical to test shifts in age structure of populations, is available through horn annuli of mountain sheep. We synthesized harvest records of mountain sheep throughout their range and assessed changes to age structure and horn size over 46 years. After accounting for age, temporal trends in horn size were not explained by changes to the age structure in approximately 30% of hunt areas, but instead may be associated with selective pressures or environmental conditions. Nonetheless, age-specific horn size was stable in about 70% of hunt areas, indicating harvest practices for most populations of mountain sheep in North America have not resulted in evolutionary changes to weapon size.
4:20PM Effects of Sampling Time on Bone Marrow Fat Estimates
Jacob Kay; Dr. James W. Cain III
Bone marrow fat content has commonly been used to assess the health of ungulates. Evaluating body condition of individuals provides important insight for wildlife managers that allow them to better understand local population dynamics and predator-prey interactions in order to sustainably manage herds. Studies have compared different methods of measuring bone marrow fat content as well as identified which bones are most representative of an individual’s health. However, no previous research has examined how the amount of time from death to sample collection affects bone marrow fat estimates of ungulates in natural conditions. Marrow samples are rarely collected at the time of mortality, which could potentially bias fat estimates from bone marrow samples. We examined how bone marrow fat content is affected by time post mortem and other factors by collecting multiple bones from individual elk (Cervus elaphus) and deer (Odocoileus hemionius) at different time intervals in central New Mexico. We found that marrow fat content can change significantly during the period between when an animal dies and when the sample is collected. Our top model that explained this change included time between samples, initial fat content and sex of the species. Marrow fat content increased over time and changed more rapidly in samples with intermediate starting fat contents and in male ungulates. Future research efforts that utilize bone marrow fat content should attempt to retrieve bone samples immediately after an animal has died. Failure to do so can lead to false conclusions regarding the nutritional state of individual animals and subsequent mismanagement of predator and prey populations.
4:40PM Quantifying Endocrine Response to Anthropogenic Stressors Associated with Border Activity in Free Ranging Pronghorn
David Christianson; Stephanie Doerries; Susannah Woodruff; Lisette Waits
Quantifying anthropogenic stressors can be difficult in sparse, wide-ranging, and protected species where most physiological assays are impractical. Non-invasively collected fecal glucocorticoids have been used in many wild populations to measure baseline stress hormone levels but strong inference regarding anthropogenic stressors is limited by two primary constraints, (1) spatio-temporal matching of stressors and endocrine responses and (2) individual level variation in endocrine profiles compounded by pseudoreplication in small populations. Here, we present results from a novel fecal glucocorticoid sampling design that addresses both these issues through repeat sampling at fixed sites where temporal variation in human activity was continuously monitored with motion-sensing cameras and fecal microsatellite genotypes were used to identify repeat sampling of known individuals. We measured fecal glucocorticoids in 520 fecal samples genotyped to just 112 individuals (4.6 cortisol estimates per individual). Mixed effects models revealed large random effects (21.1% of the variation) arising from variation across individuals, a comparable amount to that seen between low and high periods of human activity and between genders or age classes. Accounting for pronghorn identity estimated individual level responses to spatio-temporal variation in human activity and addressed bias resulting from imbalanced sampling across sites, sex, and age classes. Male and female pronghorn exhibited similar levels of stress hormone levels (43.9 ng/g ± 2.6 95% CI) , while fawns showed glucocorticoids 10% lower than adults. Adult male and female pronghorn both responded, but in a different manner, to both increased pronghorn activity and human activity by increasing fecal glucocorticoids suggesting social interactions at artificial water and food sources provoke an endocrine response comparable to interactions with humans. While genotyping samples to account for individual level covariates affecting non-invasively collected fecal glucocorticoids is not common practice, our results suggest this critical step may be important for studies of endocrine function in many species.


Contributed Paper
Location: Albuquerque Convention Center Date: September 25, 2017 Time: 1:10 pm - 5:00 pm