Conservation and Ecology of Mammals – Cervids I

Contributed Paper
ROOM: Room 230 – Pecos
SESSION NUMBER: 32
 

10:30AM Weather and Landscape Factors Affect White-tailed Deer Neonate Survival at Ecologically Important Life Stages in the Northern Great Plains
Eric S. Michel; Jonathan A. Jenks; Kyle D. Kaskie; Robert W. Klaver; William F. Jensen
Offspring survival is generally more variable than adult survival and may limit population growth. Although white-tailed deer (Odocoileus virginianus) neonate survival has been intensively investigated, recent work has emphasized how specific cover types influence neonate survival at local scales (single study area). These localized investigations have often led to inconsistences within the literature. Developing specific hypotheses describing the relationships among environmental, habitat, and landscape factors influencing white-tailed deer neonate survival at regional scales may allow for detection of generalized patterns. Therefore, we developed 11 hypotheses representing the various effects of environmental (e.g., winter and spring weather), habitat (e.g., hiding and escape cover types), and landscape factors (e.g., landscape configuration regardless of specific cover type available) on white-tailed deer neonate survival at one- and three-months of age. At one-month, surviving fawns experienced a warmer lowest recorded June temperature and more June precipitation than those that perished. At three-months, patch connectance (percent of patches of the corresponding patch type that are connected within a predefined distance) positively influenced survival. Our results are consistent with white-tailed deer neonate ecology: increased spring temperature and precipitation are likely associated with a flush of nutritional resources available to the mother, promoting increased lactation efficiency and fawn growth early in life. In contrast, reduced spring temperature with increased precipitation place neonates at risk to hypothermia. Increased patch connectance likely reflects increased escape cover available within a neonate’s home range after they are able to flee from predators. If suitable escape cover is available on the landscape, then managers could focus efforts towards manipulating landscape configuration (patch connectance) to promote increased fawn survival while monitoring spring weather to assess potential influences on current year neonate survival.
10:50AM Juvenile Survival of Mule Deer in the Blue Mountains of Oregon
NATHAN J. JACKSON; KELLEY M. STEWART; DARREN A. CLARK; MICHEAL J. WISDOM
Declines in mule deer (Odocoileus hemionus) populations over the past half century have become a concern to wildlife managers across the west. Mule deer in temperate regions face varying seasonal challenges with respect to nutrition and environmental conditions, as well as, variation occurring from year to year. Despite these challenges, adult survival is generally high and stable across most populations. We focused our efforts on assessing juvenile survival and recruitment as an indicator of population performance. We used the nest survival module in program MARK to investigate juvenile survival in an environment experiencing years of variable winter severity. We investigated the relative effects of body size, body weight, mother’s nutritional status, timing of parturition, snow depth, and location or characteristics of birth site on survival of young. We modeled juvenile survival out to weaning (120 days) and recruitment (226 days). Juvenile survival to weaning was 0.34 (SE= 0.06) across three years of the study. Juvenile age was positively correlated with survival. We observed the highest rate of juvenile mortality during the first month of life. Supplemental feeding of the mother during winter and being born with a sibling increased the probability of survival. Juvenile survival to recruitment was 0.21 (SE= 0.07) across 2 years of the study. Snow depth and body size were negatively correlated with survival over winter, but snow depth was the strongest indicator of over winter survival of neonates. Our results suggest that there is a bottom up effect on juvenile survival in our study population.
11:10AM Modeling White-tailed Deer Survival and Recruitment with Novel Spatial Capture-Recapture Models and Camera Data
Kristin N. Engebretsen; Michael J. Cherry; Elina Garrison; Karl V. Miller; Richard B. Chandler
In South Florida, white-tailed deer (Odocoileus virginianus) are the primary prey of the endangered Florida panther (Puma concolor coryi) and are an economically and culturally important game species. Due to recently reported declines in deer populations, we are conducting a comprehensive study investigating the effects of hydrology, hunting, and predation on deer population dynamics. We deployed 180 passive trail cameras across three separate grids in the Florida Panther National Wildlife Refuge and Big Cypress National Preserve. To estimate fawn recruitment, we uniquely identified each detected fawn by their spot patterns and created spatially-referenced encounter histories with each detection of a spotted fawn. We developed a spatial capture-recapture (SCR) model that uses these encounter histories to estimate population parameters such as birth rate, survival, and recruitment. Unlike previous SCR models, we allowed survival and detection rates to vary with age using a continuous-time formulation. Using images from January 1 through June 30 2016, we uniquely identified 28, 31, and 65 fawns at three separate camera grids within the 550 km2 study area. Peak parturition date was February 16, with the majority of fawning events occurring from January to March. Approximately 75% of all fawns (both detected and undetected) survived to 20 days old, and 50% survived to 120 days. 37.5% (95% CI: 19.3-59.1%) of fawns reached recruitment (180 days). We estimated the effects of spatial variation on survival and recruitment, as well as the relationships between fawn age and both survival rate and detection probability. We also evaluated the effects of covariates such as habitat type, surface water depth, human activity, proximity to road, and predator activity. Our model provides a cost-effective, flexible, and non-invasive method to estimate fawn recruitment at broad spatial and temporal scales while addressing questions about the underlying birth and juvenile survival processes.
11:30AM Responses of Female White-tailed Deer to Hunting Activity in Two Different Ecoregions of Missouri
Chloe A. Wright; Jon T. McRoberts; Joshua J. Millspaugh; Barbara J. Keller; Kevyn H. Wiskirchen
Hunting is the largest mortality source for many white-tailed deer (Odocoileus virginianus) populations and is used as a management tool to help regulate populations. During the hunting season deer might select for refugia or change space use patterns as a result of the increased hunting pressure, thus potentially making harvest a less effective management tool. We compared female deer movements and resource selection 10 days before, 11 days during and 10 days following the firearms hunting season in the Glaciated Plains (GP) and Ozark (OZ) ecoregions of Missouri. We captured 136 female deer from January – March 2015-16 and fitted them with GPS radio-collars programmed to collect 1 location/90 minutes. We used the dynamic Brownian bridge movement model to estimate home range size, quantified the proportion of space use overlap, and calculated average movement speed during the 3 periods. In both the NW (n=60, F=3.19, p=0.044) and OZ (n=76, F=6.44, p=0.002) female deer altered their home range size between the 3 periods. In the NW and OZ home range sizes increased during the firearms season by 30% and 40%, respectively. After the hunting season, home range size returned to the pre-hunt size. Average movement speed was not different between the 3 periods in either area. The overlap between 50% home ranges in all 3 periods was low (24% – 35% overlap) in both study areas, indicating a shift in space use over time. Female deer in Missouri responded to hunter pressure by using a larger area and shifting where they spent the majority of their time, but did not increase their movement speed. This shift in space use might have affected their harvest potential. Examination of resource selection will aid our understanding of whether habitat features explain these shifts.
11:50AM Habitat Selection by Female Mule Deer: Tradeoffs Associated with Reproduction
Levi J. Heffelfinger; Kelley M. Stewart; Kevin T. Shoemaker; Neal W. Darby; Vernon C. Bleich
Wildlife species occupying arid regions throughout the west are faced with an array of environmental stressors. These regions typically have higher maximum daytime temperatures, which causes individuals to increase metabolic rates and thermoregulation, which exaggerates the physiological demand for nutrition and water. Mule deer (Odocoileus hemionus) have adapted to arid regions by increasing energy expenditure to meet these needs. We studied the effects these factors have on movements of a mule deer population in an arid ecosystem surrounding the time of reproduction. We focused on selection of resources by females pre-parturition, during the intense lactation period, and the post-lactation recovery period. Since pregnancy and lactation are considered the most nutritionally demanding period annually for individuals in this system, energetic costs should change rapidly throughout the stages of reproduction and after the loss of an offspring. We established 3 study areas on the Mojave National Preserve in southern California, USA that have varying topography, habitat, and number of water sources. We evaluated habitat and resource selection using the Random-forest machine learning technique with a data set of used and randomly generated points to quantify availability at an individual scale. During the pre-parturition period, individuals did not select specific habitat attributes and were not closely tied to water. Females selected higher elevation areas closer to water while young were at heel and relatively more herbaceous habitat types post-neonate mortality. These findings show that females select areas that increase survival of their young and support water demands during lactation. Our research could have substantive implications for management strategies throughout arid ecosystems by informing managers about tradeoffs associated with habitat selection during the rearing of young and the nutritionally demanding period of lactation.

 

Contributed Paper
Location: Albuquerque Convention Center Date: September 25, 2017 Time: 10:30 am - 12:10 pm