Understanding spatial and temporal patterns in movement and habitat use of black-tailed deer in Northern California, USA

Black-tailed deer (BTD, Odocoileus hemionus columbianus), a socio-economically important deer species in western North America is steadily declining throughout much of its range over the last century. Though a large number of studies have been carried out on forage availability, predation pressure, and population dynamics of the species, there still remain broad gaps in current understanding of the underlying causes, mechanisms, and spatio-temporal patterns of habitat use which can affect the population dynamics and distribution of BTD. So, the central aim of my thesis was to identify the spatial and temporal scale that may affect habitat selection, movement and ultimately long-term persistence of the BTD population in the Mendocino National Forest, California. Understanding population structuring in BTD is vital to underpin the spatial scale for conservation. So, I tested for presence of population sub-structuring among female BTD in the study area by analysing the combined effect of site fidelity and philopatry on the population. Fidelity analyses from radio-telemetry data revealed BTD to have extremely small seasonal home ranges (0.71 km²) and very high site fidelity to these ranges. Direct fitness benefits of fidelity were observed as individuals with decreased site fidelity to their ranges suffered elevated risks of mortality. Results from mtDNA sequencing revealed high genetic differentiation (FST > 0.30) and low haplotype sharing even among geographic areas separated by as little as 4–10 km. Combined, the results indicated prolonged period of philopatric behaviour resulting in demographic isolation and very small scale population sub-structuring that can impact the population dynamics at a finer spatial scale than previously assumed. Next, I examined the effect of temporal scale on resource selection by BTD, through comparing habitat characteristics selected by BTD from a pooled model (all telemetry locations pooled across activity states) versus habitat characteristics associated with foraging (active state) and resting or ruminating (inactive state). The main factors that influenced resource selection in BTD were: 1) seasonal changes associated largely with variable selection towards slope, aspect, and elevation and 2) activity states influenced fine-scale selection towards vegetation type, edge density, and cover within the home-ranges. The comparative analysis also revealed that due to larger proportion of resting and ruminating locations, the pooled model frequently failed to identify critical foraging habitats and reflected habitats associated with resting. The frequent misidentification for important ecological covariates associated with foraging was a testimony that pooling data across activity states in BTD can negatively impact our understanding about habitat selection by the species. Finally, I developed a movement model to understand the spatial and temporal patterns of risk-forage trade-offs by female BTD as a function of landscape familiarity. The results showed that familiarity affects the trade-off patterns by BTD in a heterogeneous landscape, with differential selection towards productivity and risk that also varied largely with habitat types. The results further revealed strong selection towards highly familiar areas by BTD during the night time and at dawn while stepping into less familiar areas during the daytime. The demonstrated preference for familiar locations within their home ranges when their primary predator (puma) is most active emphasizes that spatial familiarity is important not only for large scale processes like selection of home range, but also for striking fine-scale trade-offs between forage and risk within individual home ranges. The knowledge of this fine scale selection pattern is critical for maintaining habitat heterogeneity at a spatial scale comparable to the size of their home ranges, as they have vital consequences on fitness of BTD that ultimately affects the population dynamics of the species

Understanding spatial and temporal patterns in movement and habitat use of black-tailed deer in Northern California, USA

Black-tailed deer (BTD, Odocoileus hemionus columbianus), a socio-economically important deer species in western North America is steadily declining throughout much of its range over the last century. Though a large number of studies have been carried out on forage availability, predation pressure, and population dynamics of the species, there still remain broad gaps in current understanding of the underlying causes, mechanisms, and spatio-temporal patterns of habitat use which can affect the population dynamics and distribution of BTD. So, the central aim of my thesis was to identify the spatial and temporal scale that may affect habitat selection, movement and ultimately long-term persistence of the BTD population in the Mendocino National Forest, California. Understanding population structuring in BTD is vital to underpin the spatial scale for conservation. So, I tested for presence of population sub-structuring among female BTD in the study area by analysing the combined effect of site fidelity and philopatry on the population. Fidelity analyses from radio-telemetry data revealed BTD to have extremely small seasonal home ranges (0.71 km²) and very high site fidelity to these ranges. Direct fitness benefits of fidelity were observed as individuals with decreased site fidelity to their ranges suffered elevated risks of mortality. Results from mtDNA sequencing revealed high genetic differentiation (FST > 0.30) and low haplotype sharing even among geographic areas separated by as little as 4–10 km. Combined, the results indicated prolonged period of philopatric behaviour resulting in demographic isolation and very small scale population sub-structuring that can impact the population dynamics at a finer spatial scale than previously assumed. Next, I examined the effect of temporal scale on resource selection by BTD, through comparing habitat characteristics selected by BTD from a pooled model (all telemetry locations pooled across activity states) versus habitat characteristics associated with foraging (active state) and resting or ruminating (inactive state). The main factors that influenced resource selection in BTD were: 1) seasonal changes associated largely with variable selection towards slope, aspect, and elevation and 2) activity states influenced fine-scale selection towards vegetation type, edge density, and cover within the home-ranges. The comparative analysis also revealed that due to larger proportion of resting and ruminating locations, the pooled model frequently failed to identify critical foraging habitats and reflected habitats associated with resting. The frequent misidentification for important ecological covariates associated with foraging was a testimony that pooling data across activity states in BTD can negatively impact our understanding about habitat selection by the species. Finally, I developed a movement model to understand the spatial and temporal patterns of risk-forage trade-offs by female BTD as a function of landscape familiarity. The results showed that familiarity affects the trade-off patterns by BTD in a heterogeneous landscape, with differential selection towards productivity and risk that also varied largely with habitat types. The results further revealed strong selection towards highly familiar areas by BTD during the night time and at dawn while stepping into less familiar areas during the daytime. The demonstrated preference for familiar locations within their home ranges when their primary predator (puma) is most active emphasizes that spatial familiarity is important not only for large scale processes like selection of home range, but also for striking fine-scale trade-offs between forage and risk within individual home ranges. The knowledge of this fine scale selection pattern is critical for maintaining habitat heterogeneity at a spatial scale comparable to the size of their home ranges, as they have vital consequences on fitness of BTD that ultimately affects the population dynamics of the species

Data from: Implications of fidelity and philopatry for the population structure of female black-tailed deer

Site fidelity and philopatry are behavioral adaptations found in many species and their fitness benefits are well documented. The combined population level consequences of site fidelity and philopatry, however, have received little attention despite their importance for understanding spatial patterns in connectivity and population dynamics. We used an integrative approach to explore consequences of fidelity and philopatry on the fine-scale genetic structure of black-tailed deer (Odocoileus hemionus columbianus). We assessed fidelity to seasonal home ranges based on location data from 64 female deer fitted with global positioning system (GPS) collars between 2004 and 2013. We assessed philopatry from mitochondrial DNA (mtDNA) haplotypes using DNA extracted from 48 deer. Results based on location data revealed very small movements and seasonal home ranges together with high site fidelity. Fidelity improved survival; every 1 km increase in mean interlocation distances between consecutive summers increased the risk of mortality by 56.5%. Results from mtDNA sequencing revealed high genetic differentiation (FST > 0.30) and low haplotype sharing among geographic areas separated by as little as 4–10 km. The high genetic differentiation indicated multigenerational periods of philopatric behavior in the matrilineage of black-tailed deer. Combined these results suggest that site fidelity together with strong sex-biased philopatry can create marked short- and long-term demographic isolation and trap matriarchal units as a subset of the larger population with locally determined vital rates. Where such fine-scale population structuring as a consequence of fidelity and philopatry occurs, matrilineal groups might in some cases best serve as the basic units of conservation and management

Implications of fidelity and philopatry for the population structure of female black-tailed deer

No description supplie

Implications of fidelity and philopatry for the population structure of female black-tailed deer

No description supplie

Weekly location data deer fidelity analysis

File contains individual deer ID as well as date, latitude, longitude and allocated season of GPS locations used to determine site fidelity of black-tailed deer in the Mendocino National Forest, California, USA

Fidelity_deer_summary

File contains information on deer ID, age, area and period of time a deer was colalred, number of seasons (summer and winter) a deer was monitored, info on weather a deer was non-migratory (column N0 = 1) and status at the end of the monitoring period to estimate cox proportional hazards

Weekly location data deer fidelity analysis

File contains individual deer ID as well as date, latitude, longitude and allocated season of GPS locations used to determine site fidelity of black-tailed deer in the Mendocino National Forest, California, USA