Thursday, June 01, 2006
Bobcat Research
KINSHIP AND SOCIAL STRUCTURE OF BOBCATS INFERRED FROM MICROSATELLITE AND RADIO-TELEMETRY DATA
Researchers: Jan Janecka, Terry L. Blankenship (Welder Wildlife Foundation), David Hirth (University of Vermont), C. William Kilpatrick (University of Vermont), and Michael Tewes
The applications of genetics to social structure has received little attention in cat species. We are comparing kinship data from microsatellite genotypes to radio-telemetry data from previous studies to gain insights into social structure of bobcats at the Welder Wildlife Refuge and Aransas National Wildlife Refuge. Genetically identified kinship relationships combined with available radio-telemetry data are being used to reconstruct pedigrees. Family groups are genetically identified from parent-offspring pairs and sibling groups and compared to spatial distribution of the individuals.
To date all parents identified by genetic analysis at the Welder Wildlife Refuge had established home ranges, although low sample size prevents rigorous analysis. Individuals with no distinct home ranges were not genetically observed to have offspring among the bobcats sampled at Welder Wildlife Refuge. This suggests that establishing a home range is necessary for bobcats in order to breed. Juvenile females established home ranges and breed in the vicinity of their mothers. This study is ongoing and as more bobcats in these areas are trapped and collared, we will gain additional insights in to the social structure of bobcats.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
DISPERSAL PATTERNS IN BOBCATS
Researcher: Jan Janecka, Terry Blankenship (Welder Wildlife Refuge), David Hirth (University of Vermont), William Kilpatrick (University of Vermont)
Dispersal is a mechanism which has evolved to minimize resource competition and inbreeding. Bobcats exhibit high dispersal rates. However, bobcat dispersal has never been directly studied due to the limitations associated with traditional research methods. In previous studies the limited number of dispersal events observed has prevented a rigorous characterization of dispersal patterns in bobcats.
We examined dispersal patterns in a bobcat population in south Texas using eight variable microsatellites. Relatedness among females (r = -0.013, S.E. = 0.014) was significantly higher than among males (r = -0.077, S.E. = 0.005). The distribution of pair-wise relatedness values in females was significantly different from the expected random distribution and skewed towards first- and second-degree relatives. In contrast, the male distribution of pair-wise relatedness values was not significantly different from the expected random distribution. Genetically identified parent-offspring dyads were also over-represented in females and underrepresented in males. These data provided evidence that the higher group relatedness value in females was due to a greater tendency for females to exhibit philopatric behavior than males (more first-degree relatives among females). The results supported the hypothesis that dispersal in bobcats is male-biased. The patterns of genetic variation were also consistent with observations made during a bobcat radio-telemetry study at the Welder Wildlife Refuge.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
MICROSATELLITE ANALYSIS OF POPULATION STRUCTURE OF BOBCATS IN SOUTHERN TEXAS USING SCAT SAMPLES
Researcher: Jan Janecka, David Hirth (University of Vermont), C. William Kilpatrick (University of Vermont), and Michael Tewes
Population genetics can provide important information on population structure and dispersal of bobcats. Advances in genetics have provided methods to extract DNA suitable for population studies from samples such as scat and hair. These methods allow non-invasive sampling of bobcat populations. Obtaining blood samples is difficult due to the time necessary for trapping cats. Collecting scats can provide an efficient method for sampling bobcat populations.
We are using bobcat scat samples for the genetic analysis of population structure in south Texas. The success rate of amplification of microsatellite loci from DNA extracted from scat is low. In preliminary research, seven scat samples were analyzed from the King Ranch (Texas) for the FCA26 microsatellite locus. There were two unique alleles in King Ranch population that were not observed in the Welder Wildlife Refuge population during a previous study. The WWR population also had two rare alleles not observed in the King Ranch population. The observation that the King Ranch population has two unique alleles suggested that the bobcats from WWR and King Ranch may represent two different populations. We are optimizing amplification of other microsatellite loci. Six to eight loci will be required to examine population structure.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
EFFECTS OF ROADS ON BOBCAT SPATIAL PATTERNS AND MORTALITY
Researchers: Michael Tewes, Jan Janecka, Stephen Webb, and Rob Hughes
Road development may influence the distribution and population dynamics of species. Developed highways may fragment populations in certain areas. Road accidents are one of the main causes of bobcat mortality in parts of Texas. The objective of this study is to examine the effects of developed roads on bobcat ecology.
We have home range data from several areas that have road networks. We are examining the avoidance/selection of home range habitat in bobcats based on road density. Results of this study will be used to plan future crossing structures in sensitive areas, as well as to develop alternatives to reduce road impacts on bobcat, and possibly ocelots.
BOBCAT USE OF DENSE THORNSHRUB IN THE TAMAULIPAN BIOTIC PROVINCE
Researchers: Nathan Cook and Michael Tewes
Ocelots prefer dense thornshrub with greater than 95% horizontal canopy cover, whereas bobcats use a variety of cover types with an emphasis on intermediate cover densities. In areas containing both types of cover, ocelot and bobcat home ranges overlapped. This study will determine whether bobcats show a higher competitive potential in areas with large tracts of dense thornshrub.
Our study area is located on private ranches in the Lower Rio Grande Valley containing large tracts of dense thornshrub communities. Although ocelots have been previously documented in our study area, none have been captured during this study. Eight bobcats have been captured and radio-collared, with one adult female lost to a vehicle collision after dispersing over 30 miles. Home range and movement patterns are being established via radio tracking of the collared bobcats. Position information will be added to a GIS database and compared to previous studies of felid use of dense thornshrub communities. Our efforts will lead to a better understanding of bobcat use of large tracts of dense thornshrub communities, and may have management implications for the endangered ocelot.
SPATIAL PATTERNS AND HABITAT USE OF AN UNHARVESTED BOBCAT POPULATION
Researchers: Jennifer M. Mock, John Hitchcock, and Michael E. Tewes
Bobcats are the most adaptable and widest ranging wild cat in North America. They occupy many diverse habitats from northern forests to southern cypress swamps. Historically, the bobcat was harvested and trapped for its spotted pelt throughout its entire range. Although pelt prices have declined over the years reducing fur trade profitability, most bobcat populations across the continent are still harvested. However, an unharvested bobcat population exists on the peninsula of Aransas National Wildlife Refuge. This provides a unique opportunity to study the spatial patterns and habitat use of an unharvested bobcat population.
Thirty-four adult bobcats were trapped and radio-collared in 1995, and tracked via radio-telemetry through October 1996. Bobcat movements were monitored to examine their home range dynamics and habitat use. We are examining the home range dynamics of this protected bobcat population and we will compare them to a harvested bobcat population from previous Feline Research Program studies. We will also contrast spatial patterns and habitat use of these different populations to better understand the spatial differences between bobcat populations and possible effects of harvesting.
Numerous studies have analyzed bobcat survival in temperate regions of North America. This study compared survival and cause-specific mortality rates of resident and transient bobcats in a sub-tropical region of southern Texas in the United States. Our objectives were to estimate seasonal and annual survival rates and cause-specific mortality rates for resident and transient bobcats, and evaluate differences between resident and transient bobcats. We conducted this study on the Welder Wildlife Foundation Refuge in San Patricio County, Texas. We radio-monitored 30 resident (15 F, 15 M) and 23 transient (9 F, 14 M) bobcats from 31 December 1993 through 1 January 2004, with 19 transients being juvenile or subadult bobcats and 26 residents being adult bobcats. Annual (P = 0.09) and seasonal (P > 0.53) survival rates did not differ significantly between male and female resident bobcats. Seasonal survival did not differ for resident (P = 0.64) and transient (P = 0.72) bobcats. Resident bobcats had a higher (P < se =" 0.04)" p =" 0.04)" p =" 0.01)">
Researchers: Jan Janecka, Terry L. Blankenship (Welder Wildlife Foundation), David Hirth (University of Vermont), C. William Kilpatrick (University of Vermont), and Michael Tewes
The applications of genetics to social structure has received little attention in cat species. We are comparing kinship data from microsatellite genotypes to radio-telemetry data from previous studies to gain insights into social structure of bobcats at the Welder Wildlife Refuge and Aransas National Wildlife Refuge. Genetically identified kinship relationships combined with available radio-telemetry data are being used to reconstruct pedigrees. Family groups are genetically identified from parent-offspring pairs and sibling groups and compared to spatial distribution of the individuals.
To date all parents identified by genetic analysis at the Welder Wildlife Refuge had established home ranges, although low sample size prevents rigorous analysis. Individuals with no distinct home ranges were not genetically observed to have offspring among the bobcats sampled at Welder Wildlife Refuge. This suggests that establishing a home range is necessary for bobcats in order to breed. Juvenile females established home ranges and breed in the vicinity of their mothers. This study is ongoing and as more bobcats in these areas are trapped and collared, we will gain additional insights in to the social structure of bobcats.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
DISPERSAL PATTERNS IN BOBCATS
Researcher: Jan Janecka, Terry Blankenship (Welder Wildlife Refuge), David Hirth (University of Vermont), William Kilpatrick (University of Vermont)
Dispersal is a mechanism which has evolved to minimize resource competition and inbreeding. Bobcats exhibit high dispersal rates. However, bobcat dispersal has never been directly studied due to the limitations associated with traditional research methods. In previous studies the limited number of dispersal events observed has prevented a rigorous characterization of dispersal patterns in bobcats.
We examined dispersal patterns in a bobcat population in south Texas using eight variable microsatellites. Relatedness among females (r = -0.013, S.E. = 0.014) was significantly higher than among males (r = -0.077, S.E. = 0.005). The distribution of pair-wise relatedness values in females was significantly different from the expected random distribution and skewed towards first- and second-degree relatives. In contrast, the male distribution of pair-wise relatedness values was not significantly different from the expected random distribution. Genetically identified parent-offspring dyads were also over-represented in females and underrepresented in males. These data provided evidence that the higher group relatedness value in females was due to a greater tendency for females to exhibit philopatric behavior than males (more first-degree relatives among females). The results supported the hypothesis that dispersal in bobcats is male-biased. The patterns of genetic variation were also consistent with observations made during a bobcat radio-telemetry study at the Welder Wildlife Refuge.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
MICROSATELLITE ANALYSIS OF POPULATION STRUCTURE OF BOBCATS IN SOUTHERN TEXAS USING SCAT SAMPLES
Researcher: Jan Janecka, David Hirth (University of Vermont), C. William Kilpatrick (University of Vermont), and Michael Tewes
Population genetics can provide important information on population structure and dispersal of bobcats. Advances in genetics have provided methods to extract DNA suitable for population studies from samples such as scat and hair. These methods allow non-invasive sampling of bobcat populations. Obtaining blood samples is difficult due to the time necessary for trapping cats. Collecting scats can provide an efficient method for sampling bobcat populations.
We are using bobcat scat samples for the genetic analysis of population structure in south Texas. The success rate of amplification of microsatellite loci from DNA extracted from scat is low. In preliminary research, seven scat samples were analyzed from the King Ranch (Texas) for the FCA26 microsatellite locus. There were two unique alleles in King Ranch population that were not observed in the Welder Wildlife Refuge population during a previous study. The WWR population also had two rare alleles not observed in the King Ranch population. The observation that the King Ranch population has two unique alleles suggested that the bobcats from WWR and King Ranch may represent two different populations. We are optimizing amplification of other microsatellite loci. Six to eight loci will be required to examine population structure.
Co-operative funding by the Rob and Bessie Welder Wildlife Foundation and the American Museum of Natural History.
EFFECTS OF ROADS ON BOBCAT SPATIAL PATTERNS AND MORTALITY
Researchers: Michael Tewes, Jan Janecka, Stephen Webb, and Rob Hughes
Road development may influence the distribution and population dynamics of species. Developed highways may fragment populations in certain areas. Road accidents are one of the main causes of bobcat mortality in parts of Texas. The objective of this study is to examine the effects of developed roads on bobcat ecology.
We have home range data from several areas that have road networks. We are examining the avoidance/selection of home range habitat in bobcats based on road density. Results of this study will be used to plan future crossing structures in sensitive areas, as well as to develop alternatives to reduce road impacts on bobcat, and possibly ocelots.
BOBCAT USE OF DENSE THORNSHRUB IN THE TAMAULIPAN BIOTIC PROVINCE
Researchers: Nathan Cook and Michael Tewes
Ocelots prefer dense thornshrub with greater than 95% horizontal canopy cover, whereas bobcats use a variety of cover types with an emphasis on intermediate cover densities. In areas containing both types of cover, ocelot and bobcat home ranges overlapped. This study will determine whether bobcats show a higher competitive potential in areas with large tracts of dense thornshrub.
Our study area is located on private ranches in the Lower Rio Grande Valley containing large tracts of dense thornshrub communities. Although ocelots have been previously documented in our study area, none have been captured during this study. Eight bobcats have been captured and radio-collared, with one adult female lost to a vehicle collision after dispersing over 30 miles. Home range and movement patterns are being established via radio tracking of the collared bobcats. Position information will be added to a GIS database and compared to previous studies of felid use of dense thornshrub communities. Our efforts will lead to a better understanding of bobcat use of large tracts of dense thornshrub communities, and may have management implications for the endangered ocelot.
SPATIAL PATTERNS AND HABITAT USE OF AN UNHARVESTED BOBCAT POPULATION
Researchers: Jennifer M. Mock, John Hitchcock, and Michael E. Tewes
Bobcats are the most adaptable and widest ranging wild cat in North America. They occupy many diverse habitats from northern forests to southern cypress swamps. Historically, the bobcat was harvested and trapped for its spotted pelt throughout its entire range. Although pelt prices have declined over the years reducing fur trade profitability, most bobcat populations across the continent are still harvested. However, an unharvested bobcat population exists on the peninsula of Aransas National Wildlife Refuge. This provides a unique opportunity to study the spatial patterns and habitat use of an unharvested bobcat population.
Thirty-four adult bobcats were trapped and radio-collared in 1995, and tracked via radio-telemetry through October 1996. Bobcat movements were monitored to examine their home range dynamics and habitat use. We are examining the home range dynamics of this protected bobcat population and we will compare them to a harvested bobcat population from previous Feline Research Program studies. We will also contrast spatial patterns and habitat use of these different populations to better understand the spatial differences between bobcat populations and possible effects of harvesting.
Numerous studies have analyzed bobcat survival in temperate regions of North America. This study compared survival and cause-specific mortality rates of resident and transient bobcats in a sub-tropical region of southern Texas in the United States. Our objectives were to estimate seasonal and annual survival rates and cause-specific mortality rates for resident and transient bobcats, and evaluate differences between resident and transient bobcats. We conducted this study on the Welder Wildlife Foundation Refuge in San Patricio County, Texas. We radio-monitored 30 resident (15 F, 15 M) and 23 transient (9 F, 14 M) bobcats from 31 December 1993 through 1 January 2004, with 19 transients being juvenile or subadult bobcats and 26 residents being adult bobcats. Annual (P = 0.09) and seasonal (P > 0.53) survival rates did not differ significantly between male and female resident bobcats. Seasonal survival did not differ for resident (P = 0.64) and transient (P = 0.72) bobcats. Resident bobcats had a higher (P < se =" 0.04)" p =" 0.04)" p =" 0.01)">
BOBCAT PREDATION ON QUAIL, BIRDS, AND MESOMAMMALS
Researchers: Michael E. Tewes, Jennifer M. Mock, and John Young (Texas Parks and Wildlife)
The role of bobcat predation on quail is often debated by wildlife managers and hunters. Although researchers have gathered information and performed studies about the predators of specific quail populations, quail were often the research focus while a variety of predators were monitored. Food habit studies focusing on particular predators have often been overlooked by wildlife biologists and managers. One reason is this literature occurs in a variety of sources and under titles exclusive of quail. Consequently, many biologists and managers are unaware of these sources of information.
This study extensively reviews literature and information about the food habits and foraging ecology of bobcats in the United States to determine the relative importance of various quail species in bobcat diets. Also, the use of avian prey was related to mammalian prey to better understand their relative importance in bobcat diets. Mesomammal presence in bobcat scats and stomachs was identified to determine possible interrelationships of mammalian predation on quail.
We surveyed 54 scientific articles about bobcat food habits to determine the occurrence of quail, birds, and mesomammals. Quail were found in 9 diet studies and constituted >3% of the bobcat diet in only 2 of 54 studies. Birds occurred in 47 studies, but were also a minor dietary component in most studies. Mesomammals were infrequently encountered in bobcat diets, and showed regional patterns of occurrence. Bobcats are a minor quail predator, but felid effects on mesomammals and secondary impacts on quail need to be studied.
