Black Bear Research in Connecticut using GPS...
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Black Bear Research in Connecticut using GPS Technology - Black bears began recolonizing the rural northwestern corner of Connecticut through range expansion from Massachusetts during the mid 1900’s. A resident population became evident in the 1980’s as numerous sightings of adult females (sows) with cubs were reported to CT DEEP’s Wildlife Division. Since then, the state’s population of black bears has continued to increase in numbers and expand in range. The Wildlife Division has solicited bear sightings from the public for over 30 years. These public sightings have been a valuable index of black bear population growth and range expansion in the state. In 2001, the Wildlife Division initiated a bear research project to determine population growth rates (reproduction and survival) and sow home range characteristics. Initially, this research included maintaining and monitoring a sample of 15-25 sows fitted with Very High Frequency (VHF) radio-collars. Collared sows were located in their winter dens which provided valuable reproduction and survival information. Locations of VHF collared sows were determined through triangulation which is effective but often time consuming. While using VHF collars, each collared sow was located on average once each week during the spring and summer, or 20-30 times a year. Recent advances in wildlife monitoring technology have made Global Positioning System (GPS) collars a far more reliable and efficient tool for studying wildlife movement patterns. In 2007, the Wildlife Division began to replace VHF collars with GPS collars with the goal of collecting more detailed information on spatial and temporal movements of bears. Currently, 30 sows are being monitored via GPS collars in Connecticut. Since switching to GPS collars, the number of data points collected on each sow per year has been between 4,500 and 5,500. This GPS data has provided far more accurate and detailed information which is being used to estimate current population size and carrying capacity through resource selection analysis which will help guide management decisions for Connecticut’s bear population into the future. Black bear sighting reports from the public have been collected and mapped by the Wildlife Division since the early 1980’s. This information has been a valuable index of bear population growth and range expansion. The population initially established in the northwest corner of the state, but has slowly been expanding south and east. Sightings are still being used as an index today, and average over 3,000 each year, compared to 20-30 each year in the 1980’s. All bears captured are given highly visible ear tags with individual identification numbers. Ear-tags allow for individual bears to be identified through public sighing reports. We obtain 1000’s of locations per year for bears fitted with GPS collars. This data is far more extensive and accurate than what was collected with VHF collars, allowing us to examine home range characteristics, resource selection and seasonal movement patterns. A young sow being fitted with a VHF collar in the winter den. Jason Hawley and Paul Rego Connecticut Department of Energy and Environmental Protection Wildlife Division Annual locations of sow number 4-4 using VHF technology. GPS collars provide researchers with up to 24 locations per day for each collared bear . Annual locations of sow 4-4 the following year using GPS technology. Both VHF and GPS collars can be used to locate winter dens using telemetry. - A statewide habitat suitability analysis was performed for black bears using 2011-2012 GPS data from collared female bears and 2006 Connecticut land use/land cover data in ArcGIS. Annual home ranges were calculated in Geospatial Modeling Environment (GME) for collared bears using a fixed kernel density estimator with least squares cross validation used for bandwidth selection (mean home range size from 2012 data = 16mi 2 and 13mi 2 from 2013 data). Resource selection functions (RSF) and a use vs. available design fit to a logistic regression function were used to identify resource selection by bears. In this design, selection is defined as a bear using a resource or habitat disproportionately to its availability. Resource measurements or “variables” in our model included distance to road, distance to water, habitat type, housing density, slope, elevation, aspect and forest patch size. The model suggested that bears selected for low housing density, steep slope, longer distances to water, medium forest patch size (50-250 acres), closed canopy wetlands, softwoods and selected against agriculture and grasslands. This RSF predictor model was then used to develop a statewide map of suitable bear habitat (Figure 1). RSF scores were normalized (0 to 1) to produce a relative probability of use for 295x295 ft map units covering the state. Suitable habitat was defined as map units with a RSF > 0.5. Bear home range estimates for 2011-2012 were then overlaid on the habitat suitability map to estimate the minimum amount of suitable habitat required for a female bear home range in Connecticut (Figure 2). Based on our analysis of bear home ranges, we estimated that each bear requires approximately 4.6mi 2 of suitable habitat within their home range. We then calculated the number of adult female bears each town in Connecticut could support (based on the 4.6mi 2 of required suitable habitat) along with a measure of the proportion of suitable habitat within each town (Figure 3). Using these methods we estimated a statewide biological carrying capacity of approximately 950 adult (>1 year old) female bears. Most recent estimates of black bear sex ratios are near or at 1:1, which would give Connecticut a population carrying capacity of approximately 1900 adult bears. Using established black bear range only (roughly the northwest quadrant of the state), we estimate the current population at approximately 450 adult bears Home range estimates using kernel density estimators Each color represents an individual sow’s home range during 2011. Statewide black bear habitat suitability map GPS data reveals valuable information on how bears use Connecticut’s highly fragmented landscape. Red dots represent locations from sow A-8 during 2011 (note the proximity to Bradley Airport). Home range estimated using GPS data points from a collared sow GPS technology revealed that some bears move many miles out of their home range during the autumn foraging season. This behavior would likely not have been documented with VHF collars. The red dots on the map on the right represent 2012 locations of sow A-8. The red and yellow dots on the map on the left represent 2012 locations of sow 8-6 and C-3, respectively. Resource Selection
Transcript of Black Bear Research in Connecticut using GPS...
Black Bear Research in Connecticut using GPS Technology
- Black bears began recolonizing the rural northwestern corner of Connecticut through range expansion from Massachusetts during the mid 1900’s. A resident population became evident in the 1980’s as numerous sightings of adult females (sows) with cubs were reported to CT DEEP’s Wildlife Division. Since then, the state’s population of black bears has continued to increase in numbers and expand in range. The Wildlife Division has solicited bear sightings from the public for over 30 years. These public sightings have been a valuable index of black bear population growth and range expansion in the state. In 2001, the Wildlife Division initiated a bear research project to determine population growth rates (reproduction and survival) and sow home range characteristics. Initially, this research included maintaining and monitoring a sample of 15-25 sows fitted with Very High Frequency (VHF) radio-collars. Collared sows were located in their winter dens which provided valuable reproduction and survival information. Locations of VHF collared sows were determined through triangulation which is effective but often time consuming. While using VHF collars, each collared sow was located on average once each week during the spring and summer, or 20-30 times a year. Recent advances in wildlife monitoring technology have made Global Positioning System (GPS) collars a far more reliable and efficient tool for studying wildlife movement patterns. In 2007, the Wildlife Division began to replace VHF collars with GPS collars with the goal of collecting more detailed information on spatial and temporal movements of bears. Currently, 30 sows are being monitored via GPS collars in Connecticut. Since switching to GPS collars, the number of data points collected on each sow per year has been between 4,500 and 5,500. This GPS data has provided far more accurate and detailed information which is being used to estimate current population size and carrying capacity through resource selection analysis which will help guide management decisions for Connecticut’s bear population into the future.
Black bear sighting reports from the public have been collected and mapped by the Wildlife Division since the early 1980’s. This information has been a valuable index of bear population
growth and range expansion. The population initially established in the northwest corner of the state, but has slowly been expanding south and east. Sightings are still being used as an index
today, and average over 3,000 each year, compared to 20-30 each year in the 1980’s.
All bears captured are given highly visible ear tags with individual identification numbers.
Ear-tags allow for individual bears to be identified through public sighing reports.
We obtain 1000’s of locations per year for bears fitted with GPS collars. This data is far more extensive and accurate than what was collected with VHF collars, allowing us to examine home range characteristics, resource selection and seasonal movement patterns.
A young sow being fitted with a VHF collar in the winter den.
Jason Hawley and Paul Rego Connecticut Department of Energy and Environmental Protection
Wildlife Division
Annual locations of sow number 4-4 using VHF technology.
GPS collars provide researchers with up to 24 locations per day for each collared bear.
Annual locations of sow 4-4 the following year using GPS technology.
Both VHF and GPS collars can be used to locate winter dens using telemetry.
- A statewide habitat suitability analysis was performed for black bears using 2011-2012 GPS data from collared female bears and 2006 Connecticut land use/land cover data in ArcGIS. Annual home ranges were calculated in Geospatial Modeling Environment (GME) for collared bears using a fixed kernel density estimator with least squares cross validation used for bandwidth selection (mean home range size from 2012 data = 16mi2 and 13mi2 from 2013 data). Resource selection functions (RSF) and a use vs. available design fit to a logistic regression function were used to identify resource selection by bears. In this design, selection is defined as a bear using a resource or habitat disproportionately to its availability. Resource measurements or “variables” in our model included distance to road, distance to water, habitat type, housing density, slope, elevation, aspect and forest patch size. The model suggested that bears selected for low housing density, steep slope, longer distances to water, medium forest patch size (50-250 acres), closed canopy wetlands, softwoods and selected against agriculture and grasslands. This RSF predictor model was then used to develop a statewide map of suitable bear habitat (Figure 1). RSF scores were normalized (0 to 1) to produce a relative probability of use for 295x295 ft map units covering the state. Suitable habitat was defined as map units with a RSF > 0.5. Bear home range estimates for 2011-2012 were then overlaid on the habitat suitability map to estimate the minimum amount of suitable habitat required for a female bear home range in Connecticut (Figure 2). Based on our analysis of bear home ranges, we estimated that each bear requires approximately 4.6mi2 of suitable habitat within their home range. We then calculated the number of adult female bears each town in Connecticut could support (based on the 4.6mi2 of required suitable habitat) along with a measure of the proportion of suitable habitat within each town (Figure 3). Using these methods we estimated a statewide biological carrying capacity of approximately 950 adult (>1 year old) female bears. Most recent estimates of black bear sex ratios are near or at 1:1, which would give Connecticut a population carrying capacity of approximately 1900 adult bears. Using established black bear range only (roughly the northwest quadrant of the state), we estimate the current population at approximately 450 adult bears
Home range estimates using kernel density estimators Each color represents an individual sow’s home range during 2011.
Statewide black bear habitat suitability map
GPS data reveals valuable information on how bears use Connecticut’s highly fragmented landscape. Red dots represent locations from sow A-8 during 2011 (note the proximity to Bradley Airport).
Home range estimated using GPS data points from a collared sow
GPS technology revealed that some bears move many miles out of their home range during the autumn foraging season. This behavior would likely not have been documented with VHF collars. The red dots on the map on the right represent 2012 locations of sow A-8. The red and yellow dots on the map on the left represent 2012 locations of sow 8-6 and C-3, respectively.
Resource Selection
